STS-121 MISSION ARCHIVE (FINAL)
Updated: 07/20/06

Return to Flight

By William Harwood
CBS News/Kennedy Space Center

The following copy originally was posted on the Current Mission space page at http://cbsnews.com/network/news/space/current.html.

Comments, suggestions and corrections welcome!

TABLE OF CONTENTS


09:20 a.m., 07/17/06, Update: Shuttle Discovery returns to Earth UPDATED at 10:20 a.m., 11:10 a.m. and 3:40 p.m. with revised landing time, crew quotes and additional details

Under an overcast sky, the shuttle Discovery glided to a smooth touchdown on runway 15 at the Kennedy Space Center today, closing out a successful space station repair and resupply mission that appears to clear the way for resumption of station assembly in September.

With commander Steve Lindsey at the controls, Discovery settled to a tire-smoking, high-speed touchdown at 9:14:43 a.m. A few moments later, pilot Mark Kelly deployed the shuttle's braking parachute, the ship's nose gear dropped to the runway and Discovery rolled to a stop to close out a voyage spanning 5.3 million miles and 202 complete orbits since blastoff July 4.

"Wheels stopped, Houston," Lindsey radioed mission control.

"Roger wheels stopped. Welcome back, Discovery," astronaut Steve Frick replied from Houston. "Congratulations on a great mission expanding our knowledge and experience with orbiter repair and bringing the space station back to a full crew complement."

"Thanks. It was a great mission, a really great mission," Lindsey said. "Enjoyed the entry and the landing."

Mission duration was 12 days 18 hours 36 minutes and 48 seconds.

Lindsey, Kelly flight engineer Lisa Nowak, Piers Sellers, Mike Fossum and Stephanie Wilson plan to spend the night in Florida before flying back to Houston on Tuesday.

"It's a thrill and a pleasure to be here again, especially under these circumstances," NASA Administrator Mike Griffin told reporters after landing. "In fact, it's such a great day I don't think even a press conference can spoil it."

Griffin expressed optimism that Discovery's flight will pave the way to launch of the shuttle Atlantis late next month on the first in a series of daunting space station assembly missions. But he said NASA would not launch Atlantis before completing a detailed analysis of Discovery's mission.

"This is as good a mission as we've ever flown," he said. "But we're not going to get over confident, we're going to keep looking at the data and we're going to make our decisions based on the data just as we did on this flight. We have to take it flight by flight. We've got 16 flights to go to assemble the station and hopefully do a Hubble (Space Telescope) repair. And that's what we want to do, but we've got to take it one flight at a time."

Still, Discovery's mission was a clear step in that direction. NASA Launch Director Mike Leinbach said an initial inspection of the shuttle turned up no surprises.

"We had to search for dings to the tile and the couple that we saw were very, very minor," he said. "Just a great looking vehicle."

Discovery's descent began over the eastern Indian Ocean when Lindsey and Kelly fired the shuttle's twin braking rockets at 8:07 a.m. to drop the ship out of orbit. Five minutes before the "burn," Kelly started auxiliary power unit No. 1, a hydraulic powerplant with a small leak in its hydrazine fuel system.

Engineers concluded Sunday the leak was most likely nitrogen gas used to pressurize APU 1's hydrazine fuel tank and not an actual fuel leak. APU 1 appeared to run normally throughout Discovery's descent today as did the shuttle's other two redundant hydraulic power units.

The only technical issue occurred late in the descent when one of two air data probes failed to deploy. But it eventually slipped into place and in any case, the other probe deployed on time and worked properly.

The major concern all morning was the weather, with rain clouds popping up near the runway well after Discovery's braking rockets were fired. Flight director Steve Stich told Lindsey to switch from runway 33 to 15 to avoid possible showers toward the south end of the runway.

"I would give Steve a perfect 10 today," Stich said later. "He did a superb job. ... It was a perfect landing."

There were no obvious problems during final approach and landing and infrared views of the shuttle on the runway showed normal looking APU exhaust puffing from ports by the shuttle's tail fin. Technicians did not detect any hydrazine vapors near the shuttle's aft compartment.

"Houston, Discovery, looks like everybody's off and I'm about to go off comm," Lindsey radioed a few minutes past 10 a.m. "I just wanted to tell Steve (Stich) and Steve (Frick) and the entire entry team it was a pleasure working with you today. Really enjoyed it. It was a fun entry, it was beautiful!

"At the high mach numbers at night going towards dawn - I just wanted to describe the picture for you - we could see the bright orange glow above and I could see the Earth moving below and it was just spectacular. We actually also saw the moon through the plasma. So it was a great entry and a great landing. Appreciate working with you and training with you."

"Thanks very much for those words, Steve," Frick replied. "We appreciate it. It was an exciting entry for us, too, and we envy you the view. We look forward to seeing you when you get back to Houston."

"All right, I can't wait," Lindsey said. "Talk to you later."

The astronauts, wearing blue jump suits, were greeted on the runway by Griffin, Leinbach, Bill Gerstenmaier, director of spaceflight, space center Director Jim Kennedy and other senior managers.

Smiling and looking none the worse for two weeks in weightlessness, Lindsey and his crewmates took a moment to inspect the shuttle's heat shield, walking about under the orbiter, pointing up at Discovery's belly from time to time and discussing the flight with Griffin. There were no obvious signs of damage in wide-angle television views. "I'd like to just thank the folks at Kennedy Space Center for a really, really clean vehicle," Lindsey said, standing with his crew mates in front of Discovery. "This is my fourth flight and I've done four walkarounds and I've never seen a vehicle as clean as this one is.

"We had two major objectives on this flight. The first one was to complete the return-to-flight test objectives and the second one was to get us ... back for space station assembly. And I think we accomplished both of those objectives and we're ready to go assemble station and we're ready to start flying shuttles on a more regular basis.

"And finally, I'd like to thank this crew standing here," Lindsey said. "They were absolutely superb the entire flight, I couldn't have asked more out of them, they were nearly perfect. They got everything done that we needed to get done. I actually had to throttle them back to give them a little bit of time off. They were all focused, they did a great job and it was a privilege for me to serve with them. Thanks a lot. We're going to go see our families now. Have a good day."

The 115th shuttle mission was a make or break flight for NASA, coming nearly a full year after Discovery's launch on the first post-Columbia mission. The unexpected loss of foam insulation from the ship's external fuel tank showed the space agency still had work to do.

After months of redesigns, computer modeling and exhaustive testing, Discovery was cleared for blastoff July 4 on a flight to pave the way for the resumption of space station assembly.

During their two weeks in space, Lindsey and company delivered fresh water and more than 3.2 tons of supplies and equipment to the international space station and carried out a successful spacewalk to fix a stalled robot arm transporter on the complex that had to be restored to normal operation before station assembly can proceed.

Discovery also ferried European Space Agency astronaut Thomas Reiter to the outpost, boosting crew size back the three for the first time since downsizing after the Columbia disaster. Reiter was launched aboard Discovery as part of a commercial contract between ESA and the Russian space agency, Roscosmos.

Spacewalkers Fossum and Sellers rode on the end of a long boom attached to the shuttle's robot arm, demonstrating its possible use as a shuttle repair platform. Thanks to a one-day mission extension, Sellers and Fossum also staged a third spacewalk to test wing leading edge repair techniques. The exercises may help pave the way for an eventual flight to service the Hubble Space Telescope.

In the near term, Discovery's flight was a critical milestone for NASA. Facing a Bush administration 2010 deadline for completing the space station and retiring the shuttle, NASA needs to ramp up station assembly as soon as possible to finish the lab complex before time runs out. Discovery's flight doesn't guarantee success, but it at least clears the way for assembly flights to resume.

"I think we were all hoping for two things to come out of STS-121," Sellers said during an orbital interview. "The first thing is that the shuttle would fly with no problems, no big dings on ascent and we'd have a clean vehicle. We seem to have achieved that.

"The second thing is, that we would leave station in good shape and ready to pick up the assembly sequence and the line would be drawn where it was rubbed out before Columbia, we would start again with the next mission and continue the assembly. I think we're there now. We repaired the external equipment that will allow the assembly to continue. So, two for two!" Said space station flight director Rick LaBrode: "All in all, it was just a great mission. This is just a roaring success for the station team and we're ready to proceed with assembly ops."

Throughout the mission - the day after launch, during docked operations at the station and even after their departure - the astronauts carried out time-consuming, inch-by-inch inspections of Discovery's fragile heat shield to make absolutely sure nothing was damaged during the climb to space or after reaching orbit.

As it turned out, Discovery's foam-covered external fuel tank performed well and the shuttle's heat shield tiles suffered only a few cases of very minor damage. NASA managers were elated at the performance of the tank after a frustrating year of redesigns and exhaustive testing.

"All the work that all the folks have done on the ET ... and how clean the 121 tank is kind of gives everybody a really good feeling that we're getting there, we're going in the right direction," said lead flight director Tony Ceccacci. "You've seen how clean the vehicle is and that's just a testament to all the work that everyone has done."

In an orbital interview, Nowak agreed, saying "we feel like we've done all the tests and met the objectives and we feel like the whole program is back on track to assemble the space station and move on back to the moon and to Mars. And we're looking forward to all of that."

With Discovery back on the ground in Florida, NASA engineers will now turn their attention to the shuttle Atlantis, scheduled to blast off around Aug. 27 or 28 on a mission to deliver a set of huge solar arrays to the space station.

Atlantis is expected to be hauled out to launch pad 39B around Aug. 1. A practice countdown is on tap Aug. 10 and NASA managers will meet Aug. 15 and 16 for a formal flight readiness review to assess Atlantis' processing and to set an official launch date. The launch window opens Aug. 27 or 28 - a final decision hasn't been made - and closes Sept. 7.

"Someone asked the other day if the space shuttle was back," shuttle program manager Wayne Hale said today. "When we lqunched and looked at the external tank, we saw exactly what we predicted. We delivered about 4,000 pounds of scientific equipment to the international space station versus about 300 pounds of scientific equipment that had been delivered in the last four years by our international partners.

"And in addition to that, we brought the third crew member up to the international space station and made vital repairs on it. We made a number of repair related activities that proved that our repair capability is getting more and more robust. And of course, the orbiter worked in an almost flawless manner.

"So yes, I think the conclusion is the shuttle is back," Hale said. "We are launching in just about six weeks from today on probably the most complicated assembly mission that's every been scheduled in human space flight before and we have the team that is now practiced and battle hardened and ready to go do that.

If all goes well, NASA will close out 2006 by launching Discovery in mid December on another station assembly flight.


08:10 a.m., 07/17/06, Update: Shuttle braking rockets fired

Flying upside down and backward over the eastern Indian Ocean, commander Steve Lindsey and pilot Mark Kelly fired Discovery's twin braking rockets at 8:06:55 a.m. for three minutes and two seconds, slowing the shuttle by 206 mph. That was enough to drop the far side of the shuttle's orbit deep into Earth's atmosphere, setting up a landing at the Kennedy Space Center around 9:14:06 a.m. This status report will be updated after landing or as conditions warrant.


08:00 a.m., 07/17/06, Update: Discovery cleared for entry

Entry flight director Steve Stich has cleared the Discovery astronauts to fire their braking rockets on time at 8:06:50 a.m. to set up a landing on runway 33 at the Kennedy Space Center around 9:14 a.m. Earlier concern about electrically active anvil clouds north of the space center dissipated and Stich felt comfortable enough to give the crew a "go" for the deorbit burn. Astronaut Mike Bloomfield, assessing the weather in a shuttle training just, told flight controllers the shuttle would fly into a broken deck of clouds around 16,000 feet above the landing site but would break out into the clear around 10,000 feet. He also reported smooth air and no turbulence.


05:40 a.m., 07/17/06, Update: Payload bay doors closed for entry

The shuttle Discovery's payload bay doors have been closed and latched for re-entry and the ship's flight computers are now running OPS-3 entry software. The astronauts and the mission control team at the Johnson Space Center in Houston are continuing to monitor the weather while pressing ahead toward a deorbit rocket firing at 8:07 a.m. Landing at the Kennedy Space Center remains targeted for 9:14 a.m.


04:20 a.m., 07/17/06, Update: Discovery astronauts gear up for entry

Keeping tabs on the weather, the Discovery astronauts are gearing up for re-entry and landing today at the Kennedy Space Center to close out a successful space station repair and resupply mission.

Flying upside down and backward over the eastern Indian Ocean, commander Steve Lindsey and pilot Mark Kelly plan to fire Discovery's twin braking rockets at 8:06:55 a.m. for three minutes and two seconds, slowing the shuttle by 206 mph. That's enough to drop the far side of the shuttle's orbit deep into Earth's atmosphere, setting up a landing at the Kennedy Space Center around 9:14:06 a.m.

Lindsey, Kelly, flight engineer Lisa Nowak, Piers Sellers, Mike Fossom and Stephanie Wilson plan to close Discovery's cargo bay doors around 5:30 a.m. to rig the ship for entry.

There are no problems of any significance aboard Discovery and flight controllers are confident the shuttle's three hydraulic power units, including one with a known but very small leak of either nitrogen gas or toxic hydrazine fuel, will operate normally during the descent.

But the weather could pose problems for Lindsey and his crewmates. Forecasters with the Spaceflight Meteorology Group at the Johnson Space Center in Houston predict a chance of showers in the landing area due to a stationary front north of the Florida spaceport. But forecasters said early today they are hopeful the showers will dissipate.

"We think we have a good shot," astronaut Steve Frick radioed the crew from Houston. "OK, that sounds great," Lindsey replied.

Discovery has two landing opportunities today, one at 9:14 a.m. and the second, one orbit later, around 10:50 a.m. If Lindsey and company can't make it back to Florida today, they'll remain in orbit one more day and try again Tuesday. The forecast for Tuesday is somewhat worse and entry flight director Steve Stich said Sunday he would activate the shuttle's backup landing site at Edwards Air Force Base, Calif., if re-entry slips to Tuesday.

Here is the timeline for today's landing attempt. Note: The time of deorbit ignition for the first landing opportunity has moved 20 seconds earlier than previously posted. The times below reflect that change (all tiems in EDT and subject to change):

TIME			EVENT
_____________________________________________________

01:08:00 AM		Crew wakeup (flight day 14)
03:13:00 AM		Group B computer powerup
03:28:00 AM		Navigation system alignment
03:43:00 AM		Laptop computer teardown
04:09:00 AM		Deorbit timeline begins
05:27:00 AM		Payload bay door closing
07:47:00 AM		Mission control 'go' for deorbit burn
07:53:00 AM		Astronauts strap in
08:02:00 AM		Single APU start (APU 1)
08:06:55 AM		Deorbit ignition (duration: 3:02)
08:09:57 AM		Deorbit burn complete (velocity change: 206 mph)
08:42:13 AM		Entry interface (altitude: 400,000 feet)
08:47:19 AM		1st roll command to left
08:57:10 AM		1st left-to-right roll reversal
09:00:40 AM		C-band radar acquisition
09:07:42 AM		Velocity less than mach 2.5
09:09:50 AM		Velocity less than mach 1
09:10:11 AM		Shuttle banks to line up on runway
09:14:06 AM		Landing
		
			BACKUP LANDING OPPORTUNITY
		
09:23:00 AM		Mission 'go' for deorbit burn
09:38:00 AM		Single APU start (APU 1)
09:43:25 AM		Deorbit ignition (dT: 3:01; dV: 205 mph)
09:46:26 AM		Deorbit burn complete
10:18:04 AM		Entry interface (altitude: 400,000 feet)
10:23:04 AM		1st roll command to left
10:36:21 AM		1st left-to-right roll reversal
10:43:25 AM		Velocity less than mach 2.5
10:45:34 AM		Velocity less than mach 1
10:46:12 AM		Shuttle banks to line up on runway
10:49:48 AM		Landing

11:23:00 AM		Deorbit backout (if re-entry waved off 24 hours)
11:48:00 AM		Group B computer powerdown
04:23:00 PM		Crew sleep begins
12:23:00 AM		Crew wakeup (07/18)


04:00 p.m., 07/16/06, Update: Astronauts eager for landing; flight director optimistic about weather

The shuttle Discovery is in excellent condition for landing and with a successful space station repair and resupply mission now in the books, NASA should be clear to resume assembly flights with launch of shuttle Atlantis in late August, Discovery skipper Steve Lindsey said today.

"It's been very, very clean throughout the mission, we've had very, very few issues with it," Lindsey said of Discovery in an interview with CBS News. "The vehicle's been clean, the (external fuel) tank looked pretty clean, we got a clean bill of health today to enter after inspecting for micrometeorite damage yesterday and the day before. So I think this vehicle has done great."

As for Discovery's mission to deliver supplies to the international space station, to repair a critical robot arm transporter and to ferry a third full-time crew member to the lab complex, Lindsey said "we achieved all of those objectives."

"Two big objectives were to get the space station ready for assembly as well as bring the crew back up to three people," Lindsey said. "I think we are ready to go back to space station assembly and start flying the shuttle, hopefully, as soon as August.

"Having said that, we'll stay vigilant with the shuttle, we'll continue watching it, taking care of it, paying attention to ice-frost ramps and areas like that. Just because we're going to be back to flight doesn't mean we're going to change the way we're operating. We're going to be very careful, very cautious, look at everything and we'll leave no stone unturned as we continue with this program."

NASA managers hope to launch Atlantis as early as Aug. 27 to install a huge set of solar panels on the end of the station's main solar array truss. To ensure good lighting for photo documentation, and to avoid a conflict with the planned launch of a Russian Soyuz rocket carrying the station's next crew, Atlantis must get off the ground between Aug. 27 or 28 and Sept. 7.

If the shuttle isn't off the ground by then, the flight will slip into late October at the earliest.

Asked if he was concerned about pressure to get Atlantis off in the September window, Lindsey said he was confident NASA managers would make the right decisions.

"Every program and project I've ever been involved in, every one I know of, there is schedule pressure," he said. "And there are other kinds of pressures, too. There is technical pressure, their are cost pressures, all those are a part of every program and project that I know of. ... As long as we can carefully balance those pressures, I think we'll be fine.

"The diligence that went into launching us ... I think the same will happen for Atlantis. We will shoot for August and if something happens and we can't make August, then we'll go for the next launch date. I'm not worried about it, everybody's paying attention, we're especially conscious of that sort of thing and we talk about it a lot. So I think the program will make the right decisions."

But first, entry flight director Steve Stich and his team must make the right decision about when to bring Discovery back to Earth. In a pre-entry briefing today, Stich said the only concern is the weather, with forecasters predicting a chance of showers that could cause problems.

Discovery will have two chances to land at the Kennedy Space Center Monday, the first at 9:14 a.m. and the second around 10:50 a.m. If the weather doesn't cooperate - and it looks slightly better for the first opportunity than the second - Lindsey and his crewmates will remain in orbit an extra day.

In that case, Stich likely will activate the shuttle's backup landing site at Edwards Air Force Base, Calif., and bring Discovery down on one coast or the other Tuesday. The forecast in Florida calls for possible showers Tuesday while Edwards is expected to be "go" Monday and Tuesday. The shuttle has enough on-board supplies to remain in orbit until Wednesday.

"The weather looks fairly reasonable for tomorrow," Stich said. "Of course, at the Kennedy Space Center in the summertime, even though it's a morning landing, they're always looking at a chance of showers and that's the main thing we're looking at tomorrow. There's a frontal boundary just to the north of the Kennedy Space Center and they're worried about that front pushing to the south and causing showers. That's about the only concern for weather."

Otherwise, he said, Discovery is in excellent condition for landing.

Lindsey, pilot Mark Kelly, flight engineer Lisa Nowak, Piers Sellers, Mike Fossom and Stephanie Wilson spent the day packing up and rigging Discovery for entry. Thomas Reiter, the European Space Agency astronaut who blasted off with Lindsey and company July 4, was left behind on the space station to boost crew size back to three for the first time since downsizing in the wake of the Columbia disaster.

Discovery's mission featured one of the busiest flight plans in recent memory, with dual robotic arm operations virtually every day, three spacewalks and work to move tons of supplies and equipment from the shuttle to the station.

"I've got to tell you, about the first seven to nine days, depending on what your role was on this flight, it was a pretty tough timeline," Lindsey told CBS News. "It was tough. This is my fourth flight and it's probably the toughest one I've ever seen.

"We actually did, on flight day 10, get about three quarters of a day off where everybody could just kind of goof off. I actually ordered the crew, because i couldn't get them to stop, they were not allowed to work and they had to go look around station, tour station, take pictures and just have fun. I think everybody took advantage of it, came out of it refreshed and ready to pick up with the last part of the mission."


10:30 a.m., 07/16/06, Update: Discovery cleared for entry; no debris impacts seen; APU 1 looks good

NASA managers reviewing laser scans of Discovery's nose cap and wing leading edge panels have found no signs of any micrometeoroid impacts and have cleared the shuttle for re-entry Monday, weather permitting, to close out a space station repair and resupply mission.

In a brief chat with shuttle commander Steve Lindsey, mission control also said engineers believe a leaking hydraulic power unit that was tested earlier today can be safely used during re-entry and landing at the Kennedy Space Center.

Entry flight director Steve Stich has decided not to staff NASA's backup landing site at Edwards Air Force Base, Calif., Monday and instead to focus on Florida only. The crew will have two landing opportunities on successive orbits, the first leading to a touchdown at 9:14 a.m. and the second around 10:50 a.m.

If they can't make it back to Florida Monday because of weather or any other problems, Discovery will remain in orbit an extra day and likely land Tuesday in either Florida or California.

"After finishing the review for the port and starboard wings and the nose cap, they did not see anything new so they all look pretty good," astronaut Steve Frick radioed from the Johnson Space Center. "For weather ... the clouds shouldn't be an issue tomorrow, however there's still a chance of showers for the first rev and a little higher chance probably for the second rev. There's a front extending off into the Atlantic and depending on how it moves tonight, it may be close enough to cause some showers in the area. So we'll be looking real close at that. Edwards is looking real good both tomorrow and Tuesday if we need it."

"OK, we copy that," Lindsey said. "And is the vehicle cleared for entry?"

"That's affirm, I'm being told I can use that word. You are cleared for entry."

"OK, thanks," Lindsey said. "And a question about tomorrow. Will we land no matter what? Or will we just go for KSC tomorrow?"

"Tomorrow is KSC only," Frick replied. "For Tuesday, we'll look at other sites. But for tomorrow, we're just calling up KSC. However, the weather does look good for the West Coast for at least the next two days."

"OK, copy that."

Frick then passed on the latest thinking about APU 1, the hydraulic power unit in Discovery's engine compartment that is leaking either nitrogen gas or toxic hydrazine fuel. Engineers believe the small leak is nitrogen, used to pressurize the tank, and that more than enough will be available for entry.

While they cannot rule out a more hazardous hydrazine leak, results from a test run earlier today indicate APU 1 can safely be used for a normal re-entry and landing.

"They are feeling more and more confident it's likely not an internal ... hydrazine leak," Frick said. "There's always the chance, but we're feeling a little bit more comfortable with it. So the plan for APU 1 tomorrow will be nominal ops, we're not going to try to start it early or do anything unusual to burn extra hydrazine out of there. We'll be looking at it close like we did to day during FCS (flight control system) checkout. And it looked just fine today."

"OK, we copy that," Lindsey said. "Sounds great, thanks."


04:30 a.m., 07/16/06, Update: APU 1 runs normally during flight control system checkout

A hydraulic power unit with a leak in its fuel system was fired up early today as part of an otherwise routine flight control system checkout aboard the shuttle Discovery. A quick look at telemetry from APU 1 indicated normal operation and no obvious problems, but it will take several hours to make sure the leak rate stayed constant as engineers predicted.

Shuttle commander Steve Lindsey and pilot Mark Kelly began the hydraulic power test portion of FCS checkout around 4 a.m., turning on APU 1 to test the hydraulic actuators that will be used for steering during re-entry Monday.

"Discovery, Houston, just for a summary of part one three, we saw normal activity on all of the secondary actuator check," astronaut Steve Frick radioed from mission control in Houston. "Everything looked good to us. Also, the quick look on APU 1, we saw normal fuel useage, normal parameters for all of its run time."

"OK, great news," Lindsey replied. "Thank you, Steve."

APU 1 is on of three redundant powerplants in the shuttle's main engine compartment that generate the hydraulic pressure needed to move the ship's wing flaps, rudder, body flap and landing gear. The pressure in APU 1's hydrazine fuel tank has been dropping ever so slightly since launch July 4, indicating a leak of either nitrogen gas, used to pressurize the tank, or a leak of toxic hydrazine.

Because engineers cannot tell which material is leaking, mission managers have to assume it's hydrazine, an extremely hazardous material, and plan accordingly. Mission Management Team Chairman John Shannon said Saturday the team's strategy was as follows: If the leak stayed constant during the FCS checkout, APU 1 will be considered healthy enough for normal use during entry. If the leak worsened, the astronauts will simply run APU 1 until all of its fuel is exhausted and then return to Earth Monday with two operational APUs.

"It will be a good test for us, because it will start the APU up, it will run the APU, it will put it through some vibration, all the things we would expect to do prior to entry," Shannon said. "And then we'll just go and assess the leak.

"I would sway it's going to take between six and 12 hours to see if the pressure decay rate has changed at all. If there's a significant change, then the ops team will go burn it off just because you would have lost confidence in the integrity of the system. I don't expect that to happen."

Based on the quick-look data, no immediately obvious change was seen.

Here is an updated timeline of today's activity in space (in EDT and mission elapsed time; includes revision Q of the NASA TV schedule):

01:08 AM	11	10	30	Crew wakeup (flight day 13)
03:58 AM	11	13	20	FCS checkout
05:08 AM	11	14	30	Cabin stow begins
05:08 AM	11	14	30	RCS hotfire
08:58 AM	11	18	20	Crew meal
09:58 AM	11	19	20	L-1 communications check 1
09:58 AM	11	19	20	Entry video setup
11:38 AM	11	21	00	L-1 communications check 2
12:03 PM	11	21	25	PAO event (all crew members)
12:23 PM	11	21	45	Deorbit briefing
12:30 PM	11	21	52	Mission status briefing on NASA TV
12:53 PM	11	22	15	PILOT landing training
01:08 PM	11	22	30	Wing leading edge gear stow
01:28 PM	11	22	50	Laptop computer teardown
01:33 PM	11	22	55	Ergometer stow
01:58 PM	11	23	20	NC7 rocket firing
02:03 PM	11	23	25	KU antenna stow
05:08 PM	12	02	30	Crew sleep begins
06:00 PM	12	03	22	Daily video highlights reel on NASA TV
In the crew's morning "execute package" of timeline changes and instructions from mission control, flight controllers jokingly signed off after a successful mission.

"This is the last execute package youÕre going to get from us," flight controllers wrote. "We've had it. We're done with execute packages, finished, over, our cooked indicator has popped, the fat lady is singing (and she's not singing the Aggie War Hymn). No more... O.K., maybe that's a little bit of an exaggeration.

"Actually, if the truth be told, we really have enjoyed working this mission and if the Ku antenna wasn't going to be stowed (today), we would gladly do another execute package. Thanks for making this a great mission - one we're proud to be part of. Take care and see you back in Houston - and we'll buy the first adult malted beverage."


08:30 p.m., 07/15/06, Update: Quick-look at wings, nose cap show no obvious problems; Suffredini confirms shortened launch window for next shuttle flight

A quick-look assessment of post-undocking laser scans of the shuttle Discovery's nose cap and wing leading edges shows no obvious impact damage from space debris or micrometeoroids. Final clearance to proceed with landing Monday at the Kennedy Space Center will not be given until Sunday, however, after a detailed assessment is completed. "From what they've looked at, there's nothing of any concern that we can report at this time," astronaut Lee Archambault radioed the crew from Houston late today. "So all looks good. Of course, the analysis will continue to crank out overnight and through tomorrow, and hopefully we'll have final words tomorrow."

"Thanks for the update," shuttle commander Steve Lindsey replied.

In the meantime, a key test is on tap early Sunday to assess the health of a hydraulic power unit that has a small leak in its fuel system. Lindsey and pilot Mark Kelly plan to fire up auxiliary power unit No. 1 around 3:58 a.m. Sunday as part of an otherwise routine flight control system check out.

APU 1 is on of three redundant powerplants in the shuttle's main engine compartment that generate the hydraulic pressure needed to move the ship's wing flaps, rudder, body flap and landing gear. The pressure in APU 1's hydrazine fuel tank has been dropping ever so slightly since launch July 4, indicating a leak of either nitrogen gas, used to pressurize the tank, or a leak of toxic hydrazine.

Because engineers cannot tell which material isleaking, mission managers have to assume it's hydrazine, an extremely hazardous material, and plan accordingly. Mission Management Team Chairman John Shannon says the team's strategy is unchanged from Saturday: If the leak doesn't get worse during the FCS checkout, APU 1 will be considered healthy enough for normal use during entry. If the leak worsens, the astronauts will simply run APU 1 until all of its fuel is exhausted and then return to Earth Monday with two operational APUs.

"The mission operations team put together their final plan," Shannon said. "The ops team will use APU 1 during the flight control system check out, they will run it the normal amount of time then they'll go assess it, make sure the leak rate did not change.

"If the leak rate changes at all, if it's perceptible to the ops team, they will burn it off, burn all the fuel out of that hydrazine system. We don't expect that to be the case. Assuming everything looks good after flight control system check out, that APU will be used as the first APU that's started pre deorbit burn and then used nominally throughout the entry."

Shannon said one member of the MMT dissented with the majority opinion, arguing "that maybe we did not know enough about the conditions back there and suggested we go ahead and burn it off for extra caution. But the other 31 people I polled were all in agreement that we go with the nominal plan."

The concern is that a major hydrazine leak could result in a fire late in re-entry under worst-case conditions. While engineers believe the leak is more likely nitrogen, which poses no threat, NASA's flight rules require conservatism to ensure the team errs on the side of caution.

A shuttle can safely land with just one operational APU, but APU 1 is required to deploy the ship's landing gear. If APU 1 isn't available for use Monday, Kelly will use a backup system to deploy the gear, firing pyrotechnic charges to blow the doors open and release the hooks that hold the gear in place. While that's never been done before, the system is redundant and Shannon said it would pose no problems for Discovery's crew.

APU 1 will be run for five to six minutes early Sunday to provide the power needed to check out the hydraulic system and movement of Discovery's aerosurfaces.

"It will be a good test for us, because it will start the APU up, it will run the APU, it will put it through some vibration, all the things we would expect to do prior to entry," Shannon said. "And then we'll just go and assess the leak.

"I would sway it's going to take between six and 12 hours to see if the pressure decay rate has changed at all. If there's a significant change, then the ops team will go burn it off just because you would have lost confidence in the integrity of the system. I don't expect that to happen."

In addition to the FCS checkout and test firings of Discovery's maneuvering jets, Lindsey and Kelly also will carry out tests to troubleshoot an erratic controller in the ship's flash evaporator cooling system. The system, used to cool the shuttle's electronics after the ship's payload bay doors are closed, is difficult to test on the ground and NASA wants to collect as much data as possible to speed any possible repairs.

NASA hopes to launch the shuttle Atlantis around Aug. 28 on a long-awaited mission to restart assembly of the international space station. Discovery must be "turned around" quickly to serve as a potential rescue shuttle in case of problems that might prevent Atlantis from safely returning to Earth at the end of mission STS-115.

As reported here Friday, a conflict with the planned launch of a Russian Soyuz capsule carrying the station's next crew - Expedition 14 - has forced NASA to shorten Atlantis' launch window. As it now stands, according to station program manager Mike Suffredini, the window will open Aug. 28 - possibly as early as Aug. 27 if lighting permits - and close Sept. 7, nearly a week earlier than had been planned.

That's because NASA managers and their Russian counterparts want to ensure a separation between the shuttle's undocking and the arrival of the Soyuz to give the station crew time to make preparations and to adjust their body clocks to a different schedule.

For a variety of reasons, the Soyuz must take off by Sept. 18. Any later and the Soyuz carrying the station's outgoing crew would return to Earth about 10 days later in darkness. The Russians are using a recovery team with new personnel and want to ensure mostly daylight conditions for the recovery operation.

So the shuttle/Soyuz launch window will work like this: If Atlantis takes off between Aug. 28 and Sept. 3, the Soyuz carrying the Expedition 14 crew to the station will blast off from the Baikonur Cosmodrome Sept. 14. If Atlantis goes between Sept. 4 and Sept. 7, the Soyuz will take off Sept. 18. For a shuttle launch on Sept. 7, for example, Atlantis would dock with the lab complex Sept. 9 and undock Sept. 17. That would provide a three-day cushion between undocking and arrival of the Soyuz.

If Atlantis doesn't get off the ground by Sept. 7, NASA will stand down and the Soyuz launch will move back to Sept. 14. The next daylight launch window for the shuttle opens Oct. 26 and closes Oct. 29.


01:45 p.m., 07/15/06, Update: Updated deorbit burn and landing times through Wednesday

Flight controllers have updated deorbit burn and landing times for the shuttle Discovery. Here are all the landing times and sites from Monday through Wednesday (in EDT and subject to change):

SITE..REV...DEORBIT.....LANDING

Monday, July 17
KSC...202...08:07 a.m...09:14 a.m. (planned)
NOR...203...09:42 a.m...10:46 a.m.
KSC...203...09:43 a.m...10:50 a.m.
EDW...204...11:19 a.m...12:20 p.m.
NOR...204...11:22 a.m...12:21 p.m.
EDW...205...12:56 p.m...01:54 p.m.

Tuesday, July 18
KSC...218...08:19 a.m...09:21 a.m.
EDW...219...09:48 a.m...10:50 a.m.
NOR...219...09:50 a.m...10:52 a.m.
KSC...219...09:56 a.m...10:56 a.m.
EDW...220...11:23 a.m...12:24 p.m.
NOR...220...11:26 a.m...12:26 p.m.
EDW...221...01:01 p.m...01:58 P.m.

Wednesday, July 19
KSC...233...06:47 a.m...07:51 a.m.
KSC...234...08:23 a.m...09:25 a.m.
EDW...235...09:52 a.m...10:54 a.m.
NOR...235...09:54 a.m...10:56 a.m.
EDW...236...11:28 a.m...12:28 p.m.
NOR...236...11:31 a.m...12:30 p.m.


11:45 a.m., 07/15/06, Update: Entry ground tracks, data posted; mission status update

The Discovery astronauts are wrapping a final inspection of the shuttle's right-side wing leading edge panels and reinforced carbon carbon nose cap as part of a "late inspection" to look for signs of damage from micrometeoroids.

Lead flight director Tony Ceccacci said it will take engineers a day to assess the laser scans and compare the data to inspections conducted July 5, the day after Discovery reached orbit. Assuming no problems are found, NASA's Mission Management Team will give the crew a "go" Sunday to press ahead for deorbit and landing Monday at the Kennedy Space Center.

"As you saw today, we had a by-the-book undocking from the station," Ceccacci said. "Everything went per the procedures. ... After the crew gets done with the inspection, they'll be berthing the OBSS (inspection boom) and the shuttle robotic arm, getting it ready for entry. They'll be doing additional tasks to get the vehicle ready for entry, starting their cabin stow and such."

Commander Steve Lindsey, pilot Mark Kelly and flight engineer Lisa Nowak will check out the shuttle's re-entry systems Sunday, test one of the shuttle's cooling systems and test fire a hydraulic power unit that appears to have a small fuel leak. If the leak stays constant, the crew will use all three of Discovery's auxiliary power units - APUs - during re-entry Monday. If the leak in APU 1 worsens, however, the astronauts will restart the power unit, run it until its fuel is exhausted and return to Earth using APUs 2 and 3.

Ceccacci said NASA's Mission Management Team should complete its assessment of Discovery's nose cap and wing leading edges tomorrow afternoon.

The Spaceflight Meteorology Group at the Johnson Space Center is predicting cloudy weather at the Kennedy Space Center Monday with a deck of broken clouds at 10,000 feet, broken at 25,000 feet, light winds and showers within 30 nautical miles of the runway. Virtually identical conditions are expected Tuesday.

NASA has posted entry ground track maps and predicted entry milestones:

http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts121/mission_docs/landing.html Here is that data, plus standard re-entry milestones (all times in EDT):

TIME			EVENT

				Orbit 203 Deorbit to Kennedy Space Center

07:47:00 AM		MCC 'go' for deorbit burn
07:53:00 AM		MS seat ingress
08:02:00 AM		Single APU start
	
08:07:15 AM		Deorbit ignition (dT: 3:02; dV: 206 mph)
08:10:17 AM		Deorbit burn complete
	
08:42:33 AM		Entry interface (altitude: 400,000 feet)
08:47:39 AM		1st roll command to left
08:57:30 AM		1st left-to-right roll reversal
09:08:02 AM		Velocity less than mach 2.5
09:10:10 AM		Velocity less than mach 1
09:10:31 AM		Shuttle on the HAC
09:14:26 AM		Landing
		
				Orbit Deorbit to Kennedy Space Center
		
09:23:00 AM		MCC 'go' for deorbit burn
09:29:00 AM		MS seat ingress
09:38:00 AM		Single APU start
		
09:43:25 AM		Deorbit ignition (dT: 3:01; dV: 205 mph)
09:46:26 AM		Deorbit burn complete
		
10:18:04 AM		Entry interface (altitude: 400,000 feet)
10:23:04 AM		1st roll command to left
10:36:21 AM		1st left-to-right roll reversal
10:43:25 AM		Velocity less than mach 2.5
10:45:34 AM		Velocity less than mach 1
10:46:12 AM		Shuttle on the HAC
10:49:48 AM		Landing


06:30 a.m., 07/15/06, Update: Shuttle Discovery undocks from space station

The shuttle Discovery undocked from the international space station early today, leaving European Space Agency astronaut Thomas Reiter behind to boost crew size to three for the first time since downsizing in the wake of the Columbia accident.

Undocking occurred on time at 6:08 a.m. as the two spacecraft sailed high above New Zealand.

"And we have physical separation," a Discovery astronaut said as the shuttle's docking system disengaged.

"Discovery, station, roger, we're watching here in the cameras," station flight engineer Jeff Williams radioed. "Have a safe journey back, soft landings and we'll see you on the ground in a few months."

With pilot Mark Kelly at the controls, Discovery drifted straight away from the station, pulling out in front to a distance of about 400 feet before beginning a slow loop up and over the international outpost.

The shuttle's departure trajectory was designed to keep Discovery within about 40 nautical miles of the station until the astronauts can complete a final survey of the shuttle's nose cap and right wing leading edge panels.

They inspected the left wing leading edge Friday, looking for any signs of damage from impacts by micrometeoroids or space debris. Lisa Nowak and Stephanie Wilson will use Discovery's robot arm and a long inspection boom today to make laser scans of the ship's reinforced carbon carbon nose cap and right wing leading edge panels beginning around 9 a.m.

If any serious problems are found, Discovery has enough propellant on board to re-rendezvous with the space station. But if the wings and nose cap are sound, Discovery will leave the area and the crew will begin gearing up for a landing opportunity Monday at the Kennedy Space Center. Based on the latest calculations by mission control, the shuttle's twin braking rockets will be fired at 8:11 a.m. Monday for a landing at 9:14 a.m.

Here is an updated timeline of today's activities in space (in EDT and mission elapsed time):

TIME		DD	HH	MM	EVENT
_____________________________________________________

07/15/06
01:08 AM	10	10	30	STS crew wakeup (flight day 12)
01:38 AM	10	11	00	ISS crew wakeup
03:38 AM	10	13	00	Farewell ceremony
03:53 AM	10	13	15	Hatch closure
04:28 AM	10	13	50	Centerline camera installation
04:38 AM	10	14	00	Group B computer powerup
04:38 AM	10	14	00	Orbiter docking system leak check
05:23 AM	10	14	45	Undocking timeline begins
06:08 AM	10	15	30	UNDOCKING
07:08 AM	10	16	30	Shuttle separation burn
07:43 AM	10	17	05	Group B computer powerdown
07:43 AM	10	17	05	Crew meals begin
08:43 AM	10	18	05	Robot arm maneuvers to survey attitude
08:58 AM	10	18	20	OBSS starboard survey
10:08 AM	10	19	30	ISS: PMA-2 depressurization
10:28 AM	10	19	50	OBSS nose survey
11:00 AM	10	20	22	Mission status briefing on NASA TV
12:28 PM	10	21	50	OBSS berthing
01:33 PM	10	22	55	Shuttle robot arm powerdown
03:24 PM	11	00	46	NC-5 rocket firing
05:00 PM	11	02	22	Post-MMT briefing on NASA TV
05:08 PM	11	02	30	STS crew sleep begins
06:00 PM	11	03	22	Daily video highlights reel on NASA TV
Revision P of the NASA television schedule has been posted on the CBS News STS-121 Quick-Look Page.


08:00 p.m., 07/14/06, Update: 07:50 p.m., 07/14/06, Update: MMT defers APU decision until after test firing Sunday; updated deorbit and landing times

Editor's Note...
This story has been updated with the results of today's Mission Management Team meeting to discuss APU landing strategy. MMT Chairman John Shannon provided additional details, but our earlier story is essentially unchanged. Engineers continue to study a variety of options on the assumption hydraulic power system No. 1 has a small hydrazine leak. APU 1 will be fired up during a routine flight control system checkout Sunday. If the leak rate doesn't get worse, the unit likely will be used during entry Monday. If it does worsen, engineers will run the unit until the fuel is exhausted and Discovery will return to Earth with just two operational APUs. Quotes and details from Shannon have been added to our story.

Astronauts Lisa Nowak and Stephanie Wilson, dubbed the "robo chicks" by mission control, used the space station's robot arm to detach a 10-ton cargo module from the lab complex and remount it in Discovery's cargo bay for return to Earth. Engineers, meanwhile, continue assessing the health of the shuttle's hydraulic system but senior managers are optimistic the issue will not have a major impact on Discovery's re-entry and landing Monday.

The shuttle has three auxiliary power units - APUs - to provide the hydraulic power needed to move the ship's wing flaps, rudder, brakes and runway steering system during re-entry and landing. Any one operational APU can provide the hydraulic power needed for a safe landing, but three are on board to provide redundancy and NASA has complex flight rules governing how APUs must be managed in the event of failures.

Earlier this week, engineers noticed a very small pressure decay in the fuel tank of APU 1. It could be leaking nitrogen gas used to pressurize the system or it could be leaking hydrazine. If it's the former, there are no problems for landing; at the current leak rate, more than enough nitrogen would be available to fully pressurize the fuel tank.

If the leak is hydrazine, however, engineers will need to convince themselves the leak won't get worse before proceeding with a "nominal" re-entry. While the shuttle can land with just one operational APU, hydrazine is a dangerous material and leaks are definitely frowned upon. In addition, APU 1 is the only hydraulic system that can deploy the shuttle's landing gear. If APU 1 is out of action, pilot Mark Kelly would have to manually fire pyrotechnic charges to deploy the gear.

Shuttle program manager Wayne Hale said in an interview with CBS News today that he's optimistic APU 1 will work normally during re-entry and landing Monday at the Kennedy Space Center. But the jury is out until engineers complete their analysis.

"We actually went through all the flight rules yesterday at the MMT (Mission Management Team meeting) and the rule would say if it's suspected to be hydrazine, which as we've said, this little bitty pressure decay could be a few drops of hydrazine leaking, from the letter of the law you have to declare that that APU could potentially not be there for landing.

"But losing one APU is still nominal end of mission," Hale said. "We might think real hard about the weather rules, you don't want tight weather wherever you're going. You look around at the weather a little bit for higher ceilings, lower crosswinds, all that kind of stuff and you pick the best place to go."

Forecasters with the Spaceflight Meteorology Group at the Johnson Space Center are predicting good weather at the Kennedy Space Center on Monday with showers more likely Tuesday.

"I've got this real optimistic weather forecast, which worries me four days out," Hale joked. "The forecast will change, and this one's only got one direction to change."

MMT Chairman John Shannon said it's unlikely engineers will be able to rule out a hydrazine leak in APU 1. As a result, the astronauts will fire up APU 1 on Sunday as part of a routine flight control system checkout. After the test, engineers will monitor the fuel tank pressure. If the leak stays the same, APU 1 likely will be used in the normal fashion for re-entry Monday.

If the leak worsens, however, Shannon said the astronauts will be told to restart APU 1 and run the unit until all the hydrazine is exhausted. They would then fly back to Earth with just two operational APUs, which Shannon said was a "certified" procedure.

"The consensus of the team was the best thing to do with this small a leak rate is to go run it for flight control system checkout on Sunday morning," Shannon said. "Then we'll shut it down and we'll go look at the pressure trace. I fully expect to see we won't have any change at all and if that's true, I would expect we'll use it for a nominal entry.

"If we did see a change in the decay rate, it got higher - it has a long way to go to get above flammmability limits - but if it changed, that would say it's not really a stable situation and the operations team would go ahead and burn it off in orbit and get all the hydrazine out of that tank. We'd re-enter on two APUs.

"Two APUs is fine, it's certified," Shannon said. "It's not as good as three APUs. You'd lose some things with hydraulic system No. 1 not being active, the most important probably is that you don't hydraulically deploy your landing gear, you end up doing a pyro deploy. ... While that is perfectly certified and it is dually redundant, you'd rather do a hydraulic deploy."

An analysis shows that at the current leak rate, even if it's hydrazine, there is no ignition threat. But Hale agreed with Shannon that "the potential for a hydrazine leak is a very serious concern."

"What I am feeling very good about is the team has put a full court press on understanding what's going on and what the potential outcomes are and put together a plan to deal with it as best we can. We're going to get another report at today's MMT.

"So far, the news would indicate that if this is indeed a hydrazine leak, and again, we can't tell, but if indeed it's a hydrazine leak and stays at this level, it will pose no credible hazard to us. The real key question is, how good do we feel about the potential this will not get worse?"

According to NASA's flight rules, a presumed hydrazine leak is grounds for declaring an APU failed, Hale said, "but the real operative rule says, and I can't quote you the words exactly, but it says with a credible expectation of combustion. Again, at this leak level, there's no credible expectation of combustion. I would say there's a very good chance the crew will come down to a nominal entry. However, the jury is still out, the folks are still doing the analysis. If they come back and say we need to go, after we undock, and burn it off ... until the tank bottoms out ... that's a decision we still have a couple of days to talk about."

A senior manager familiar with the discussions told CBS News the flight rules assumed a leak of liquid hydrazine. In this case, the leak rate is so small the presumed hydrazine vaporizes instantly and is vented to space.

Shannon agreed late today, saying the engineers who wrote the flight rules said they were intended for much larger leaks. Sensors show APU 1's plumbing is tight downstream of a set of fuel valves. The presumed leak, therefore, is many feet away from the APU itself and far from any hot spots that could provide an ignition source.

Otherwise, Discovery's nearly trouble-free mission has increased Hale's optimism about launching the shuttle Atlantis around Aug. 28 to restart space station assembly. The only wild cards today are the APU issue and whether any extensive inspections or work are required on Atlantis; resolution of a shuttle cooling system issue that may or may not be a problem; and troubleshooting to explain slightly higher pressures in main engine No. 3 during a post-shutdown purge.

NASA's official launch window for Atlantis opens Aug. 28 and closes around Sept. 13. But because of a potential conflict between the planned launch of a Russian Soyuz capsule carrying the station's next crew, NASA may be forced to close the shuttle window Sept. 9 or even a few days earlier. Hale said he has asked the shuttle team to look into the possibility of launching the next mission a day or two earlier than Aug. 28 if possible.

Resuming space station assembly represents a major step forward for NASA and managers are elated with the results of Discovery's flight.

"All in all, it was just a great mission," said Rick LaBrode, lead space station flight director. "This is just a roaring success for the station team and we're ready to proceed with assembly ops."

The shuttle-station crew transferred more than 7,000 pounds of equipment and supplies from the Leonardo cargo module to the space station. For return to Earth, the module was loaded with around 4,600 pounds of no-longer-needed equipment and trash. Another 1,800 pounds or so of equipment was transferred from Discovery's crew cabin to the station, along with 171 gallons of fresh water, a by product of the shuttle's fuel cell system.

"This particular flight, we've transferred more payload cargo than any other shuttle flight," LaBrode said.

The astronauts planned to spend the afternoon using the shuttle's robot arm and a long sensor boom to closely inspect Discovery's left wing leading edge for any signs of impact damage from micrometeoroids. The flight plan called for the shuttle's nose cape and right wing leading edge to be inspected Saturday, after Discovery undocks from the international space station.

Nowak and Wilson ran into problems with the space station's robot arm that took time to resolve. The port wing inspections were delayed and rather than forcing the crew to work into their sleep preparations, flight director Norm Knight gave commander Steven Lindsey the option of eliminating the inspections all together.

"The program does not consider this mandatory," astronaut Lee Archambault radioed from mission control. "It's highly desireable, but not mandatory. We don't want to push you into this."

But Lindsey said he and pilot Mark Kelly would press ahead with the port wing inspection as planned to get it out of the way today.

Assuming no problems are found after the inspections are completed post undocking Saturday, the shuttle crew will depart the area and begin packing up for re-entry and landing Monday. The Spaceflight Meteorology Group ss predicting light winds and scattered clouds at landing time.

Here are all the deorbit ignition and landing times for Discovery's crew through next Wednesday at the Kennedy Space Center (KSC), Edwards Air Force Base, Calif. (EDW) and Northrup, N.M. (NOR). "Rev" refers to the shuttle's orbit (all times in EDT and subject to change):

SITE..REV...DEORBIT......LANDING

Monday, July 17
KSC...202...08:11 a.m...09:14 a.m. (planned; updated times)
NOR...203...09:35 a.m...10:39 a.m.
KSC...203...09:40 a.m...10:42 a.m.
EDW...204...11:09 a.m...12:11 p.m.
NOR...204...11:11 a.m...12:13 p.m.
EDW...205...12:45 p.m...01:46 p.m.

Tuesday, July 18
KSC...218...08:18 a.m...09:21 a.m.
EDW...219...09:47 a.m...10:51 a.m.
NOR...219...09:49 a.m...10:52 a.m.
KSC...219...09:54 a.m...10:56 a.m.
EDW...220...11:23 a.m...12:25 p.m.
NOR...220...11:25 a.m...12:27 p.m.
EDW...221...12:59 p.m...02:00 P.m.

Wednesday, July 19
KSC...233...06:56 a.m...08:00 a.m.
KSC...234...08:32 a.m...09:35 a.m.
EDW...235...10:01 a.m...11:04 a.m.
NOR...235...10:03 a.m...11:06 a.m.
EDW...236...11:37 a.m...12:39 p.m.
NOR...236...11:40 a.m...12:41 p.m.


03:10 p.m., 07/14/06, Update: NASA, Russians assess launch options for Soyuz, next shuttle flight

NASA and the Russian space agency are discussing launch options that almost certainly will shorten the launch window for the agency's next shuttle flight. It now is expected to open Aug. 27 or 28 and may close a week or so earlier than planned because of a requirement to provide time for the station crew to sleep shift between the departure of a U.S. space shuttle and the arrival of a Russian Soyuz capsule.

Based on a photo documentation requirement to launch Atlantis on the next shuttle mission in daylight - and to ensure external tank separation in daylight - NASA had been planning on a launch window that opens Aug. 28 and closes Sept. 13.

But the Russians are scheduled to launch the next full-time station crew aboard a Soyuz capsule Sept. 14, docking two days later. Joint U.S. and Russian flight rules require a separation between the departure of a shuttle and the arrival of a Soyuz to give the station crew time to adjust their body clocks for different sleep shifts and to make necessary preparations.

If the shuttle launch was delayed until the end of the original window - Sept. 13 - and if the Russians tried to stick with their original launch date - Sept. 14 - the Soyuz would arrive at the station while the shuttle was still there, boosting the combined crew to 12, violating long-standing agreements and greatly complicating the shuttle crew's space station assembly work.

If Atlantis took off Sept. 13 and the Russian delayed the Soyuz until after undocking, launching the next station crew no earlier than Sept. 24, re-entry and landing of the outgoing station crew would occur Oct. 4, long before sunrise in the Kazakhstan landing zone.

The Russian recovery team includes new personnel for this flight and space managers do not want the new team to face a nighttime landing and recovery operation the first time around.

To resolve the potential conflict, U.S. and Russian space managers are discussing options that would shorten the shuttle launch window and delay the Soyuz launch to Sept. 18 or 20. On board will be Expedition 14 commander Michael Lopez-Alegria, Soyuz commander Mikhail Tyurin and Japanese space tourist Daisuke Enomoto.

Assuming a launch on Sept. 20, the Soyuz would dock Sept. 22 and the outgoing station crew - Expedition 13 commander Pavel Vinogradov, Jeff Williams and Enomoto - would return to Earth Sept. 30. While re-entry would occur in pre-dawn darkness in Kazakhstan, the sun would rise in time for recovery crews to do the bulk of their work in daylight.

Backing up from a Soyuz launch on Sept. 20, Atlantis must undock by Sept. 19. That means launch cannot occur any later than Sept. 9. For a Soyuz launch on Sept. 18, Atlantis must be off the pad by Sept. 7.

Shuttle program manager Wayne Hale has formally asked the Air Force Eastern Range for an Aug. 28 launch slot for Atlantis. In an interview with CBS News, Hale said he has asked shuttle managers to look into whether the flight could be moved up a day or so to add a bit more cushion to the front end of the launch window.

"We have four or five days of contingency (time in Atlantis' processing schedule) right now, which is less than what historically we've needed," Hale said. "But based on a really outstanding performance by the Kennedy folks, there's some probability we would have four or five days where the vehicle's out at the pad and we could launch earlier.

"So I have asked the imagery folks to take a look again at the predicted lighting, and it's not outside the realm of possibility when they run the lighting predictions with the final space station trajectory and so on and so forth, that the 27th might become available. That would ease a little bit the traffic model of the station."

He said station program managers "have been talking very hard with their Russian partners about that."

"The Russians really would like to kind of go pretty close to the schedule they've established, which doesn't leave a lot of room for weather days in Florida," Hale said. "So the earlier we can count down, the more likely we are to get off in time to deconflict the traffic."

Assuming the Russians stick to their guns and only delay the Soyuz launch by a few days, Atlantis' crew will lose a week or so off the back end of their launch window. And if Atlantis isn't off the ground by the time the window closes, the next daylight launch opportunity will be a short window opening Oct. 26 and closing Oct. 29.

At the Kennedy Space Center, engineers are readying Atlantis for rollout to the launch pad around Aug. 2. Work is already underway to address a handful of minor problems seen during Discovery's current flight, including replacement of additional gap fillers on the shuttle's belly and replacement of insulation blanket patches.

Engineers say any additional inspections or work required because of problems experienced by Discovery's hydraulic power system can be accomplished at the launch pad.

A wild card is an apparent problem with the helium pressurization system aboard Discovery that is used to operate main engine valves and to flush left over propellant out of the system after main engine cutoff - MECO - in orbit.

Engineers studying data from Discovery's launch noticed an eight- to 10-pound-per-square-inch shift in the helium pressure used to purge main engine No. 3 after MECO.

That shift was considered "to be of note and caused them some concern there might be a blocked filter or a check valve or something else," Hale said.

The issue did not affect the performance of engine No. 3 but the helium system is used to control the operation of the powerplants and engineers want to make sure whatever caused the purge problem is not something potentially more serious.

Hale said Discovery's engines will be removed shortly after landing to permit detailed tests and inspections. As of this writing, however, there are no indications of any similar problems aboard Atlantis.


02:00 p.m., 07/14/06, Update: Leonardo module back in payload bay; Hale optimistic about APU issue

Editor's Note...
This story has been updated with the results of today's Mission Management Team meeting to discuss APU landing strategy. MMT Chairman John Shannon provided additional details, but the story is essentially unchanged. Engineers continue to study a variety of options on the assumption hydraulic power system No. 1 has a small hydrazine leak. APU 1 will be fired up during a routine flight control system checkout Sunday. If the leak rate doesn't get worse, the unit will be used during entry Monday. If it does worsen, engineers will run the unit until the fuel is exhausted and Discovery will return to Earth with just two operational APUs.

Astronauts Lisa Nowak and Stephanie Wilson, dubbed the "robo chicks" by mission control, used the space station's robot arm to detach a 10-ton cargo module from the lab complex and remount it in Discovery's cargo bay for return to Earth. Engineers, meanwhile, continue assessing the health of the shuttle's hydraulic system but senior managers are optimistic the issue will not have a major impact on Discovery's re-entry and landing Monday.

The shuttle has three auxiliary power units - APUs - to provide the hydraulic power needed to move the ship's wing flaps, rudder, brakes and runway steering system during re-entry and landing. Any one operational APU can provide the hydraulic power needed for a safe landing, but three are on board to provide redundancy and NASA has complex flight rules governing how APUs must be managed in the event of failures.

Earlier this week, engineers noticed a very small pressure decay in the fuel tank of APU 1. It could be leaking nitrogen gas used to pressurize the system or it could be leaking hydrazine. If it's the former, there are no problems for landing; at the current leak rate, more than enough nitrogen would be available to fully pressurize the fuel tank.

If the leak is hydrazine, however, engineers will need to convince themselves the leak won't get worse before proceeding with a "nominal" re-entry. While the shuttle can land with just one operational APU, hydrazine is a dangerous material and leaks are definitely frowned upon. In addition, APU 1 is the only hydraulic system that can deploy the shuttle's landing gear. If APU 1 is out of action, pilot Mark Kelly would have to manually fire pyrotechnic charges to deploy the gear.

Shuttle program manager Wayne Hale said in an interview with CBS News today that he's optimistic APU 1 will work normally during re-entry and landing Monday at the Kennedy Space Center. But the jury is out until engineers complete their analysis.

"We actually went through all the flight rules yesterday at the MMT (Mission Management Team meeting) and the rule would say if it's suspected to be hydrazine, which as we've said, this little bitty pressure decay could be a few drops of hydrazine leaking, from the letter of the law you have to declare that that APU could potentially not be there for landing.

"But losing one APU is still nominal end of mission," Hale said. "We might think real hard about the weather rules, you don't want tight weather wherever you're going. You look around at the weather a little bit for higher ceilings, lower crosswinds, all that kind of stuff and you pick the best place to go."

Forecasters with the Spaceflight Meteorology Group at the Johnson Space Center are predicting good weather at the Kennedy Space Center on Monday with showers more likely Tuesday.

"I've got this real optimistic weather forecast, which worries me four days out," Hale joked. "The forecast will change, and this one's only got one direction to change."

MMT Chairman John Shannon said it's unlikely engineers will be able to rule out a hydrazine leak in APU 1. As a result, the astronauts will fire up APU 1 on Sunday as part of a routine flight control system checkout. After the test, engineers will monitor the fuel tank pressure. If the leak stays the same, APU 1 likely will be used in the normal fashion for re-entry Monday.

If the leak worsens, however, Shannon said the astronauts will be told to restart APU 1 and run the unit until all the hydrazine is exhausted. They would then fly back to Earth with just two operational APUs, which Shannon said was a "certified" procedure.

"The consensus of the team was the best thing to do with this small a leak rate is to go run it for flight control system ceckout on Sunday morning," Shannon said. "Then we'll shut it down and we'll go look at the pressure trace. I fully expect to see we won't have any change at all and if that's true, I would expect we'll use it for a nominal entry.

"If we did see a change in the decay rate, it got higher - it has a long way to go to get above flammmability limits - but if it changed, that would say it's not really a stable situation and the operations team would go ahead and burn it off in orbit and get all the hydrazine out of that tank. We'd re-enter with on APUs.

"Two APUs is fine, it's certified," Shannon said. "It's not as good as three APUs. You'd lose some things with hydraulic system No. 1 not being active, the most important probably is that you don't hydraulically deploy your landing gear, you end up doing a pyro deploy. ... While that is perfectly certified and it is dualy redundant, you'd rather do a hydraulic deploy."

An analysis shows that at the current leak rate, even if it's hydrazine, there is no ignition threat. But Hale agreed with Shannon that "the potential for a hydrazine leak is a very serious concern."

"What I am feeling very good about is the team has put a full court press on understanding what's going on and what the potential outcomes are and put together a plan to deal with it as best we can. We're going to get another report at today's MMT.

"So far, the news would indicate that if this is indeed a hydrazine leak, and again, we can't tell, but if indeed it's a hydrazine leak and stays at this level, it will pose no credible hazard to us. The real key question is, how good do we feel about the potential this will not get worse?"

According to NASA's flight rules, a presumed hydrazine leak is grounds for declaring an APU failed, Hale said, "but the real operative rule says, and I can't quote you the words exactly, but it says with a credible expectation of combustion. Again, at this leak level, there's no credible expectation of combustion. I would say there's a very good chance the crew will come down to a nominal entry. However, the jury is still out, the folks are still doing the analysis. If they come back and say we need to go, after we undock, and burn it off ... until the tank bottoms out ... that's a decision we still have a couple of days to talk about."

A senior manager familiar with the discussions told CBS News the flight rules assumed a leak of liquid hydrazine. In this case, the leak rate is so small the presumed hydrazine vaporizes instantly and is vented to space.

"We're not at the flammability limit with this leak rate, with it vaporizing," he said. "We know it's vening overboard. So we're not worried about building up in the aft until about 15 minutes before touchdown. At some point, the air pressure will rise enough so it's not going to be vapor anymore. So from now until then, we're not hurrying up to declare this APU failed."

Shannon agreed late today, saying the engineers who wrote the flight rules said they were intended for much larger leaks.

Otherwise, Discovery's nearly trouble-free mission has increased Hale's optimism about launching the shuttle Atlantis around Aug. 28 to restart space station assembly. The only wild cards today are the APU issue and whether any extensive inspections or work are required on Atlantis; resolution of a shuttle cooling system issue that may or may not be a problem; and troubleshooting to explain slightly higher pressures in main engine No. 3 during a post-shutdown purge.

NASA's official launch window for Atlantis opens Aug. 28 and closes around Sept. 13. But because of a potential conflict between the planned launch of a Russian Soyuz capsule carrying the station's next crew, NASA may be forced to close the shuttle window Sept. 9 or even a few days earlier. Hale said he has asked the shuttle team to look into the possibility of launching the next mission a day or two earlier than Aug. 28 if possible.

Resuming space station assembly represents a major step forward for NASA and managers are elated with the results of Discovery's flight.

"All in all, it was just a great mission," said Rick LaBrode, lead space station flight director. "This is just a roaring success for the station team and we're ready to proceed with assembly ops."

The shuttle-station crew transferred more than 7,000 pounds of equipment and supplies from the Leonardo cargo module to the space station. For return to Earth, the module was loaded with around 4,600 pounds of no-longer-needed equipment and trash. Another 1,800 pounds or so of equipment was transferred from Discovery's crew cabin to the station, along with 171 gallons of fresh water, a by product of the shuttle's fuel cell system.

"This particular flight, we've transferred more payload cargo than any other shuttle flight," LaBrode said.

The astronauts planned to spend the afternoon using the shuttle's robot arm and a long sensor boom to closely inspect Discovery's left wing leading edge for any signs of impact damage from micrometeoroids. The flight plan called for the shuttle's nose cape and right wing leading edge to be inspected Saturday, after Discovery undocks from the international space station.

Nowak and Wilson ran into problems with the space station's robot arm that took time to resolve. The port wing inspections were delayed and rather than forcing the crew to work into their sleep preparations, flight director Norm Knight gave commander Steven Lindsey the option of eliminating the inspections all together.

"The program does not consider this mandatory," astronaut Lee Archambault radioed from mission control. "It's highly desireable, but not mandatory. We don't want to push you into this."

But Lindsey said he and pilot Mark Kelly would press ahead with the port wing inspection as planned to get it out of the way today.

Assuming no problems are found after the inspections are completed post undocking Saturday, the shuttle crew will depart the area and begin packing up for re-entry and landing Monday. The Spaceflight Meteorology Group ss predicting light winds and scattered clouds at landing time.

Here are all the deorbit ignition and landing times for Discovery's crew through next Wednesday at the Kennedy Space Center (KSC), Edwards Air Force Base, Calif. (EDW) and Northrup, N.M. (NOR). "Rev" refers to the shuttle's orbit (all times in EDT and subject to change):

SITE..REV...DEORBIT......LANDING

Monday, July 17
KSC...202...08:11 a.m...09:14 a.m. (planned; updated times)
NOR...203...09:35 a.m...10:39 a.m.
KSC...203...09:40 a.m...10:42 a.m.
EDW...204...11:09 a.m...12:11 p.m.
NOR...204...11:11 a.m...12:13 p.m.
EDW...205...12:45 p.m...01:46 p.m.

Tuesday, July 18
KSC...218...08:18 a.m...09:21 a.m.
EDW...219...09:47 a.m...10:51 a.m.
NOR...219...09:49 a.m...10:52 a.m.
KSC...219...09:54 a.m...10:56 a.m.
EDW...220...11:23 a.m...12:25 p.m.
NOR...220...11:25 a.m...12:27 p.m.
EDW...221...12:59 p.m...02:00 P.m.

Wednesday, July 19
KSC...233...06:56 a.m...08:00 a.m.
KSC...234...08:32 a.m...09:35 a.m.
EDW...235...10:01 a.m...11:04 a.m.
NOR...235...10:03 a.m...11:06 a.m.
EDW...236...11:37 a.m...12:39 p.m.
NOR...236...11:40 a.m...12:41 p.m.


10:25 a.m., 07/14/06, Update: Undocking timeline

Revision O of the NASA TV schedule is posted on the CBS News STS-121 Quick-Look Page. And here is the timeline for the shuttle Discovery's undocking from the international space station Saturday (in EDT and mission elapsed time):

TIME		DD	HH	MM	EVENT
_____________________________________________________

05:00 AM	10	14	22	Sunrise
05:28 AM	10	14	50	Noon
05:39 AM	10	15	01	U.S. solar arrays feathered
05:40 AM	10	15	02	Russian solar arrays feathered
05:56 AM	10	15	18	Sunset
06:08 AM	10	15	30	UNDOCKING
06:09 AM	10	15	31	Initial orbiter separation (+10 seconds)
06:10 AM	10	15	32	ISS holds current attitude
06:13 AM	10	15	35	Range: 50 feet
06:15 AM	10	15	37	Range: 75 feet
06:21 AM	10	15	43	Range: 150 feet
06:31 AM	10	15	53	Sunrise
06:37 AM	10	15	59	Range: 400 feet
06:40 AM	10	16	02	Separation burn No. 1; start fly over
06:52 AM	10	16	14	Shuttle directly above space station
06:52 AM	10	16	14	Shuttle in separation burn attitude
06:59 AM	10	16	21	Noon
07:08 AM	10	16	30	Separation burn No. 2
07:28 AM	10	16	50	Sunset


06:10 a.m., 07/14/06, Update: Astronauts confident Discovery in good shape for entry; say NASA has turned the corner after Columbia disaster, ready to resume station assembly

The Discovery astronauts closed up the Leonardo logistics module today and geared up to detach it from the space station and re-install in the shuttle's cargo bay for return to Earth. With undocking from the station on tap Saturday, shuttle pilot Mark Kelly said the crew has accomplished virtually all of the mission's objectives, clearing the way for station assembly to resume this fall.

"We're getting close to meeting all our mission objectives," Kelly told CBS News during an in-flight interview. "Our commander, Steve Lindsey, right now about 30 feet behind us is closing out the logistics module. We've completed all the (supply and equipment) transfers, we've completed all the objectives with our three EVAs (spacewalks), the space shuttle Discovery's in great shape for a return trip home on Monday."

Asked if Discovery's flight will help NASA turn the corner and shift its focus from recovering from Columbia to resuming space station assembly, spacewalker Mike Fossum said he hoped so, adding "we needed this mission to get a lot of these objectives (accomplished), to reinforce our ability to do our own inspections, to test our ability to get access to different places on the shuttle's wing and underbelly if we needed to get there to do repair. We've done some testing on the future repair capability. So we're feeling good about that, we've answered a lot of those questions almost completely and I think we're ready to get rolling."

Before the 2003 Columbia disaster, when NASA was gearing up to begin the same stretch of assembly missions currently facing the agency, mission managers frequently spoke of the "wall" of spacewalk challenges facing construction crews.

Piers Sellers, who joined Fossum for three spacewalks during DiscoveryÕs current mission, agreed "there's really a lot to be done. It is kind of a wall."

"Every flight has got to get through its EVA tasks and install its equipment before the next flight can go," he said. "I mean, that's really the way the sequence works, so it's going to be a lot of hard work. ItÕs a lot of hard work for a lot of people on the ground working furiously to make this happen."

NASA hopes to resume station assembly flights with launch of the shuttle Atlantis around Aug. 28 to mount a huge solar array and a massive rotary joint on one side of the station's main truss. The Russians plan to launch a fresh space station crew later in September and bring two outgoing crew members back to Earth. If all goes well, Discovery will return to the lab complex in late December to continue building the solar array truss, to deliver another full-time station crew member and to give European Space Agency astronaut Thomas Reiter a ride home.

"This flight and the one last summer, together they're the 'return to flight' missions and we feel like we've done all the tests and met the objectives and we feel like the whole program is back on track to assemble the space station and move on back to the moon and to Mars," robot arm operator Lisa Nowak told another reporter. "And we're looking forward to all of that."

In a morning execute package of daily instructions to the crew, flight controllers said Nowak and crewmate Stephanie Wilson had completed more robotic arm work than any other shuttle crew.

"Good morning, Discovery," the morning message to the crew read. "We hoped you enjoyed your time off (Thursday), Ōcause guess what, itÕs time for more arm ops. Unofficially, we believe this flight has had the most robotic operations to date. The PDRS and ROBO folks would like to say thanks to you all, and especially the 'ROBO chicks.' They have definitely earned the title.'

Today, the "robo chicks" plan to use Discovery's robot arm and a long inspection boom to carry out laser scans of the shuttle's left wing leading edge panels. After undocking Saturday, they will re-inspect the shuttle's nose cap and starboard leading edge panels for any signs of damage due to impacts that might have occurred after the ship reached orbit.

Here is an updated timeline of today's activities (in EDT and mission elapsed time; includes NASA TV sked/rev. O):

01:08 AM	09	10	30	STS crew wakeup (flight day 11)
01:38 AM	09	11	00	ISS crew wakeup
03:48 AM	09	13	10	MPLM egress
04:03 AM	09	13	25	MPLM deactivation
04:03 AM	09	13	25	PAO event (combined crew)
04:23 AM	09	13	45	Middeck transfers
05:28 AM	09	14	50	Spacesuit transfer
05:53 AM	09	15	15	MPLM vestibule depressurization
07:13 AM	09	16	35	Crew meals begin
08:13 AM	09	17	35	SSRMS grapples MPLM
08:23 AM	09	17	45	MPLM bolts backed out
09:00 AM	09	18	22	Mission status briefing on NASA TV
09:08 AM	09	18	30	MPLM pulled away from Unity
10:43 AM	09	20	05	MPLM berthed in shuttle bay
11:23 AM	09	20	45	SSRMS ungrapples MPLM
11:38 AM	09	21	00	SSRMS grapples MBS
12:28 PM	09	21	50	SSRMS ungrapples lab
01:18 PM	09	22	40	OBSS port survey
03:13 PM	10	00	35	Rendezvous tools checkout
05:00 PM	10	02	22	Post MMT briefing on NASA TV
05:08 PM	10	02	30	STS/ISS crew sleep begins
06:00 PM	10	03	22	Daily video highlights reel on NASA TV
The so-called "late inspections" were added to the flight late in the crew's training flow after engineers decided the risk of catastrophic damage from such orbital impacts warranted an additional looks.

Kelly said engineers "don't really know what the risk is. It's pretty low, we've been flying space shuttles for a long time and we've never had any kind of critical damage from a micrometeoroid. So it's pretty remote."

Before launch, Steve Poulos, manager of the orbiter projects office at the Johnson Space Center, said the odds of a catastrophic impact due to space debris or micrometeoroids "is about 1-in-210, something on that order." By doing the late inspections, the odds will improve to 1-in-280 and possibly as low as 1-in-350, based on the performance of the sensor package on the end of the inspection boom.

It will take ground engineers a day or so to assess the late inspection data, but "based on what we've seen over the last 10 days, the inspections we've done, we've got a great ship," Kelly said. "It's ready to come home. We'll be doing that on Monday morning and it's going to be a safe landing, hopefully at the Kennedy Space Center if the weather's good.

"The space shuttle is ready to go and after this flight, I think we're really in a good configuration and we're pretty much set up to continue assembly of the space station and continue to fly the shuttle, hopefully like we did before 2003."

Asked how confident he is about the health of Discovery's heat shield, Kelly said: "We're real confident. We're going to look at it one more time, but based on what we've seen so far, knowing what the risk is, I think all of us feel really comfortable."

"Looking out the window the other day and looking down both wings, they're looking like they're in great shape, similar to when we saw them when the orbiter was being processed," he said.

The only technical problems of any significance are a very slight pressure decrease in the fuel tank of an auxiliary power unit, or APU, and trouble with stuck thermostats in a second APU.

Engineers are not yet sure whether the leak is nitrogen, used for pressurization, or hydrazine, the volatile fuel that powers the APU. Either way, Kelly said the leak was so small it was not a major concern.

"It's pretty minor," he said.

But given the critical nature of APUs, NASA engineers are keeping a close eye on the hydraulic powerplants. For readers interested in additional details, here's the latest thinking on the issue from NASA's Mission Management Team:

APU 3 GG/Fuel Line/Pump/Valve Heater Š As a quick review, both the A and B heaters appear to be controlling the upper limit on the overtemp thermostat. We are currently on the A heaters and the system is controlling well. Functionally, there are no issues with operating on the overtemp thermostat. We are still investigating the fault tree to try and determine what would cause both the A and B control thermostats to fail. Some work was done at KSC in this area, but neither of the control thermostats was disturbed. The leading theory continues to be that either the thermostats or the heaters may have locally debonded. Workarounds exist for the next failure - if the B heater failed, we would switch back to the A. If that B heater failed, we would change attitudes after undocking to keep APU 3 warm or ask you to perform switch throws to manually control the heaters. If the heater fails on, the crew reaction time is about an hour after you get the alarm so there are no concerns for out of control temps on the fuel line.

APU 3 is not considered failed for entry or to even have a loss of redundancy. There is one small delta for entry - weÕll swap to the B heater in the entry checklist to meet the APU injector temperature limits and likely turn the heaters off after APU 3 start.

APU 1 Tank Pressure Decay Š The APU 1 fuel tank pressure continues to decay slowly. As of today it does not appear that we will be able to conclusively determine if the leak is N2 or hydrazine. The pressure decay has remained stable throughout the mission and there is no reason to assume that the leak rate will change. If the leak is GN2, we have lost about 18 psi so far and will have lost 33 psi by EOM - there will be plenty of GN2 still remaining to support entry operations on the APU. The minimum start pressure is 100 psi and we expect to be at 213 psi for EOM.

If the leak is hydrazine and of course we are not sure of that, we have lost about 10 lbs so far and will have lost 17 lbs by EOM. The leak rate of hydrazine is calculated to be 18 cubic centimeters per hour - very small. At this leak rate and based on the pod environment, analysis has shown that the hydrazine will phase directly into vapor and not form ice or liquid. The vapor exits the vent doors on orbit and there is a minimal concentration remaining. In fact at this leak rate, the hydrazine vapor concentrations will remain well below the flammability limits in the aft compartment for entry. This theory is somewhat corroborated by the fact that there are no indications of localized cooling on any temp sensors that would be indicative of a liquid fuel leak. Of course that also supports the possibility that the leak is N2, which is obviously the best case.

As mentioned yesterday, the N2 fill Quick Disconnect (QD) did have a leak preflight prior to the APU confidence run, but after cycling the QD poppet the leak was cleared (fairly common occurrence) and a flight cap is currently installed on the QD. It is still not clear that this preflight N2 leak could be related to the in-flight leakage we are seeing. The pre-flight data has been reviewed and there was no fuel leak observed pre-launch.

For information the APU 1 and 2 fuel tanks are located on the port sidewall of the aft compartment about 8 feet below the APUÕs which are near the top of the 1307 bulkhead. The teams continue to work around the clock on the ground to quantify the effects of the small N2 or fuel leak and the forward plan for entry.


05:30 a.m., 07/13/06, Update: Shuttle crew enjoys day off; MMT updates APU issue

The Discovery astronauts took the day off today, relaxing and enjoying the view from space after a hectic week in orbit highlighted by three spacewalks and work to transfer supplies and equipment to the international space station. Texas Gov. Rick Perry plans to call fellow Texas A&M graduate Mike Fossum later today and flight engineer Lisa Nowak will join Fossum for two media interviews. Engineers, meanwhile, continue analysis of two seemingly minor issues with Discovery's hydraulic system.

In the morning "execute package" of instructions and timeline changes uplinked to the astronauts, mission control passed along some ideas for spending an off-duty day in space:

Good morning, Discovery. Since today is an off-duty day for you, the planning shift team has come up with a few ideas* to help you pass the time:

1. Who can toss the laptop the furthest down the station before it bounces off the wall (of course, we would appreciate it if you use Station assets for this one).

2. Arm wrestling: Big [robot] arm vs. little arm, David and Goliath II, the battle begins.

3. Boom toss - toss the [robot arm inspection] boom between arms (just donÕt tell the Canadians if you lose it)

4. Take all the CWCs [water transfer bags] into the Crew Lock, close the hatch, empty the CWCs and go for a swim (PBAs might be needed).

5. Lawn darts (if you need a target, remember thatÕs an Aggie compatible task)

6. Marco polo (the whole fish-out-of water thing would need to be tweaked though)

7. We could up-link a few appropriate computer games for you if you like - Asteroids, Space Invaders, or Star Wars' Wing Commander.

And last but not least, hereÕs a haiku from our GC,

Day of Freedom Launch
Leonardo and Spacewalks
Crew now Chillaxin'

Enjoy your day off, itÕs well deserved.

*None of these ideas have been approved by the MMT

The morning execute package also included the latest thinking from NASA's Mission Management Team about the status of two of Discovery's auxiliary power units, or APUs, which provide the hydraulic power necessary to operate the shuttle's aerosurfaces, landing gear brakes and nose wheel steering during entry and landing.

The shuttle is equipped with three APUs and can safely land with just one. But given the critical nature of the system, engineers pay close attention when anything out of the ordinary occurs.

In a brief call to the crew late Wednesday, mission control told shuttle commander Steve Lindsey that engineers were monitoring two unrelated issues with APUs 1 and 3. The pressure in APU 1's fuel tank appears to be decaying faster than expected, indicating a possible hydrazine fuel leak or a leak in the nitrogen (N2) gas system used to provide pressurization. And APU 3 is experiencing heater problems.

Both issues may be related to work done before Discovery's launch, but that remains to be seen. Here is the MMT explanation of what has been observed to date:

APU 1 Tank Pressure Decay - The APU 1 fuel pressure is decaying differently than the other two tanks which is indicative of a small N2 or hydrazine leak. The data is very subtle so it has taken eight days to detect this change in slope between the three APU fuel tank plots. APU 2 and APU 3 shows a normal pressure decay of 6 psi over the eight days of the mission. This is due to the temperature change in the tanks which is caused by a 9-10 degrees Fahrenheit decrease in the tank temperatures as the aft structure cools. It takes some time to see this change because ascent does a good job of warming up this part of the vehicle.

APU 1 Tank pressure has dropped a total of 22 psi over these eight days which is indicative of a leak which is most likely N2. The Entry Flight Director, CB (astronaut office) Reps, and the entire APU community are meeting several times daily to understand the data and determine a forward plan of action. There was an N2 leak at the QD (quick-disconnect) panel during a portion of the STS-121 OPF (orbiter processing facility) flow that was later fixed; that has many in the community thinking that the leak is N2. Analysis is in work to determine if it is feasible to leak hydrazine based on the very slow leak rate and the propensity of hydrazine to freeze and slow an actual fuel leak. We hope to have more details on this subject (Thursday) but as of today there is no change to any mission plans based on the data collected. The APU is not considered failed and the N2 pressure will be more than 100 psi above the lower operating limit at EOM (end of mission).

APU 3 GG/Fuel Line/Pump/Valve Heater - Both the A and B heaters appear to be controlling at their upper limit on the overtemp thermostat. Initially the B heater appeared to fail ON, as indicated by the Supply Line Temp, increasing from ~82 deg F to 190 deg F. The heater then operated nominally for two cycles, and then failed ON again. MMACS (mission control mechanical systems officer) asked to reconfigure the heater to the A system, where it is also operating on the overtemp thermostat.

There are a few theories on the failure mode that could affect both the A and B heaters. This area was reworked before STS-121 with a new sealant such that the heaters were removed and rewrapped. If the wrap came loose on orbit, it would bias both thermostats cold and would appear as a failed on heater. If the heater is debonded, a similar signature would be expected. The teams continue to meet multiple times each day on this topic and additional data will be provided as the analyses mature. APU 3 is not considered failed for entry at this time and there are no significant impacts to entry operations.

At present, these do not appear to be serious issues, but given the critical nature of the APU system they bear watching. More information will be posted here as it becomes available.

The Mission Management Team congratulated the Discovery astronauts on the successful completion of their third spacwalk Wednesday and told the crew a lost spatula posed no threat of returning to the shuttle-station complex.

Shuttle and station managers "were extremely happy with the results of EVA 3 including the get-ahead task of transferring the grapple bar to ISS. FYI - The spatula that was released inadvertently during the EVA is well clear of the orbiter and ISS. It was 4 miles in front of the ISS/Shuttle at crew sleep on FD9 and continues to move in front of and below the ISS with the distance increasing about 2 miles each rev."

Here is an updated timeline of today's activities (in EDT and mission elapsed time):

TIME...........DD...HH...MM...EVENT

07/13/06
01:08 AM...08...10...30...STS crew wakeup (flight day 10)
01:38 AM...08...11...00...ISS crew wakeup
03:43 AM...08...13...05...Crew off duty time begins
04:13 AM...08...13...35...ISS European Space Agency PAO event
09:03 AM...08...18...25...Crew meal
09:08 AM...08...18...30...ISS Russian PAO event
10:00 AM...08...19...22...ESA, Russian briefings replay with translation
10:03 AM...08...19...25...Crew off duty time resumes
10:18 AM...08...19...40...ISS CPA installation
11:00 AM...08...20...22...Mission status briefing on NASA TV
12:53 PM...08...22...15...MPLM cleanup
12:58 PM...08...22...20...Texas Gov. Rick Perry calls Mike Fossum
01:23 PM...08...22...45...MPLM racks configured
01:23 PM...08...22...45...MSNBC, FOX News interviews Fossum and Nowak
03:30 PM...09...00...52...ISS-14 crew news conference
05:08 PM...09...02...30...STS/ISS crew sleep begins
06:00 PM...09...03...22...Daily video highlights reel on NASA TV


05:00 p.m., 07/12/06, Update: NASA managers pleased with third successful spacewalk; engineers monitor hydraulic system

The Discovery astronauts chalked up a third successful spacewalk today, demonstrating repair techniques that could help a future shuttle crew fix damage to a ship's wing leading edge panels. While engineers will not be able to fully assess the repair tests until samples are returned to Earth for laboratory analysis, flight controllers said they were pleased with the crew's performance.

"This might sound like a broken record, but we had a very successful flight day nine today," said lead flight director Tony Ceccacci. "We completed the last of our three planned EVAs (spacewalks) for the mission. Not only did we accomplish all our high priority objectives, but we also did get one of our get-ahead tasks completed."

Just before bidding the astronauts good night, mission control informed commander Steve Lindsey that engineers were monitoring two potential issues with the shuttle's hydraulic system.

Auxiliary power unit - APU - No. 1 has shown signs of a very slow leak in its fuel tank, or perhaps a problem with the nitrogen gas system used to pressurize it. So far, the pressure has dropped about 22 pounds per square inch since the unit was shut down following launch July 4.

In addition, thermostats in heaters used to keep APU 3 at the proper temperature acted a bit erratically today, resulting in a slightly broader range of temperatures than usual. But Lindsey was told both APUs are considered operational and available for use during re-entry next Monday.

"What this could be is a number of things," astronaut Lee Archambault in mission control said of the presumed leak in APU 1. "It could be an N2 leak, it could be a fuel decay, it could be none of the above and something completely different. Of course, the MMT (Mission Management Team) and MER (mission evaluation room) is looking at it. But for now, we are ops nominal on APU 1 and we expect to use it during entry."

The shuttle is equipped with three APUs to generate the hydraulic power needed to move the shuttle's engine nozzles during launch and its wing flaps, body flap, rudder/speedbrake and landing gear brakes during re-entry and touchdown. While a shuttle can safely land with just one operational APU, "we're keeping a couple of sets of eyeballs on it," Archambault promised Lindsey.

The astronauts then signed off for the night.

"Tomorrow, the crew is going to get a well-deserved day off," Ceccacci said. "Basically, the only thing they'll be doing at the end of the day is starting the MPLM (cargo module) closeout activities and just doing the standard taking a break, looking out the window and enjoying the day in orbit."

Tomas Gonzalez-Torres, the lead spacewalk officer in mission control, said astronauts Piers Sellers and Mike Fossum were able to complete five test panel repairs during today's spacewalk, about the same number engineers expected based on pre-flight simulations.

Using spatulas to spread on a thick sealant called NOAX, short for "non-oxide adhesive experimental," Sellers and Fossum attempted to fill in deliberate cracks and gouges similar to what might be expected from ascent impact damage.

NOAX is very sensitive to temperature, which can cause gases to bubble out of the mixture. In weightlessness, such bubbles can combine and merge inside the material, forming a void when it hardens.

"You don't want a direct path down through into the damage area," Gonzalez-Torres said. "The repair itself, you're trying to have a protective layer, a protective coating."

During re-entry, when wing leading edge temperatures can exceed 3,000 degrees, "you have some slight erosion," he said. "If you have that erosion and you get into a void and that void actually goes all the way down to the damage, you haven't enacted a good repair. So we want to minimize those voids and make sure whatever voids we do have, if we've done a good repair, they shouldn't be one big void that wouldn't be able to protect us."

Sellers and Fossum practiced applying the material in thin layers, working it with spatulas to help with "outgassing" and then smoothing it in place. Then another thin layer would be applied.

Gonzalez-Torres said the test samples will be subjected to thermal-vacuum cycling after their return to the Johnson Space Center, along with 3D laser scans, CT scans and finally, arc jet testing to see how well the repairs stand up to re-entry temperatures.

Based on video from the astronauts, it appeared the material was properly applied and that the new layer-by-layer technique resulted in fewer bubbles than astronauts experienced during tests last year.

The spacewalkers ran into one minor problem when one of six spatulas used for today's repair work floated away from Sellers unnoticed. Flight controllers said it posed no threat.

Asked to rate his concern over the lost spatula and earlier problems with safety tethers, Ceccacci said, "If that's all that happened, we're happy."

"You're kidding yourself not to expect little things like that to happen," he said. "If that's all that happens, you know, like everyone was talking about forgetting to lock the tether or unlock it, if that's all that happens, we're happy with that."


02:35 p.m., 07/12/06, Update: Spacewalk ends

Astronauts Piers Sellers and Mike Fossum re-entered the space station's Quest airlock module, closed the hatch and began repressurization at 2:31 p.m. to officially end the third and final spacewalk planned for Discovery's mission.

The 68th spacewalk staged in the space station era lasted seven hours and 11 minutes, pushing Sellers' and Fossum's three-EVA total to 21 hours and 29 minutes. The total for all 68 station-era spacewalks now stands at 412 hours and 23 minutes by 42 U.S. astronauts, 13 Russian cosmonauts, one Frenchman, one Canadian and one Japanese astronaut. Sellers, a veteran of three previous spacewalks, has now logged 41 hours and 10 minutes of EVA time.

Today's spacewalk ran 41 minutes longer than originally planned after flight controllers asked the astronauts to move a robot arm grapple fixture to a different mounting point on the station's hull.

"Time for dinner and a shower," Sellers said as he finally made his way to the airlock."

Sellers and Fossum complete simulated repairs of five out of 10 samples of nose cap and wing leading edge material mounted in a pallet at the back of the shuttle's cargo bay. Using a high-tech caulk gun, the astronauts squeezed out dollops of NOAX, a heat-resistant sealant, and used spatulas to spread the material into cracks and gouges.

A major question mark is how the thick material sets up in the extreme temperatures and weightless environment of space. Trapped air can cause bubbles that can affect the materia's ability to reject heat.

"I'm looking at (sample) 4," Fossum said as he wrapped up the second of two repairs. "The bubbles ... appear only to be in the finishing layer. They're so small, kind of like a rash, they're not the big ones that seem to come up when you're lifing a lot of material. This will be very interesting to see how it cures out over the next week or so. When I finished them, they both looked very much alike. Now, 3 has noticeable bubbles that have formed under the surface. One of them at least is probably three or four millimeters across."

During cleanup, the astronauts did an inventory of their tools to make sure nothing was left behind.

"So Mike, you have six total spatulas, is that correct?" pilot Mark Kelly asked.

"Negative, five," Fossum said, indirectly referring to one that was lost earlier by Sellers.

"OK, yeah, that's correct," Kelly said.

"Rub it in, Mark, rub it in," Sellers laughed.

"I'm not rubbing it in. It's been a long day."

"You're torturing me," Sellers said. "That was my favorite spatch."

Flight controllers later told the astronauts not to worry about it, that the spatula did not pose any sort of "FOD" (foreign object debris) threat in the cargo bay.


11:15 a.m., 07/12/06, Update: Heat shield sealant 'behaves well,' astronauts report

Spacewalk-3
EV-1: Piers Sellers (red stripes on suit)
EV-2: Mike Fossum (no stripes)
Elapsed Time: 3:55

Astronauts Piers Sellers and Mike Fossum are wrapping up their simulated heat shield repair work, touching up and smoothing out an experimental sealant they've spread over deliberately cracked and damaged panels of wing leading edge material.

"The best practice for this is to have an old house in Houston," Sellers said as he used a putty knife to smooth the NOAX sealant.

"Done that," laughed Fossum.

"Yep, renovating an old house, that would do it," shuttle pilot Mark Kelly agreed from Discovery's flight deck.

Working at a pallet mounted in the back of the shuttle's cargo bay, Sellers and Fossum troweled on NOAX and "worked it" with spatulas to get suspended air bubbles out. The material is very sensitive to temperature changes, hardly bubbling when the shuttle is in orbital darkness and then outgassing in direct sunlight.

"On the whole, the material's behaving very well. You agree, Mike?"

"Yeah," Fossum said.

"Looks kind of like thick peanut butter now?" Kelly asked.

"Yeah. It's tearing now a little bit. But it's OK," Sellers said.

A few minutes later, Sellers reported he had lost one of his applicator spatulas.

"Guys, I've got to tel you, I think my spatula's escaped," he said. "I don't see it on me."

"OK, we'll take a look," Kelly said.

"Is it caught on me anywhere?

"No, it's not on those hooks," Fossum said.

"Man, it escaped, how 'bout that?"

A few minutes later, he added "I think it's gone, gone, gone."

The spacewalkers currently are finishing up a final two samples. They then plan to use an experimental infrared camera to photograph the samples, two in sunlight and two in shadow, to test the camera's ability to spot damage in reinforced carbon carbon panels.


09:35 a.m., 07/12/06, Update: Repair tests underway; sealant applied to test panels

Spacewalk-3
EV-1: Piers Sellers (red stripes on suit)
EV-2: Mike Fossum (no stripes)
Elapsed Time: 2:15

Astronauts Piers Sellers and Mike Fossum began their first heat shield repair test run around 9 a.m., after Fossum relatched a loose safety tether. Using a high-tech caulk gun, Sellers squeezed out thick NOAX sealant on a wing leading edge sample with deliberate cracks and/or gouges. The idea is to find out how the heat-resistant material performs in weightlessness, how easy or difficult it might be to spread over cracks using putty knife applicators and how suspended air bubbles out at higher temperatures.

"OK. We're starting to get goo," Sellers said as he squeezed the trigger ofthe caulk gun. "Got goo, good goo!"

"You're going to want to push it into the exposed carbon carbon, swiping in multiple directions and you want to wet the surface," Kelly advised from the flight deck.

"This is taking a little bit of force," Sellers commented. "Really a small, like, kid's marble's worth..."

"We're gonna fill that groove pretty soon," Fossum said.

"It continues to come out after I've shut the valve off," Sellers said.

The NOAX did not bubble, or outgas, as much as the astronauts expected, in large part because it was applied in shadow and not in direct sunlight. Tests on the ground show the material works best when applied when the temperature is between 100 and 35 degrees and dropping.

"It feels like soft putty," Sellers commented. "It's a little stiffer than expected and it's tearing a little. ... This is not like wet stuff, Mark, but sticky stuff."

"Yeah, it's freezing, it's cold," Fossum agreed.

"Now it's behaving, as it's cooled off more, like clay."

"So it doesn't seem like it's outgassing very much, does it?" shuttle pilot Mark Kelly asked from Discovery's flight deck.

"No at all," Sellers said.

"It was a little bit at first, when it sets in thicker layers, you could see some bubbles rising," Fossum said.

"I saw a tiny bit when it came out, but now it's doing nothing," Sellers said.

"I think we want to just keep working it here until it starts outgassing some more," Kelly advised.

For a NOAX repair to be effective, the material must be worked with a spatula to remove any air bubbles that could reduce its heat rejection capability. The reinforced carbon carbon nose cap and wing leading edge panels experience the most extreme heat during re-entry - more than 3,000 degrees - and any repair must be able to stand up to that hellish environment.

Sellers and Fossum are filling cracks in test panels with NOAX, working the material in and then applying a "finishing" layer to smooth it out. Sellers said the NOAX pulled, or tore, as he tried to spread it but he said it wasn't a major problem.

The test samples will be analyzed back on Earth and subjected to re-entry level temperatures in an arc jet facility to find out how well the material works.

Views from the astronauts' helmet cams showed Sellers working the NOAX into various sample panels, working the material like caulk with a putty knife. He said it had the consistency of peanut butter.

"This is quite hard work," Sellers said. "I'm getting warm, just mashing stuff in, compensating for the arm."

Fossum said the NOAX "was definitely like thick putty. It is smooth in consistency, so it goes on fairly easily in that regard."

In direct sunlight, the material appeared quite pliable and it outgassed as expected.


09:00 a.m., 07/12/06, Update: Fossum fixes loose tether

Spacewalk-3
EV-1: Piers Sellers (red stripes on suit)
EV-2: Mike Fossum (no stripes)
Elapsed Time: 1:40

Astronaut Mike Fossum ran into another problem with safety tethers today. Moving toward the back of Discovery's cargo bay for wing leading edge repair tests, flight controllers noticed the far end of his safety tether, hooked on a space station hand rail, appeared unlocked.

"Houston, Discovery. Just to let you know we're looking at it in camera A, the elbow camera, and based on what we see, Mike, we suspect it's unlocked. It's really hard to tell, but we think it's unlocked."

"OK, it could happen," Fossum replied. "That would be a first for me, but that could happen."

Flight controllers then asked Fossum, using a second tether as a backup, to make his way back to the space station tether point. When he got there, he discovered the latch was, in fact, unlocked.

"Sure enough, there it is," he radioed. "Good catch, guys."

"And Houston, Discovery, thanks, good catch," shuttle pilot Mark Kelly radioed from the cockpit. "It's now locked."

This was Fossum's second run in with safety tethers. During the crew's first spacewalk last Saturday, he and Sellers struggled to retract an 85-foot-long tether only to find the reel mechanism was locked. During their second spacewalk Monday, latches holding Sellers' emergency jet backpack in place somehow disengaged, but the backpack was tethered and later tightened down by Fossum.

The incidents had no impact on the results of the spacewalks and the astronauts were never in any increased danger.


08:20 a.m., 07/12/06, Update: Infrared camera tested

Spacewalk-3
EV-1: Piers Sellers (red stripes on suit)
EV-2: Mike Fossum (no stripes)
Elapsed Time: 1:00

Astronaut Piers Sellers, anchored to the end of the space station's robot arm, was maneuered to a point high "above" one of the shuttle Discovery's wings today to photograph critical leading edge panels with an infrared camera. The goal was to assess the camera's ability to collect infrared data that might help engineers assess the health of the wing leading edge panels.

Astronaut Mike Fossum, meanwhile, made his way to the back of Discovery's cargo bay to set up tools and equipment at a worksite pallet where the astronauts will test leading edge panel repair techniques. Sellers, on the arm, was maneuvered to the work site by the robot arm.

"Hey Mike, you're doing great. You're doing great, right on time," Sellers radioed Fossum.

"Well, I'd hoped to be there with the box open by now, but that's not happening today," Fossum said as he moved aft along the port payload bay sill.


07:25 a.m., 07/12/06, Update: Spacewalk begins

Spacewalk-3
EV-1: Piers Sellers (red stripes on suit)
EV-2: Mike Fossum (no stripes)
Elapsed Time: 0:05

Floating in the Quest airlock module, astronauts Piers Sellers (call sign EV-1; red stripes on suit) and Mike Fossum (EV-2; no stripes) switched their spacesuits to internal battery power at 7:20 a.m. to officially begin a planned 6.5-hour spacewalk.

This is the 68th spacewalk of the space station assembly era, the third for Sellers and Fossum and the 21st staged out of the Quest airlock. Going into today's outing, 58 U.S., Russian, Japanese, French and Canadian astronauts had logged 405 hours and 12 minutes of station-based spacewalk time, including 14 hours and 18 minutes by Sellers and Fossum.

The goal of today's spacewalk is to test repair materials and techniques that one day could be used to repair relatively minor damage to the shuttle's wing leading edge panels.


05:30 a.m., 07/12/06, Update: Sellers, Fossum don suits, prepare for spacewalk

Astronauts Piers Sellers and Mike Fossum have donned their spacesuits and are in the final stages of preparing for a planned six-and-a-half-hour spacewalk to test wing leading edge repair techniques. Preparations are generally on schedule and the spacewalk should begin around 7:13 a.m.

A detailed preview of today's excursion was posted Tuesday. A detailed flight plan update is available in the crew's Daily Execute Package for Flight Day 9. Here is a summary timeline (in EDT and mission elapsed time):

TIME		DD	HH	MM	EVENT
__________________________________________________________________

05:28 AM	07	14	50	EVA-3: Spacesuit prebreathe
06:28 AM	07	15	50	EVA-3: Crew airlock depressurization
07:13 AM	07	16	35	EVA-3: Airlock egress
07:28 AM	07	16	50	EVA-3: Station robot arm (SSRMS) setup
07:28 AM	07	16	50	SSRMS foot restraint installation
07:58 AM	07	17	20	ISS meals
08:03 AM	07	17	25	SSRMS moves to RCC repair demo work site
08:08 AM	07	17	30	EVA-3: Payload bay setup; IR RCC photography
08:48 AM	07	18	10	EVA-3: Heat shield repair demonstration
08:58 AM	07	18	20	ISS crew resumes MPLM transfers
11:48 AM	07	21	10	EVA-3: Payload bay cleanup
12:33 PM	07	21	55	EVA-3: SSRMS cleanup
12:48 PM	07	22	10	SSRMS moves to airlock
01:08 PM	07	22	30	SSRMS foot restraint removal
01:28 PM	07	22	50	EVA-3: Airlock ingress 
01:28 PM	07	22	50	SSRMS moves to cargo module demate inspection point
01:43 PM	07	23	05	EVA-3: Airlock repressurization
01:58 PM	07	23	20	Post EVA spacesuit water recharge
05:08 PM	08	02	30	Crew sleep begins


06:00 p.m., 07/11/06, Update: Heat shield repair demonstration spacewalk on tap Wednesday

The Discovery astronauts are set for a third spacewalk Wednesday, this one to test tools and a temperature-sensitive sealant with the consistency of peanut butter that may prove useful for repairing small cracks or other minor damage to critical wing leading edge panels.

Astronauts Piers Sellers and Mike Fossum are scheduled to begin the planned six-and-a-half-hour excursion around 7:13 a.m. Wednesday, exiting the international space station's Quest airlock module and making their way to a sample pallet at the back of Discovery's cargo bay.

Compared to two earlier spacewalks - one to test a long inspection boom as a work platform and another to repair a stalled robot arm transporter on the space station - Wednesday's outing "is more like a kind of a careful, meticulous lab experiment," Sellers said.

"Mike and I are going to be very careful, (pilot Mark Kelly is) going to coach us through this on how to get the material to the right temperature and apply it to a set of samples. It really is lab work and we're going to do the best, most careful job we can."

The repair demonstration ranked third on NASA's spacewalk priority list and was only added to the mission timeline when Discovery's flight was extended a day.

Some engineers questioned whether the spacewalk was justified, arguing laboratory testing on the ground is adequate for assessing the strengths and weaknesses of the repair materials and procedures. Given the inherent risks associated with any spacewalk, those engineers favored "real work" content more directly focused on building or servicing the international space station.

Lead flight director Tony Ceccacci disagreed, but only mildly.

"The key thing you're getting out of this is how does the material behave in zero G?" he said. "It was the lowest priority EVA, but we have the time and I think overall it's worth doing. As Mike Fossum and the crew said, we're going to get some really good data out of this. From where I stand, and since we did get that extra day, I think it's worth doing."

So does Sellers, who said in an interview that NASA is making a serious effort to develop viable repair techniques.

"It's been in parallel with the main effort, which is to stop stuff falling off the (external fuel) tank, remove the problem at its root cause," he said. "But knowing what we know about foam, you can't guarantee that nothing will fall off. And if something falls off, you can't guarantee it won't hit the orbiter. So it's prudent to try and develop some repair techniques.

"I think these repair techniques are going to be limited in capability," he said. "You cannot repair huge damage to the heat shield. i don't think it can be done. But maybe, who knows, if you see some nicks you don't like it might be a good idea to get yourself some insurance. It's nice to have that capability."

Ever since Columbia went down three years ago, NASA and contractor engineers have been struggling to come up with reliable techniques for repairing minor damage to the shuttle's thermal protection system - TPS - tiles and the reinforced carbon carbon panels protecting the nose and wing leading edges from the extreme heat of re-entry. Repairing Columbia-class damage is not considered possible.

During Discovery's last flight a year ago, the astronauts tested modest techniques for repairing tile damage and while those procedures are not yet officially certified for use, the equipment and repair material were on board again in case it was actually needed.

This time around, Sellers and Fossum will focus on techniques for repairing small cracks and other damage to wing leading edge panels and nose cap material mounted in a special carrier at the rear of Discovery's cargo bay.

The nose cap and wing leading edge panels experience the most extreme heating during the return to Earth - more than 3,000 degrees Fahrenheit - and developing repairs that can stand up to the extreme environment of re-entry is a daunting technological challenge.

"The main focus is to evaluate repair techniques for cracks in the carbon carbon material that makes up the leading edge of the shuttle," Sellers said in a NASA interview. "This is hard, black material; it's laid down a bit like fiberglass layers of carbon matting with resin, then matting, then resin built up in layers. This was the material that got damaged during Columbia's launch. So obviously we're very interested in trying to find a fix for it.

"We're going to take up some materials ... and test different techniques for repairing these on a special set of samples in the back of the payload bay of the shuttle. That's going to be the bulk of the content of that EVA. But we're also testing an infrared camera which, basically, sees heat or the disturbing of heat flows in materials. We can see how well that does at picking up cracks in the carbon carbon."

Small cracks in the RCC material might not be visible to the human eye, Sellers said, "but the heat will have to flow around the crack, it can't jump across the crack. So, the surface temperature is distorted. And, hopefully this infrared camera that detects heat will be able to see some changes in heat flow around crack fields."

Sellers plans to test the camera right off the bat, shooting stills and video from the end of the space station's robot arm as he's being moved to the back of the cargo bay for the RCC repair tests. If time is available, Fossum will shoot additional footage of test samples later in the day.

Here is a timeline of the crew's day Wednesday (in EDT and mission elapsed time):

TIME		DD	HH	MM	EVENT
__________________________________________________________________

01:08 AM	07	10	30	STS crew wakeup (flight day 9)
01:38 AM	07	11	00	ISS crew wakeup
02:38 AM	07	12	00	EVA-3: Preparations with ISS oxygen
05:13 AM	07	14	35	EVA-3: Spacesuit purge
05:13 AM	07	14	35	MPLM cargo module transfers resume
05:28 AM	07	14	50	EVA-3: Spacesuit prebreathe
06:28 AM	07	15	50	EVA-3: Crew airlock depressurization
07:13 AM	07	16	35	EVA-3: Airlock egress
07:28 AM	07	16	50	EVA-3: Station robot arm (SSRMS) setup
07:28 AM	07	16	50	SSRMS foot restraint installation
07:58 AM	07	17	20	ISS meals
08:03 AM	07	17	25	SSRMS moves to RCC repair demo work site
08:08 AM	07	17	30	EVA-3: Payload bay setup; IR RCC photography
08:48 AM	07	18	10	EVA-3: Heat shield repair demonstration
08:58 AM	07	18	20	ISS crew resumes MPLM transfers
11:48 AM	07	21	10	EVA-3: Payload bay cleanup
12:33 PM	07	21	55	EVA-3: SSRMS cleanup
12:48 PM	07	22	10	SSRMS moves to airlock
01:08 PM	07	22	30	SSRMS foot restraint removal
01:28 PM	07	22	50	EVA-3: Airlock ingress 
01:28 PM	07	22	50	SSRMS moves to cargo module demate inspection point
01:43 PM	07	23	05	EVA-3: Airlock repressurization
01:58 PM	07	23	20	Post EVA spacesuit water recharge
05:08 PM	08	02	30	Crew sleep begins
The temperature-dependent RCC repair material, which works best between 35 and 100 degrees, is a "pre-ceramic polymer sealant impregnated with carbon-silicon carbide power," according to NASA's shuttle press kit. It is known as NOAX for short, which stands for non-oxide adhesive experimental.

Sellers and Fossum call it "the black goo."

"We have a special space caulking gun that we'll use to squirt out a small amount of this repair material," Fossum explained. "In the vacuum of space, the stuff boils. It's just amazing to see it in a vacuum. The black goo literally, it boils and sputters. We work it with a putty knife until it settles down and becomes more workable. We'll then use that to make repairs, filling small cracks and holes in the sample tiles."

A pallet at the back of DiscoveryÕs cargo bay carries 12 RCC samples. Eight of them have cracks or gouges or both, two have been deliberately damaged to serve as targets for the infrared camera and two are blanks that will be used by the astronauts to "work" the NOAX prior to application.

Because NOAX works best when the temperature is decreasing, Sellers and Fossum will wait for orbital sunset to begin a repair run. The work is prioritized as follows:

  1. Repair two of four RCC panels with impact cracks
  2. Photograph a wing leading edge with the infrared camera
  3. Photograph damaged RCC samples on the cargo bay pallet with the IR camera
  4. Repair the two remaining RCC panels with cracks
  5. Repair any remaining crack samples.
Using applicators similar to putty knives, the spacewalkers will work NOAX into the RCC samples to fill in cracks and gouges and to build up additional layers of protection. "Imagine the scenario that somethingÕs hit and cracked one of the wing leading edge panels," Sellers said in a NASA interview. "We have a black material called NOAX, which is non-oxidizing, non-oxidative adhesive experimental; weÕre going to apply this over a series of deliberately damaged RCC samples under a range of conditions. These are going to be brought home and theyÕre going to be tested to see how well they would have stood up to an entry. WeÕre hopeful that we will have, you know, helped develop a technique that could be used to repair a shuttle wing leading edge in space. ThatÕs the goal."

The sort of damage a future shuttle crew might face involves an impact "where you hit something hard and the impact knocks material off the back side as well as making a crack and knocking material off the front side," Sellers said.

"There are straight cracks, which is like mechanical damage, which youÕre trying to fill in, and thereÕs coating loss, where the thin layer of glass over the top of the RCC has been eroded off," he said. "So weÕre going to try applying this material in different ways to repair all these different kinds of damage.

"Now, the 'different conditions' part is that this material doesnÕt seem to work very well when itÕs very, very cold. Likewise when itÕs very hot, it behaves badly. So weÕre going to try and catch it under the optimal conditions between extreme heat and extreme cold when the surface is cooling, and see how well we do."

The experiment pallet carries more RCC samples than Sellers and Fossum will have time to repair. They hope to complete about a half dozen. All of the samples will be returned to Earth and put through a battery of tests to find out how well the repairs might stand up to re-entry heating.

"The first thing we're getting out of this is the behavior of the NOAX material," said Ceccacci. "The second thing you're looking at is hey, for these specific damages, this stuff worked pretty good or it didn't. It'll be dependent on the arc jet testing they do post flight."

While some observers question whether NASA would ever trust a heat shield repair enough to risk a crew during re-entry, agency managers say they hope to certify at least some of the tile and RCC repair techniques for possible use repairing minor damage by the end of the year.


09:20 a.m., 07/11/06, Update: Astronauts say flight proves shuttle back on track

The Discovery astronauts, working through a relatively relaxed day of space station equipment and supply transfers, say the shuttle's trouble-free launch and lack of significant impact damage show NASA is finally ready to put the Columbia tragedy behind it.

"My brother put it very well," pilot Mark Kelly, whose twin brother, Scott, is also an astronaut, told The Associated Press. "I spoke to him on what's called the IP phone, which is an internet phone, and he said 'we're back, baby!'"

Spacewalker Piers Sellers agreed, telling USA Today "I think we were all hoping for two things to come out of STS-121. The first thing is that the shuttle would fly with no problems, no big dings on ascent and we'd have a clean vehicle. And we seem to have achieved that.

"The second thing is that we would leave station in good shape and ready to pick up the assembly sequence and the line would be drawn where it was rubbed out before Columbia, we would start again with the next mission and continue the assembly. I think we're there now."

During a spacewalk Monday, he said, "we repaired the external equipment that will allow the assembly to continue. So, two for two!"

A third spacewalk by Sellers and Mike Fossum is on tap Wednesday to demonstrate potential wing leading edge repair techniques. Repair techniques and materials intended to fix minor heat-shield tile damage was tested during the first post Columbia mission last year.

Sellers described the first two spacewalks of Discovery's current mission as "kind of heavy lifting, I mean they really were. We were moving huge pieces of equipment around and doing hard work."

"EVA-3 is more like a kind of a careful, meticulous lab experiment," he said. "Mike and I are going to be very careful, Mark's going to coach us through this on how to get the material to the right temperature and apply it to a set of samples. It really is lab work and we're going to do the best, most careful job we can. But it won't be very tiring!"

Here is an updated timeline of today's activity in orbit (in EDT and mission elapsed time):

TIME.......DD...HH...MM...EVENT

07/11/06
02:38 AM...06...12...00...STS crew wakeup (flight day 8)
02:38 AM...06...12...00...ISS crew wakeup
04:38 AM...06...14...00...MPLM transfers
05:28 AM...06...14...50...Spacesuit servicing
05:58 AM...06...15...20...Middeck transfers
07:18 AM...06...16...40...Spacewalk tools configured for EVA-3
08:18 AM...06...17...40...AP/USA Today interviews
08:38 AM...06...18...00...Infrared camera setup for EVA-3
09:33 AM...06...18...55...Joint crew meal
10:33 AM...06...19...55...Crew downlink opportunity
10:58 AM...06...20...20...MPLM, middeck transfers resume
12:00 PM...06...21...22...Mission status briefing on NASA TV
01:08 PM...06...22...30...EVA-3: Procedures review
01:08 PM...06...22...30...Video File on NASA TV
05:08 PM...07...02...30...STS/ISS crew sleep begins
06:00 PM...07...03...22...Video highlights reel on NASA TV
Revision M of the NASA television schedule is posted on the CBS News STS-121 Quick-Look page, along with an updated flight plan. A detailed preview of the crew's third spacewalk will be posted here later today.


05:40 p.m., 07/10/06, Update: NASA managers pleased with results of spacewalk

Space station flight director Rick LaBrode sweated bullets going into today's spacewalk to fix a stalled robot arm transporter on the international lab complex. But months of planning, tests and simulations paid off with a successful repair job, clearing the way for resumption of station assembly.

"Man, do I feel better!" LaBrode exclaimed at a post-spacewalk news briefing. "I'll tell you, I've spent the better part of the last three years of my life putting together this mission. And this particular day was my main concern.

"The obvious reasons are, one, It was extremely complex and challenging. And two, there were huge implications for continued space station operations. So it was a big deal, and getting it behind us successfully is a great feeling."

Astronauts Piers Sellers and Mike Fossum spent six hours and 47 minutes carrying out a dramatic spacewalk today, moving a cooling system pump module from the shuttle Discovery's cargo bay to an external storage platform on the station and repairing the mobile transporter.

The transporter, designed to carry the station's robot arm along a huge solar array truss to assist with the lab's construction, has been out of action since last December when a cable cutter inadvertently fired, severing one of two redundant power, data and video cables.

NASA flight rules forbid moving the transporter without redundant power and data and today, Fossum and Sellers installed a new cable reel assembly and a replacement for the mechanism that malfunctioned last year. With the completion of today's spacewalk, the transporter once again has redundant power. The one remaining cable cutter was disabled during a spacewalk Saturday when Sellers and Fossum bolted on a device to physically block the blade from reaching the cable even if it fires.

LaBrode said late today it would take several hours to thoroughly check out the mobile transporter, but engineers were optimistic about positive results.

"We have done a preliminary checkout of connections that they made to the mobile transporter and those connectors all check out nominally," he said. "We still have some more checkouts to do. We've applied power to the mobile transporter and we've tested the telemetry connections. We still are in the process of driving some of the integrated motor control assemblies and we also are going to be looking at some video that passes through that TUS cable. But thus far, everything looks great."

Later, astronaut Lee "Brew" Archambault radioed more good news to the astronauts on board the shuttle-station complex.

"ISS control room reports that so far, they've checked out everything with the exception of the video (from one camera) and everything they have checked out so far has been outstanding, looks great," Archambault said.

"That's great news, we're really glad to hear that," shuttle skipper Steve Lindsey replied.

Phil Engelauf, chief of NASA's flight directors office, said the initial success of Discovery's mission gives the agency optimism about a fast turn around to get Atlantis off the ground in late August.

"We're about at the halfway point here and we have behind us most of the initial evaluation of the shuttle," he said. "The health of the vehicle is great, we're not working any particular problems and now that we've got the early inspection and review of the inspection data behind us, the emphasis of the mission is turning now to the actual tasks at hand. With the completion of the second EVA today, all of that is going really well.

"It's very gratifying, now that we've gotten through a couple of ascents here and are starting to get comfortable with the new tools that we have available to us, it is letting us feel a lot better about proceeding into the (space station) assembly sequence. It's great to be focused on how well everything's going on 121 (Discovery's mission). But we have a huge amount of work coming ahead and the success of this mission so far, I think, is a good indicator that we're heading towards another launch in the August time frame unless anything new comes up."

For readers looking ahead to Atlantis' launch on mission STS-115, here's the latest processing schedule (some dates under review and subject to change):

DATE.......EVENT

07/17/06...Discovery lands
07/25/06...Atlantis rollover to Vehicle Assembly Building (may change)
07/27/06...Payload to launch pad (may change)

08/04/06...Shuttle stack rollout to launch pad (may move up a few days)
08/07/06...Crew flies to Kennedy Space Center
08/08/06...Terminal Countdown Demonstration Test begins
08/09/06...Astronaut Q & A at launch pad
08/10/08...TCDT ends with dress-rehearsal countdown
08/11/06...Pre-flight briefings at the Johnson Space Center
08/15/06...Flight readiness review begins
08/16/06...FRR ends; official launch date announced
08/25/06...Countdown begins
08/28/06...Launch (current estimate: 4:04 p.m. EDT)
09/13/06...Shuttle launch window closes

"The assembly sequence is set to proceed fast and furious here," Engelauf said. "We're only six to seven weeks out from the next mission. The big thing on our plate now, I think, is seeing how well everything worked here, we have a green flag to press ahead and that's where our attention is focused."

The Discovery astronauts will focus Tuesday on continued work to transfer supplies and equipment from the shuttle and the Leonardo cargo module to the space station. A third spacewalk by Fossum and Sellers is on tap Wednesday to test wing leading edge panel repair techniques.


03:15 p.m., 07/10/06, Update: Spacewalk ends; robot arm transporter believed repaired

Astronauts Piers Sellers and Mike Fossum returned to the space station's Quest airlock module today and ended a six-hour 47-minute spacewalk after completing a complex repair job to restore redundant power to a stalled robot arm transporter. The second spacewalk of shuttle Discovery's mission ended at 3:01 p.m.

This was the 67th spacewalk devoted to space station assembly and maintenance, pushing total EVA time by 58 astronauts and cosmonauts representing five nations to 405 hours and 12 minutes since construction began in 1998.

When the final electrical cables were hooked up, astronaut Julie Payette in mission control radioed congratulations from Mike Suffredini, manager of the space station program.

"Excellent job, outstanding teamwork on your part," she called. "And just so you know, there is a certain Mr. Suffredini here just a while ago checking on you guys and he was all smiles."

Minutes after the spacewalk ended, Payette told station flight engineer Jeff Williams that testing showed good electrical connections between the transporter and the new cable assembly installed by Sellers and Fossum. But she said it would take two hours or so to thoroughly check out the mobile transporter.

"So far so good," Williams said.


01:30 p.m., 07/10/06, Update: Cable reel in place on truss

EVA-2
EV-1: Piers Sellers (red stripes on suit)
EV-2: Mike Fossum (no stripes)
Elapsed Time: 5:15

After a bit of a struggle, spacewalkers Piers Sellers and Mike Fossum finally wrestled a 334-pound cable reel assembly into place on the space station's solar array truss in a major step toward repairing the lab's robot arm transporter.

The astronauts had trouble getting the reel asembly lined up properly so locks could engage to hold it in place.

"Ready? Say when," Sellers said as they made an attempt.

"Three, two, one, now," Fossum said and they pushed.

"No."

"OK, let me rotate it a little bit more," Fossum said. "That's the max rotation there, it's up against the stop."

"OK."

"Yeah, it shouldn't be up against the stop," pilot Mark Kelly radioed from Discovery's flight deck.

"I know it, I know it," Fossum said. "But we're kind of feeling it."

"It looks like, hmmm, 30 degrees maybe out," Sellers said.

After another unsuccessful attempt, the astronauts checked to make sure nothing was blocking the mechanism and then tried again. This time, they were successful.

"Got it!" one exclaimed. A moment later, a second latch was engaged.

"Yay! Two for two."

"Great job, guys," Kelly radioed.

"What else could happen, man?" one of the astronauts quipped.

"Don't ask."


01:15 p.m., 07/10/06, Update: Astronauts work to install cable reel assembly; Sellers jetpack secured

EVA-2
EV-1: Piers Sellers (red stripes on suit)
EV-2: Mike Fossum (no stripes)
Elapsed Time: 5:00

Astronaut Mike Fossum is struggling to install a new cable reel assembly on the space station's solar array truss to restore redundant power, data and video between the lab and a robot arm transporter cart. Spacewalker Piers Sellers, meanwhile, back in Discovery's cargo bay, ran into problems with an apparently disengaged latch holding his jet backpack in place.

Earlier today, Sellers' crewmates noticed one of the two extensions, or "towers," that hold the jetpack to his spacesuit, had come loose. The jetpack is known by its acronym, SAFER, for "simplified aid for EVA rescue."

"Mark, we've been looking at a SAFER tower issue," astronaut Julie Payette radioed shuttle pilot Mark Kelly from space station control. "And at this point, we'd like to secure that tower. The only problem is it's the second one, the right one, comes off then the SAFER is no longer attached to the crew member. So at the time, we'd like for Mike to go and help out and put a tether between the tower and Piers."

That was done and the spacewalk proceeded. But just before 1 p.m., astronauts on Discovery's flight deck noticed the one remaining latch appeared to be loose.

There was no danger of losing the SAFER - it was still tethered to Sellers on the other side - but flight controllers wanted to resolve the issue and told Sellers to carefully make his way up to the solar array truss so Fossum could help lock the backpack down. As soon as Sellers floated into reach, Fossum secured the right latch with no problem.

Fossum, meanwhile, had run into problems locking the new cable reel assembly in place in the truss, lacking the leverage needed to push it into position. With Sellers now up on the truss, the two astronauts worked together to secure the cable assembly.


11:25 a.m., 07/10/06, Update: Broken transporter power cable reel removed

EVA-2
EV-1: Piers Sellers (red stripes on suit)
EV-2: Mike Fossum (no stripes)
Elapsed Time: 3:10

Astronauts Mike Fossum and Piers Sellers have completed installation of a 1,379-pound cooling system pump module on a storage platform mounted to the hull of the international space station. Fossum has now anchored himself on the end of the station's robot arm to hand carry a large trailing umbilical system - TUS - cable reel assembly from the station's solar array truss to the shuttle Discovery's cargo bay. After handing off the old TUS and picking up a replacement, the spacewalkers will move back to the solar array truss to finish today's repair of the station's robot arm transporter.

Working to release the old TUS assembly, Sellers took his time changing positions, saying at one point he was "going slow here. Don't want to bump anything expensive."

"It's ALL expensive," Fossum replied.

A few moments later, hand carrying the 334-pound reel assembly, the spacewalker began his slow trip to the cargo bay on the end of the robot arm.

"Time for an elevator ride down to the payload bay," he said. "Controllability is not an issue. The thing's like a feather."


10:45 a.m., 07/10/06, Update: Cable cutter replaced; pump module installtion on tap (two-hour update)

EVA-2
EV-1: Piers Sellers (red stripes on suit)
EV-2: Mike Fossum (no stripes)
Elapsed Time: 2:30

Piers Sellers and Mike Fossum have completed installation of a replacement interface umbilical assembly, or IUA, on the downward, or nadir, side of the space station's robot arm transporter. This is the first step in a two-part repair job to replace a severed power, data and video cable and restore the cart's electrical redundancy.

The astronauts currently are working to install a 1,389-pound cooling system pump module that was pulled from Discovery's cargo bay earlier today by the station's robot arm. The module will be added to the station's cooling system during an upcoming assembly flight. Despite the mass of the bulky pump module, the astronauts had no trouble taking it from the robot arm and mounting it on the storage platform.

"That went very smoothly," Sellers reported. "Just for the record, it was very easy to move, just gentle wrist action to change the angle of rotation."

"Very, very easy," Fossum agreed.

"And the whole thing was extremely easy. It's basically like just easing a rowing boat toward a dock with your hand," Sellers said.


09:30 a.m., 07/10/06, Update: Pump module lifted from payload bay

EVA-2
EV-1: Piers Sellers (red stripes on suit)
EV-2: Mike Fossum (no stripes)
Elapsed Time: 1:15

Astronauts Piers Sellers and Mike Fossum attached a grapple bar to the new space station pump module mounted in Discovery's cargo bay. Lisa Nowak and Stephanie Wilson, operating the space station's robot arm, plucked it out of the astronauts' gloved hands one hour into the spacewalk and slowly lifted the 1,400-pound freezer-sized module out of the bay.

"Piers and Mike, we have captured the pump module," Wilson radioed from Discovery's flight deck.

"Copy, Stephanie," confirmed pilot Mark Kelly. "And Piers and Mike, you can let go of the pump module."

"Copy, letting go," Sellers said.

"Letting go. Clear," Fossum said. "Cool! And Mark, you can tell our commander he can breathe now."

It will take about a half hour to manuever the pump module to an external stowage platform on the station where it will be locked down by Sellers and Fossum.

Before exiting the Quest airlock module earlier today, the spacewalkers joked about working in orbital darkness, marveled at the view and frequently broke out in laughter.

I think we'll be coming out in the dark, mate," Sellers said.

"I think so," said Fossum. "I've done that before."

"Nothing to be afraid of in the dark there," Kelly joked.

"No..." Fossum said.

"Everyone can hear you scream," one of the astronauts said.

"Yeah, Mike, we'll all hear you scream," Kelly said.

"I've got time to get outside, put on my alien costume and wait for Mike to come out," Sellers joked.

After handing off the pump module, Sellers and Fossum took a moment to enjoy the view as the space station sailed 210 miles above South America.

"Mark, what river are we flying over?" Sellers asked.

"Amazon."

"You're kidding," Fossum said.

"That's a BIG river," Kelly said.

"It is huge," Sellers agreed.


08:15 a.m., 07/10/06, Update: Spacewalk begins

Astronauts Piers Sellers (call sign EV-1; red stripes on suit) and Mike Fossum (EV-2; no stripes) switched their spacesuits to internal battery power at 8:14 a.m. today to officially begin a planned seven-hour spacewalk to fix a stalled robot arm transporter on the international space station.

This is the Discovery crew's second spacewalk, the 20th staged from the U.S. Quest airlock module and the 67th since space station assembly began in 1998. Going into today's excursion, 58 astronauts from the United States, Russia, Japan, Canada and France have logged 398 hours and 25 minutes of station spacewalk assembly time, including seven hours and 31 minutes by Sellers and Fossum Saturday.


06:15 a.m., 07/10/06, Update: Astronauts set for critical spacewalk to clear way for station assembly

The most critical task planned for Discovery's mission is arguably the one that must be accomplished to permit continued assembly of the international space station: repair of a stalled robot arm transporter on the station's unfinished solar array truss that "killed itself" late last year.

Astronaut Piers Sellers and Mike Fossum plan to venture out of the station's Quest airlock module today at 08:13 a.m. to begin a planned seven-hour spacewalk to replace a cable cutter that inadvertently fired last December, along with a complex cable reel mechanism to restore redundant power to the transporter.

"Basically, it killed itself just before Christmas," Sellers said. "It's a complicated task. If we don't get this thing fixed, we can't move this truck that moves up and down the front face of the station and we can't continue with assembly. So we absolutely have to get it fixed before the next mission.

"And it's a complicated business because it's a large, difficult-to-handle object, it sits inside a bay and it's got multiple, multiple electrical connections. So there are a number of significant obstacles to getting this done. We've thought about it a lot. I think we'll manage to do it OK, the engineering team has put an enormous amount of effort into this and I think it's going to work out. But it's one of the more daunting tasks (of the mission)."

Critical, in fact. As Sellers said, the solar arrays scheduled for launch aboard the shuttle Atlantis Aug. 28 cannot be attached to the truss unless the robot arm transporter is fully operational.

Here is an updated timeline of today's activities (in EDT and mission elapsed time):

  
TIME		HH	MM	SS	EVENT

07/10/06
02:08 AM	05	11	30	STS crew wakeup
02:38 AM	05	12	00	ISS crew wakeup
03:38 AM	05	13	00	EVA-2: Preparations with ISS oxygen
06:13 AM	05	15	35	EVA-2: Spacesuit purge
06:13 AM	05	15	35	MPLM cargo module transfers
06:28 AM	05	15	50	EVA-2: Spacesuit prebreathe
07:28 AM	05	16	50	EVA-2: Quest airlock depressurization
08:13 AM	05	17	35	EVA-2: Airlock egress
08:28 AM	05	17	50	EVA-2: EV1 (Sellers): FGB retrieval
08:28 AM	05	17	50	EVA-2: EV2 (Fossum): APFR setup
09:08 AM	05	18	30	EVA-2: EV2: Pump module retrieval
09:08 AM	05	18	30	Station arm (SSRMS) grapples pump module
09:28 AM	05	18	50	SSRMS moves pump module to ESP-2 stowage platform
09:28 AM	05	18	50	EVA-2: EV1: Nadir IUA (cable cutter) replacement
09:28 AM	05	18	50	EVA-2: EV2: APFR reconfig and TUS setup
10:18 AM	05	19	40	EVA-2: Pump module installation
10:53 AM	05	20	15	SSRMS removes TUS (cable reel assembly)
10:58 AM	05	20	20	EVA-2: Nadir TUS removal
11:23 AM	05	20	45	SSRMS maneuvers to cargo carrier
11:53 AM	05	21	15	SSRMS TUS swap
12:18 PM	05	21	40	SSRMS moves to S0 truss
12:53 PM	05	22	15	SSRMS supports TUS installation
01:23 PM	05	22	45	SSRMS to park position
01:43 PM	05	23	05	EVA-2: TUS cable routing
02:28 PM	05	23	50	EVA-2: Airlock ingress
02:48 PM	06	00	10	EVA-2: Airlock repressurization
03:30 PM	06	00	52	Mission status briefing
04:08 PM	06	01	30	TUS checkout by mission control
06:08 PM	06	03	30	Crew sleep begins
07:00 PM	06	04	22	Daily video highlights reel on NASA TV
The transporter is a robotic cart designed to creep along rails on the front face of the station's unfinished solar array truss, carrying the lab's Canadian-built robot arm from one work station to another. At each work station, the transporter and arm can be locked down to provide stability. The long truss eventually will sport four huge sun-tracking solar array panels that will generate the electrical energy needed to support a six-member crew and a full suite of scientific experiments.

But the outer segments of the truss cannot be built without the station's robot arm and the arm cannot be moved from point to point unless the transporter is operational and has redundant power, video and data cables.

As the transporter moves along the truss it plays out or rolls up ribbon-like power and data cables. To provide redundancy, two trailing umbilical system - TUS - reel assemblies play out and rewind separate cables. The transporter was launched with powerful cable cutters in devices on the transporter itself, called interface umbilical assemblies - IUAs - in case of a jam in either TUS reel that might otherwise strand the work platform.

On Dec. 16, TUS cable No. 1 on the Earth-facing, or nadir, side of the transporter was severed when the cable cutter in the nadir interface umbilical assembly suddenly fired for no apparent reason, slamming down with 960 pounds of force. Engineers still do not know why the spring-driven cutter fired.

But the incident left the mobile transporter with just one set of power and data cables and NASA flight rules forbid its movement along the truss unless full redundancy is available. The concern is that a second failure could leave the transporter stranded between work sites and unable to be safely latched down. That, in turn, would pose a risk during shuttle dockings or other events when unwanted movement could prove dangerous.

"We have rules in place that say we do not base the (station's robot) arm on the mobile transporter during that time and we do not maneuver the mobile transporter," said Kirk Shireman, deputy manager of the space station project. "It's very important for us to restore full functionality before we continue assembly. That's because to continue assembly, we have to move the mobile transporter out on the truss, base the arm out there to actually install the next piece of truss. That's a very important piece of this mission for us, to return to full functionality."

Earlier this year, worried that the cable cutter on the upward facing, or zenith, side of the transporter might fire, Expedition 12 commander William McArthur and flight engineer Valery Tokarev attempted to disable the zenith cable cutter during an already planned spacewalk. But they were unable to drive in a "safing" bolt and rather than leave the cable in place, they removed it from the cutting mechanism and tied it off. That had the effect of stranding the mobile transporter at work site 4.

Sellers and Fossum fixed the zenith cable system during their first spacewalk Saturday by inserting a blade blocker designed to prevent any damage to the cable even if the cutter fires later. With the blade blocker in place, they re-inserted the zenith cable in the interface umbilical assembly and thus restored the transporter to single-cable operation.

That's important because the transporter must be moved from work site 4 to work site 5 this morning to get the access needed to repair the nadir cable system during today's spacewalk.

The goals today are to replace the nadir interface umbilical assembly and its deployed cable cutter with a new unit carried up aboard Discovery; and to replace the nadir trailing umbilical system reel assembly and its severed cable.

But first, Sellers and Fossum will move a large liquid ammonia pump module to a spare parts depot on the station. The pump module, part of a complex system that circulates ammonia coolant through external trusses and the U.S. laboratory module, will be installed during an assembly flight now targeted for launch in December.

With the pump module safely stowed, Sellers and Fossum will install the new interface umbilical assembly and then remove the 334-pound trailing umbilical system reel assembly. Fossum, riding on the end of the station's robot arm, will hand-carry it down to the shuttle cargo bay. Sellers will hand him the new reel assembly and both astronauts will move back up to the truss for its installation. After routing the cable back though the IUA, Sellers and Fossum will be done and the mobile transporter will be restored to normal, fully redundant operation.

"I'm excited by the TUS task," Fossum said in an interview. "It failed in December and within weeks, when we came back after ... Christmas, they had one in the (training) pool all wrapped up with a big bow on it. And we started working on this task.

"It's very important to get that redundancy in the mobile base system, the mobile transporter that moves up and down the truss. If anything was to go wrong with that remaining one we would not be able to move it to a different location. Finishing assembly, adding on pieces of the truss, the solar arrays out on the ends, requires this mobile transporter to be mobile. And so it's been a big effort."


07:30 p.m., 07/09/06, Update: Discovery officially gets clean bill of health

After around-the-clock analysis, NASA managers today officially gave the shuttle Discovery's h eat shield a clean bill of health, concluding there are no problems with tiles, the ship's nose cap or wing leading edge panels that require any repair work by the astronauts.

It was a long awaited moment for thousands of NASA and contractor engineers and managers who have put in long hours since Discovery's last flight to correct potentially catastrophic problems with foam insulation.

As it turned out, Discovery's external tank lost less foam than any tank before it and the orbiter suffered virtually no impact damage or other serious problems with its fragile heat shield.

Discovery's crew was given the news just before bedtime, after engineers worked through the night to resolve questions about a protruding gap filler and tears in two small insulation blankets.

"So with that, we've closed out all issues on the TPS (thermal protection system) and we deem the TPS as 100 percent cleared for entry," astronaut Lee Archambault radioed from mission control.

"Well, that is great news, that's fantastic," replied Discovery commander Steve Lindsey. "To get all that done by the end of flight day six, when we did focused inspection on flight day four, is just amazing. So our thanks to the imagery team, the MMT and all the engineers working on this to get the vehicle cleared this quickly. That's very impressive."

"Everyone here around the room as you can imagine is most happy," Archambault said. "I think you'll be delighted when you see the images that you guys sent down after you get back. They really were amazing."

Flight controllers were equally wowed by stunning movies shot by cameras mounted in the shuttle's twin solid-fuel boosters. The rocketcam videos made it back to the Johnson Space Center today, providing engineers with never-before-seen views of launch and booster separation. The giant solid-fuel rockets performed normally, officials said today, with no problems of any significance.

John Shannon, chairman of NASA's Mission Management Team, said he remains optimistic NASA will resolve the few problems that have cropped up during Discovery's flight in time to launch the shuttle Atlantis Aug. 28 on a space station assembly mission, the first shuttle construction flight since Columbia went down in 2003.

"This has really been two missions for us," he said. "The first was to go and do ... a lot of things to assess orbiter health and potential repair capabilities. The other piece of it that's just as important is what we have done for the space station.

"We've talked a lot about how wonderful the orbiter looks and how well the external tank performed and how good the boom was. But I don't want to lose sight of the other half of this, which is how much we're doing to get ourselves ready in August for beginning the assembly of the space station again."

The August mission depends on the success of a spacewalk Monday by astronauts Piers Sellers and Mike Fossum to repair a stalled robot arm transporter on the station's solar array truss. The robotic transporter is required to move the station's robot arm from work site to work site on the unfinished truss and until it is fixed, station assembly is on hold.

Last December, a spring-loaded cable cutter inadvertently fired, severing one of two power and data cables leading to the transporter. Sellers and Fossum plan to replace the cable reel mechanism Monday during a tricky make-or-break spacewalk.

"We need that thing to be working, to move big pieces around during the assembly," Sellers said today. "Right now, it's dead on one side. Our job (Monday) is basically to replace the unit that supplies power to the truck so it can be ready for the next stage of assembly. It's important to get that done before the next guys show up."

A detailed overview ot Monday's spacewalk will be posted here shortly.

A third spacewalk is on tap Wednesday to test wing leading edge repair techniques. Engineers briefly worried the astronauts might have to pluck a protruding gap filler from Discovery's belly during the third excursion, but Steve Poulos, manager of the orbiter projects office at the Johnson Space Center, said today a detailed analysis showed Discovery can safely re-enter the atmosphere as is.

"Nobody had any concerns whatsoever we were going to exceed any of their limits," he said. "We had no dissension across the entire community, everybody was 100 percent on board."

Gap fillers are thin, heat-resistant spacers between tiles to prevent chafing during the vibrations and temperature extremes of launch and orbital flight. Some 16,000 gap fillers are in place, including more than 5,000 that were replaced in wake of Discovery's flight last summer on the first post-Columbia mission.

Gap fillers can occasionally shake loose and if they stick up too far into the air stream during re-entry, they can break up the smooth flow across the belly of the shuttle, creating turbulence that can raise downstream temperatures.

During Discovery's approach to the space station earlier this week, engineers saw a gap filler sticking up from tiles near a propellant feedline access door. The high-resolution photography by the station's crew showed the gap filler was damaged and creased.

Poulos said engineers conducted tests showing the gap filler most likely will roll over in the re-entry air stream. But even if it doesn't, testing showed Discovery is in no danger of excessive heating.

During a normal re-entry, the tiles in that area should not experience temperatures higher than 2,300 degrees at their surface, more than 625 degrees at the bondline where they attach to the shuttle's skin and 350 degrees for the aluminum skin itself.

In a worst-case scenario, Poulos said, one in which the protruding access door gap filler disturbed the insulating "boundary layer" just after atmospheric entry at 24.7 times the speed of sound, temperatures on the tile surface would not exceed 2,254 degrees. The bondline temperatures would not rise above 579 degrees and the shuttle's skin down stream of the gap filler would not get hotter than about 344 degrees. If the gap filler rolls over like engineers expect, tripping the boundary layer around 19.5 times the speed of sound, conditions will be even more benign: 2,254 degrees at the downstream tile surface; 496 degrees at the bondline; and 289 degrees on the skin.

"With all that data, we were able to clear that gap filler as a non constraint for entry," he said.

Engineers worked one other open item overnight, conducting tests and computer analyses to show two small, damaged thermal blankets near the shuttle's nose will not pull off during entry and pose an impact threat to Discovery's cockpit windows or other areas.

Testing showed the blankets would not begin to peel away unless relatively large "loads" were applied - more than five pounds of pull. The testing and computer analysis showed the blankets would experience no more than about 0.9 pounds of loading during entry.

"In my terminology, not only did the team pound these issues flat, they put a dimple in the board when it was all said and done," Poulos said. "So we are absolutely clear and ready to bring this vehicle home whenever the mission is accomplished."

In one minor correction, Shannon said additional analysis showed a piece of foam insulation that peeled off Discovery's external tank during launch weighed just .055 pounds instead of .11 pounds as he earlier reported. Either way, it was well below NASA's safety limit of .25 pounds for potentially serious impact damage.


02:45 p.m., 07/09/06, Update: Astronauts enjoy slighly more relaxed day

The Discovery astronauts are enjoying a slightly more relaxed day in space today, settling in for relatively routine supply transfers from the shuttle to the international space station and gearing up for a critical spacewalk Monday.

Fielding questions from reporters earlier today, Discovery commander Steve Lindsey said the flight plan was so loaded with activity the first five days of the mission - launch, heat shield inspections, docking and a spacewalk - that it was "a very hectic pace."

"We worked really hard with the timeline ... to be as efficient as possible," he said. "It has been very, very hectic, but we have managed to keep up with the timeline and get all the objectives accomplished.

"A lot of the lessons we're learning is how to be more efficient with our time to deal with these new (heat shield inspection) objectives we have to deal with and try to get everything done. We only have 16 shuttle flights left and we want to get the maximum out of them we possibly can."

Pilot Mark Kelly agreed, but added the crew was fortunate "not to have a lot of stuff to trip us up and we've been staying on top of it and the transfer's going very well."

"Today has been a relatively light day compared to the others, so it's really going great, I mean, we're really staying on top of it."

First time shuttle flier Lisa Nowak, Discovery's flight engineer, said it took her body several days to adapt to weightlessness.

"The first day, the first 24 hours, I didn't feel so great and it took me a while to adapt," she said. "Then I started feeling better and then after we got to space station and you have to turn different directions to enter each module, that took a while to get used to. But I'm happy to say I think I'm completely adapted now."

About half the men and women who fly aboard the shuttle experience space sickness in one form or another as their neurovestibular systems adapt to weightlessness. Symptoms usually disappear after two days or so but those first few days are typically among the busiest of a mission.

"We take our meals on the run, we really push to keep up with the timeline, we knew that was the way it was going to be," Lindsey said. "When you timeline a mission, you run a very fine line between squeezing the maximum amount of work out that you can or doing too much and pushing over the edge.

"The first few days we were walking that line. I think we stayed on the good side of that line and managed to get through it to flight day six today, where we're doing transfer, working hard, but not at the same intensity as we've been working the last five days.

"So we're watching that real close, that's one of my jobs as commander ... to make sure everybody gets enough to eat, gets enough time to sleep. So I push really hard to get us to bed on time every night. We haven't always been successful. Generally speaking, we're doing OK and we're certainly recovering today."

Lead flight director Tony Ceccacci agreed "it's been intense" going "110 miles per hour getting work done."

"Today it's more of a pack mule type of operation, where you've just got to move one thing from another, you've got to make sure it's in the right location, of course, but it's not that intense, paying attention to every second of every minute here. They're still pretty busy. And if they're not, we'll have to give them a call."

Spacewalker Mike Fossum, asked what he would write home about if this was a more normal trip, said he was awed by the view out the windows of the shuttle.

"First, using the mirror to look out the overhead windows as we lifted off the pad, just unbelievable to see all that conflagration taking place and the smoke billowing," he said of launch July 4. "The second would be (flying) across the California coast at an altitude of only about 85 miles. We had a beautiful view of the Los Angeles basin, came across the high desert and saw Edwards Air Force Base. I worked for Edwards for many years in the Air Force and it was really just an awesome sight to see it from such a low altitude."

He also marveled at the view of Earth and sky during a spacewalk Saturday to test the stability of a long robot arm boom as a possible work platform.

"The third thing would be just the incredible view being outside yesterday," he said. "We had a little bit of time when we were actually on the boom, all we had to do was ride it and hang on for the ride to the next test point, so that gave us time to look around. A lot of that was in pitch black and that alone was kind of stunning. But then to see a sunrise or a sunset from the end of the boom, just beyond words."

The 50-foot-long boom was designed to help astronauts inspect the shuttle's heat shield for signs of damage. But the boom, attached to the end of the shuttle's 50-foot-long robot arm, also provides a way to get astronauts to virtually any part of the shuttle if repairs are needed.

During tests Saturday, Fossum and crew mate Piers Sellers rode on the end of the long boom and found it more stable than they had anticipated.

"I think it was more stable than we feared it might be," Fossum said. "We were pleased in the amount of motion we got, and not necessarily the predictability but the repeatability of it. You could learn the motions at a certain position and then learn how to compensate for it. And the motion was not so great that it would be impossible to get things done from the end of it. It will be challenging, but ... in the realm of doable with due care and diligence."


07:40 a.m., 07/09/06, Update: Astronauts transfer supplies; prepare for second spacewalk

The Discovery astronauts are busy moving equipment and supplies from the Leonardo multi-purpose logistics module - MPLM - into the international space station. The crew also is checking out and preparing tools for a spacewalk Monday to repair the station's robot arm transporter. A crew news conference is planned for 11:48 a.m. Here's an updated timeline of today's activities in orbit (in EDT and mission elapsed time):

EDT			DD	HH	MM	EVENT

03:08 AM	04	12	30	STS crew wakeup
03:38 AM	04	13	00	ISS crew wakeup
05:38 AM	04	15	00	Lab rack transfer to ISS
06:13 AM	04	15	35	MPLM transfers
07:48 AM	04	17	10	Spacewalk tools configured
09:18 AM	04	18	40	Spacesuit checkout
10:18 AM	04	19	40	SAFER jet pack checkout
10:48 AM	04	20	10	Joint crew meal
11:48 AM	04	21	10	Joint crew news conference
12:28 PM	04	21	50	Joint crew photo
12:48 PM	04	22	10	MPLM transfers resume
12:48 PM	04	22	10	Lithium hydroxide transfer for CO2 removal
01:00 PM	04	22	22	Mission status briefing on NASA TV
01:53 PM	04	23	15	MPLM transfer tagup
02:08 PM	04	23	30	EVA-2: Procedures review
02:30 PM	04	23	52	Crew conference replay on NASA TV
05:00 PM	05	02	22	Post-MMT news conference on NASA TV
06:08 PM	05	03	30	STS/ISS crew sleep begins
07:00 PM	05	04	22	Daily video highlights reel on NASA TV
NASA has generated a detailed flight plan reflecting the one-day mission extension and it will be posted here later today. A summary overview timeline is posted on the CBS News STS-121 Quick-Look page, along with revision J of the NASA television schedule. The summary overview timeline is also available in the Flight Day 6 Execute Package (1-meg pdf) uplinked to the crew.

Here is NASA's morning mission status report:

STS-121
Report 10
5 a.m. EDT, Sunday, July 9, 2006
Mission Control Center, Houston, Texas

Continued unloading of the Multi-Purpose Logistics Module will be the focus of the Space Shuttle Discovery and International Space Station's crew today. Some preparations for the second spacewalk, on Monday, also are on today's plan.

The Discovery crew was awakened at 3:08 a.m. EDT with "I Have a Dream," by ABBA, for shuttle pilot Mark Kelly. It was requested by his children. The station's crew woke up at 3:38 a.m. EDT for the third day of joint operations.

Every member of the two crews would have at least some involvement in the cargo activities throughout the day. Mission specialist Stephanie Wilson is leading the transfer effort, which will ultimately relocate the more than 7,400 lbs of equipment and supplies that were brought up in the cargo module named "Leonardo" and 1,800 lbs from the shuttle's middeck.

Flight controllers reported that 14 percent of equipment and supplies from the MPLM has already been transferred, including the Minus Eighty Lab Freezer and the 1,400 lb Oxygen Generation System that will expand the station's ability to support up to six crewmembers. Six percent of equipment from the shuttle's middeck has been relocated thus far.

All nine crewmembers will participate in a joint news conference that will air on NASA TV at 11:48 a.m. EDT. They will field questions from U.S. media at NASA centers and journalists at the European Astronaut Center in Cologne, Germany.

Throughout the day, Mission Specialists Mike Fossum and Piers Sellers will work on post- and pre-extravehicular activity tasks. The two completed the first spacewalk of the mission on Saturday and are preparing for the second, scheduled for Monday. They will make configurations to the Quest Airlock and prepare the tools needed for this second trip into the vacuum of space. The rest of the Discovery's crew, Commander Steve Lindsey, Kelly, Wilson, and Mission Specialist Lisa Nowak, will all participate in an EVA procedures review.

The next STS-121 mission status report will be issued Sunday evening, or earlier if events warrant.


07:20 p.m., 07/08/06, Update: NASA managers clear shuttle nose cap, wing leading edges for entry; still assessing gap filler; spacewalk hailed

With the Discovery astronauts chalking up a surprisingly successful spacewalk, NASA's Mission Management Team today cleared the shuttle's critical nose cap and wing leading edge panels for re-entry and expressed optimism two final question marks about the ship's heat shield will be resolved Sunday.

MMT Chairman John Shannon also unveiled a spectacular eight-second video clip from a camera mounted in one of DIscovery's twin solid-fuel boosters showing the shuttle and its external tank rocketing out of the atmosphere, a view of the shuttle never before seen.

The cameras were on board the boosters to look for signs of foam insulation falling from Discovery's external tank and footage from both rockets is expected to be released Sunday.

As it is, Shannon said analysis of radar data, wing leading edge sensors, high-resolution photographs, laser scans and focused inspections by the astronauts show Discovery suffered less ascent damage than any shuttle ever launched and its tank lost less foam than any in NASA's 115-flight history.

"I would say by far. By far," Shannon said. "Seeing no tile damage that exceeded any of the inspection requirements was a great, pleasant surprise. The tank performance was as expected. We saw a little bit of loss that was consistent with our flight history, the areas we redesigned performed really well."

Said Steve Poulos, manager of the orbiter projects office at the Johnson Space Center: "This was the best, cleanest orbiter I've seen."

Even the tank's ice-frost ramps, which remain officially classified as a "probable/catastrophic" risk, performed well, with no major loss of foam. A thin sheet of insulation just in front of an ice-frost ramp peeled away about two minutes and 50 seconds after launch, but it posed no threat to the shuttle.

While NASA still plans to redesign the ramps to eliminate thick foam around 34 brackets, "this flight was really, really good. It will add to our understanding of it," Shannon said.

"When we do a redesign, we need to make sure that it's the right redesign," he said. "Now, do I have more confidence flying STS-115 (the shuttle Atlantis) in August with these ice-frost ramps? I would tall you yeah, I do."

Late last week, engineers identified six "regions of interest," that is, areas where potential damage was seen on Discovery's heat shield. By today, all but two had been officially eliminated, including lingering concerns about potential punctures or cracks in the shuttle's reinforced carbon carbon nose cap and RCC wing leading edge panels. The nose cap and RCC panels experience the most extreme heating during re-entry and it was a breach in an RCC panel that brought down Columbia in 2003.

A white, circular marking on Discovery's nose cap, which engineers initially worried might be a hyper-velocity impact site, is now believed to be bird droppings. Discoloration on two leading edge panels is thought to be harmless discoloration, perhaps caused by launch pad spills of hydraulic fluid or some other material.

Protruding gap filler material near Discovery's nose was deemed no threat after high-resolution photographs showed it extended just two-tenths of an inch above the surrounding tile.

But engineers are continuing to assess the potential impact of a protruding gap filler near a propellant feedline access door in Discovery's belly and the potential impact of a slightly damaged thermal protection blanket in front of the ship's cockpit windows.

Poulos showed extremely sharp pictures taken with a new digital camera on Discovery's inspection boom that clearly show the gap filler in question tore apart at some point during ascent. The part that's remaining likely will bend over or break off during entry and pose little threat of increased heating. But engineers have not yet finished their evaluation and the gap filler remains an open issue.

Likewise, tests are being conducted to make sure the slightly damaged blanet in front of the cockpit windows on Discovery's forward reaction control system rocket pod poses no impact threat if a piece rips away during the descent. Poulos said it looks like the blanket will hold up, but additional tests are needed to make sure.

Even so, he said he was confident the Mission Management Team would be able to give Discovery a clean bill of health Sunday.

"These last two development flights have been phenomenal," he said. "We have learned so much about what the capability of the boom sensor system is. We now understand what different defects or areas of interest look like and we're just going to be much smarter as we go into our future flights."

Late today, mission control shared the news with the Discovery astronauts.

"As of now, we've been able to clear all the RCC," mission control radioed. "We continue to march forward and by tomorrow's MMT (meeting), we will have resolution on the ET door gap filler as well as the forward RCS blanket. We're very happy with our current situation."

"Well, that's great news," commander Steve Lindsey replied. "We'll look forward to hearing that word."

In the meantime, the MMT formally cleared Discovery and its crew for emergency descent if some major malfunction forced the astronauts to make a swift return to Earth.

Good performance from the shuttle and its external tank are only part of the big picture for NASA. The space agency also is trying to develop techniques for fixing heat shield damage in orbit if something goes wrong on the way up hill.

The Discovery astronauts took a big step in that direction today by successfully testing a novel approach to gaining access to damage sites that could play into an eventual decision to launch a Hubble Space Telescope servicing mission.

The idea was to find out if the shuttle's 50-foot-long robot arm and the 50-foot-long boom used to inspect the shuttle's heat shield could be used as a work platform to repair impact damage.

During a seven-hour 31-minute spacewalk, astronauts Piers Sellers and Mike Fossum tested the stability of the spindly space crane and found it performed better than engineers had predicted.

"We had some fantastic results,:" said Tomas Gonzales-Torres, the lead spacewalk officer in mission control. "The crew went through the various positions and I think the most impressive thing we saw was that the boom did dampen (oscillations) faster than we had expected. Many of the activities, we had expected around one minute of damping and it actually took around 15 or 20 seconds. In addition, some of the deflections were smaller as well."

Shannon said the results show the crew of a Hubble servicing mission would have access to damage sites even though the space station, in a different orbit, would not be available for safe haven.

"I think today was a significant step forward in that decision process because previously, we had said we would like to have the space station as our work platform to repair any tile or RCC," Shannon said. "If the results from the test of the boom hold (up), then we'll show we have an ability to put a crew member, without a station there, anywhere on the shuttle to do any kind of repairs."

Lead flight director Tony Ceccacci summed up his part of a status briefing by saying, "it was a really super, super day today."


05:00 p.m., 07/08/06, Update: Spacewalk ends

Piers Sellers and Mike Fossum floated into the Quest airlock module, sealed the hatch and officially ended a seven-hour 31-minute spacewalk today at 4:48 p.m. It was the first of three planned spacewalks for Sellers and Fossum and the 66th devoted to space station assembly and maintenance. With the conclusion of today's excursion, 42 U.S. astronauts, 13 Russian cosmonauts, one Japanese flier, one Frenchman and one Canadian have logged 398 hours and 25 minutes of spacewalk time since station assembly began in 1998.


02:40 p.m., 07/08/06, Update: Fossum demonstrates heat shield repair work on end of 100-foot boom

Astronaut Mike Fossum, anchored to the end of a 100-foot space crane positioned at one end of the space station's solar array truss, pretended to make heat shield repairs today, measuring the forces imparted to the untried space crane to judge its stability as a repair platform.

The tests appeared to go well and while some exercises were easier to accomplish than others, the shuttle robot arm/inspection boom combination seemed stable enough to serve as a repair platform if real repairs are ever needed.

If an engineering analysis confirms that, future shuttle crews would have a way to reach virtually any part of a shuttle's heat shield to make repairs, regardless of whether the space station was available. That could be a factor in any decisions down the road to approve a mission to repair the Hubble Space Telescope. Because the observatory is in a different orbit, a Hubble crew would not be able to reach the space station in an emergency.

But it will take engineers time to fully evaluate the data from today's test and to debrief the crew after the flight. As such, it's too soon to say whether the crane might be a viable option.

Television views from the station were spectacular, showing Fossum and Piers Sellers floating high "above" the shuttle's open cargo bay, making various movements, or inputs, to help engineers characterize the crane's rigidity.

"You guys look pretty lonely out there," shuttle pilot Mark Kelly radioed from Discovery's flight deck.

"Well, I'm just looking at MIke," said Sellers. "That's all I've got to look at right now, There's nothing else!"

"We can see you out the window of our warm, comfortable cabin," Kelly joked.

"Drinking tea..."

"As a matter of fact, I am."

With both astronauts on the end of the boom, large swaying motions resulted from crew movement. But the swaying appeared to damp out quickly. The mock repair work up on the space station's solar array truss went to the point of the exercise.

One technique for repairing damaged heat shield tiles calls for spacewalking repairmen to spread on a viscous material called "emittance wash" to help restore the tiles' ability to reject heat.

Using a stand-in for an emittance wash application tool, Fossum went through the motions of applying the material, lightly holding a hand rail with one hand for stabilization and wielding the tool with the other.

"You have a desired point you want to apply it in, desired plus or minus a tenth of an inch, adequate a half of an inch, and you're going to use a handrail lightly for stabilization while you do this," Kelly said, reviewing the procedure.

"Ready to start... ready, ready, now," Fossum said. "Input stop. It was very easy to get the desired performance. No problem at all."

Next, he repeated the test using an open hand for stabilization, reporting he "had to work harder."

"To do the task in general, you have to, you've got to lean in, put a light pressure on it and then offset with the other hand," he said.

Finally, he repeated the test without doing anything for stabilization.

"Ready, ready, now... You know, this isn't bad," he reported. "The back and forth that time was eight, a little more compensation required, I still think I got desired performance. A moderate amount of compensation."

Fossum then went through the motions of other tile and wing leading edge panel repair techniques, reporting varying degrees of success. Before the robot arm/inspection boom can be used for an actual repair, engineers will need to evaluate videos and data from instruments that precisely measured how much force the astronauts put into the system.


12:40 p.m., 07/08/06, Update: Dramatic robot arm/work platform put through paces

Astronaut Piers Sellers, his feet anchored to the end of a 50-foot-long boom attached to the shuttle Discovery's robot arm, bobbed about and simulated repair work today in a dramatic test of the space crane's stability for possible use in future shuttle repairs.

With fellow spacewalker Mike Fossum looking on from the shuttle's cargo bay, Sellers went through a scripted sequence of movements - lay backs, rotations, simulated tool retrievals and foot platform relocations - and the long, spindly looking arm/inspection boom combination appeared relatively stable.

It swayed in gentle, slow-motion fashion as Sellers moved about, causing the brakes on the arm's wrist joint to slip at one point. But to the untrained eye, it appeared stable enough to use as a work platform. Whether NASA managers will deem it safe for actual repair work, when an astronaut would be much closer to the shuttle's fragile heat shield, remains to be seen.

"OK, Piers, first test point," shuttle pilot Mark Kelly called from Discovery's flight deck. "You're going to retrieve the digital camera, pick a target, take two photos and put the camera back."

"I've got the camera in my hand," Sellers replied a moment later, floating 14 feet or so above the open payload bay. "Taking a photo ... one, two. Putting the lens cover back on."

"No detectable motion against the moving background," someone observed.

"Camera stowed. Complete," Sellers reported. "Movement stopped."

"I saw almost no motion," Fossum said. "Just a tiny bit."

"Yeah, we didn't see any here," Kelly agreed.

Next, Sellers did a slow "lay back," bending at the knees and reclining for a few seconds before pulling upright again.

"There's a pretty view," Sellers observed as the shuttle-space station sailed high above the South Pacific Ocean. "And coming forward again. Stopped. Got a very slow gentle sway in and out of the bay. Still continuing. Period about six or seven seconds, it looks like. Motion stopped."

"Roger. Next test point is a medium to normal layback," Kelly said.

"The sway this time is a kind of circular, fore and aft and in and out of the bay," Sellers reported. "Period is about six seconds again. Motion stopped. Wow. Damped out quick."

As the testing continued, Sellers got smoother in his motions.

"Just a general comment. It gets easier as you go along, doing all these tasks, you know, at the end of a skinny little pole. A little practice makes perfect. Or adequate."

After working through the entire sequence, Lisa Nowak, operating the robot arm, brought Sellers back down into the cargo bay. Fossum was supposed to join Sellers on the boom, but his 85-foot-long safety tether refused to retract properly. The spacewalkers attempted to manually wind the reel, but it wouldn't work.

Flight rules forbid anyone from riding on the boom without a safety tether all the way back to the shuttle's robot arm just in case the boom somehow separated from the arm. Flight controllers eventually told the spacewalkers to retrieve a spare tether before proceeding.

Then, almost as an afterthought, mission control asked the astronauts to make sure the reel's winding mechanism was unlocked.

"Discovery, Houston, for EVA, with one more question about the damaged safety tether. We want to just make sure it's in the unlocked position."

"OK, we'll check," Kelly said.

"It's in the locked position," Sellers said.

"No," Fossum said.

"Look!"

"Oh, no!"

"Houston, Discovery, thanks for that recommendation," Kelly radioed.

"Oh, that's pretty embarrassing," Fossum said.

"OK, we'll be good to go in just a moment," Kelly said.

Television views from space have been spectacular this morning, with Sellers silhouetted against the limb of the Earth, with blue seas and white clouds on one side and the stark black of deep space on the other. Both astronauts clearly enjoyed the view.

"Hey Piers, take a second and look at the Earth here," Kelly called from Discovery's flight deck before the crane tests began. "I think you've got Ireland and England coming up there."

"My left? Oh!" exclaimed Sellers, who was born in Crowborough, Sussex.

"Wow," Fossum marveled.

"Oh my goodness. It's a beautiful day in Ireland!"

"Indeed it is."

"So to everybody in Ireland, hello!" Sellers said. "You look beautiful today."

A few moments later, Fossum laughed aloud as he floated above central Asia at five miles per second, saying "This is a cool view."

"That's the Caspian sea down there, Mike," Kelly replied.

"OK, I was going to ask," Fossum said, a few minutes later adding, "I'm in a dream. Nobody wake me up."


10:00 a.m., 07/08/06, Update: Astronauts complete phase one of mobile transporter repair

Spacewalkers Piers Sellers and Mike Fossum successfully installed a blade blocker in a critical space station crane transporter system today in a bid to restore the rail car to limited operation. If all goes well, the astronauts will complete the repair work Monday during a second spacewalk when they replace a severed cable and restore full redundancy.

Sellers and Fossum currently are preparing to carry out dramatic tests of the shuttle Discovery's robot arm and a 50-foot inspection boom to find out if the system is rigid enough to serve as a work platform for future repair work. As of this writing, the spacewalkers are running about 10 minutes ahead of schedule.


09:20 a.m., 07/08/06, Update: Spacewalk No. 1 begins

Astronauts PIers Sellers and MIke Fossum, floating in the space station's Quest airlock module, switched their spacesuits to internal battery power at 9:17 a.m. today to officially kick off the first of three planned spacewalks during shuttle Discovery's mission.

The goals of today's six-and-a-half-hour excursion are to begin the repair of a stalled transporter on the station's solar array truss and to test the stability of a 50-foot-long boom attached to the end of the shuttle's robot arm for possible use as a work platform.

An astronaut on the end of the OBSS boom

This is the 66th spacewalk devoted to space station assembly and maintenance since construction began in 1998. Going into today's spacewalk, 57 U.S., Russian, French, Japanese and Canadian astronauts had logged 390 hours and 54 minutes of EVA time working on the station. Sellers participated in three space station spacewalks in 2002 totaling 19 hours and 41 minutes. Fossum is making his first EVA and thus pushes the number of station spacewalkers to 58.

The first task today is to restore the station's stalled crane transporter platform to limited operation in preparation for a complex repair job during the crew's second spacewalk Monday.

The transporter is designed to creep along rails on the front face of the station's unfinished solar array truss, carrying the station's Canadian-built robot arm from one work station to another. At each work station, the transporter and arm can be locked down to provide stability. The long truss eventually will sport four huge sun-tracking solar array panels that will generate the electrical energy needed to support a six-member crew and a full suite of scientific experiments.

But the outer segments of the truss cannot be built without the station's robot arm and the arm cannot be moved from point to point unless the transporter is operational and has redundant power, video and data cables.

As the transporter moves along the truss it plays out or rolls up ribbon-like power and data cables. To provide redundancy, two trailing umbilical system - TUS - reel assemblies play out and rewind separate cables. The transporter was launched with powerful cable cutters in devices on the transporter itself, called interface umbilical assemblies, in case of a jam in either TUS reel that might otherwise strand the work platform.

On Dec. 16, TUS cable No. 1 on the Earth-facing, or nadir, side of the transporter was severed when the cable cutter in the nadir interface umbilical assembly suddenly fired for no apparent reason, slamming down with 960 pounds of force. Engineers still do not know why the spring-driven cutter fired.

But the incident left the mobile transporter with just one set of power and data cables and NASA flight rules forbid its movement along the truss unless full redundancy is available. The concern is that a second failure could leave the transporter stranded between work sites and unable to be safely latched down. That, in turn, would pose a risk during shuttle dockings or other events when unwanted movement could prove dangerous.

"Basically, it killed itself just before Christmas," Sellers said in an interview. "It's a complicated task. If we don't get this thing fixed, we can't move this truck that moves up and down the front face of the station and we can't continue with assembly. So we absolutely have to get it fixed before the next mission."

Earlier this year, worried that the cable cutter on the upward facing, or zenith, side of the transporter might fire, Expedition 12 commander William McArthur and flight engineer Valery Tokarev attempted to disable the zenith cable cutter during an already planned spacewalk. But they were unable to drive in a "safing" bolt and rather than leave the cable in place, they removed it from the cutting mechanism and tied it off. That had the effect of stranding the mobile transporter at work site 4.

Sellers and Fossum will attempt to fix the zenith cable system today by inserting a blade blocker designed to prevent any damage to the cable even if the cutter fires later. If the blade blocker fits properly, they will re-insert the zenith cable in the interface umbilical assembly and thus restore the transporter to single-cable operation.

That's important because the crew needs to move the transporter from work site 4 to work site 5 to get the access needed to repair the nadir cable system during the second spacewalk Mondaay.

Once the cable blocker is in place, Sellers and Fossum will press ahead with the boom stability tests. See the 5:15 a.m. status report below for complete details.


07:00 a.m., 07/08/06, Update: Big Brother is watching!

In a morning uplink package of daily instructions to the Discovery astronauts, flight controllers showed just how closely they monitor activities aboard the space shuttle and just how thoroughly the orbiter is instrumented, including the crew's high-tech toilet, or waste collection system (WCS):

"Just as an example of how closely Big Brother watches, we would like to remind you that remaining fluid in drink bags should not be poured down the WCS but stowed in Wet Trash (yes, they can tell). There is a concern that the additives may react with the oxone in the WCS to form precipitates, which may cause blockages in the waste lines."


05:15 a.m., 07/08/06, Update: Sellers, Fossum set for dramatic spacewalk

Astronauts Piers Sellers and Mike Fossum are gearing up for a dramatic six-and-a-half-hour spacewalk today to test Discovery's robot arm and a long inspection boom as a potential platform to make heat shield repairs down the road.

First Sellers and then both spacewalkers will secure themselves to the end of the 50-foot-long orbiter boom sensor system - OBSS - while the shuttle's 50-foot-robot arm moves them from point to point to test the stability of the arm/boom combination. At one point, the boom will be extended some six stories or more from the shuttle's cargo bay.

"The question we want to answer is, can you use the boom as a worksite, as a platform to repairing underneath the orbiter?" shuttle commander Steve Lindsey said in a NASA interview. " So, the scenario is you have a problem, you want to go repair a tile or a leading edge (panel) or something like that. Can you put (one or two spacewalkers) out on the end of this boom, maneuver them underneath the vehicle, and is the platform stable enough to allow them to do repairs?"

The shuttle's robot arm is 50 feet long as is the OBSS extension.

"If an EVA crewmember puts a load or pushes at the end of the boom, how much flex do you get in that boom, how much flex do you get in the arm?" Lindsey asked. "Do the joints on the arm back drive? How much do they back drive? And, is it stable enough to be able to do work, precise work, where you have to be careful in how you do it?

"We're going to put one and then two crewmembers on that boom, go to a couple of positions, and they're going to do some typical EVA-type maneuvers. For example, they'll lean back aggressively while they're standing at the end of the arm to see what kind of drive you get on the joint. They might reach back for a tool and just kind of simulate those kinds of motions.

"And then, one of the test points will go actually to structure, where they're pushing against a truss structure in the payload bay, and see what kind of flex you're doing. So, we're going to get two things out of that. We're going to get loads information; in other words, how much force you're putting into the arm, how much do the joints move? And we're going to get an operational assessment, if you will. The EVA crewmember will simulate doing a repair and say, 'Can I do a repair with the arm in this configuration?' So, the goal is to be able to figure out at what points underneath the Orbiter do we need a further way to stabilize the crew, like some, putting something to stabilize them on the bottom of the vehicle itself? Or, can we get away without doing that at all?"

The success of today's tests may play into a decision on what to do about a protruding gap filler seen poking up between heat shield tiles on the underside of Discovery near a propellant feedline access door. Other than undocking and repositioning the shuttle - a complex, time-consuming procedure - the only way for spacewalking astronauts to reach the site is to use the shuttle arm/OBSS combination. NASA managers have not yet decided whether the gap filler needs removal.

Today's spacewalk, the first of three by Sellers and Fossum, is scheduled to begin around 9:13 a.m. Here is an updated timeline of today's activities (in EDT and mission elapsed time):


07/08/06

EDT			DD	HH	MM	EVENT

03:08 AM	03	12	30	STS crew wakeup (flight day 5)
03:38 AM	03	13	00	ISS crew wakeup
04:23 AM	03	13	45	EVA-1: Preps with ISS oxygen
07:13 AM	03	16	35	EVA-1: Spacesuit purge
07:28 AM	03	16	50	MPLM cargo module transfers
07:28 AM	03	16	50	EVA-1: Spacesuit prebreathe
08:23 AM	03	17	45	Station robot arm (SSRMS) ungrapples lab module
08:28 AM	03	17	50	EVA-1: Crew lock depressurization
09:13 AM	03	18	35	EVA-1: Airlock egress; tool setup
09:33 AM	03	18	55	EVA-1: Zenith IUA replacement
10:03 AM	03	19	25	EVA-1: Tool setup
10:43 AM	03	20	05	EVA-1: OBSS setup (part 1)
10:48 AM	03	20	10	MELFI lab freezer transfer
11:33 AM	03	20	55	EVA-1: 1 EV position 1 evaluation
11:48 AM	03	21	10	Oxygen generation system transfer
12:13 PM	03	21	35	EVA-1: OBSS setup (part 2)
12:43 PM	03	22	05	EVA-1: 2 EV position 3 evaluation
01:18 PM	03	22	40	EVA-1: 2 EV push evaluation
01:48 PM	03	23	10	EVA-1: OBSS cleanup
02:38 PM	04	00	00	EVA-1: Tool cleanup
03:23 PM	04	00	45	MPLM transfer tagup
03:28 PM	04	00	50	EVA-1: Airlock ingress
03:43 PM	04	01	05	EVA-1: Airlock repressurization
05:00 PM	04	02	22	Mission status/MMT briefing on NASA TV
07:08 PM	04	04	30	STS/ISS crew sleep begins
08:00 PM	04	05	22	Daily video highlights reel on NASA TV
Sellers and Fossum will exit through the station's Quest airlock module, first moving up to the lab's main solar array truss to install a device designed to prevent a cable cutter from inadvertantnly severing critical video and data cables leading to a stalled rail car used to move the station's robot arm. Repairing the stalled transporter is the primary objective of the crew's second spacewalk Monday.

Making their way down to the shuttle's payload bay, Sellers and Fossum will rig safety tethers and attach a foot restraint to the end of the OBSS along with sensors to record how much force is imparted to the boom when they move about. Sellers then will climb onto the OBSS, connected to the shuttle's robot arm by a long tether and to the sensor boom by another, shorter tether. Fossum said they refer to the latter as "our sissy tether."

Safely tethered, Sellers will be moved to a point just above the starboard sill of the cargo bay, about 14 feet from any other structure. This is considered a "strong" configuration for the boom. After moving about to impart various forces, he will be moved to a point high above the port wing for another round of "bouncing the boom" tests. Extended some 60 feet from the shuttle, the boom is expected to exhibit a slow back-and-forth sway as Sellers moves about.

"The idea is to see if you could do a repair while standing on the end of this," Sellers said in a NASA interview. "The problem is, of course, that it's a very long, bendy fishing pole with somebody standing on the end, so it's not a completely stable platform. It sways around a bit; we've tested it in virtual reality, we've tested it on an air-bearing floor. We know that it has some motion, some sway, associated with it."

In an interview with CBS News, he likened it to painting the side of a boat while standing in a raft bobbing up and down.

"It will have a long, slow sway, about four to eight seconds period," he said. "So I want you to imagine that you're standing in a little row boat that's going up and down in the swell, slowly, and you're trying to paint the side of a ship that's not moving, or the side of a dock next to you. You have to put quite a lot of compensation in, you have to be careful, but it's not impossible. You just have to think about what you're doing."

After the first two tests, the arm will be maneuvered back into the cargo bay and Fossum will climb aboard. The boom then will take both spacewalkers back out over the port wing and finally, to a cargo truss in the payload bay that Fossum will push against to mimic actual repair work.

"After we test it out with one person, we'll bring the boom back down to the payload bay and I'll get into the foot restraint," Fossum said. "Piers will be hanging on to the boom. This is to simulate the kind of situation where we'll actually (be) doing a repair, where I would be the one in the foot restraint, with both hands free so I can do the repair, and Piers will be moving around the outside.

"We'll have kind of a tool stanchion and some other support equipment set up, so he'll act as if he's getting tools out and handing them to me. We'll be able to evaluate the stability of the system with both of us moving around and putting force into the whole boom and arm just to make sure that it's stable enough. We'll be doing some basic maneuvers in free space.

"And then, we'll go down to some structure and I'll actually put force into the structure as if I'm tamping down, the repairs, like for a tile repair that requires a continuous tamping motion to push all of the repair material down into the patch site. We'll just do that to see if it holds us stable enough to accomplish those kinds of basic tasks."

The work could help clear the way for an eventual mission to service the Hubble Space Telescope. The observatory circles the globe in a different orbit from the space station and the crew of any proposed servicing mission would not be able to take advantage of the space station.

As a result, NASA needs credible ways to make repairs if any impact damage is seen and with the OBSS, the astronauts would have a potential way to work on the belly of the shuttle.

Ground testing indicates the robot arm/OBSS combination will be relatively sturdy and the astronauts said they had no concerns about the possibility the OBSS - and the astronauts - could somehow break free of the shuttle's robot arm.

"We've thought about that and all the different ways to get ourselves out of trouble," Sellers said. "We'll still be tethered, by the way, to the main shuttle arm so if we came off, that's our first recourse. So the first thing you've got to do is get off the boom, then you've got to stabilize yourself (and) use the tether to get back to the arm. So a multi-step process, but I think pretty safe."


07:25 p.m., 07/07/06, Update: Imagery analysis continues; shuttle not yet cleared for entry; Shannon says more time needed to complete analysis

NASA's Mission Management Team today officially approved a one-day mission extension for shuttle Discovery's crew, allowing the astronauts to stage a third spacewalk next week to test wing leading edge repair techniques. Piers Sellers and Mike Fossum plan to stage their first excursion Saturday, starting around 9:13 a.m., to test the ability of a long boom on the end of the shuttle's robot arm to serve as a work platform for future repair work.

With spacewalk preparations in high gear, engineers are still assessing the health of two leading edge panels on DiscoveryÕs right wing, along with a protruding gap filler just in front of a propellant feedline access door on the orbiter's belly. Mission Management Team Chairman John Shannon said today it might take another day or two before engineers can either give Discovery a clean bill of health or show the "regions of interest" represent potentially serious problems. While many engineers are optimistic - Discovery appears to be one of the "cleanest" shuttles ever launched - Shannon said he would not speculate on the possible outcome of the ongoing engineering analysis.

Asked if he could at least give reporters guidance as to how he thinks the analysis might play out, Shannon said simply, "No. I am completely withholding judgment until the analysts come back. Just like we said, we're going to give them time to do their work and they'll come back and tell us what we have."

It is a sensitive issue because the fate of the post-Columbia shuttle program clearly rides on successful launches and re-entries. A serious problem with Discovery's heat shield could force the astronauts to abandon ship and move into the international space station to await rescue. And that almost certainly would mean the end of the shuttle program.

Engineers are optimistic no such doomsday scenarios are actually in play, but Shannon clearly wants to give the team time to reach a technically sound conclusion before making any official announcements.

On a more positive note, initial worry about a potential hypervelocity impact on the shuttle's reinforced carbon carbon - RCC - nose cap has lessened, thanks to high-resolution imagery shot by the shuttle astronauts today as part of a so-called focused inspection. Whatever the white, circular marking is - and it could be a bird dropping - it is not thought to be a potentially dangerous puncture caused by the impact of high-velocity space debris.

"That really got our attention and that was the number one priority of the focused inspection," said Steve Poulos, manager of the orbiter projects office at the Johnson Space Center. But after looking at today's photos, it would appear "that's not the case."

"It's a white horseshoe-looking artefact," he said later. "I'll let you use your imagination on what it might be."

The shuttle's nose cap and RCC wing leading edge panels experience the most extreme heating during re-entry and any punctures or cracks would be cause for serious concern. Discovery's nose cap, at least, appears to be sound, although it remains officially classified as an open issue.

Likewise, engineers are still examining two RCC panels on Discovery's right wing - RCC panels 5R and 9R - that show apparent discoloration or other unexpected markings. Engineers are hopeful analysis of data from earlier laser scans and high-resolution imagery shot by the crew today will show no cracks or other serious defects exist. But given the high stakes involved, the RCC community is taking a thorough look at both panels.

Data from sensors behind Discovery's wing leading edge panels indicate six potential impacts, three on each wing, during the climb to space Tuesday, the most significant peaking at 1.6 times the force of Earth's gravity. During ground tests, however, impacts of 10 Gs or more were required to cause the kind of damage that might preclude a safe re-entry.

"But what this does do then is require our inspection team for the wing leading edge to spend more time and energy looking at these particular panels, these regions where we've identified potential impacts," Poulos said.

Engineers now believe what appeared to be a protruding gap filler just behind Discovery's nose cap is more likely a bit of cloth batting-like material extending slightly above the surrounding tile. As such, it would not appear to be a problem for re-entry. Likewise, a gap filler seen extending between tiles near left wing RCC panel 17 has been ruled acceptable as is for entry.

But a protruding gap filler sticking up about an inch just in front of a propellant feedline access door on the belly of the ship could cause heating problems during entry if it is not removed. Such protrusions in the otherwise smooth flow of air over the shuttle's belly can trigger turbulence in the so-called "boundary layer" that provides an insulating effect. If the boundary layer breaks down and transitions from laminar to turbulent flow at high velocities, higher downstream temperatures result, along with possible damage to the shuttle.

Along with analyzing the aerodynamic effects of the gap filler in question, engineers also must calculate the structural effects of downstream heating, a complex process that likely will take another day or two to complete. Poulos said the proximity of the access door was not an issue and the primary issue is damage that might have to be repaired after landing.

"We really have to go off and understand the load paths and the reduction in margins because it is going to be a little warmer than we would plan for," he said.

Astronaut Steve Robinson removed two protruding gap fillers during Discovery's last flight, plucking them from adjacent tiles with his gloved fingers. But reaching the gap filler in question on this flight would be more difficult and likely would require an astronaut to ride on the end of a long inspection boom carried by the shuttle's robot arm.

As coincidence would have it, Sellers and Fossum plan to test the arm-boom combination Saturday to evaluate its strength and usefulness as a work platform for future repair work. If those tests go smoothly, NASA could opt to use the boom to remove the offending gap filler during the crew's third planned spacewalk next Wednesday.

As of this writing, however, no such decisions have been made.

In other developments, Shannon said a large 12-by-14-inch sheet of foam that peeled away from Discovery's external tank in about a half-dozen pieces two minutes and 50 seconds after takeoff likely weighed just .11 pounds, or .18 ounces. Engineers believe foam debris must weigh .25 pounds - four ounces - or more to pose a serious impact threat and in any case, no tile damage has been seen in the area.

Shannon also said engineers have recovered Discovery's twin booster rockets and hope to deliver film from on-board cameras by Sunday. Those new views may show previously seen foam releases from different angles and help engineers improve their understanding of the timing of such events.

Finally, Shannon said part of the launch pad hydrogen ignitor system, used to burn away excess hydrogen gas just before main engine start, broke off, shot out and hit the nozzle of main engine No. 1 prior to Discovery's launch. Analysis of data from the engine, however, showed the powerplant worked normally throughout the ascent.


03:40 p.m., 07/07/06, Update: Mission extension virtual certainty

With a one-day mission extension considered a done deal, the Discovery astronauts are using a high-resolution camera to inspect a half-dozen areas of the shuttle's heat shield for signs of damage during launch Tuesday. Engineers at the Johnson Space Center, meanwhile, are starting to think about whether the astronauts might need to remove one or two protruding gap fillers during a third spacewalk expected to be added to the mission now that engineers know Discovery will have enough power to support the extra day in orbit.

Lead flight director Tony Ceccacci said NASA's Mission Management Team, which has the final say in such matters, likely will complete its analysis of Discovery's heat shield Saturday, after evaluating high-resolution photographs taken today by a camera on the end of a long boom attached to the shuttle's robot arm. "The smallest damage of concern that we have is on the order of .08, eighty thousands of an inch, and that camera is certified to be able to show us that level of damage," Steve Poulos, manager of the space shuttle projects office at the Johnson Space Center, said before launch.

Lisa Nowak, Stephanie Wilson and pilot Mark Kelly are inspecting six regions of interest on the shuttle based on imagery collected during launch and the day after. One site is on the shuttle's reinforced carbon carbon nose cap, three are on two RCC panels on the ship's right wing leading edge and two involve protruding gap fillers, one up near the nose of the shuttle and the other back near a propellant feedline access door.

"There's a team working on the possibility of them having to remove the gap fillers or cutting the gap fillers in the two locations I mentioned previously," Ceccacci said. "We're just getting prepared. That way, if we have to do something we're ready to go. If we did have to do that, most likely it will be on EVA 3 (the third spacewalk)."

That excursion by spacewalkers Piers Sellers and Mike Fossum is planned for next Wednesday. By coincidence, the primary goal of the outing is to test leading edge repair techniques.

Sellers and Fossum plan to stage their first spacewalk Saturday, evaluating whether the long inspection boom on the end of the shuttle's robot arm can be used to support astronauts if heat shield or other repairs are ever needed. A second spacewalk is on tap Monday to repair a stalled transporter that is needed to move the station's arm from point to point along a huge solar array truss. Of the three spacewalks, the second is most critical because station assembly cannot proceed until the transporter is repaired.

"After we get the focused inspection data today and get all the pictures down, the imagery folks will take a look at it and I'm sure by sometime this evening, maybe eight hours or so, they'll have enough information to determine if they're concerned about those gap fillers. ... Probably tomorrow for sure, at the MMT, they'll have the final decision."

Astronaut Steve Robinson removed two gap fillers during Discovery's flight last summer, riding on the end of the space station's robot arm to gain access to the shuttle's underside. Sellers or Fossum could ride the station arm to reach a protruding gap filler near Discovery's nose, if engineers decide it must be removed. But the shuttle arm and inspection boom likely would be required if the gap filler near the feedline access door toward the back of the orbiter is deemed a threat.

"The one over by the ET door, we'd have to get on the boom to do that," Ceccacci said. But engineers believe gap fillers that far back on the belly are not a much of a threat as protrusions near the nose.


11:30 a.m., 07/07/06, Update: Focused inspections and gap filler 101

The Discovery astronauts have successfully installed the 10-ton Leonardo cargo module on the international space station. Pilot Mark Kelly, Lisa Nowak and Stephanie Wilson are gearing up carry out so-called focused inspections of Discovery's heat shield to double check several areas of interest that were noticed during earlier inspections.

One area of concern involves three gap fillers seen protruding above the surface of surrounding heat-shield tiles on the shuttle's belly. One is toward the edge of the shuttle's left wing, another is near a propellant feedline access door and the third (assuming it actually is a gap filler) is located just behind Discovery's reinforced carbon carbon nose cap.

Gap fillers are thin, ceramic cloth spacers used to smooth the flow of air across the gaps between tiles and to prevent adjacent tiles from rubbing against each other too much during the vibration and stress of launch. The gap fillers are bonded in place, pull tested before launch and their upper surfaces are flush with the surrounding tiles.

Gap fillers occaionally shake loose and extend up into the airflow during re-entry and disrupt the smooth, laminar flow of supersonic air across the belly of the shuttle. Known as "tripping the boundary layer," this phenomenon can create eddies of turbulence that, in turn, result in higher downstream heating.

Boundary layer transitions occur normally when the shuttle's velocity has dropped to around eight to 10 times the speed of sound, starting toward the back of the heat shield and moving forward. But a protruding gap filler in a 1995 shuttle mission tripped the boundary layer at Mach 18, causing significant tile damage during entry.

An early boundary layer transition also can overheat the reinforced carbon carbon panels on the shuttle wing leading edges. Yet another concern is an asymmetric boundary layer transition, changing the aerodynamics and causing the shuttle's flight computers to compensate by firing rocket thruysters or adjusting the ship's elevons.

During Discovery's flight last summer, NASA managers decided to have astronaut Steve Robinson remove two protruding gap fillers during an already planned spacewalk. The removals went smoothly, but NASA engineers decided to change the way gap fillers are attached before launching Discovery on its current mission.

Steve Poulos, manager of the orbiter projects office at the Johnson Space Center, said before launch more than 5,000 gap fillers were replaced. To make sure they were firmly bonded in place, an eight-ounce pull test was replaced with a five-pound test.

NASA did not have time to replace all 16,000 of Discovery's gap fillers. Instead, engineers prioritized the shuttle's underbelly into zones of relative danger, removing and replacing gap fillers in the most critical areas. In general, the most critical zones are toward the front of the shuttle's belly.

"That was a very good effort in a short amount of time to identify the root cause of the problem," Poulos said. "The amount of work done by the technicians, inspectors and engineers at Kennedy to get the 5,000 removed and replaced was just basically awesome."

There were two fundamental concerns: gap fillers that could pull loose and pose an impact threat to the orbiter's heat shield; and gap fillers that could trip the boundary layer and threaten the RCC wing leading edge panels or downstream tiles.

"Priority one is the area that ended up being a concern from a thermal boundary layer transition perspective for the reinforced cabon carbon panels," Poulos said. "That's actually what caused us to make the final decision to remove and replace gap fillers on (Discovery's last flight). Because they were so forward on the vehicle, up close to the nose, the boundary layer trip was actually going to cause an over heating for the RCC panels themselves. By r-and-r'ing all those in (the nose region), we have mitigated that risk in totality. There is no opportunity now for a boundary layer trip to impinge on any of the reinforced carbon carbon."

It is not yet known whether the presumed protruding gap filler seen just behind Discovery's nose cap Thursday extends far enough above the surrounding tiles to represent a boundary layer threat.

"Then as we looked at it a little further," Poulos said in his pre-flight briefing, "we realized from our debris transport work there was a potential for some gap fillers to liberate and potentially impact the RCC, RCC being less compliant from an impact perspective than our tile. So we generated a priority 2A zone. We have removed and replaced all of those gap fillers as well.

"So on the bottom of the vehicle, our real focus was to mitigate the thermal concern for RCC, mitigate the impact concern for RCC. The residual or remaining items, priority 2B and 3 - the risk associated with liberation and impact relative to the tile - is a very small risk.

"From a boundary layer transition perspective, we have done a significant amount of analysis and in most instances at Mach 21 (21 times the speed of sound) or less, in terms of our prediction for boundary layer transition, we will be able to clear the vehicle. If we have a gap filler that is extended above the outer mold line to a significant extent ... then we might have to consider doing something about that. But at the end of the day, we have the analytical tools in place to go off and assess if ... it is a concern or not."


07:00 a.m., 07/07/06, Update: Cargo module installation; inspections planned for 'areas of interest'

Astronauts aboard the international space station, operating the lab's Canadian-built robot arm, gently plucked a 10-ton cargo module from the shuttle Discovery's payload bay today for attachment to the international space station.

The multi-purpose logistics module, or MPLM, will be robotically bolted to the Unity module's downward-facing, or nadir, port. Known as Leonardo, the Italian-built cargo module is loaded with about 5,100 pounds of supplies and equipment, including a high-tech laboratory freezer, a European plant biology experiment rack and a U.S.-built oxygen generator that ultimately will help support a crew of six.

The mating procedure was interrupted briefly when the astronauts reported what appeared to be foreign object debris, or FOD, near critical seals where the modules lock together, but flight controllers said it posed no threat and the crew was told to continue the mating operation.

After the module is safely in place, shuttle commander Steve Lindsey and European Space Agency astronaut Thomas Reiter will begin the work to activate and open Leonardo while pilot Mark Kelly, Lisa Nowak and Stephanie Wilson begin work with the shuttle's robot arm to carry out additional inspections of the shuttle's heat shield.

NASA's Mission Management Team has identified five so-called "areas of interest" for focused inspections to double-check potential damage sites seen during earlier surveys:

In the morning "execute package" uplinked to the astronauts, the Mission Management Team reported that a small left-pointing steering jet known as L5L had dropped below the minimum temperature needed for safe operation. The jet experienced a heater problem during Discovery's countdown and while it was warm enough to use during Thursday's rendezvous and docking with the space station, it is now disabled. The station's four big control moment gyroscopes normally control the attitude, or orientation, of the mated station/shuttle spacecraft, but for larger movements needed for shuttle water dumps Saturday and next Tuesday, flight controllers may use Discovery's larger primary jets. The station's thrusters also can be used if necessary.

The Mission Management Team also reviewed the status of a balky flash evaporator, used during launch and re-entry to provide cooling to the shuttle's electronics, that acted up during ascent July 4. The shuttle has two such systems but they are critical and engineers are working up a post-undocking troubleshooting plan to collect additional insight into the operation of flash evaporator system B.

Otherwise, the MMT had little to report.

"The MMT reviewed the pad debris environment and vehicle performance during ascent. Pad B is in very good shape after a slight sand blasting by the SRBs (solid rocket boosters). No vehicle flight hardware has been found and the Pad environment was considered to be very nominal based on previous flight experience. Additionally, the preliminary ascent data shows that powered flight and post MECO (main engine cutoff) were very nominal with no issues. The ET umbilical photography also showed that the tank performed very well and a summary of those pictures will be provided later in the mission for your review."

Review of wing leading edge laser scans Wednesday is nearly complete and initial analysis of photographs of the shuttle's belly during an end-over-end flip during final approach to the station "indicates that the tile is in good shape with very little damage," the MMT reported. A more extensive discussion of that photography will take place later today.

Here is the updated timeline for today's activities (in EDT and mission elapsed time):


07/07/06

03:08 AM	02	12	30	STS crew wakeup (flight day 4)
03:38 AM	02	13	00	ISS crew wakeup
05:18 AM	02	14	40	Station robot arm (SSRMS) grapples cargo module
05:48 AM	02	15	10	Cargo module (MPLM) unberthing
06:43 AM	02	16	05	MPLM installation
07:48 AM	02	17	10	MPLM bolt torquing; crew meals begin
08:28 AM	02	17	50	Astronaut interviews (audio only; includes CBS Radio)
08:58 AM	02	18	20	SSRMS ungrapples MPLM
09:13 AM	02	18	35	SSRMS grapples MBS
09:53 AM	02	19	15	MPLM vestibule pressurization
09:58 AM	02	19	20	SSRMS ungrapples lab
10:13 AM	02	19	35	Spacesuit transfer and reconfig
10:28 AM	02	19	50	SSRMS moves to survey support position
10:48 AM	02	20	10	OBSS heat shield focused inspection survey
12:08 PM	02	21	30	MPLM activation (part 1)
01:00 PM	02	22	22	Mission status briefing on NASA TV
01:28 PM	02	22	50	SSRMS grapples lab
01:38 PM	02	23	00	MPLM vestibule ingress
02:23 PM	02	23	45	MPLM ingress
03:38 PM	03	01	00	EVA-1: Procedures review
04:33 PM	03	01	55	Astronaut interviews on NASA TV (includes CBS News)
05:00 PM	03	22	22	Post-MMT briefing
07:08 PM	03	04	30	STS/ISS crew sleep begins
08:00 PM	03	05	22	Daily video highlights reel on NASA TV
Getting Leonardo attached and unloaded is a major objective of Discovery's mission. Just as important, the cargo module will be used to bring down no-longer-needed equipment and trash.

"We're re-supplying them with some rack experiments, a lot of food, clothing, things like that, hardware replacements - there's a whole laundry list of things that we're supplying to the space station," Lindsey said in a NASA interview. "The other purpose, of course, of the MPLM is to bring things down. And so, we're going to bring back a whole bunch of stuff that they don't need anymore. That includes experiment samples, used articles they're not using anymore, and trash - you name it.

"One of the issues with space station since we've lost Columbia is we've been putting things on board, but we haven't been able to get very many things off. So, one of the goals will be to help them with their stowage issues and logistics issues by bringing a bunch of things off the space station as well."

Once Leonardo has been robotically bolted in place, the astronauts will perform leak checks to make sure the MPLM is firmly mated to Unity and pressurize the vestibule between Unity and the supply module. Then they'll open the module, float inside and begin the process of moving supplies into the space station.


07:30 p.m., 07/06/06, Update: No signs of appreciable damage on shuttle Discovery; analysis continues

Preliminary assessment of the shuttle Discovery's heat shield after a dramatic end-over-end flip today while approaching the international space station shows no signs of appreciable damage to the ship's fragile heat shield tiles from debris impacts during launch, officials said.

John Shannon, chairman of NASA's Mission Management Team, said a full assessment of the 352 photographs taken by station commander Pavel Vinogradov and flight engineer Jeff Williams would take another day to complete.

But the initial assessment of laser surveys of the wing leading edges and nose cap carried out Wednesday, and a quick-look at the heat-shield tiles today, showed no signs of any significant problems.

"Tomorrow will be the full story," Shannon said. "But the quick-look of the wing leading edge we looked at with the laser system yesterday showed there were no issues with the wing leading edge itself and we do not expect to do any focused inspections on that.

"The early look at the tile from the rotational pitch maneuver ... showed there were no tile areas that exceeded our criteria to go look at with a focused inspection."

He said the heat shield appeared in such good shape it was "somewhat of a surprise, but a very pleasant surprise."

Engineers planned to work through the night, analyzing the imagery in detail, to identify possible areas to examine Friday morning during so-called focused inspections. A four-hour block of time is built into the crew's flight plan to use a long boom equipped with a high-resolution camera to inspect anything out of the ordinary.

At least two gap fillers have been seen protruding from surrounding tiles. Gap fillers are heat resistant spacers used to prevent adjacent tiles from rubbing against each other when the shuttle's aluminum skin flexes during launch. One of those is toward the outboard edge of the left wing while the other is just in front of a propellant feedline access door near the back of the orbiter.

During Discovery's flight last year, a spacewalking astronaut was asked to pluck out two protruding gap fillers to ensure smooth aerodynamic flow over the shuttle's belly during entry. Material protruding above the tiles can trigger turbulent airflow, which generates more heat.

Shannon said engineers have not yet decided what, if anything, might need to be done about the two gap fillers seen so far in the current mission, or what to do about a very small bit of unidentified material just behind the nose cap of the shuttle.

But overall, he said, Discovery is "a really clean vehicle, we're extremely happy with the performance of all the systems that we've looked at so far."

Shannon down played any concern about a large piece of foam insulation that peeled away from an area just in front of an ice-frost ramp on Discovery's external tank. During a briefing Wednesday, Shannon said the piece measured roughly eight by 10 inches. Today, he said additional analysis showed the missing foam measured 12.3 inches by 14.2 inches.

Engineers say the foam broke apart into a half-dozen pieces as it peeled away. And it came off after Discovery was out of the thicker regions of the atmosphere. For foam to pose a threat to the shuttle, it most separate in the lower atmosphere, which causes the lightweight material to rapidly decelerate. The shuttle can then ram into it at a high relative velocity.

Shannon said even if the foam in question came off earlier in Discovery's climb to space it would not have caused any problems.

"They're still working on the mass," he said. "The prediction was between a half inch and an inch thick, which makes it very light, very small. The initial report from the external tank project was we did not violate any limits we had set pre flight."

He said engineers expected to calculate actual mass estimates over the next two days.

"My initial thought, and what the ET project was thinking, was even if it had come off in the time of aerodynamic concern before 135 seconds, it still would not have been an issue," Shannon said. "It was absolutely not a surprise at all to see that. That is consistent with the behavior we've seen from the ice-frost ramp area in the past."


01:20 p.m., 07/06/06, Update: Shuttle Discovery docks with space station; lab crew welcomes shuttle colleagues aboard

With commander Steve Lindsey at the controls, the shuttle Discovery glided to a smooth, picture-perfect docking with the international space station today as the two spacecraft sailed 220 miles above the South Pacific Ocean.

During final approach, Lindsey flew the shuttle through a spectacular 360-degree pitch-around maneuver as the spaceplane sailed above the Rock of Gibraltar and then central Europe at five miles per second, exposing the ship's fragile heat shield to cameras operated by station commander Pavel Vinogradov and flight engineer Jeff Williams.

As the belly rotated into view, no obvious signs of damage were seen in downlinked television views, but flight controllers won't know for sure until studying much-higher-resolution digital images shot by the station crew. All of the images were downlinked to mission control within two hours or so of docking.

At least two bits of debris appeared to hit the shuttle during launch Tuesday, but mission managers said neither occurred in the aerodynamic environment required to cause significant damage. The station photos may confirm that and spot any protruding gap fillers that might have shaken loose during ascent.

Gap fillers are heat-resistant spacers between tiles that prevent abrasive contact when the shuttle's skin flexes and vibrates. One gap filler was seen earlier, sticking up about a half inch near the back of the left wing. During Discovery's flight last July, two protruding gap fillers had to be removed by astronaut Stephen Robinson during an already-planned spacewalk. The gap filler spotted earlier in the current mission is in a more aerodynamically benign position and may not need any similar attention.

Docking occurred at 10:52 a.m. when Discovery's payload bay docking module engaged its counterpart on the front end of the Destiny laboratory module.

"Docking confirmed," a Discovery astronaut radioed.

"Discovery, Houston. Station free drift is confirmed," mission control replied.

Vinogradov and Williams shook hands and smiled broadly for cameras in the lab module as Discovery settled into port. After leak checks, a final hatch leading into the Destiny module was opened at 12:30 p.m. and Vinogradov and Williams welcomed the shuttle astronauts on board with hugs, smiles and handshakes.

European Space Agency astronaut Thomas Reiter seemed especially pleased, floating in front of a camera, grinning broadly and flashing an enthusiastic thumbs up to flight controllers on Earth. Reiter will remain aboard the station when Discovery departs, boosting the lab's crew size back to three for the first time since downsizing after the Columbia accident.

"Everybody's having fun, I don't see a sad person in the crowd," joked Williams.

He and Vinogradov then gave the shuttle visitors a safety briefing before the combined crews got down to work, starting the long process of transferring supplies and equipment from the shuttle to the station.

Jim Voss, who spent 163 days aboard the station in 2001 as a member of the lab's second full-time crew, said Discovery's arrival provided an emotional lift for Vinogradov and Williams, who were launched to the outpost in late March.

"It's greatly anticipated when a new crew's coming up on board," Voss said in an interview with CBS News. "The station crew hasn't seen anyone for several months and just seeing another face in person is just a wonderful thing.

"So you spend several days getting psyched up for them coming on board. And when they get there, you see on television there's a lot of hugging and smiling. Well, that's very genuine, you're really happy to see those people come up there. It's not only that you're seeing old friends, but they're bringing up a lot of supplies and other things you need to continue your work on the space station."

Voss said Reiter is an especially welcome addition to the crew.

"It's really special having them bring up a third crew member," he said. "They've been just the two of them on board, Pavel and Jeff, and there is a real difference when you have another person you can chat with. And Thomas is a particularly good person to come up because he is fluent in Russian and English. So he'll be able to speak with both the other crew members fluently and he'll really add to that social dynamic that they have on board."

The German astronaut, on board as part of a commercial contract between ESA and the Russian space agency Roscomos, also will add to the crew's productivity.

"They should be able to do a lot more science instead of just maintenance of the station and personal things you have to do to live in spade," Voss said. "So this is getting us back to where we were before and let us anticipate expanding the crew to even larger, to six or maybe even seven people in the future."

NASA hopes to do just that in 2009.


07:15 a.m., 07/06/06, Update: Discovery closing in on space station; Mission Management Team update on debris incidents; updated timeline

The shuttle Discovery is closing in on the international space station today for a long-awaited linkup that will boost the lab's crew size to three, provide more than 5,000 pounds of equipment and supplies and give mission managers their first detailed view of the fragile heat shield tiles on the shuttle's belly.

"Good morning, Discovery!" mission control told the crew in a morning uplink package. "Great day yesterday, finishing flight day 2 early, thatÕs amazing. As for today, just a rendezvous. However, you will be losing a crewmember at the end of the day, but then again, youÕre gaining a Station."

European Space Agency astronaut Thomas Reiter will remain aboard the station when Discovery departs, boosting the lab's crew size to three for the first time since downsizing in the wake of the Columbia disaster.

But first, shuttle commander Steve Lindsey has to get him there. Lindsey will follow a standard rendezvous profile, approaching the lab complex from behind and below. The terminal phase of the rendezvous procedure begins around 8:05 a.m. with the shuttle trailing the station by about 9.2 miles.

On final approach, at a distance of about 600 feet directly below the station, with Discovery's nose facing forward and its open payload bay facing the station, Lindsey will carry out a slow 360-degree rendezvous pitch maneuver, or RPM, that will point the belly of the shuttle at the station. The maneuver is expected to begin around 9:51 a.m.

As the shuttle's underside rotates into view, Expedition 13 commander Pavel Vinogradov and flight engineer Jeff Williams will photograph Discovery's belly with handheld digital cameras equipped with 400mm and 800mm lenses. The 800mm lens provides one-inch resolution to look for signs of even small damage around sensitive areas like the shuttle's landing gear doors. The 400mm lens provides three-inch resolution.

Imagery from the station will be downlinked to Houston for detailed analysis.

In the morning "execute package" uplinked to the shuttle crew, flight controllers passed on a detailed update from NASA's Mission Management Team on what engineers have seen so far assessing video, radar data, still images and data from wing leading edge impact sensors during launch Tuesday:

Wing Leading Edge Sensors - All the WLEIDS data has been downlinked and the preliminary assessment is that the system detected 6 probable impacts during ascent (tripped the .87 Grms sensor limit). Three of these were on the port wing and three were on the starboard wing. This is very similar to the number of probable impacts that were observed on STS-114 (Editor's note: Discovery's last mission) and there may be some correlation between the two missions.

Imagery - The teams continue to review the ascent imagery data (ET LOX feedline camera, 2 ground cameras, WAVE aircraft video, and debris radar). The preliminary characterization is the debris environment was substantially less than that observed for STS-114 (Editor's note: Discovery's last flight). These reports show two events that may have impacted the Orbiter. The first event was at approximately 19 seconds and the other was at about 285-294 seconds. Both of these are outside the critical debris region of concern that spans from 35 seconds to 140 seconds. Exact size and velocity estimates are still being refined.

The 19 second event that was observed to be a single piece of debris traveling between ET (Editor's note: External Tank) and Orbiter fuselage which could indicate an impact although the image quality is poor. For the 285-294 second event, multiple (5-12) pieces of ET debris were observed and one piece possibly impacted the Orbiter. The debris originated from aft of bipod on -Y side of LO2 feedline, traveled toward the Orbiter fuselage, changed direction abruptly, and then fell aft breaking into several pieces after possible contact with Orbiter. Early prediction are a 33 feet/sec average velocity with a maximum velocity of 67 feet/sec. The ascent camera views have not detected any visible signs of TPS (Editor's note: Thermal Protection System) damage as a result of these events.

The LDRI (Editor's note: Laser Dynamic Range Imager) FD2 imagery shows a protruding gap filler on the port side near outer edge of wing. It is located in an area where GAP fillers were not replaced with a tile thickness of 2.6 inches. Initial measurements estimate the protruding GAP filler to be about 1/2 inch. The aeroheating community is analyzing this to determine if any future action is required to remove. Additionally, all of the Tyvek covers on the FRCS thrusters were reported to have come off within about 8 seconds MET, which meets the velocity requirements for all of these covers. Finally, the imagery experts reviewed the ET handheld photography and confirmed the MCC assessment of ice being the unusual item reported by Mike Fossum. Ice was also observed in the STS-114 handheld photography and this has been observed on other missions as well.

Of course weÕll have a better assessment of the TPS (wing leading edge RCC and tile) after tomorrowÕs FD 3 MMT when the FD2 inspection data.

After completing the RPM maneuver, Lindsey will position Discovery about 400 feet directly ahead of the space station with the shuttle's nose facing deep space and its cargo bay facing the lab complex. He then will guide the spacecraft to a docking with a pressurized mating adaptor attached to the Destiny laboratory module. Docking is expected around 10:52 a.m.

After leak checks, Vinogradov and Williams will welcome the shuttle crew aboard the station and provide a safety briefing before all nine astronauts get down to work.

One of the first items on the agenda is to transfer a Soyuz seat liner from Discovery to the station and to check out Reiter's re-entry pressure suit. Once those tasks are accomplished, about four hours after docking, the European astronaut will become an official member of the Expedition 13 crew. He is scheduled to remain aboard the outpost until late December, returning to Earth with the crew of the year's third shuttle mission.

While Reiter's equipment is being transferred, Wilson and Nowak will use the station and shuttle robot arms to redeploy the OBSS boom for additional inspection work and photo support of the upcoming spacewalks. Because of clearance issues after the shuttle is docked, Discovery's robot arm cannot unberth the OBSS on its own. Instead, the space station's arm - the SSRMS - will pluck the sensor boom from the shuttle's cargo bay and hand it off to Discovery's arm about five hours after docking.

The astronauts also will begin moving station equipment stowed in the shuttle's middeck area over to the space station, along with tools that will be used in the upcoming spacewalks.

Here is the Flight Day 3 timeline, including a detailed rendezvous timeline:

TIME		DD	HH	MM	EVENT

03:38 AM	01	13	00	STS crew wakeup
03:38 AM	01	13	00	ISS crew wakeup
04:53 AM	01	14	15	Group B computer powerup
05:13 AM	01	14	35	Rendezvous timeline begins
06:34 AM	01	15	56	NC4 rendezvos rocket firing
07:23 AM	01	16	45	RPM photo setup verification
08:05 AM	01	17	27	Terminal phase (TI) rendezvous rocket firing
08:43 AM	01	18	05	Sunset
09:03 AM	01	18	25	Range: 10,000 feet
09:12 AM	01	18	34	Range: 5,000 feet
09:18 AM	01	18	40	Range: 3,000 feet
09:20 AM	01	18	42	Sunrise
09:22 AM	01	18	44	MC-4 rendezvous burn
09:26 AM	01	18	48	Range: 1,500 feet
09:31 AM	01	18	53	Range: 1,000 feet
09:34 AM	01	18	56	KU antenna to low power
09:35 AM	01	18	57	+R bar arrival 725 feet directly below ISS
09:40 AM	01	19	02	Range: 600 feet
09:47 AM	01	19	09	Noon
09:51 AM	01	19	13	RPM start window open
09:51 AM	01	19	13	Start pitch maneuver
09:55 AM	01	19	17	RPM full window close
09:59 AM	01	19	21	End pitch maneuver
10:02 AM	01	19	24	Initiate TORVA pitch up maneuver to +V bar
10:04 AM	01	19	26	RPM start window close
10:13 AM	01	19	35	+V bar arrival; range: 310 feet in front of ISS
10:14 AM	01	19	36	Range: 300 feet
10:15 AM	01	19	37	Sunset
10:18 AM	01	19	40	Range: 250 feet
10:22 AM	01	19	44	Range: 200 feet
10:25 AM	01	19	47	Range: 170 feet
10:27 AM	01	19	49	Range: 150 feet
10:31 AM	01	19	53	Range: 100 feet
10:34 AM	01	19	56	Range: 75 feet
10:38 AM	01	20	00	Range: 50 feet
10:41 AM	01	20	03	Range: 30 feet; start stationkeeping
10:46 AM	01	20	08	End stationkeeping; push to dock
10:51 AM	01	20	13	Sunrise
10:51 AM	01	20	13	Range: 10 feet
10:52 AM	01	20	14	DOCKING
11:13 AM	01	20	35	Leak checks
11:43 AM	01	21	05	Group B computer powerdown
11:43 AM	01	21	05	Orbiter docking system preps for ingress
12:13 PM	01	21	35	Hatches open; welcome aboard!
01:03 PM	01	22	25	Safety briefing
01:28 PM	01	22	50	Russian seat liner installation
01:48 PM	01	23	10	OBSS grapple by space station arm (SSRMS)
02:13 PM	01	23	35	OBSS unberthing
02:43 PM	02	00	05	SSRMS moves to OBSS handoff position
02:43 PM	02	00	05	ROOBA leak check
03:28 PM	02	00	50	Reiter officially joins ISS crew
03:53 PM	02	01	15	OBSS handoff to shuttle arm (SRMS) from SSRMS
04:23 PM	02	01	45	Spacewalk tools transfer
04:23 PM	02	01	45	SRMS moves to logistis module inspection point
07:08 PM	02	04	30	Crew sleep begins


09:20 p.m., 07/05/06, Update: Shuttle external tank performed well; recent fixes appear sound; no obvious signs of damage to shuttle

After a full day of image analysis and inspections, NASA engineers are increasingly optimistic that major changes to the foam insulation on the shuttle Discovery's external fuel tank worked as required to minimize the release of potentially catastrophic debris during the ship's Fourth of July climb to space.

If they're right, and if preliminary indications are confirmed during continued observations and around-the-clock analysis, NASA will move a major step closer to putting its painful post-Columbia return-to-flight effort behind it, shifting the focus instead to resuming assembly of the international space station.

"We have in hand all the data we're going to get from the external tank and the performance was very good," said John Shannon, chairman of NASA's Mission Management Team. "And we got some good data, too, which was really important. We really want to be able to verify what kind of redesigns we were doing."

Shannon said the most significant change made to the external tank since Discovery last flew a year ago - removal of a long foam wind deflector - worked well. Known as a protuberance air-load - PAL - ramp, the wind deflector was in place to smooth the flow of turbulent air over two pressurization lines and a cable tray during the shuttle's climb out of the dense lower atmosphere.

During Discovery's launching last year, a one-pound chunk of foam broke away from the tank's hydrogen PAL ramp and while it didn't hit the orbiter, it was a major surprise and source of concern. Much of the 11 months preparing Discovery for its current mission was focused on proving the PAL ramps could be safely removed and that the pressurization lines and cable tray could, in fact, stand up to the aerodynamic rigors of launch on their own.

Computer modeling and wind tunnel tests convinced agency managers the ramps were not needed and Discovery's launching Tuesday appeared to verify those conclusions. While a final answer will depend on analysis of data captured by sensors mounted in the cable tray - work that is not yet done - Shannon was clearly optimistic.

"The only thing we have to do is go make sure all the aerodynamic modeling that we did is corroborated by the sensors that we flew on this flight," he said. "This was one data point and it was a really good data point, but we want to make sure we are not on the edge of anything. We don't think we are, but we need to go make sure."

During Discovery's launch last year, foam debris also broke away from an area where two struts attach the nose of the shuttle to the tank. Engineers came up with a fix and it, too, appeared to work. Photographs of the tank after it was jettisoned in space showed no foam losses in the area.

Even the ice-frost ramps on the tank appeared to work well. The ice-frost ramps, hand-sculpted foam insulation applied to 34 brackets holding the cable tray and pressurization lines in place, generated controversy before launch when two top NASA managers voted to delay the flight until they could be redesigned. The insulation in question was officially deemed an unacceptable risk, in large part because engineers lacked a solid understanding of foam failure mechanisms.

Shannon said the IFRs on Discovery's tank performed well, with only minimal foam shedding in one ramp extension that was added after the PAL ramps were removed.

Just in front of one ice-frost ramp, however, an eight-by-10-inch sheet of foam apparently peeled away in a half-dozen pieces about two minutes and 50 seconds after launch. The debris posed no impact threat to Discovery because the releases happened after the shuttle was beyond the aerodynamic danger zone.

"It's all about the mass," Shannon said. "If it was a very thin sheet, which is what we think it was, then it won't have enough kinetic energy to damage the vehicle. And this one came off in a time when aerodynamically, we don't have a concern."

Engineers have long suspected that changes in the tank's temperature as supercold propellants are drained by the shuttle's main engines plays a role in foam failure, especially in areas where foam is applied on top of other foam.

Shannon said the location of the missing sheet may help engineers verify that theory or at least gain insights into how the changing thermal environment of the tank plays a role in foam loss as propellant levels change.

"The important part is to understand the physics of why it's coming off," he said. "I think that liquid level is going to make a big difference."

Shannon cautioned that analysis of the tank is not yet complete. Engineers have yet to assess recorded cable tray data about the actual "loads" experienced in the absence of the PAL ramps, and they have yet to recover recorded imagery shot by cameras mounted in the shuttle's solid-fuel boosters. But so far, so good.

The next major question mark is the condition of the shuttle and its heat shield. The astronauts spent the day Wednesday using a sophisticated laser sensor to map out every square inch of the reinforced carbon carbon wing leading edge panels and the shuttle's RCC nose cape, which experience the most extreme heating during re-entry. Shannon said a preliminary look at the data showed no major problems. But the analysis is not yet complete.

"Today, I have the tank imagery that we showed you and the performance was really good," he said. "Tomorrow, we'll have our initial assessment of the wing leading edge and nose cap data that the crew took today and we'll have our early assessment of the underside of the vehicle, the tile of the vehicle, when we do the rotational pitch maneuver as we approach station."

Shannon was referring to a 360-degree pitch-around maneuver commander Steve Lindsey will perform when Discovery is 600 feet directly below the space station during the final stages of rendezvous Thursday. As the shuttle's underside rotates into view, station commander Pavel Vinogradov and flight engineer Jeff Williams will use 400mm and 800mm lenses to photograph the heat shield with one- to three-inch resolution.

So far, engineers have only noticed one protruding "gap filler," a heat-resistant spacer between tiles near the rear leading edge of the shuttle left wing. Two protruding gap fillers had to be removed from Discovery's belly last year during an impromptu spacewalk repair job, but the gap filler seen sticking up today is in a benign location and likely will not need removal.

NASA replaced some 5,000 gap fillers in more critical parts of the shuttle's underside and the rendezvous pitch maneuver during final approach to the station Thursday will give engineers a good look at those areas.

Asked if the data, observations and analyses so far indicated NASA had turned the corner in its external tank redesign work, Shannon said "that's the feeling we have right now. But we'll see what we find tomorrow."

Shuttle program manager Wayne Hale, meanwhile, gave engineers permission to press ahead with work to attach the next external tank to a set of boosters at the Kennedy Space Center. Assuming no major surprises with Discovery, NASA hopes to launch the shuttle Atlantis at the end of August on the next space station assembly mission.

The commander of that flight, veteran astronaut Brent Jett, told CBS News today he was encouraged by the preliminary assessment of Discovery and its tank.

"Seeing the successful launch, getting back to space, is great for the country and to have it happen on Independence Day made it really great," said Jett, who would serve as commander of a rescue flight should one be needed. "The vehicle looks pretty clean so far. So now we can focus on getting ready for (the next mission) STS-115 in just a little over a month and a half.

Asked how difficult NASA might find it to pull off such a fast turnaround, Jett agreed "it'll be real tough for the program, we haven't done that in a while."

"We used to turn missions around pretty quick, but I think with the extra scrutiny and the extra analysis we put into each mission now, it's going to be a tough job. They've got the plans in place, they think they can do it. Our FRR (flight readiness review) happens, I think, about two weeks after landing. So it's going to be tight."


04:00 p.m., 07/05/06, Update: Astronauts inspect wing leading edges; gear up for station rendezvous

The Discovery astronauts carried out painstaking, inch-by-inch inspections of the shuttle's carbon composite nose cap and wing leading edge panels today, using a laser sensor on the end of a long boom to look for signs of ascent impact damage. White markings thought to be bird droppings were spotted at one point, and a few other whitish streaks were visible, but no obvious signs of significant damage were seen on downlinked TV.

Along with analyzing the results of today's inspections, engineers also are poring over launch-day photographs and video, assessing data from wing leading edge impact sensors, radar data, footage from a jet equipped with a powerful telescope and imagery captured by the astronauts and by robotic cameras mounted in the belly of the orbiter.

The goal is to assess the integrity of Discovery's heat shield tiles, nose cap and wing leading edge panels to make sure the ship can safely re-enter the atmosphere at the end of the mission.

Some of the most valuable observations are yet to come. Commander Steve Lindsey and his crewmates are slowly catching up with the international space station for a rendezvous and docking Thursday. During final approach, Lindsey will oversee a slow 360-degree pitch-around maneuver 600 feet directly below the lab complex that will expose Discovery's belly to cameras wielded by station commander Pavel Vinogradov and Jeff Williams.

With resolutions between one and three inches, the cameras are expected to spot any significant damage to the shuttle's belly. But again, NASA's Mission Management Team is not expected to reach any final conclusions until after additional post-docking inspections to look at any sites of special interest.

Otherwise, it appears Discovery came through it's ground-shaking launch and climb to space in good condition. One of six small steering jets that suffered a heater failure before launch has been warmed up by exposing it to sunlight and engineers plan to use the thruster during the space station rendezvous.

With no other problems of any significance, the attention Wednesday was on the heat shield inspections, now a standard part of every shuttle flight.

Black-and-white video from today's scans of the wing leading edge panels showed several areas with whitish streaks or other markings but the grainy imagery is difficult to interpret and similar markings were seen during Discovery's last flight.

As for the apparent bird droppings, Ceccacci said he and station flight director Rick LaBrode "saw that out at the pad when we were down there a couple of weeks ago."

"Basically, it's in exactly the same place, RCC (reinforced carbon carbon) panels 18 and 19," Ceccacci said. "This is my speculation, it's bird droppings. That's what it looked like. But we'll let the LDRI (laser dynamic range imager) guys look at that."

Here is a timeline of Thursday's rendezvous with the space station (in EDT and mission elapsed time). The TI rocket firing that begins the terminal phase of the rendezvous will occur with the shuttle trailing the space station by eight nautical miles:

EDT			DD	HH	MM	EVENT

08:05 AM	01	17	27	TI rendezvous rocket firing
08:43 AM	01	18	05	Sunset
09:03 AM	01	18	25	Range: 10,000 feet
09:12 AM	01	18	34	Range: 5,000 feet
09:18 AM	01	18	40	Range: 3,000 feet
09:20 AM	01	18	42	Sunrise
09:22 AM	01	18	44	MC-4 rendezvous burn
09:26 AM	01	18	48	Range: 1,500 feet
09:31 AM	01	18	53	Range: 1,000 feet
09:34 AM	01	18	56	KU antenna to low power
09:35 AM	01	18	57	+R bar arrival 725 feet directly below ISS
09:40 AM	01	19	02	Range: 600 feet
09:47 AM	01	19	09	Noon
09:51 AM	01	19	13	RPM start window open
09:51 AM	01	19	13	Start pitch maneuver
09:55 AM	01	19	17	RPM full window close
09:59 AM	01	19	21	End pitch maneuver
10:02 AM	01	19	24	Initiate TORVA pitch up maneuver to +V bar
10:04 AM	01	19	26	RPM start window close
10:13 AM	01	19	35	+V bar arrival; range: 310 feet in front of ISS
10:14 AM	01	19	36	Range: 300 feet
10:15 AM	01	19	37	Sunset
10:18 AM	01	19	40	Range: 250 feet
10:22 AM	01	19	44	Range: 200 feet
10:25 AM	01	19	47	Range: 170 feet
10:27 AM	01	19	49	Range: 150 feet
10:31 AM	01	19	53	Range: 100 feet
10:34 AM	01	19	56	Range: 75 feet
10:38 AM	01	20	00	Range: 50 feet
10:41 AM	01	20	03	Range: 30 feet; start stationkeeping
10:46 AM	01	20	08	End stationkeeping; push to dock
10:51 AM	01	20	13	Sunrise
10:51 AM	01	20	13	Range: 10 feet
10:52 AM	01	20	14	DOCKING


09:50 p.m., 07/04/06, Update: External tank loses foam, but not in danger zone; Hale pleased with tank performance

The shuttle Discovery's external tank lost only small pieces of foam insulation during launch today, and those were well after the period when aerodynamic effects can lead to dangerous impacts with the orbiter, officials said late today.

But it will take several days to complete a detailed analysis of still photos, videotape, film, radar data and wing leading edge sensor data and to confirm Discovery came through its ground-shaking July Fourth launching in good health. But the preliminary reports were positive.

"I think the tank performed very, very well indeed," Hale told reporters after an initial look at ascent video. "I'm very pleased. As opposed to where we were last year, we saw nothing that gives us any kind of concern about the health of the crew or the vehicle or any pause to think that we wouldn't be safe to fly the next tank."

During Discovery's climb to space, a camera mounted on the external tank looking down across the belly of the orbiter, caught at least five foam shedding incidents between about three minutes and five minutes and 40 seconds into flight.

For foam insulation to cause damage to the shuttle's heat shield, engineers believe it must be released in the dense, lower atmosphere, which causes the lightweight foam to quickly decelerate. The shuttle then can run into it at a high relative velocity, damaging heat shield tiles or critical wing leading edge panels.

During Columbia's ill-fated launch in January 2003, a 1.67-pound chunk of foam broke away from a so-called bipod ramp on the external tank and slammed into a wing leading edge panel at a relative velocity of more than 530 mph, blasting a catastrophic hole in the wing.

During Discovery's launching last July on the first post-Columbia flight, a one-pound piece of foam fell away from a long wind deflector. It missed the shuttle, but had it been released earlier it might have caused serious damage.

NASA ultimately removed the wind deflectors, but left in place so-called ice-frost ramp foam covering 34 brackets that hold external pressurization lines and a cable tray to the tank. That foam is considered high risk, primarily because engineers do not yet have a good understanding of what can cause the foam to break away. They are especially eager to find out how much foam might have been released from Discovery's tank and, just as important, when it was released.

Engineers now believe foam debris poses a serious threat only in the first two minutes and 15 seconds of flight. After that, the shuttle is above the sensible atmosphere and debris released at that point or beyond would not decelerate enough to cause a dangerously high relative velocity impact.

NASA has spent the past three years working to minimize foam shedding and to ensure that any insulation that is released is smaller than the critical threshold of .25 pounds that could cause catastrophic damage. But until now, a major unknown has been the timing of foam releases.

"We put the tank under a microscope this time," Hale said. "We have lots and lots of data coming in, imagery coming in. As you know, we're very concerned about foam coming off the tank. We've worked very hard to eliminate, in so far as possible, the major losses of foam off the tank. The tank performed very well.

"In particular, I'm pleased that it performed well in the time period early in the flight where we're traveling at supersonic speeds in the lower atmosphere."

Discovery's flight, he said, will provide valuable data to engineers struggling to develop a better understanding of the foam and how it behaves during launch.

"Because we have the ET under a microscope, we're looking at every little thing," he said. "And I want you to know it did not perform flawlessly in the sense that we still lost some foam off the tank. And we told you that as going to happen, we knew that was going to happen and the really good news is it happened late. That helps us a tremendous amount.

"Previously, when we were looking at the photographs that were taken at external tank separation (from the shuttle), when we're trying to build these statistical models which go into our risk analysis, we knew that pieces came off the tank but we didn't know when they came off the tank.

"And so, we had to calculate our worst-case probabilities based on those pieces coming off at the worst time. Based on what we saw today, we are losing some pieces off the tank, that's number one. Number two is, with one possible exception we are pretty clear that they are below the allowable masses, or below the mass size that we worry about. And number three, in every case they happen considerably later than the time that we worry about and that is to say pretty near the vacuum of space. So from that standpoint, we got an excellent report on the tank."

In addition, video from the external tank camera showed the pressurization lines and cable tray stood up to the aerodynamic rigors of launch without the protection of the protuberance air-load - PAL - ramp wind deflectors that were removed after Discovery's last flight.

"We saw no vibration or any indication of abnormal loads on the cable tray or the pressurization line protuberances, which as you know were of some interest to us because we did remove the PAL ramp, the wind deflector as it were," Hale said. "So that all performed in an outstanding manner."

The astronauts went to bed around 10 p.m. after preparing still more pictures of the tank for overnight downlink to mission control. Still photos and video shot by cameras in an umbilical cavity in the belly of the shuttle should provide sharp views of the tank as it separated from the shuttle to help engineers map out exactly where foam losses occurred.

"I just wanted to tell you that for both NASA and the entire country, this was a spectacular Fourth of July present for us to have such a beautiful launch," mission control radioed the crew at bed time. "We feel the vehicle is in great shape."


06:25 p.m., 07/04/06, Update: Fossum debris sighting believed to be ice

Debris spotted by astronaut Mike Fossum shortly after the shuttle Discovery reached orbit today appears to be harmless ice, not an insulating blanket as Fossum first speculated, flight controllers confirmed.

In a brief radio message to the crew, mission control reported "the initial assessment here is it does indeed look like ice. We saw a similar event on STS-114 (Discovery's last flight a year ago) but we're going to continue to look at it further and we certainly appreciate you getting that video to us pronto."

"Wow, that's real good news," a Discovery astronaut replied.


06:00 p.m., 07/04/06, Update: Launch debris update; Fossum reports unusual debris sighting

Astronaut Mike Fossum, photographing the shuttle DIscovery's external fuel tank as it tumbled away in space, told flight controllers today that he also noticed what appeared to be a large piece of debris, presumably from the shuttle itself, floating away in space.

Fossum said the debris looked like flexible reuseable surface insulation, blanket-like fabric insulating material that covers the upper surfaces of the shuttle. But Fossum said he was not and engineers in Houston speculated it might have been ice breaking away from the orbiter's main engine nozzles.

Whatever it was, Fossum said he captured the debris on video that will be downlinked to mission control for analysis.

"We saw what really appeared to be some cloth, probably some FRSI or advanced FRSI, that's pure speculation on my part," Fossum radioed. "But it seemed to be stitched-type material, at least four to five feet long, perhaps six to eight. I couldn't really guess at the distance away from us. It was sort of tumbling and twisting, it was kind of a combination of straps and a little bit of squarish material, which is why it really looks a lot like the insulation."

He later estimated the debris, whatever it might have been, was perhaps 40 yards away from Discovery when he spotted it, between the orbiter and the external fuel tank.

Fossum was in the process of photographing the tank to help engineers understand how its foam insulation stood up to the rigors of launch. Astronaut Steve Frick in mission control at the Johnson Space Center in Houston told commander Steve Lindsey that flight controllers saw at least two instances of what appeared to be foam debris breaking away from the tank. But in both cases, the debris separated after the shuttle was out of the thicker, more dangerous regions of the atmosphere.

For foam insulation to pose a threat to the shuttle's heat shield, it must come off in dense enough air to slow down rapidly, allowing the shuttle to ram into it at a high relative velocity. At extreme altitudes, the relative velocity is too low to result in major impact damage.

At about 250 seconds into flight, Frick advised the crew, "they saw some pieces, maybe about five, that came off near the LO2 (liquid oxygen) feedline area. They don't know if they're ice-frost ramps or not. They know that some came near the fuselage, but they didn't see any contact or see any damage. Also, just to note it was about 240,000 feet and the Q (dynamic pressure in pounds per square foot) was all the way down to about one-and-a-half PSF."

"OK, copy that," Lindsey replied.

"The only other item they noticed was noticed later, almost five minutes, about four-forty-five (four minutes and 45 seconds). They saw a piece come off the mid part of the tank, not sure if it's acreage (foam) or close to the feedline, and it did seem to strike the midbody (of the shuttle) somewhere about halfway between the main landing gear and the nose landing gear door.

"We'll, of course, look at it on the (space station approach) photos but the PSF there was about zero, you were way up at 350,000 feet, so that should not be a concern."

Shuttle program manager Wayne Hale plans to brief reporters on the results of quick-look analysis of launch video starting around 7:30 p.m.


03:40 p.m., 07/04/06, Update: Discovery thunders into space; ascent debris seen, nature and impact unclear

The space shuttle Discovery and its flag-waving crew thundered into space today, putting on a spectacular Fourth of July skyshow as it rocketed away on a long-awaited mission to repair and resupply the international space station.

NASA managers warned reporters before launch that small bits of foam insulation would fall from the shuttle's external tank during launch and that they were confident nothing large enough to cause damage would hit the orbiter.

As promised, what appeared to be a half dozen or so small pieces of debris could be seen separating from the tank about two minutes and 47 seconds after liftoff, but it was not immediately clear whether it posed any concern or not. At that point in the ascent, Discovery was out of the thicker regions of the atmosphere, greatly reducing the threat posed by debris.

"What we saw happened after the time we're concerned about debris coming off," said shuttle Program Manager Wayne Hale. "And that is really good news."

After back-to-back delays Saturday and Sunday because of showers and unpredictable clouds, the shuttle's main engines flashed to life and throttled up to full power followed seconds later by ignition of Discovery's twin solid-fuel boosters at 2:37:55 p.m.

Climbing smoothly away from pad 39B atop twin pillars of 5,000-degree flame and a churning cloud of dirty brown exhaust, Discovery majestically wheeled about and arced away on a trajectory up the East Coast of the United States, thrilling thousands of tourists and area residents lining area roads and beaches.

At the controls were commander Steven Lindsey, pilot Mark Kelly and flight engineer Lisa Nowak. Their crewmates are Stephanie Wilson, spacewalkers Piers Sellers and Mike Fossum and European Space Agency astronaut Thomas Reiter.

It was the first manned spaceflight ever launched on the Fourth of July, and the astronauts waved small American flags as they departed crew quarters to head for the launch pad. A few minutes later, they strapped in to await the final moments of the countdown.

"Looks like Discovery is ready, the weather is beautiful, America is ready to return the space shuttle to flight," Launch Director Mike Leinbach radioed Lindsey. "Good luck and godspeed, Discovery."

"Thank you very much, Mike. I can't think of a better place to be on the Fourth of July," Lindsey replied from the flight deck. "Tell all the folks on the Florida east coast that we hope to very soon give you an up close and personal look at the rocket's red glare."

Discovery lived up to Lindsey's promise, climbing skyward and rocketing away, visible for miles around as it roared toward orbit.

"We did not plan to launch on the Fourth of July, but it sure did turn out to be great to launch on Independence Day," Hale said. "Great nations dare great things and take risks along the way and I can think of no better way to explore the spaace frontier than the way we set out today."

A camera mounted on the shuttle's external tank provided spectacular views of the spaceship's heat-shielded underside as Florida's east coast dropped away in the background. The ascent appeared free of foam debris from the tank until about two minutes and 47 seconds when a half-dozen seemingly small pieces of debris could be seen suddengly separating. NASA managers said before launch that foam debris shedding after about 165 seconds was of no concern because by that point, the atmosphere is so thin it cannot carry debris to a dangerous impact. The debris seen today separated around 172 seconds after launch.

"About two minutes and 47 seconds give or take, we saw three, perhaps four pieces come off," Hale said. "Could be an ice-frost ramp, could be something else. We also saw another piece or two come off about four minutes and 50 seconds (after launch). Both of those are interesting because they are after the time that we're concerned about aerodydnamic transport causing damage to the shuttle tiles. That is the very raw preliminary data.

"We are beginning the analysis, we're going to do a thorough engineering analysis. ... These guys have a lot of film to review and it will probably take a couple or three days before we get the whole story together."

The foam insulation on the tank has been a source of concern ever since the 2003 Columbia disaster and, more recently, because of foam on Discovery's tank that was officially deemed a "probable/catastrophic" risk.

Another foam problem cropped up Monday when engineers spotted a small piece of insulation on Discovery's mobile launch platform that broke away from a liquid oxygen feedline bracket after a launch delay Sunday. After a hurried analysis and photographic inspection, however, engineers convinced NASA managers the defect posed no threat to the shuttle or its crew.

Eight-and-a-half minutes after liftoff, Discovery's main engines shut down and the spacecraft coasted into space. Thirty seven minutes after that, the shuttle's twin orbital maneuvering system rockets fired, raising the low point of the orbit and putting Discovery on course to rendezvous with the international space station Thursday.

Discovery is ferrying Reiter to the station to join Expedition 13 commander Pavel Vinogradov and flight engineer Jeff Williams as a full-time crew member. Launched under a commercial contract between the European Space Agency and the Russian space agency Roscosmos, Reiter will boost crew size back to three for the first time since downsizing in the wake of the Columbia disaster.

Along with delivering Reiter to the outpost, Discovery is carrying 5,100 pounds of supplies, equipment and experiment hardware, including a laboratory freezer, a European plant biology rack and a NASA oxygen generator that eventually will help boost station crew size to six.

At least two spacewalks are planned, one to test the shuttle's robot arm and a long heat-shield inspection boom as a space crane for possible repair work in the future, and to repair a broken transporter on the station's solar array truss that must be fixed before assembly can continue.

Because Discovery's on-board fuel cell supplies were topped off Monday, the crew is expected to have enough on-board oxygen and hydrogen to generate the electricity needed for a one day mission extension. If so, Sellers and Fossum will stage a third spacewalk to test wing leading edge repair techniques.

Despite the back-to-back launch delays Saturday and Sunday, Discovery's countdown was one of the smoothest in recent memory with no problems other than concern about the weather. And as it turned out, the weather was virtually ideal, with slightly high but acceptable crosswinds at the shuttle's emergency runway.

Lindsey and Kelly will carry out a series of rocket firings over the next day and a half to find tune Discovery's approach and if all goes well, the shuttle will dock with the huge lab complex around 11 a.m. Thursday.

Throughout today's ascent, dozens of cameras and a trio of radars were trained on the shuttle and its external tank, including three on each solid-fuel booster, one on the external tank and another in the belly of the space shuttle where propellant lines enter the engine compartment.

The goal was to look for any signs of foam insulation breaking away and any possible impacts on the shuttle's heat shield. To ease the aerodynamic stress on the tank, Discovery's flight computers used a so-called low-Q profile that throttled the main engines down a bit more than normal, for slightly longer than normal, during the region of maximum aerodynamic pressure. At the same time, the trajectory was lofted slightly to get the shuttle out of the dense lower atmosphere as quickly as possible.

Discovery's last flight a year ago - the first post-Columbia mission - clearly demonstrated the unknowns that still face the shuttle program. Agency managers thought they had corrected the foam insulation problem that doomed Columbia. And in a sense, they had. The so-called bipod ramp that was the source of the foam that did in NASA's original shuttle was removed before Discovery's flight.

But during ascent, a one-pound chunk of foam broke away from a wind deflector known as a protuberance air-load - PAL - ramp, one of two on the ship's external tank. The foam ramps were in place to smooth the flow of turbulent air across two external pressurization lines and a cable try as the shuttle climbs out of the dense lower atmosphere.

NASA managers ultimately decided to remove the PAL ramps, too, before today's flight, accelerating engineering work that was already underway. The decision ultimately was supported by extensive computer modeling and wind tunnel tests showing the pressurization lines, cable tray and support brackets are tough enough to stand up to worst-case aerodynamic loads.

Discovery's launch was the first actual flight test of the design change, the most significant aerodynamic modification to the tank since shuttle flights began in 1981.

But engineers have not yet come up with a new design for the foam insulation covering the 34 brackets on the external tank that support the pressurization lines and cable tray. It was that so-called ice-frost ramp foam that poses what NASA officially classified as "probable/catastrophic" in an integrated risk matrix.

During a flight readiness review earlier this month, NASA chief engineer Chris Scolese and Bryan O'Connor, the agency's top safety manager, voted to delay Discovery's launch until the ice-frost ramp foam could be redesigned.

NASA Administrator Mike Griffin decided to press ahead, however, because everyone agreed that even in a worst-case scenario, an IFR failure would not directly threaten the crew. In the event of catastrophic impact damage, Lindsey and his crewmates could move into the space station to await rescue by another shuttle crew.

"Everyone agrees that there is no elevated risk to crew from this decision and I personally think a very minor elevated risk to the orbiter, if any," Griffin told CBS News in a pre-launch interview.

In an earlier interview, O'Connor said the threat was officially defined as a system that "is likely to cause loss of the vehicle over the life of the program," O'Connor said in an interview with CBS News. "And 'likely' doesn't mean 'assuredly.' It's interpreted as a 50-50 chance that over 100 missions this thing would take out an orbiter.

Engineers estimated there was a 1-in-75 to chance ice-frost ramp foam could damage a typical heat-shield tile and a 1-in-100 chance it could cause catastrophic impact damage to beefed up tiles around landing gear doors and other critical areas.

It will take about six days, however, to complete analysis of ground-, air- and shuttle-based cameras and instruments. Data from wing leading edge impact sensors will be downlinked later today, along with video shot by Discovery's crew as the shuttle separated from the orbiter. Footage from the booster cams will be retrieved after the spent rockets are towed back to Port Canaveral.

The astronauts plan to spend most of the day Wednesday carrying out a detailed inspection of the shuttle's nose cap and wing leading edge panels, which experience the most extreme heating - more than 3,000 degrees - during re-entry. In addition, the station astronauts will photograph Discovery's belly during final approach and additional inspections are planned after docking.


11:30 a.m., 07/04/06, Update: Astronauts strap in for launch

The Discovery astronauts began strapping in for a July Fourth launch attempt today, hoping the weather will cooperate long enough to permit blastoff on a twice-delayed space station repair and resupply mission. There are no technical problems at pad 39B and weather remains the only major concern.

Forecasters are hopeful an afternoon sea breeze will kick in to keep the launch area clear, but low clouds and showers remain a possibility. The forecast for Wednesday is 60 percent no-go.

Hoping for the best, commander Steven Lindsey and his crewmates - pilot Mark Kelly, flight engineer Lisa Nowak, Piers Sellers, Mike Fossum, Stephanie Wilson and European Space Agency astronaut Thomas Reiter - began strapping in around 11:15 a.m.

Launch remains targeted for 2:37:55 p.m., although the exact launch time may be updated by a few seconds depending on final tracking of the international space station.


05:20 a.m., 07/04/06, Update: Discovery refueled for launch

With forecasters now predicting an 80 percent chance of good weather, engineers began pumping a half-million gallons of supercold liquid oxygen and liquid hydrogen rocket fuel into the shuttle Discovery's external tank early today for a launch attempt at 2:37:55 p.m.

This is NASA's third attempt in four days to get Discovery and its seven-member crew off the ground a long-awaited space station repair and resupply mission after bad weather forced delays Saturday and Sunday.

The three-hour fueling procedure began a few minutes ahead of schedule at 4:33 a.m. today when frigid oxygen and hydrogen began flowing from huge dewars to Discovery's mobile launch platform, into the ship's main engine compartment and then into the external tank.

The forecast improved overnight, from 60 percent to 80 percent "go," with the primary concern being a possibility of showers in the area. There are no technical problems of any significance at pad 39B and NASA spokesman George Diller said critical low-level fuel sensors in the ship's external tank are operating normally.

Engineers will pay special attention this morning to one of the five brackets holding a 17-inch-wide liquid oxygen feedline to the side of the huge fuel tank. A small piece of foam insulation broke away from the bracket after Sunday's launch scrub and engineers will be watching to make sure no dangerous ice buildups occur.

NASA's Mission Management Team met Monday night and cleared Discovery for flight after a hurried engineering analysis that indicated the foam loss posed no threat to Discovery or its crew.

Commander Steve Lindsey, pilot Mark Kelly, flight engineer Lisa Nowak, spacewalkers Piers Sellers and Mike Fossum, Stephanie Wilson and European Space Agency astronaut Thomas Reiter plan to begin donning their pressure suits a few minutes past 10 a.m. They are expected to head to the launch pad around 10:50 a.m. to strap in for launch.

Here is a timeline for the remainder of today's countdown:

TIME		EVENT

07:42 AM	Begin 3-hour built-in hold
07:42 AM	Closeout crew to white room
07:57 AM	Astronaut support personnel comm checks
08:27 AM	Pre-ingress switch reconfig
08:59 AM	Crew photo opportunity
10:08 AM	Crew weather briefing
10:08 AM	Astronauts begin donning pressure suits
10:42 AM	Resume countdown
10:48 AM	Astronauts depart crew quarters
11:17 AM	Crew ingress
12:07 PM	Astronaut communications checks
12:32 PM	Hatch closure
01:07 PM	White room closeout
01:22 PM	Begin 10-minute built-in hold
01:24 PM	NASA test director countdown briefing
01:32 PM	Resume countdown
01:33 PM	Backup flight computer loads OPS 1 software
01:37 PM	KSC area clear to launch
01:43 PM	Begin final built-in hold
01:53 PM	NTD launch status verification
	
02:28:55 PM	Resume countdown
02:30:25 PM	Orbiter access arm retraction
02:32:55 PM	Launch window opens
02:32:55 PM	Hydraulic power system (APU) start
02:33:00 PM	Terminate liquid oxygen replenish
02:33:55 PM	Purge sequence 4 hydraulic test
02:33:55 PM	Navigation system to inertial
02:34:00 PM	Aerosurface movement check
02:34:25 PM	Main engine steering test
02:35:00 PM	Liquid oxygen tank pressurization
02:35:20 PM	Fuel cells to internal reactants
02:35:25 PM	Clear caution-and-warning memory
02:35:55 PM	Crew closes visors
02:35:58 PM	Liquid hydrogen tank pressurization
02:37:05 PM	Booster joint heater deactivation
02:37:24 PM	Shuttle flight computers take control of countdown
02:37:34 PM	Booster steering test
02:37:48 PM	Main engine ignition (T-6.6 seconds)
02:37:55 PM	Booster ignition (LAUNCH)


09:30 p.m., 07/03/06, Update: Shuttle Discovery cleared for July Fourth launch try; posting countdown timeline

NASA managers Monday night decided to press ahead with a Fourth of July launch of the shuttle Discovery, weather permitting, after engineers concluded the loss of foam insulation from an external oxygen feedline posed no threat to the orbiter or its crew.

The decision was announced after an evening Mission Management Team meeting to review a hurried analysis of the foam loss incident and its potential impact. Officials said a boroscope inspection and close-up photographs of the bracket in question gave engineers confidence no additional foam will break away and that no dangerous ice will build up on the remaining insulation that could pose an impact threat to the shuttle's fragile heat shield.

Bill Gerstenmaier, NASA's chief of spaceflight operations, said the decision was based on sound engineering analysis and was not the result of "go fever."

"I think we ask ourselves that question all the time, are we doing something here or are we pushing too hard, are we trying to make this flight occur? And the answer is no. The answer is, we've laid out the data, we've looked at it calmly, we're ready to go fly because we're ready to go fly. We're not ready to go fly because of some launch window or some other condition. I think the teams have done a very good job of avoiding the tendency to try to get launch fever."

And so, with forecasters calling for a 60 percent chance of acceptable weather, engineers plan to begin refueling DIscovery for its third launch try in four days around 4:45 a.m. Liftoff from pad 39B at the Kennedy Space Center is targeted for 2:37:55 p.m. The launch window closes exactly five minutes later.

Should launch slip to Wednesday, forecasters are predicting a 60 percent chance of showers and cloud cover that would force yet another delay. The launch window Wednesday opens at 2:07:13 p.m. and closes at 2:17:13 p.m. The preferred launch time is 2:12:13 p.m.

The triangular piece of foam that broke away from a bracket supporting a 17-inch-wide liquid oxygen feed line was found on the surface of Discovery's mobile launch platform MOnday during a standard post-fueling inspection after a launch delay Sunday.

The piece weighed just .0057 pounds - .091 ounces, or about the weight of a penny - and was roughly half of the mass that would result in a 1-in-100 chance of catastrophic damage to the shuttle's heat shield.

Sources said Discovery commander Steven Lindsey and his crewmates - pilot Mark Kelly, flight engineer Lisa Nowak, Piers Sellers, Mike Fossum, Stephanie Wilson and European Space Agency astronaut Thomas Reiter - told managers Monday morning that they favored delaying launch one day to Wednesday to give engineers time to make a close-up, hands-on inspection of the bracket insulation.

Steve Altemus, the newly named director of engineering at the Johnson Space Center, and Terrence Wilcutt, director of safety and mission assurance at the Texas space center, also said they supported additional inspections.

The engineering debate hinged on three broad questions:

As it turned out, engineers were able to obtain close-up photographs of the upper and back sides of the bracket late today using a long plastic pipe with a flexible boroscope camera. No additional problems were found and engineers believe the remaining foam will remain in place.

"Those views showed the foam was structurally intact," said Gerstenmaier. "There's no loose foam in there, it all looks fine and the structure is in good shape."

He said the camera operators "did as good an inspection or probably a better inspection than they could have if they'd gotten out there with a platform."

The aerothermal analysis showed the bracket had more than enough foam remaining to easily handle the expected heating from Discovery's high-speed ascent. Finally, engineers concluded the remaining insulation should prevent any excessive buildup of ice.

"We've satisfied all the criteria we need," Gerstenmaier said. "We're ready to continue on with tanking."

Lindsey and his crewmates were scheduled to go to bed Monday evening at 7:05 p.m., before the final decision was announced. But Gerstenmaier said the astronauts were tied into the meeting via telephone and that Lindsey did not voice any objections to the decision to proceed with flight. Altemus and Wilcutt also attended this evening's meeting and they, too, agreed with the decision.

Here are countdown highlights:

TIME		EVENT

07/03/06
10:52 PM	Fuel cell activation
11:42 PM	Pad clear of non-essential personnel
11:42 PM	MCC-Houston in launch comm configuration
	
07/04/06
12:12 AM	Booster joint heater activation
01:57 AM	Final fueling preps; launch area clear
02:42 AM	Begin 2-hour built-in hold
02:52 AM	Safe-and-arm PIC test
03:17 AM	External tank ready for fueling
03:32 AM	Mission management team tanking meeting
04:42 AM	Resume countdown
04:42 AM	LO2, LH2 transfer line chilldown
04:52 AM	Main propulsion system chill down
04:52 AM	LH2 slow fill
05:22 AM	LO2 slow fill
05:27 AM	Engine cutoff sensors go wet
05:32 AM	LO2 fast fill
05:42 AM	LH2 fast fill
06:57 AM	LH2 topping
07:37 AM	LH2 replenish
07:42 AM	LO2 replenish
07:42 AM	Begin 3-hour built-in hold
07:42 AM	Closeout crew to white room
07:47 AM	External tank in stable replenish mode
07:57 AM	Astronaut support personnel comm checks
08:27 AM	Pre-ingress switch reconfig
08:59 AM	Crew photo opportunity
10:08 AM	Crew weather briefing
10:08 AM	Astronauts begin donning pressure suits
10:42 AM	Resume countdown
10:48 AM	Crew departs O&C building
11:17 AM	Crew ingress
12:07 PM	Astronaut comm checks
12:32 PM	Hatch closure
01:07 PM	White room closeout
01:22 PM	Begin 10-minute built-in hold
01:24 PM	NASA test director countdown briefing
01:32 PM	Resume countdown
01:33 PM	Backup flight computer to OPS 1
01:37 PM	KSC area clear to launch
01:43 PM	Begin final built-in hold
01:53 PM	NTD launch status verification
	
02:28:55 PM	Resume countdown
02:30:25 PM	Orbiter access arm retraction
02:32:55 PM	Launch window opens
02:32:55 PM	Hydraulic power sy stem (APU) start
02:33:00 PM	Terminate LO2 replenish
02:33:55 PM	Purge sequence 4 hydraulic test
02:33:55 PM	IMUs to inertial
02:34:00 PM	Aerosurface profile
02:34:25 PM	Main engine steering test
02:35:00 PM	LO2 tank pressurization
02:35:20 PM	Fuel cells to internal reactants
02:35:25 PM	Clear caution-and-warning memory
02:35:55 PM	Crew closes visors
02:35:58 PM	LH2 tank pressurization
02:37:05 PM	SRB joint heater deactivation
02:37:24 PM	Shuttle GPCs take control of countdown
02:37:34 PM	SRB steering test
02:37:48 PM	Main engine start (T-6.6 seconds)
02:37:55 PM	SRB ignition (LAUNCH)
This status report will be updated after fueling begins or as conditions warrant.


03:20 p.m., 07/03/06, Update: Shuttle launch in limbo; NASA assesses foam crack options; decision expected late today

Engineers are readying the shuttle Discovery for a third launch try Tuesday amid hurried work to assess the potential impact of missing foam insulation on the ship's external tank that broke off Sunday after a launch scrub.

The triangular piece of foam that broke away from a bracket supporting a 17-inch-wide liquid oxygen feed line was found on the surface of Discovery's mobile launch platform during a standard post-fueling inspection.

The piece weighed just .0057 pounds - .091 ounces, or about the weight of a penny - and was roughly half of the mass that would result in a 1-in-100 chance of catastrophic damage to the shuttle's heat shield.

"The obvious question is, well gee, if this were to happen in flight and this piece of foam were to come off, would that have been in issue?" said John Shannon, chairman of NASA's Mission Management Team. "And the answer is no, absolutely, it would not have been an issue. It was less than half the size that we think can cause damage to the orbiter. So although it is in an area where we don't like to have foam come off, it would not have caused any damage to the orbiter itself."

Liquid oxygen feedline crack near the right bipod strut on the shuttle Discovery's external tank

But engineers want to make sure the remaining foam on the bracket in question will stay in place; that the loss won't lead to dangerous ice buildups on the bracket prior to launch; and that enough insulation remains in place to prevent the underlying structure from heating up too much during Discovery's climb to space.

A piece of foam insulation found on the surface of Discovery's mobile launch platform

The Mission Management Team plans to meet again at 6:30 p.m. this evening to review the results of additional analysis and to decide whether to press ahead with launch Tuesday at 2:37:55 p.m. or whether to hold the countdown to give technicians a chance to inspect the area more closely. In that case, launch likely would slip to Wednesday.

The forecast for Tuesday calls for a 60 percent chance of acceptable weather with the major concerns being rain showers in the area and heavy cloud cover. The forecast for Wednesday is 60 percent no-go.

"Tomorrow's a good day, the next day's a good day, I cannot differentiate between 40 percent go or no go or 60 percent go or no go," Shannon said of Florida's mercurial summertime weather. "Weather really doesn't play into this discussion at all. It's are we good from a technical standpoint to go fly or are we not? And if we're not, we'll go get the technical data."

NASA has spent more than three years following the Feb. 1, 2003, Columbia disaster trying to minimize foam shedding from the shuttle's huge external tank. The bipod foam responsible for Columbia's destruction has been removed, as have long foam wind deflectors that were the source of a chunk of foam that broke away during Discovery's launch last year.

NASA Administrator Mike Griffin cleared Discovery for flight over the objections of his chief engineer and safety manager, who raised questions about yet another area of insulation on the tank that is officially classified as an unacceptable risk.

That foam, which covers 34 brackets on the tank that support two pressurization lines and a cable tray, is not an issue in today's discussion. The bracket in question is one of several that support the much larger 17-inch liquid oxygen feedline that carries oxygen from the top of the external tank to the shuttle's engine compartment.

NASA attempted to launch Discovery Saturday and Sunday, only to be blocked both times by afternoon showers and associated electrical activity. The team was told to stand down after Sunday's attempt in order to top off on-board supplies of liquid hydrogen before making another attempt Tuesday.

During inspections of the tank after Sunday's fueling, engineers first noticed a crack in the foam on the uppermost oxygen feedline bracket. Later, after a rotating service structure was moved back into place around the orbiter, engineers discovered the small piece of foam that broke away from the bracket.

Roughly the size and shape of a corner of a piece of toast, it's the largest such foam debris ever found on the launch pad.

"There are several brackets down the side that hold (the feedline) structurally onto the tank itself," Shannon said. "When the tank, when we fill it up, it shrinks and when you de-tank, it expands and what you need is an articulating joint here at the bracket that can move back and forth as the tank moves relative to the LOX feedline.

"What we think happened yesterday, when we had all that rain that scrubbed the launch, we had some condensation running down the LOX feedline. It froze, and we got some ice build up in that articulating joint. When the tank was emptied and it started to warm up, it started to expand and we think some of that ice stayed in that joint and it crushed a little bit of that foam.

"What the inspection team reported was a small crack in that joint," Shannon said. "That was the initial report that we got. ... When we moved the rotating service structure around, and I think this was just coincidence, any residual ice in there that was creating the pinch point that caused that crack in the first place melted and that small piece came out of that cracked area and landed down on the launch platform."

The Mission Management Team kicked off an intense, three-pronged attack:

"What we decided to do today in the MMT was to allow the team to have some time to go answer these questions, do the aerothermal analysis, go review the ice formation ... and third was to go think of ways that we could inspect the rest of that foam and make sure it's all intact," Shannon said. "And the team is looking at different options."

Engineers have never attempted a foam repair of this nature at the launch pad. But at this point, the debate seems to be more focused on whether to carry out a detailed inspection or whether engineers can develop a sound rationale to fly as is.

"We believe that we're getting much more comfortable with the ability to potentially fly," said John Chapman, manager of the external tank project for NASA> "But the team is still looking at that. We want to make sure we understand all the considerations that could cause this foam to be lost."

Shannon said the MMT is not falling prey to "go fever" and that he has no preconceived notions about how to proceed.

"If we decide we're a little bit uncomfortable with this, or we haven't completed our analysis or we need some more data, there is the potential that tonight I'll decide ... We want to go out there tomorrow with a platform and just make absolutely, 100 percent sure there are no other problems with that strut. I have no preconceived notion for how that discussion is going to go."


08:50 a.m., 07/03/06, Update: Crack found in external tank insulation

Engineers inspecting the shuttle Discovery's external tank following Sunday's launch scrub found a crack in the tank's foam insulation near a bracket holding a 17-inch oxygen feed line in place. Some engineers believe the crack must be repaired but senior managers say a variety of options are on the table, from fly as is to making repairs. As of this writing, no decisions have been made about how to proceed and it's not known what impact the work might have on plans to make a third attempt to launch Discovery Tuesday.

Engineers also found a small piece of foam insulation resting on the surface of Discovery's mobile launch platform that may be associated with the crack. The crack is located near a bracket toward the top of the hydrogen section of the external tank that holds the liquid oxygen feedline in place. It is not yet known what might have caused the crack, although extreme temperature differences because of the presence of super-cold propellants could have played a role.

"We've got a crack on the feedline bracket area at the top of the LOX feedline where it attaches to the hydrogen tank," said a NASA official. "It's the top bracket. I heard four to five inches (long). I don't know that we've not seen this before. The feedline has to flex, it has some bare metal there by design, you've got differences in temperatures."

Updates will be posted here as information becomes available.


11:15 p.m., 07/02/06, Update: Launch window updated

NASA flight controllers have fine tuned the shuttle Discovery's July 4 launch window. The window will open at 2:32:55 p.m. and close at 2:42:55 p.m. The preferred in-plane launch time is 2:37:55 p.m. and the initial orbit (post OMS-2) will measure 140.8 by 97.8 statute miles.

The rendezvous timeline has been updated as well, resulting in tweaks to the space station docking time and other events. The countdown chart on the CBS News Quick-Look page has been updated, along with the flight plan and launch windows chart.

Here is a brief overview of mission highlights for a July 4 launch:


DAY.ET.........DD...HH...MM...EVENT

07/04/06
Tue 02:38 PM...00...00...00...STS-121 Launch
Tue 03:15 PM...00...00...37...OMS-2 rocket firing
Tue 08:38 PM...00...06...00...Crew sleep begins

07/05/06
Wed 04:38 AM...00...14...00...Crew wakeup
Wed 08:38 AM...00...18...00...OBSS starboard survey
Wed 10:08 AM...00...19...30...OBSS nose survey
Wed 12:53 PM...00...22...15...OBSS port survey
Wed 02:23 PM...00...23...45...OBSS berthing
Wed 07:38 PM...01...05...00...Crew sleep begins

07/06/06
Thu 03:38 AM...01...13...00...STS crew wakeup
Thu 10:52 AM...01...20...14...ISS docking
Thu 07:08 PM...02...04...30...STS/ISS crew sleep begins

07/07/06
Fri 03:08 AM...02...12...30...STS crew wakeup
Fri 06:38 AM...02...16...00...MPLM installation
Fri 07:08 PM...03...04...30...STS/ISS crew sleep begins

07/08/06
Sat 03:08 AM...03...12...30...STS crew wakeup
Sat 09:13 AM...03...18...35...EVA-1: Airlock egress
Sat 03:28 PM...04...00...50...EVA-1: Airlock ingress
Sat 07:08 PM...04...04...30...STS/ISS crew sleep begins

07/09/06
Sun 03:08 AM...04...12...30...STS crew wakeup
Sun 10:58 AM...04...20...20...Joint crew news conference
Sun 06:38 PM...05...04...00...STS/ISS crew sleep begins

07/10/06
Mon 02:38 AM...05...12...00...STS crew wakeup
Mon 08:43 AM...05...18...05...EVA-2: Airlock egress
Mon 02:58 PM...06...00...20...EVA-2: Airlock ingress
Mon 06:38 PM...06...04...00...STS/ISS crew sleep begins

07/11/06
Tue 02:38 AM...06...12...00...STS crew wakeup
Tue 06:08 PM...07...03...30...STS/ISS crew sleep begins

07/12/06
Wed 02:08 AM...07...11...30...STS crew wakeup
Wed 05:13 AM...07...14...35...STS crew off duty time begins
Wed 06:08 PM...08...03...30...STS/ISS crew sleep begins

07/13/06
Thu 02:08 AM...08...11...30...STS crew wakeup
Thu 11:43 AM...08...21...05...MPLM berthed in shuttle bay
Thu 02:18 PM...08...23...40...OBSS port survey
Thu 06:08 PM...09...03...30...STS/ISS crew sleep begins

07/14/06
Fri 02:08 AM...09...11...30...STS crew wakeup
Fri 05:48 AM...09...15...10...ISS undocking
Fri 09:33 AM...09...18...55...OBSS starboard survey
Fri 12:03 PM...09...21...25...OBSS nose survey
Fri 05:38 PM...10...03...00...STS crew sleep begins

07/15/06
Sat 01:38 AM...10...11...00...Crew wakeup
Sat 05:38 PM...11...03...00...Crew sleep begins

07/16/06
Sun 01:38 AM...11...11...00...Crew wakeup
Sun 07:49 AM...11...17...11...Deorbit ignition (rev 186)
Sun 08:52 AM...11...18...14...Landing


01:20 p.m., 07/02/06, Update: Launch delayed by weather (updating at 4 p.m. with news briefing)

For a second straight day, the shuttle Discovery was grounded because of cloud cover over the Kennedy Space Center today, delaying a long-awaited mission to service and resupply the international space station. Launch was rescheduled for around 2:38 p.m. on the July Fourth holiday.

Commander Steve Lindsey and his six crewmates had hoped to blast off at 3:26 p.m. to kick off only the second post-Columbia shuttle mission, but the weather wouldn't cooperate and launch director Mike Leinbach called off the countdown well ahead of the opening of Discovery's launch window.

"OK, Steve, we've talked to launch weather and landing weather and the ops manager and we've concluded we are not going to have a chance to launch today," Leinbach told the crew. "And so in order to preserve as much time for the scrub-turnaround as possible to get the PRSD (fuel cell system) topped off on board the ship and to give you guys the maximum opportunity on orbit to extend a day and get your third EVA, we've decided to terminate the count today, stand down for 48 hours, do a single commodity hydrogen reactant top off, targeting the next launch attempt for Tuesday afternoon."

"Yeah, we copy, and looking out the window it doesn't look good today and we think that's a great plan," Lindsey radioed from Discovery's flight deck.

It costs NASA about $1 million to scrub a shuttle countdown during a weekend because of overtime and the price of rocket fuel. But by standing down early today and foregoing a possible launch try Monday, engineers will have time to refill on-board hydrogen tanks to power the shuttle's electricity producing fuel cells. After launch tries Tuesday and Wednesday, however, the team will need to reload fuel cell oxygen supplies, delaying another launch attempt until Saturday.

Fuel cell reactants determine how long a shuttle can stay in orbit. Had Discovery gotten off Saturday, Sunday or Monday, Discovery would have had enough electrical power generation capability to permit a one-day mission extension for a spacewalk to test wing leading edge repair techniques.

By topping off the hydrogen supply now, Lindsey and company should be able to get the mission extension if they get off Tuesday or Wednesday. The forecast for Tuesday calls for a 60 percent chance of acceptable weather, but the outlook gets worse as the week wears on.

Today's delay was a second straight disappointment for the astronauts, who have been training for this flight for nearly two years. But the day began with forecasters predicting a 70 percent chance of bad weather and as it turned out, their pessimism was justified.

The launch window Tuesday opens around 2:33 p.m. and closes 10 minutes later. The preferred in-plane launch time is 2:37:51 p.m. The launch window and preferred in-plane launch time likely will change by a few seconds based on updated tracking of the international space station.


11:55 a.m., 07/02/06, Update: Astronauts ready for second launch try

The Discovery astronauts, decked out in bright orange pressure suits, departed crew quarters and headed for launch pad 39B to strap in for blastoff today on the second post-Columbia shuttle mission.

Rain showers and thunderstorms rumbled across the Kennedy Space Center earlier today and forecasters continue to predict a good chance for unacceptable weather when Discovery's 3:26:09 p.m. launch time rolls around.

Hoping for the best, commander Steve Lindsey, pilot Mark Kelly, flight engineer Lisa Nowak, Piers Sellers, Mike Fossum, Stephanie Wilson and European Space Agency astronaut Thomas Reiter, reached the launch pad a few minutes before noon.

There are no technical problems of any significance at the pad and weather remains the only concern for today's launch attempt. Depending on how it plays out, Launch Director Mike Leinbach could elect to extend a final hold in the countdown at the T-minus nine-minute mark. But the launch window is only 10 minutes long and NASA already plans to launch in the middle of that window. Leinbach will only have a few minutes to play with.


06:10 a.m., 07/02/06, Update: Discovery refueled for launch; weather 70 percent no-go

Despite a 70 percent chance of bad weather, NASA's mission management team decided to refuel the shuttle Discovery for a second launch attempt today in hopes of getting a critical space station servicing and resupply mission off the ground.

Fueling began at 5:28 a.m. as liquid hydrogen and liquid oxygen began flowing through pipes leading from huge storage dewars to Discovery's mobile launch platform. Within minutes, the super-cold propellants were flowing through the shuttle's main engine plumbing and into the external tank.

By 6:05 a.m., the propellants had covered critical engine cutoff - ECO - sensors in the oxygen and hydrogen sections of the tank and all indicated they were wet as expected. NASA had problems with ECO sensors during launch attempts last summer, but there have been no problems during the current campaign.

Commander Steve Lindsey, pilot Mark Kelly, flight engineer Lisa Nowak, spacewalkers Piers Sellers and Mike Fossum, Stephanie Wilson and European Space Agency astronaut Thomas Reiter were awakened earlier today for final preparations. A crew photo opportunity is expected around 9:48 a.m. and if all goes well, the astronauts will suit up and depart crew quarters around 11:37 a.m. to begin strapping in shortly after noon.

A launch attempt Saturday was called off because of electrically charged anvil clouds in the launch area and more of the same is on tap today. Forecasters predict a 70 percent chance of unacceptable weather today and a 60 percent chance of the same on Monday. The outlook for Tuesday is 40 percent no go.

If Discovery doesn't get off the pad today, launch managers will debate a variety of options. They said earlier they would stand down on Monday to give the launch team a break and then make two more attempts Tuesday and Wednesday. At that point, engineers would need to top off Discovery's internal fuel cell hydrogen tanks, a procedure that would require a 48-hour stand down.

But the mission management team has not officially ruled out making a third attempt in a row Monday. If it did so, however, and if Discovery was delayed again, the launch team would be forced to stand down for four days to refill the internal fuel cell tanks with hydrogen and oxygen.

The fuel cell reactants were loaded last Thursday. They are constantly boiling off, but if Discovery can get off the ground by Tuesday, enough electrical power will be available to extend the mission one day and add a spacewalk to test wing leading edge repair techniques.

Depending on the forecast the mission management team could opt to stand down after today, reload the fuel cell system and start with a clean slate later in the week.

Here is the remainder of today's countdown:

05:31 AM		Resume countdown
05:31 AM		LO2, LH2 transfer line chilldown
05:41 AM		Main propulsion system chill down
05:41 AM		LH2 slow fill
06:11 AM		LO2 slow fill
06:16 AM		Engine cutoff sensors go wet
06:21 AM		LO2 fast fill
06:31 AM		LH2 fast fill
07:46 AM		LH2 topping
08:26 AM		LH2 replenish
08:31 AM		LO2 replenish
08:31 AM		Begin 3-hour built-in hold
08:31 AM		Closeout crew to white room
08:36 AM		External tank in stable replenish mode
08:46 AM		Astronaut support personnel comm checks
09:16 AM		Pre-ingress switch reconfig
09:48 AM		Crew photo opportunity
10:57 AM		Crew weather briefing
10:57 AM		Astronauts begin donning pressure suits
11:31 AM		Resume countdown
11:37 AM		Crew departs O&C building
12:07 PM		Crew ingress
12:56 PM		Astronaut comm checks
01:22 PM		Hatch closure
01:56 PM		White room closeout
02:11 PM		Begin 10-minute built-in hold
02:13 PM		NASA test director countdown briefing
02:21 PM		Resume countdown
02:22 PM		Backup flight computer to OPS 1
02:26 PM		KSC area clear to launch
02:32 PM		Begin final built-in hold
02:42 PM		NTD launch status verification
		
03:17:09 PM		Resume countdown
03:18:39 PM		Orbiter access arm retraction
03:21:09 PM		Launch window opens
03:21:09 PM		Hydraulic power sy stem (APU) start
03:21:14 PM		Terminate LO2 replenish
03:22:09 PM		Purge sequence 4 hydraulic test
03:22:09 PM		IMUs to inertial
03:22:14 PM		Aerosurface profile
03:22:39 PM		Main engine steering test
03:23:14 PM		LO2 tank pressurization
03:23:34 PM		Fuel cells to internal reactants
03:23:39 PM		Clear caution-and-warning memory
03:24:09 PM		Crew closes visors
03:24:12 PM		LH2 tank pressurization
03:25:19 PM		SRB joint heater deactivation
03:25:38 PM		Shuttle GPCs take control of countdown
03:25:48 PM		SRB steering test
03:26:02 PM		Main engine start (T-6.6 seconds)
03:26:09 PM		SRB ignition (LAUNCH)
03:31:09 PM		Window closes


04:00 p.m., 07/01/06, Update: Launch scrubbed due to weather

Launch of the shuttle Discovery on a long-awaited space station servicing and resupply mission was called off today because of cloud cover and the threat of lightning over the Kennedy Space Center.

Commander Steve Lindsey and his six crewmates had hoped to blast off at 3:49 p.m. to kick off only the second post-Columbia shuttle mission - NASA's first shuttle flight in nearly a year - but cloudy weather forced NASA Launch Director Mike Leinbach to extend a final hold in the countdown in hopes of an improve4ment.

It was not to be.

"NTD, launch director, (on channel) 212. Sir, we've been fighting the weather for quite some time," Leinbach told NASA test director Jeff Spaulding. "It doesn't look like we're going get a go. ... I Just don't feel good about the launch weather."

Leinback then called flight director Steve Stich in mission control, Houston.

"Launch Director, this is Houston Flight," Stich replied. "Mike I concur. This is a dynamic day and I think we're just playing it too close here. We've got (electrically charged) anvils within 20 miles and over the launch trajectory, it's not a good day to launch."

"Copy and concur," Leinbach replied. "Discovery, Launch Director. Well Steve, sorry to break your string, but we're not going to make it today. So appreciate your support, both the crew and the whole launch team and the team worldwide trying to get this vehicle off the ground today. But it's not a good day to launch the shuttle, so we're going to try again tomorrow."

"We copy all and concur," Lindsey called from Discovery. "It wasn't our time today, we'll launch when we're ready and hopefully, tomorrow will look better."

It was a frustrating disappointment to Lindsey and his crewmates, who have been training for this flight for nearly two years. But cloudy weather is normal this time of year in central Florida and the scrub, while disappointing, was not a major surprise.

Lindsey, pilot Mark Kelly, flight engineer Lisa Nowak, spacewalkers Piers Sellers and Mike Fossum, Stephanie Wilson and European Space Agency astronaut Thomas Reiter will spend the day at the Florida spaceport and turn in later this afternoon to await an early wakeup call Sunday.

The launch window Sunday opens at 3:21 p.m. and closes at 3:31 p.m. The preferred in-plane launch time is 3:26 p.m. The launch window Monday opens around 2:55 p.m. for a launch attempt around 3:00 p.m. The forecast for Sunday calls for a 60 percent chance of unacceptable weather and 70 percent no-go Monday.

Discovery has enough on-board liquid oxygen and hydrogen to power the ship's electricity producing fuel cells for four launch tries over five days. Leinbach said earlier the preferred strategy would be to make launch tries Saturday and Sunday, stand down on Monday to give the team a break, and then to make two more attempts Tuesday and Wednesday. After that, engineers will have to stand down for 48 hours to top off Discovery's on-board hydrogen supply.

The goal of the mission is to deliver 5,100 pounds of equipment and supplies to the international space station and to stage two and possibly three spacewalks, including one to repair a stalled equipment transporter that is vital to continued assembly of the outpost.

Just as important to the European Space Agency, Discovery is ferrying Mir-veteran Reiter to the lab complex to boost crew size back to three for the first time since downsizing in the wake of the Columbia disaster.

Reiter is on board Discovery as part of a commercial contract between ESA and the Russian space agency, Roscosmos. He is scheduled to return to Earth in December with the crew of a visiting space shuttle.

Discovery's launch window extends to July 19. If the shuttle is not off the ground by then, the flight will slip to late August and a launch currently targeted for that window would slip into October at the earliest.


02:55 p.m., 07/01/06, Update: Countdown enters final hold; updating weather

The shuttle Discovery's countdown entered a final hold at the T-minus nine-minute mark at 2:54 p.m. The astronauts are strapped in, the shuttle's hatch is closed and launch director Mike Leinbach and NASA's mission management team are monitoring the weather in hopes of launching at 3:48:41 p.m.

There are no issues of any technical significance at pad 39B other than an apparently faulty thermostat/heater needed to warm one of six small vernier steering jets. The mission management team, chaired by John Shannon, approved launch despite the heater issue based on an analysis showing commander Steve Lindsey and his crew can perform all the necessary maneuvers required for the 115th shuttle mission regardless of the thruster's condition.

The weather continues to be the major concern. Low clouds have built up over the space center and mission managers are assessing the threat posed by electrically charged anvil clouds near Florida's east coast.

To make the preferred launch time, Discovery's countdown must resume by 3:39:41 p.m. This status report will be updated after Discovery takes off or as conditions warrant.


01:00 p.m., 07/01/06, Update: Astronauts strap in; heater issue appears reslved; weather update

Commander Steve Lindsey and his six crewmates began strapping into their seats aboard the shuttle Discovery today around 12:30 p.m. Other than troubleshooting to resolve a steering thruster heater problem, there are no technical problems of any significance at pad 39B and the countdown is continuing to tick toward a launch attempt at 3:48:41 p.m.

Weather, however, remains a major concern with afternoon clouds building across central Florida. It's too soon to tell whether storms might build up in the area or whether any electrically charged anvil clouds might be pushed back toward the launch area from the west. But extensive cloud cover is evident.

As for the heater issue, NASA's mission management team has not yet weighed in on the issue, but sources say the engineering community and the flight control team favor pressing ahead with launch, weather permitting. The shuttle can fly its normal mission and perform all planned maneuvers with five operational vernier thrusters and if worse came to worse, the crew could use more powerful primary thrusters at the expense of higher-than-normal fuel useage.


11:05 a.m., 07/01/06, Update: Flight controllers optimistic about vernier heater

Troubleshooting of a thermostat in a heater used by one of the shuttle Discovery's small steering jets appears to be nearing resolution and sources say engineers are optimistic about pressing ahead to launch, weather permitting.

The shuttle is equipped with six so-called vernier jets, two forward and four aft, that are used to adjust the orbiter's orientation in space. Temperature readings from thruster L5L this morning indicated its heater was not operating.

The thruster must be at 90 degrees to operate but mission managers believe the shuttle can safely carry out all its planned maneuvers and stabilization work using five vernier jets if L5L cannot be warmed up enough to fire. That includes stabilization for critical heat-shield inspections planned for Sunday and orientation control when the shuttle is docked with the international space station.

Barring a leak or some other failure, jet L5L could be used if its temperature climbs above 90 degrees.

But the heater issue has not been officially resolved and it remains under discussion.


09:15 a.m., 07/01/06, Update: Countdown proceeding; engineers troubleshoot thruster issue

The shuttle Discovery's external tank has been loaded with rocket fuel and the countdown is proceeding toward a launch attempt at 3:48:41 p.m. The only technical issue of any significance is an apparent problem with a heater used to warm a steering jet.

Vernier thruster L5L, which points to the left from the shuttle's left-side orbital maneuvering system rocket pod, is one of six small steering jets - two forward and four aft - in the shuttle's suite of 44 maneuvering thrusters.

The vernier jets are used in a variety of maneuvers, including stabilization during heat-shield inspections with the shuttle's robot arm on flight day two and when the orbiter is docked to the international space station.

When thruster L5L was checked around 5:30 a.m., the temperature reading was ambient when it should have been warmer. Repairing the heater, if it has, in fact, failed, could be a fairly lengthy process, engineers say. NASA currently is looking into whether Discovery can be properly maneuvered without jet L5L if the system cannot be recovered.

Otherwise, the countdown is proceeding smoothly with no other problems of any significance.


06:50 a.m., 07/01/06, Update: ECO sensors working normally

The engine cutoff sensors at the base of liquid oxygen and hydrogen sections of Discovery's external tank appear to be working normally. As they were submerged in supercold propellants this morning early in the three-hour fueling process, the sensors registered "wet" as expected. Engineers will monitor the sensors throughout today's countdown to make sure they are working properly.

"So far, our ECO sensors on the external tank all look good, according to launch director Mike Leinbach," said NASA spokesman George Diller in Firing Room 4. "So the tanking operation is going smoothly and the external tank is peforming as intended with ECO sensors and other instrumentation on board."

The only technical problem currently under discussion is trouble with a heater for a small vernier steering jet but Diller said the issue did not appear to pose any threat to the countdown.


06:15 a.m., 07/01/06, Update: Shuttle fueling begins; weather improves to 60 percent 'go'

With forecasters now expecting a 60 percent chance of acceptable weather, engineers begin fueling the shuttle Discovery today for blastoff at 3:48:41 p.m. on a mission to service and resupply the international space station.

The three-hour-long fueling operation began around 5:59 a.m. when supercold liquid oxygen and hydrogen began flowing through the pipes leading from huge dewars at launch complex 39B to Discovery's aft engine compartment. The propellants first flow through the shuttle's main engine plumbing, conditioning the hardware to ultra-low temperatures, and then into the external tank itself through 17-inch-wide pipes.

Meteorologists say the weather has improved to 60 percent "go" since Friday's 60 percent "no-go" forecast. But NASA launch director Mike Leinbach will only have a few minutes to wait out the weather if it doesn't cooperate.

Today's launch window opens at 3:43:41 p.m. and closes exactly 10 minutes later. NASA plans to launch Discovery in the middle of that window, at 3:48:41 p.m., roughly the moment Earth's rotation permits a launch into the plane of the international space station's orbit.

With no problems at the launch pad, engineers have a decent shot at getting Discovery off on its long-awaited mision. The shuttle's crew - - commander Steve Lindsey, pilot Mark Kelly, flight engineer Lisa Nowak, spacewalkers Piers Sellers and Mike Fossum, Stephanie Wilson and European Space Agency astronaut Thomas Reiter - plan to depart their quarters around noon and to begin strapping in around 12:30 p.m.

During the campaign leading up to Discovery's launch last year on the fist post-Columbia mission, engineers ran into problems with critical engine-cutoff - ECO - sensors in the bottom of the liquid hydrogen section of the tank.

After the flight, engineers traced the problem to a suspect connection betweem sesors and electrical cables in a specific batch of ECO sensors manufactured in the late 1990s. The sensors in Discovery's tank for today's launch were replaced with a set thought to be fault free and those sensors are expected to go wet around 6:38 a.m. today. At that point, engineers will get their first indication whether all four hydrogen sensors are working properly.

The ECO sensors are part of a backup system that ensures the shuttle's main engines shut down normally before the tank runs out of fuel. NASA launch rules require all four ECO sensors to be operating before today's flight can proceed.

But if problems develop, NASA managers have approved an "exception" to the four-of-four flight rule that would permit a second launch attempt the next day if engineers can show the fault lies in the shuttle's electronics system and not the sensors themselves.

Here's the remainder of today's countdown:

July 1, 2006

05:53 AM	Resume countdown
05:53 AM	LO2, LH2 transfer line chilldown
06:03 AM	Main propulsion system chill down
06:03 AM	LH2 slow fill
06:33 AM	LO2 slow fill
06:38 AM	Engine cutoff sensors go wet
06:43 AM	LO2 fast fill
06:53 AM	LH2 fast fill
08:08 AM	LH2 topping
08:48 AM	LH2 replenish
08:53 AM	LO2 replenish
08:53 AM	Begin 3-hour built-in hold
08:53 AM	Closeout crew to white room
08:58 AM	External stable replenish mode
09:08 AM	Astronaut support personnel comm checks
09:38 AM	Pre-ingress switch reconfig
10:10 AM	Crew photo opportunity
11:19 AM	Crew weather briefing
11:19 AM	Astronauts begin donning pressure suits
11:53 AM	Resume countdown
11:59 AM	Crew departs O&C building
12:29 PM	Crew ingress
01:18 PM	Astronaut comm checks
01:44 PM	Hatch closure
02:18 PM	White room closeout
02:33 PM	Begin 10-minute built-in hold
02:35 PM	NASA test director countdown briefing
02:43 PM	Resume countdown
02:44 PM	Backup flight computer loads OPS 1 software
02:48 PM	KSC area clear to launch
02:54 PM	Begin final built-in hold
02:59 PM	RTLS runway verification
03:04 PM	NASA test director launch status verification
	
03:39:41 PM		Resume countdown
03:41:11 PM		Orbiter access arm retraction
03:43:41 PM		Launch window opens
03:43:41 PM		Hydraulic power system start
03:43:46 PM		Terminate LO2 replenish
03:44:41 PM		Purge sequence 4 hydraulic test
03:44:41 PM		Inertial measurement units (IMUs) to inertial
03:44:46 PM		Aerosurface profile
03:45:11 PM		Main engine steering test
03:45:46 PM		LO2 tank pressurization
03:46:06 PM		Fuel cells to internal reactants
03:46:11 PM		Clear caution-and-warning memory
03:46:41 PM		Crew closes visors
03:46:44 PM		LH2 tank pressurization
03:47:51 PM		Booster joint heater deactivation
03:48:10 PM		Shuttle flight computers take control of countdown
03:48:20 PM		Booster steering test
03:48:34 PM		Main engine start (T-6.6 seconds)
03:48:41 PM		Booster ignition (LAUNCH)
03:53:41 PM		Launch window closes


06:50 p.m., 06/30/06, Update: Posting ascent abort boundaries

Flight controllers at the Johnson Space Center in Houston re-computed the shuttle Discovery's launch window today. The window now is expected to open at 3:43:41 p.m. with launch targeted for 3:48:41 p.m. The window will close exactly five minutes later. The launch time may be adjusted by a few seconds during a final "hold" in the countdown at the T-minus nine-minute mark based on final tracking of the international space station and other factors.

Flight controllers also generated an ascent abort boundaries chart today showing when various abort modes will come into play during ascent if one or more main engines shuts down prematurely. These times reflect a so-called "low-Q" ascent profile that throttles the main engines down a bit more, for a bit longer than normal, to reduce aerodynamic pressure on the shuttle's external tank. The profile also extends vulnerability to various abort modes by a few seconds.

M:SS...EVENT.......................................VELOCITY (MPH)

RETURN TO LAUNCH SITE ABORT WINDOW (RTLS)

0:11...START ROLL MANEUVER..................................927
0:18...END ROLL MANEUVER...................................1002
0:32...START THROTTLE DOWN (67%)...........................1186
0:58...START THROTTLE UP (104.5%)..........................1553
1:04...MAXIMUM AERODYNAMIC PRESSURE (696 psf)..............1664
2:03...SOLID ROCKET BOOSTER SEPARATION.....................3539
2:13...START OMS ASSIST ROCKET FIRING 2:22 duration).......3682

TRANSATLANTIC ABORT WINDOW (TAL)

2:47...2 ENGINE TAL MORON SPAIN (104.5%, 2s)...............4091
2:53...2 ENGINE TAL ZARAGOZA SPAIN (104.5%, 2s)............4228
3:03...2 ENGINE TAL ISTRES FRANCE (104.5%, 2s).............4364
3:58...NEGATIVE RETURN (KSC) (104.5%, 3s)..................5523

ABORT TO ORBIT WINDOW OPENS (ATO)

5:10...PRESS TO ATO (104.5%, 2s, 160 u/s)..................7501
5:29...DROOP ZARAGOZA (109%,0s)............................8183
5:35...SINGLE ENGINE OPS-3 ZARAGOZA (109%,0s,2EO SIMO).....8387
5:52...ROLL TO HEADSUP.....................................9001
6:12...SINGLE ENGINE TAL ZARAGOZA (104.5%,2s,2EO SIMO).....9614
6:20...PRESS TO MECO (104.5%, 2s, 160 u/s)................10024
----...SINGLE ENGINE TAL MORON 
.......(109%,0s,2EO SEQ,1st EO @ 5880 VI).................11183
----...SINGLE ENGINE TAL ISTRES
.......(109%,0s,2EO SEQ,1st EO @ 6260 VI).................11456
7:01...SINGLE ENGINE PRESS-TO-MECO (104.5%, 2s, 597 u/s)..12001
7:25...NEGATIVE MORON (2@67%).............................13569
7:25...3G LIMITING........................................13569
7:47...LAST 2 ENG PRE-MECO TAL ZARAGOZA (67%).............14933
7:47...NEGATIVE ISTRES (2@67%)............................14933
7:53...LAST SINGLE ENG PRE-MECO TAL ZARAGOZA (104.5%).....15342
7:58...LAST 3 ENG PRE-MECO TAL ZARAGOZA (67%).............15683
7:58...23K................................................15683
8:23...LAST TAL DIEGO GARCIA..............................17183
8:29...MECO COMMANDED.....................................17524
8:40...ZERO THRUST........................................17605

THROTTLE PROFILE.......104.5%, 67%, 104.5%
MECO INCLINATION.......51.60 deg
MECO apogee/perigee....136.2/35.3 sm
OMS-2 apogee/perigee...191.2/141.1 sm


06:20 p.m., 06/30/06, Update: Griffin defends launch decision; expresses confidence in safe flight; denies undue schedule pressure

NASA Administrator Mike Griffin, answering questions on the eve of shuttle Discovery's launch Saturday, said today he firmly believes his decision to approve launch over objections from NASA's top safety manager and chief engineer was correct and based strictly on the technical merits of the argument.

Schedule pressure due to the Bush administration's 2010 deadline for finishing the international space station and retiring the shuttle played a role in the decision to proceed. But Griffin said the risk associated with so-called ice-frost ramp foam on the shuttle's external tank is relatively small and in any case, does not directly threaten crew safety.

If foam debris from the ice-frost ramps caused catastrophic impact damage during the climb to space - which Griffin said was a remote possibility - the astronauts could attempt repairs or move into the international space station to await rescue by another shuttle crew.

Even so, NASA's safety manager and chief engineer voted no-go for launch during a flight readiness review earlier this month after the engineering community formally classified the IFR foam as "probable/catastrophic." That means, safety chief Bryan O'Connor told CBS News, that over 100 flights - the original design life of a space shuttle - there would be a 50-50 chance of a catastrophic failure.

Discovery is the first shuttle ever cleared for flight with a system that is officially deemed an unacceptable risk. But Griffin said he was confident the decision to proceed was correct and based on sound engineering.

"Frankly, the decision to fly coming out of the FRR, which everyone seems to find so controversial, on the technical merits made itself," Griffin said today. "Flying the shuttle is not without risk for many reasons way beyond foam and in fact, I worry that we've spent so much time worrying about foam that we won't worry about other things which could get us. We've tried to address them all.

"Foam is a concern. But I very strongly feel that we are not risking crew for foam in this case, or I wouldn't feel comfortable launching. I believe I understand at a deep level the technical components that went into the decision and frankly, I think it makes itself. So I didn't regard it as (a difficult decision) at all.

"Now it was time consuming," Griffin said. "I personally, even as administrator, have spent weeks of my time on this issue to make sure I have heard everything everyone had to say and understood the analyses in a very deep way. So it was time consuming, but in the end, I think the data speaks for itself just fine."

Flight controllers at the Johnson Space Center in Houston today updated Discovery's launch time by a few seconds. The 10-minute launch window will open at 3:43:41 p.m. Saturday, but liftoff will be targeted for five minutes later, at 3:48:41 p.m., roughly the moment Earth's rotation carries pad 39B into the plane of the space station's orbit.

Astronaut Andy Thomas, a member of Discovery's crew for the first post-Columbia flight last summer, told CBS News today he agreed with the decision to proceed with flight. And like other astronauts, he said foam poses a relative risk, especially when compared to a shuttle's main engines, boosters and other high-energy systems.

"I think we are at the point where we do need to fly," he said. "I think Mike Griffin expressed that well, where you have to weigh the risks of where you are with the engineering of the foam against the bigger context of programmatic risk. And I think it's the right decision to go fly. We've got an obligation to the U.S. taxpayer, to our international (space station) partners and we need to meet those obligations."

Asked if the foam debate diverted attention from other risks that are routinely accepted for shuttle flights, Thomas said "You are absolutely right."

"You have to remember, this vehicle develops millions of pounds of thrust. When it leaves the launch pad, it's consuming fuel at a rate of 12 tons per second. There is turbo machinery in the back end of that spinning at unthinkable rates delivering unthinkable volumes of propellant. And burning it. This is very risky business. I think when you look at that, you come to recognize a fundamental truth about the shuttle. It really is, despite its problems, one of the most extraordinary human engineering accomplishments that has ever existed. It's quite amazing."

But the space shuttle, he added, is "very fragile and unforgiving of mistakes. And that's the problem it's displaying now."

NASA's analysis indicates that in a worst-case scenario, foam weighing up to two-tenths of a pound could break away from an ice-frost ramp and cause catastrophic impact damage. But the analytical model does not match the shuttle's flight history. Of the tanks that have been photographed after separation from the shuttle, no pieces of IFR foam larger than about one-tenth of a pound have ever broken away and no heat shield damage has ever resulted. That does not mean it can't, just that it's never been observed.

And therein lies the problem. That uncertainty, plus a new understanding of a possible failure mechanism, drove engineers to classify the IFR foam as probable/catastrophic. But NASA's models are overly conservative and if they err, Griffin said, it's in the right direction.

"Their performance in flight has been better than the analysis would lead you to believe," he said of the ice-frost ramps. "That's good, I mean if you're going to not understand it fully it's better if the performance is better than the analysis. But nonetheless, you look at them and you say I'd like to get rid of them, I'd like a better design. When the analysis doesn't really replicate what's happening in the flight history, that tells you there's at least something about it you don't fully understand.

NASA is working on a redesign of the ice-frost ramps that engineers hope to implement by the end of this year or early next. But Griffin said he decided to accept the risk of launching now with the old design because of the potential impact of a long delay. NASA wants to launch the next two flights in daylight to ensure good photo documentation of the tank. But launching in daylight, ensuring external tank separation in daylight and launching into the plane of the space station's orbit greatly restricts the available launch windows.

"If we stand down for longer than three or four months, then we can't fly by this fall, which means we can't get daylight photography throughout ascent and at MECO (main engine cutoff)," Griffin said. "We want to be able to see the external tank throughout the flight, throughout ascent, and after we jettison it. We need to fly in daylight to get some of the kind of test data that we have been talking about over and over again. We need data. We need to be able eventually to resume night operations, but we can't legitimately take the risk to resume night operations until we understand how the tank behaves and see it in daylight.

"So if we stand down more than a few months, then we have to stand down until next spring," Griffin said. "So that would be the better part of a year.

"Now I've said repeatedly, it is a matter of national policy above me, we are flying the space shuttles for one reason and one reason only, and that is to finish the space station project, which we believe to be valuable. It has been subject of a presidential decision and it's been ratified by Congress.

"I've been asked repeatedly, can we do this? And I've said repeatedly, that in the 25-year history of the space shuttle program we've averaged, with accidents, with down time for cracked wiring and flow liners and all the other issues we've had over the years, we've averaged four-and-a-half flights per year. So if we can resume flying this summer and then just execute our average rate, just business as usual for the next four years, we can finish the space station project quite comfortably.

"I do not want to make decisions now, attempting to be ultra cautious now, when I believe it is not warranted for crew safety as I do," Griffin said. "I do not want to make decisions now which will back risk up into the latter years of the program by having us have to fly six flights (for example) a year in order to complete the station. And again, I keep saying I want to do a Hubble repair if that's technically possible. I believe that's worth it.

"So we are trying to balance the risks of one flight and one crew against the necessity of recognizing that we're flying these shuttles at all in order to finish the space station program. And I do not accept that it is good management on my part, I do not accept that the right thing to do is be extremely cautious now at the expense of something later on in the future."

Asked if he was "playing the odds" with Discovery's launch, Griffin said: "You're not going to like this and I'm sure I'm not going to like how it sounds in print, but we ARE playing the odds."

"As taxpayers, you pay us to play the odds," Griffin said. "It's called risk management. I can't accept that as a criticism. If someone were to say we were doing it incorrectly, I would be all ears. I'd want to fix that."

As for schedule pressure, Griffin said "there are no activities that humans undertake that don't have a schedule associated with them. It matters whether you finish a job this year or in the next decade."

"I would struggle to think of an activity that the government undertakes, and this is a government activity, that doesn't have a desired performance level, a desired allowable expenditure and a desired time frame to complete it," he said. "Managers get paid to balance performance, cost and schedule against risk.

"We have a schedule for flying out and retiring the shuttle and assemble the station. Just taking our average flight rate, it's a schedule we can meet. But we need to get on with things. I do not think, I absolutely do not think and do not accept we are being unduly influenced by schedule pressure. But we pay attention to schedule because time is money. And that matters."


12:15 p.m., 06/30/06, Update: Discovery on track for launch; weather remains 60 percent 'no go'

The shuttle Discovery's countdown is on track today for a launch attempt Saturday at 3:49 p.m., weather permitting. Forecasters continue to predict a 60 percent chance of unacceptable weather Saturday, Sunday and Monday due to electrically charged anvil clouds within 23 miles of the launch area and a possibility of showers.

Thunderstorms Thursday afternoon delayed work to load Discovery's internal tanks with liquid oxygen and hydrogen for the ship's electricity producing fuel cells. But the launch team had eight hours of built-in hold time Thursday to make up for any delays and by this morning, the countdown was back on track.

Based on the actual load, flight controllers now believe Discovery may have enough power generation capability to permit a one-day mission extension - and a third spacewalk to test wing leading edge repair techniques - even if launch is delayed to July 4. Based on earlier predictions, July 3 appeared to be the cutoff for a mission extension, barring extensive crew conservation procedures. In any case, no decision will be made on a possible mission extension until well into Discovery's mission.

NASA Test Director Jeff Spaulding said today the launch strategy calls for making back-to-back attemps Saturday and Sunday, if necessary, before standing down a day to give the team a break. Two more attempts could be made Tuesday and Wednesday before a two-day stand down to top off the internal hydrogen and oxygen tanks. Discovery's launch window closes July 19.

Spaulding said the possibility of making three launch attempts in a row Saturday, Sunday and Monday has not been ruled out. But if NASA went down that road and didn't make it, launch would be delayed another four days to refill launch pad fuel tanks and to top off the fuel cell system.

Here are some useful charts for readers interested in the countdown timeline and Discovery's ascent (also available in SpaceCalc on the Downloads page):

  • CBS News countdown chart

  • STS-121 Detailed Ascent Timeline

  • STS-121 Summary Ascent Timeline
  • Here is the remainder of Discovery's countdown in text format. Note: NASA times the countdown to the opening of the shuttle's 10-minute launch window, not the actual launch time, and rounds down to the nearest minute. The latest estimate shows the launch window opens at 3:43:38 p.m. All events in the countdown prior to the release of a final hold at the T-minus nine-minute mark are based on the window open time of 3:43 p.m. The countdown will resume at the T-minus nine-minute mark based on the actual launch time, which is roughly the moment Earth's rotation carries the pad into the plane of the space station's orbit. As of today, the estimate is 3:48:38 p.m.

    HH:MM......EVENT
    
    06/30/06
    01:10 PM...Communications system activation
    01:40 PM...Crew module voice checks
    02:50 PM...Flight crew equipment late stow
    06:00 PM...Rotating service structure to park position
    07:50 PM...Ascent switch list configuration
    10:53 PM...Resume countdowns
    10:53 PM...Terminate pad tours
    
    07/01/06
    12:03 AM...Fuel cell activation
    12:53 AM...Pad clear of non-essential personnel
    12:53 AM...Mission control in launch comm configuration
    01:23 AM...Solid rocket booster joint heater activation
    03:08 AM...Final fueling preps; launch area clear
    03:53 AM...Begin 2-hour built-in hold
    04:03 AM...Safe-and-arm PIC test
    04:28 AM...External tank ready for fueling
    04:43 AM...Mission management team tanking meeting
    05:00 AM...NASA television coverage begins
    05:53 AM...Resume countdown
    05:53 AM...Liquid oxygen (LO2), hydrogen (LH2) transfer line chilldown
    06:03 AM...Main propulsion system chill down
    06:03 AM...LH2 slow fill
    06:33 AM...LO2 slow fill
    06:38 AM...Hydrogen engine cutoff sensors go wet
    06:43 AM...LO2 fast fill
    06:53 AM...LH2 fast fill
    08:08 AM...LH2 topping
    08:48 AM...LH2 replenish
    08:53 AM...LO2 replenish
    08:53 AM...Begin 3-hour built-in hold
    08:53 AM...Closeout crew to white room
    08:58 AM...External tank in stable replenish mode
    09:08 AM...Astronaut support personnel comm checks
    09:38 AM...Pre-ingress switch reconfig
    10:10 AM...Crew photo opportunity
    11:19 AM...Crew weather briefing
    11:19 AM...Astronauts begin donning pressure suits
    11:53 AM...Resume countdown
    11:59 AM...Crew departs O&C building
    12:29 PM...Crew begins strapping in
    01:18 PM...Astronaut communications checks
    01:44 PM...Hatch closure
    02:18 PM...White room closeout
    02:33 PM...Begin 10-minute built-in hold (T-minus 20 minutes)
    02:35 PM...NASA test director countdown briefing
    02:43 PM...Resume countdown (T-minus 20 minutes)
    02:44 PM...Backup flight computer (BFS) loads OPS 1 software
    02:48 PM...Kennedy Space Center area clear to launch
    02:54 PM...Begin final built-in hold (T-minus nine minutes)
    02:59 PM...RTLS runway verification
    03:04 PM...NASA test director launch status verification
    
    HH:MM:SS
    
    03:39:38 PM...Resume countdown (T-minus nine minutes)
    03:41:08 PM...Orbiter access arm retraction
    03:43:38 PM...Launch window opens
    03:43:38 PM...Hydraulic power system (APU) start
    03:43:43 PM...Terminate LO2 replenish
    03:44:38 PM...Purge sequence 4 hydraulic system test
    03:44:38 PM...Inertial measurement units (IMUs) to inertial
    03:44:43 PM...Aerosurface profile (steering test)
    03:45:08 PM...Main engine steering test
    03:45:43 PM...LO2 tank pressurization
    03:46:03 PM...Fuel cells to internal reactants
    03:46:08 PM...Crew lears caution-and-warning memory
    03:46:38 PM...Crew closes visors
    03:46:41 PM...LH2 tank pressurization
    03:47:48 PM...Soplid rocket booster joint heater deactivation
    03:48:07 PM...Shuttle flight computers take control of countdown
    03:48:17 PM...Booster steering test
    03:48:31 PM...Main engine start (T-6.6 seconds)
    03:48:38 PM...Booster ignition (LAUNCH)
    03:53:38 PM...Window closes  
    


    06:45 p.m., 06/29/06, Update: Shannon says management team unanimously 'go' for launch

    Afternoon thunderstorms delayed work to load the shuttle Discovery's fuel cell system today, but engineers expect to make up the lost time later this evening and mission managers said the orbiter will be ready for launch Saturday, weather permitting, on the second post-Columbia mission.

    "I'm very happy to report that we just had our launch-minus two-day mission management team review and other than some questionable weather, we have no constraints to launch," said John Shannon, chairman of the mission management team. "It's been a long year, with a lot of hard work by all of the team members to get to this point and I just want to say I'm extremely proud of the team and we are ready to go for Saturday and do what NASA does best."

    Liftoff from pad 39B at the Kennedy Space Center is targeted for Saturday at 3:49 p.m. EDT. But forecasters continue to predict a 60 percent chance of afternoon showers and electrically charged anvil clouds that could delay launch tries Saturday, Sunday and Monday.

    Launch Director Mike Leinbach said NASA's strategy will be to make back-to-back attempts Saturday and Sunday, if necessary, take a day off and then try again Tuesday and Wednesday. After that, the launch team would stand down for two days to reload fuel cell hydrogen. Launch managers are hopeful the weather will cooperate before that point rolls around.

    "I'm very confident the hardware we've put on the pad is the best hardware we have and I'm just looking forward to a great flight," Shannon said.

    Discovery's flight is somewhat controversial because of NASA Administrator Mike Griffin's decision to press ahead with launch over the objections of his chief safety officer and the agency's chief engineer. Both men were no-go for flight because of concern about a recently discovered failure mechanism that could result in foam debris falling away from so-called ice-frost ramps on the external tank. The debris poses an impact threat to the shuttle's fragile heat shield.

    The ice-frost ramps are officially classified by NASA as "probable/catastrophic" in the agency's integrated risk matrix, meaning that over the course of 100 flights, there is a 50-50 chance the foam could break away and lead to a catastrophic failure.

    But Griffin argued the risk is to the shuttle - not the crew - because in a worst-case scenario, the astronauts could move into the international space station to await rescue by another shuttle crew. Given a 2010 deadline to finish the space station and retire the shuttle fleet, Griffin said he decided to accept the risk posed by the ice-frost ramps and to proceed with assembly.

    Shannon defended GriffinÕs decision, saying the objections of Bryan O'Connor, director of Safety and Mission Assurance, and Chris Scolese, NASA's chief engineer, had been "mis-characterized a little bit" in the media.

    "The way I would put it, and I have attended every one of these meetings, when people are asked in your specific area, which is engineering or the safety group as well, would you change the ice-frost ramps? The answer came back yes," Shannon said. "But whenever Mike Griffin and (spaceflight chief) Bill Gerstenmaier go through the rationale for flight and you start really poking into the numbers for the ice-frost ramp and the real risk that it poses, I think we had just about 100 percent agreement that yes, we understand.

    "As engineers, we would not fly with this condition ... but we have looked at all the data, it does not look to be something you have to go fix right now, we understand the rationale to go fly. We kind of handicap people by asking them just to vote for their specific area. I think when you lay out the whole story, the whole picture, we got almost 100 percent understanding."

    But it was NASA's own engineering community that classified the ice-frost ramps as "probable/catastrophic," the only red-level threat in the risk matrix. In fact, Discovery's flight is the first in shuttle history to be cleared for launch with a system officially deemed an unacceptable risk.

    "I have no idea if it's really yellow or red," Shannon said. "What I'd say is we don't have enough information to very accurately characterize that. Some people think it's in the red because they don't know, and that's one way you might characterize it.

    "I am very comforted by the fact that we have not seen foam losses that would be catastrophic, regardless of what time they're released. I'm comforted by the fact that the geometry of the underlying metal under the foam seems to be such that a mass loss of that size is not possible. So those things make you feel better, but is that real science that you can hang your hat on and say that's really guaranteed or not? We're in a learning environment."

    Shannon said the open debate over the issue showed NASA has changed its culture since the Columbia disaster. But in this case, engineers do not have enough solid information to reach solid conclusions.

    "So then you're left to opinions," Shannon said. "The debate is the important piece and I think that was fulfilled in spades."

    NASA has been criticized in the past for proceeding with flights in the absence of solid engineering data about troublesome systems.

    Astronaut Stephen Robinson, who flew aboard Discovery for the first post-Columbia mission last July, said he agree the ice-frost ramps need fixing, but he said he tends to worry more about the high-speed rotating machinery in the shuttle's main engines and hydraulic system.

    Asked how the public should interpret the actual risk posed by the ice-frost ramps, he said "it's difficult to tell the risk of something that hasn't happened before, isn't it? That's the biggest problem in our whole business. How do you characterize the risk of something that's never occurred even once."

    "Now we have never had, for instance, a problem with the thing we worry the very most about, which are the big machines that are moving very fast during the launch phase," he said. "These are the engines and all the pumps and compressors and the hydraulic power units. Those we worry about a tremendous amount every single launch. We've been extremely fortunate ... that nothing has ever occurred with those. Worrying about ice-frost ramps doesn't even stack up to those kind of things."

    Engines have shut down before launch and once, in July 1985, in flight. But in all cases, the engines shut down safely and in the 1985 abort to orbit, the crew was able to accomplish most of the mission objectives.

    "The ice-frost ramp is something we've learned a lot about, it's one of the many things we should worry about, but it cannot keep us from launching, it cannot keep us from reaching orbit successfully," Robinson said. "The absolute worst it could do is shed some foam. We don't think it could shed foam big enough to critically hurt us and not be able to come home. So from a crew safety point of view, I completely back the administrator that it's the correct thing to do.

    "From worrying it's something that could hurt the shuttle and maybe the long-term reusability of the shuttle, I completely back our safety community and Bryan O'Connor that that is something to worry about. But you have to put it into perspective. There are many things to worry about in a shuttle launch and we should be worrying about them all. I think you can have confidence that NASA has made the right decision. The dissent you're seeing is absolutely normal. ... Remember how much we talked about culture change after Columbia? This is culture change."

    Summing up the ice-frost ramp debate, Robinson said he worries "more about rotating machinery going at tremendous rates, I really do. I'm a mechanical engineer and a pilot and those are the things that worry me the most. But I have a wide spectrum of things to be concerned about when it comes to safety and you have to decide that the risk is minimized. I think the risk for this flight is minimized. It's not gone. We're going to accept the risk we currently know about and we're going to go fly and see how the changes we have made, how much safer they've made us."


    05:00 p.m., 06/28/06, Update: Countdown begins for 115th shuttle mission

    Countdown clocks began ticking today at the Kennedy Space Center for launch of the shuttle Discovery Saturday on a space station resupply and repair mission. After a "call to stations" at 4:30 p.m., engineers in firing room 4 at the Florida spaceport began Discovery's countdown to launch at 5 p.m.

    Liftoff from pad 39B currently is targeted for 3:48:38 p.m. Saturday, but that time likely will change by a few seconds between now and then based on updated tracking of the space station. The actual launch time will be set during a final "hold" in the countdown at the T-minus nine-minute mark.

    There are no technical issues of any significance at the launch pad, but forecasters are predicting a 60 percent chance of showers and electrically charged anvil clouds Saturday, Sunday and Monday that could force a delay.


    11:45 a.m., 06/28/06, Update: Shuttle 'go,' weather iffy for Saturday launch

    The shuttle Discovery is in good shape and on track for launch Saturday, but forecasters are predicting a 60 percent chance of electrically charged anvil clouds and afternoon showers Saturday, Sunday and Monday that would prevent takeoff.

    Florida's summertime afternoon weather is always subject to change on short notice and as of this writing, launch managers plan to press ahead for what will be only the second shuttle flight in three years.

    "Our teams have been working tirelessly during the last year to make this shuttle flight and all our shuttle flights, obviously, as safe as possible for the crews," said NASA test director Jeff Spaulding. "As we approach our nation's 230th birthday, I'm proud to announce that the launch vehicle, the launch team and flight crew are ready to launch and continue our mission of completing the space station."

    Discovery's countdown is scheduled to begin at 5 p.m. today, leading up to a launch attempt at 3:49 p.m. Saturday, roughly the moment Earth's rotation carries the launch pad into the plane of the international space station's orbit.

    Spaulding dismissed concerns about the weather, pointing out that on more than one occasion NASA was able to proceed with a launch despite forecasts as bad as 90 percent no-go.

    "I think as always, if we have an opportunity to launch, the management team will sit down and make an evaluation and then make a go at trying to get off the ground," he said. "That's always our plan, to try to get off if we have an opportunity. Obviously these forecasts, while they sound a little bit gloomy, we've certainly launched with higher predictions than this, etc.. As always, we'll evaluate the weather real time and make a decision on the day of launch."

    Engineers plan to load Discovery's electricity producing fuel cell system with liquid oxygen and liquid hydrogen Thursday afternoon. Once loaded, Discovery will have five days to get off the ground before a two-day stand down to top off the hydrogen tanks. The oxygen supply will be good for 12 days.

    If Discovery can take off during the first three days of its window, enough hydrogen and oxygen will be available to permit a one-day mission extension and the addition of a third spacewalk to test heat-shield repair techniques. But after Monday, enough hydrogen will have boiled off in the fuel cell system to preclude an extra day.

    Spaulding said no decisions have been made on whether NASA would make three launch attempts in a row to get Discovery off. The usual practice is two attempts in a row and then a day off to give the launch team a break. If that policy holds up, NASA will be able to make four attempts in five days before standing down for 48 hours to top off the hydrogen tanks.

    Afternoon showers and thunderstorms are the rule on Florida's east coast in the summer months and Kathy Winter, an Air Force weather officer, said this week is no exception. While a ridge will push afternoon storms inland this weekend, electrically charged anvil clouds will pose a threat to Discovery's launch.

    "Those thunderstorms, even though they'll be pushing inland, we'll be seeing anvils coming back from those thunderstorms and those are also dangerous when it comes to triggering a lightning strike. So our main concern is going to be those anvils coming back from those thunderstorms."

    In addition, an inverted trough, or wave, to the west will bring more moisture into the area "and because of that, we could also see some isolated showers and cumulus clouds in the area of the launch pad and within 20 nautical miles of the shuttle landing facility," she said.

    The weather is expected to be acceptable for at least one emergency runway in Spain or France, along with a backup landing site at Edwards Air Force Base in California throughout the weekend.

    NASA's problem is the possibility of rocket-triggered lightning during launch and/or showers and low clouds that could prevent a safe return-to-launch site abort.

    NASA flight rules require a "go" forecast for RTLS, meaning no worse than scattered clouds below 5,000 feet, visibility of at least four statute miles and crosswinds less than 15 knots. A shuttle cannot be cleared for launch if thunderstorms, lightning or rain are within 23 miles of the runway.


    01:00 p.m., 06/27/06, Update: Astronauts fly to Florida for launch

    Commander Steve Lindsey and his six crewmates - pilot Mark Kelly, flight engineer Lisa Nowak, spacewalkers Piers Sellers and Mike Fossum, Stephanie Wilson and European astronaut Thomas Reiter - flew to the Kennedy Space Center today for final preparations before launch Saturday on a space station servicing mission.

    Arriving aboard two-seat T-38 jet trainers, the astronauts touched down on the shuttle's 3-mile-long runway at mid morning, landing one at a time in a staggered sequence.

    "We're really excited to be here, ready to go do this for real," Lindsey told reporters at the runway. "We've been training for a long time, we're as prepared as we're going to be. The vehicle is ready and everything's looking 'go.' So weather permitting, which I'm pretty confident in, we're going to be airborne on July 1."

    Discovery's launch from pad 39B is targeted for 3:48:37 p.m. Saturday, roughly the moment Earth's rotation carries the shuttle into the plane of the space station's orbit. Afternoon showers are expected, but NASA has not yet issued an official forecast.

    "I'm hoping the weather's going to improve a little bit in the next few days and we'll get off on time," said Sellers. "It's great to be here at last."

    Discovery's flight is only the second post-Columbia mission and the first launch in nearly a year as NASA has struggled to overcome ongoing problems with the foam insulation on the shuttle's external fuel tank. The goals of the 115th shuttle mission are to deliver more than 5,000 pounds of supplies and equipment to the space station; to repair a stalled robot arm transporter needed for continued assembly; and to deliver European astronaut Thomas Reiter to the outpost as a full-time crew member.

    Reiter is on board Discovery under a commercial contract between the European and Russian space agencies. He will join station commander Pavel Vinogradov and flight engineer Jeff Williams for a long-duration stay aboard the outpost, boosting crew size back to three for the first time since the immediate aftermath of the 2003 Columbia disaster.

    "I'm the one who will be left beyhind on the station," Reiter joked today. "After years and years of training, I think this is a remarkable moment. I think we all are confident our launch will signify the continuation of assembly of the station, returning to a three-man crew and utilizing the station for its (intended) purpose."

    Discovery's countdown to launch is scheduled to begin at 5 p.m. Wednesday. Here is NASA's television schedule for the rest of the week:

    REV.EVENT.........................SITE.....EDT........GMT
    
    WEDNESDAY, JUNE 28
    
    COUNTDOWN STATUS BRIEFING..........KSC.....10:00 AM...14:00
    EXPEDITION 13 COMMENTARY...........JSC.....11:00 AM...15:00
    VIDEO FILE (Media/CH-103)...........HQ.....12:00 PM...16:00
    STS-121 COUNTDOWN BEGINS...........KSC.....05:00 PM...21:00
    
    THURSDAY, JUNE 29
    
    COUNTDOWN STATUS BRIEFING..........KSC.....10:00 AM...14:00
    EXPEDITION 13 COMMENTARY...........JSC.....11:00 AM...15:00
    VIDEO FILE (Media/CH-103)...........HQ.....12:00 PM...16:00
    LAUNCH READINESS NEWS CONFERENCE...KSC.....04:00 PM...20:00
    
    FRIDAY, JUNE 30
    
    COUNTDOWN STATUS BRIEFING..........KSC.....10:00 AM...14:00
    EXPEDITION 13 COMMENTARY...........JSC.....11:00 AM...15:00
    VIDEO FILE (Media/CH-103)...........HQ.....12:00 PM...16:00
    NASA EXPLORATION BRIEFING..........KSC.....02:00 PM...18:00
    NASA AGENCY OVERVIEW BRIEFING......KSC.....03:00 PM...19:00
    
    SATURDAY, JULY 1
    
    STS-121 FUELING COVERAGE...........KSC.....05:30 AM...09:30
    STS-121 LAUNCH COVERAGE BEGINS.....KSC.....10:00 AM...14:00
    LAUNCH.............................KSC.....03:49 PM...19:49
    MECO.......................................03:57 PM...19:57
    LAUNCH REPLAYS....................KSC......04:10 PM...20:10
    POST LAUNCH NEWS CONFERENCE.......KSC......05:00 PM...21:00
    PAYLOAD BAY DOOR OPENING...................05:14 PM...21:14
    ASCENT MCC VIDEO REPLAY...........JSC......07:00 PM...23:00
    ROBOT ARM POWER UP.........................07:24 PM...23:24
    UMBILICAL WELL CAMERA DOWNLINK.............07:44 PM...23:44
    EXTERNAL TANK HAND-HELD VIDEO DOWNLINK.....08:04 PM...00:04
    IMAGERY QUICK-LOOK BRIEFING.......KSC......09:00 PM...01:00
    LAUNCH ENGINEERING REPLAYS........KSC......09:30 PM...01:30
    FLIGHT DAY 1 HIGHLIGHTS...........JSC......11:00 PM...03:00
    
    


    12:00 p.m., 06/29/06, Update: STS-121 Mission Preview

    KENNEDY SPACE CENTER, Fla (CBS) - After a frustrating year of redesign, testing and controversy, NASA is finally ready to launch the shuttle Discovery July 1 on a space station servicing and repair mission. It will be the first flight in shuttle history with a system - foam bracket insulators on the external fuel tank - officially deemed an unacceptable risk by the agency's top safety manager and chief engineer.

    The astronauts plan to deliver fresh water and some 5,100 pounds of supplies and equipment to the international space station and carry out a spacewalk to fix a stalled equipment transporter that must be restored to normal operation before station assembly can proceed.

    Discovery also will ferry European Space Agency astronaut Thomas Reiter to the outpost, boosting crew size back to three for the first time since downsizing after the Columbia disaster. Reiter is on board Discovery as part of a commercial contract between ESA and Roscosmos, the Russian Space Agency.

    Spacewalkers Mike Fossum and Piers Sellers plan to ride on the end of a long boom attached to the shuttle's robot arm to test it's stability as a shuttle repair platform. And if power permits, they'll stage a third spacewalk to test heat-shield repair techniques. The exercises may help pave the way for an eventual flight to service the Hubble Space Telescope.

    And throughout the mission - the day after launch, during docked operations at the station and even after their departure from the complex - the astronauts will carry out time-consuming, inch-by-inch inspections of Discovery's fragile heat shield to make absolutely sure nothing was damaged during the climb to space or after reaching orbit.

    It is the very real threat of worst-case catastrophic impact damage from foam insulation off the external tank that has triggered controversy and concern during the final push to ready Discovery for flight.

    Facing the Bush administration's 2010 deadline for completing the station and retiring the space shuttle - and with agreement that the risk in this case is for loss of vehicle, not crew - NASA Administrator Mike Griffin cleared Discovery for launch over the objections of Bryan O'Connor, NASA's chief of Safety and Mission Assurance, and Chris Scolese, the agency's chief engineer.

    "We're going to use this flight and the subsequent flights to complete the space station," Griffin said after a flight readiness review June 17. "We believe it is possible to do so. But if it is going to be possible to do so, we're going to have to take some programmatic risks because the shuttle will be retired in 2010.

    "This president's budget will not carry funding for shuttle vehicles beyond 2010. So if we're going to fly, we need to accept some programmatic risk and get on with it. Again, I'll point out for me to accept programmatic risk to do this is not the same as accepting a crew risk, which we believe we're not doing."

    But make no mistake. Discovery's launch on the 115th shuttle mission - only the second since the Feb. 1, 2003, Columbia disaster - is a make-or-break flight for America's manned space program, as will be each of the final 16 missions on the agency's shuttle manifest.

    "If we were to lose another vehicle, I would tell you right now that I would be moving to figure out a way to shut the program down," Griffin said. "I think at that point, we're done. I'm sorry if that sounds too blunt for some, but that's where I am. Now, we're trying to navigate some very difficult waters for the next 16 flights to get the station assembled. I think that's worth doing. I've stated that on multiple occasions. But it's not easy."

    He's right. A quarter of a century after Columbia's launch on the first shuttle mission, the numbers still boggle the mind.

    Including liquid and solid propellants, Discovery will weigh 4.5 million pounds at the moment of liftoff from launch complex 39B at the Kennedy Space Center. In just 10 seconds, it will be 800 feet off the ground going straight up at nearly 130 mph. In two minutes, after burning up half its weight in propellant, the spacecraft will be 32 miles up, traveling at some 3,000 mph - faster than a rifle bullet and accelerating at a blistering pace as fuel is consumed and its weight drops off. In eight-and-a-half minutes, the shuttle and its seven occupants will be in orbit, streaking through space at more than 17,000 mph, fast enough to cover 84 football fields in a single heartbeat.

    Those numbers illustrate the raw energy that goes into boosting a shuttle into space and serve as a reminder of the energy that must be dissipated through atmospheric friction during re-entry to permit a safe landing.

    And therein lies an enormous management and engineering challenge, one that has gotten the best of NASA and the shuttle twice in 114 missions, once going uphill and once coming down. Now, facing a 2010 deadline to complete the station and honor international commitments to its space station partners, NASA must launch a final 16 flights - 17 if a mission to service the Hubble Space Telescope is approved - without a major hiccup.

    "I think we're all going to have to work hard to maintain our vigilance, no kidding, right through until the last shuttle stops on the runway," Sellers said in an interview. "We're going to have to pay attention. You can't turn your back on this system. It's not forgiving."

    From a purely statistical standpoint, the shuttle remains roughly as risky to fly today as it was before Columbia's final flight, despite the time and money - more than $1 billion - that have been devoted to safety upgrades.

    "Basically, this vehicle, and you can take this to the bank, is about a 1-in-100 vehicle," said shuttle program manager Wayne Hale. "It is a risky vehicle to fly. And nobody should mistake that, there are a number of things that can cause bad outcomes in this vehicle. What we've tried to do is take a very serious look at every one of the areas that we think are higher risk and do our best to mitigate those."

    But that does not mean the shuttle is safe by any normal definition.

    Quoting former astronaut John Young, Hale said "if you're not a little scared when you launch the shuttle, you don't understand what's happening. And that's going to be true, by the way, after we fix all the foam on the external tank. There are plenty of other reasons to hold your breath."

    With the end of the program in sight, many would agree with Sellers' characterization of the space shuttle as "brilliant but flawed."

    "Brilliant in its incredible capability and the amazing reach of technologies that were involved in it," he said. "And flawed in some elements of its design that made it difficult to operate, expensive to operate and as we know, with some safety problems."

    In the early days of the shuttle program, the awareness of risk was an intellectual thing; NASA had never lost a manned spacecraft in flight. But now, after Challenger and Columbia - and with an awareness that another disaster will spell the end of the program - many observers will indeed be holding their collective breath when Discovery roars to life July 1. For better or for worse, America's civilian space agency will not be allowed another major malfunction, even if the crew escapes unharmed.

    Discovery's last flight a year ago - the first post-Columbia mission - clearly demonstrated the unknowns that still face the shuttle program. Agency managers thought they had corrected the foam insulation problem that doomed Columbia. And in a sense, they had. The so-called bipod ramp that was the source of the foam that did in NASA's original shuttle was removed before Discovery's flight.

    But during ascent, a one-pound chunk of foam broke away from a wind deflector known as a protuberance air-load - PAL - ramp, one of two on the ship's external tank. The foam ramps were in place to smooth the flow of turbulent air across two external pressurization lines and a cable try as the shuttle climbs out of the dense lower atmosphere.

    NASA managers ultimately decided to remove the PAL ramps, too, before Discovery's next flight, accelerating engineering work that was already underway. The decision ultimately was supported by extensive computer modeling and wind tunnel tests showing the pressurization lines, cable tray and support brackets are tough enough to stand up to worst-case aerodynamic loads.

    Discovery's launch will mark the first actual flight test of the design change, the most significant aerodynamic modification to the tank since shuttle flights began in 1981.

    But engineers have not yet come up with a new design for the foam insulation covering the 34 brackets on the external tank that support the pressurization lines and cable tray. It is that so-called ice-frost ramp foam that poses what NASA officially classifies as "probable/catastrophic" in an integrated risk matrix.

    "The definition of probable/catastrophic in the program's own terminology is that this thing that we're talking about is likely to cause loss of the vehicle over the life of the program," O'Connor said in an interview with CBS News. "And 'likely' doesn't mean 'assuredly.' It's interpreted as a 50-50 chance that over 100 missions this thing would take out an orbiter.

    Engineers estimate there's a 1-in-75 to chance ice-frost ramp foam could damage a typical heat-shield tile and a 1-in-100 chance it could cause catastrophic impact damage to beefed up tiles around landing gear doors and other critical areas.

    O'Connor, who protested Discovery's launching, said the numbers appear worse than they really are.

    "You could say maybe our threshold for something that we call probable/catastrophic is up there in the wrong place because that sounds really bad," he said. "If somebody were to apply that to a single mission, you'd say that's way worse than what we think it is."

    That's because the raw numbers don't reflect other mitigating factors. Griffin approved the flight because even in a worst-case scenario, one in which the shuttle was too severely damaged to attempt re-entry, the astronauts could attempt repairs or use the space station as a "safe haven" and await rescue by another shuttle crew.

    The station has enough supplies on board to support a combined crew of nine for at least 84 days. And that's assuming the station's Russian oxygen generator failed on launch day. The shuttle Atlantis, scheduled for its own space station flight in late August or early September, is being processed in parallel for launch on a rescue flight by Aug. 21 if necessary.

    Members of the Columbia Accident Investigation Board contacted by CBS News declined comment, saying they had not followed NASA's redesign work over the past year in enough detail to characterize Griffin's decision one way or the other.

    For Discovery commander Lindsey and his six crewmates, however, risk is relative and in interviews with CBS News, all seven said they are eager to finally get underway.

    "If you look at the overall risk numbers on the vehicle and you compare post Columbia and pre Columbia, if you're really honest with the statistics, they're about the same," Lindsey said in an interview. "The risk really hasn't changed. It's always been a pretty high risk operation to go fly the shuttle. I knew that going in prior to Columbia. I think everybody is a lot more aware of that afterwards."

    To flight engineer Lisa Nowak, "I'm worrying more about driving in a car on a highway and that being risky than I do about what might happen on a space flight."

    "Obviously, something could happen," said Nowak, former Navy F-18 pilot and mother of three. "The risks are there, but we've done so much to minimize everything that we can, I really feel confident we're going up with the safest vehicle that we can and that we have a plan in place if something does come off. I feel really good about it."

    But with two disasters in 114 flights, the shuttle has "a demonstrated risk of about 1-in-57," said pilot Mark Kelly. "Maybe the real risk is a lot less than that. It might even be a little more than that. We don't know."

    "What we do know is what the space shuttle does, its value and what we get out of it," he said in an interview. "As a country, we get a lot of return on the money we spend on the space program. I think ultimately it gives us industries we wouldn't have had before, it's a big benefit to our economy, it's also important for people to be explorers. So there's a lot of benefit there.

    "Personally, I weigh the risk to me, the personal risk of something happening to me, with the benefit to our nation. That's how I justify climbing into the thing. And it's a lot of fun. Flying in space is a lot of fun!"

    Discovery is scheduled for launch from complex 39B at the Kennedy Space Center at 3:49 p.m. on July 1, roughly the moment Earth's rotation carries the pad into the plane of the international space station's orbit. Taking the controls after a three-day orbital chase, Lindsey will guide the shuttle to a docking with the space station around 11:17 a.m. on July 3.

    Along with delivering crucial supplies and equipment, the astronauts plan to stage at least two spacewalks, on July 5 and 7, to test the boom as a potential work platform and to fix the station's mobile transporter. If Discovery gets off on time, and if the astronauts can conserve enough power in orbit, the flight will be extended one day and a third spacewalk will be staged July 9 to test heat shield repair techniques.

    But the primary goals of the flight are repairing the mobile transporter to restart assembly, boosting station crew size back to three and delivering critical supplies and equipment, including components of a U.S.-built oxygen generator that ultimately will help increase crew size to six in 2009.

    "Number one, we're getting back to a three person crew," said deputy station program manager Kirk Shireman. "We have two people now, adding a third is like a 50 percent increase in crew hours for assembly tasks that we have coming up and also for the research that we're doing on board. We have a full research program planned."

    Fixing the mobile transporter "will put us into position to get back into assembly of the ISS. Obviously, real key, we haven't had full redundancy of the mobile transporter so we can maneuver it and put the (station's robot) arm on it and complete the next major assembly task.

    "The third thing, we're actually launching a number of things on this flight ... to expand the crew size from three to six," Shireman said. "And six is where we really need to be when we have all the pressurized modules up there to conduct the kind of research the United States and the international partners want to conduct."

    Barring a mission extension, landing back at the Kennedy Space Center is planned for around 10:46 a.m. on July 13.

    "We really are wrapping up what we think of as the second of two test flights, to demonstrate that we have improved the things that led to the Columbia accident," Hale said. "We are expecting that we will be able to demonstrate that. And it is also the start of the assembly process.

    "We have 16 or so flights to complete over the next four years. That is not a tremendously hurried pace looking at the history of the shuttle program. There is time for us to stop or pause and work on problems for a little while. But certainly, we would like to have a good flight where we didn't have any major problems and allow us to turn around and demonstrate we can fly again in August."

    UNPRECEDENTED CAMERA COVERAGE OF A SLIGHTLY GENTLER ASCENT

    When the shuttle Columbia returned to Earth on Feb. 1, 2003, no one knew the ship's left wing had suffered catastrophic impact damage during launch 16 days earlier. Long-range tracking cameras showed a chunk of foam debris from the shuttle's external tank breaking away from the tank's left bipod ramp 81.7 seconds after liftoff, but they did not show where the foam hit.

    From the perspective of the only camera with a good view, the foam disappeared under the left wing followed by a shower of debris an instant later. Clearly, the foam hit the wing. But where? Engineers ultimately concluded it probably hit on the underside of the wing and, at most, damaged a few of the heat shield tiles in the area. No one believed the damage was catastrophic. But lacking good camera views, no one really knew.

    As it turned out, the 1.67-pound chunk of foam hit the left wing's leading edge at a relative velocity of nearly 550 mph, blasting a 6- to 10-inch hole in the reinforced carbon carbon insulation. During re-entry, super-heated plasma burned its way inside, melting the left wing from the inside out and triggering a catastrophic structural failure. All seven crew members - commander Rick Husband, pilot William "Willie" McCool, flight engineer Kalpana Chawla, physician Laurel Clark, payload commander Mike Anderson, physician David Brown and Israeli flier Ilan Ramon - were killed.

    Along with fixing the external tank foam - NASA eliminated the bipod ramp foam that was the actual cause of Columbia's demise - the space agency upgraded its tracking camera network at the Kennedy Space Center and Cape Canaveral Air Force Station to make sure any future damage is seen as soon as possible.

    The ability to quickly spot any impact damage, giving engineers time to assess the consequences and possible repair options, is a large part of Griffin's justification for proceeding with flight.

    At the launch pad, some 38 16mm cameras are mounted on the launch pad itself with three short-range camera sites around the pad perimeter featuring two 35mm cameras and one high definition TV camera each. Another 11 medium-range camera sites are positioned around the pad between one and six miles away, each one equipped with a 35mm camera and all but one equipped with an HDTV camera. Another 11 long-range camera sites are located between four and 40 miles of the pad. All long-range sites include 35mm cameras, two have 70mm cameras and 10 are equipped with HDTV.

    From liftoff through the first 30 seconds of flight, objects an inch wide or larger can be seen. Between 30 seconds and one minute, the resolution drops to objects three inches in diameter or larger and from one minute to 90 seconds, it drops to objects eight inches or larger. Between 90 seconds and booster separation two minutes after liftoff, ground-based tracking cameras can detect objects 15 inches across and pinpoint an impact site to within five feet.

    One WB-57 jet will be cruising 60,000 feet up, just north of Discovery's flight pat,h to photograph the shuttle using an infrared sensors and an HDTV camera attached to a powerful 11-inch telescope. The WB-57 will acquire most of its imagery in the minute leading up to solid-fuel booster separation (NASA operates two such jets, but one is grounded for maintenance).

    Finally, a radar system is in place featuring one ground-based C-band and two ship-based Doppler X-band instruments to look for debris coming off the external tank.

    For Discovery's flight, eight cameras mounted on the shuttle, its tank and twin boosters will provide close-up views of the external tank and the orbiter's belly during ascent.

    As with Discovery's last flight a year ago, a camera mounted high up on the external tank looking down on the underside of the space shuttle will beam back live television views throughout the eight-and-a-half-minute climb to orbit.

    But for this flight, four new cameras have been added, two near the top of each booster and two mounted near the back end of the powerful rockets. Each booster also carries another camera focused on a region of the tank known for losing small, popcorn-like pieces of foam.

    Imagery from the six booster cams will be available after the spent rockets are recovered and towed back to Port Canaveral a few days after launch.

    In addition, a digital camera mounted in a cavity where a propellant line enters the belly of the orbiter will photograph the tank as it separates in space.

    As if all that wasn't enough, an X-band marine radar seven-tenths of a mile from the pad will be on the lookout for vultures and other large birds. During Discovery's launch last summer, a large vulture struck the external tank a few seconds after liftoff, rammed by the shuttle at some 70 mph. If any large birds are seen prior to Discovery's launch Saturday, the countdown can be halted briefly if necessary.

    In short, if any impact damage occurs from any source, shuttle engineers expect to see it. NASA managers hope the radar systems, still somewhat experimental, eventually will provide enough resolution to permit acceptable debris coverage for night launches. But in the meantime, good lighting is required.

    In the aftermath of Columbia, NASA managers decided to launch at least two missions in daylight to optimize photo documentation of the tank and the shuttle's heat shield. Complicating the matter, launch also had to be timed to ensure external tank separation in daylight half a world away.

    Those lighting constraints and the requirement to launch into the plane of the space station's orbit severely limit when NASA can send up a space shuttle. Because of the problems experienced during Discovery's last flight, NASA is extending the daylight launch requirement to at least the next two missions. Here are the lighted launch windows for the rest of 2006:

    July 1-19
    Aug. 29 to Sept. 13
    Oct. 26-29
    Dec. 23-25

    If the next two flights go well from a foam shedding standpoint, NASA will relax the daylight launch rule, permitting much more frequent launch opportunities. But for now, the windows are limited.

    Once in orbit, the Lindsey and company will take over the inspection work, photographing the external tank as it tumbles away using a digital still camera and a movie camera. Data collected by the wing leading edge impact sensors also will be downlinked to mission control for detailed analysis.

    Located on each wing's forward spar behind every reinforced carbon carbon panel, the 132 accelerometers will provide data telling flight controllers whether anything struck the leading edges during launch.

    The sensor system generates two types of data: Peak and detailed.

    "Think about what a stereo equalizer looks like," flight director Paul Hill said before Discovery's launch last summer. "You've seen these ones that, across the frequency band, as the signal bounces up and down, it leaves a hash mark. The system works kind of like that. It's recording very high rate frequency response data across the wing leading edge from all these accelerometers that are on the wing spar for every RCC panel. And it registers the peaks, the software pulls out where those little peaks are from T-0 all the way to after we've made it into orbit.

    "The first thing we downlink is just the file that has all the peaks in it," Hill said. "That then tells us that we have a suspected impact somewhere and after we see that, then within an hour after the guys in the MER (mission evaluation room) see that and pick out the ones they think are potential impacts, then we put commands on board to downlink the detailed data around each one of those peaks."

    On flight day two, the astronauts will spend six-and-a-half hours using Discovery's robot arm and a 50-foot extension known as the orbiter boom sensor system, or OBSS, to inspect the wing leading edge panels and the shuttle's reinforced carbon carbon nose cap in excruciating detail.

    A laser sensor on the end of the boom is capable of spotting any wing leading edge damage that could pose a threat to the shuttle. The astronauts will start with the starboard, or right-side, wing leading edge, making six passes up and down the wing to cover all the angles. After scanning the nose cap, they will move on to the port wing and repeat the procedure.

    A high-resolution camera is mounted on the end of the OBSS to take close-up photographs of any potential damage sites.

    "The smallest damage of concern that we have is on the order of .08, eighty thousands of an inch, and that camera is certified to be able to show us that level of damage," said Steve Poulos, manager of the space shuttle projects office at the Johnson Space Center.

    "So if we do have a need to go out and do a focused inspection, if we find something, whether it be from the ascent imagery, the radar, wing leading edge instrumentation, our flight day two scan with the laser dynamic range imager, if we find anything of any concern we have the ability to go back with that very high fidelity digital camera and screen out once and for all whether there's a real concern there or not."

    But even that is not enough to satisfy the post-Columbia NASA.

    During final approach to the space station, at a distance of about 600 feet directly below the lab complex, Lindsey will guide Discovery through a slow end-over-end flip known as a rotational pitch maneuver, or RPM. The maneuver will take about nine minutes to complete - three quarters of a degree per second - allowing station commander Pavel Vinogradov and flight engineer Jeffrey Williams to photograph the shuttle's belly using digital cameras equipped with 400mm and 800mm telephoto lenses.

    It was during an identical flip during Discovery's flight last year that controllers spotted two so-called gap fillers protruding above the tile on Discovery's belly, prompting an impromptu spacewalk repair later in the mission. Since then, some 5,000 gap fillers have been removed and replaced.

    Additional inspections will be carried out after Discovery docks with the space station to look for signs of damage from orbiting space debris, so-called micrometeoroid damage. These late inspections prevented normal off-duty time for the crew and NASA managers, concerned about over working the astronauts, decided not to baseline the third spacewalk unless the mission is extended a day.

    The late inspections cannot be completed while docked to the station because of clearance issues between the OBSS and station structure. As a result, Discovery's crew will complete the work after undocking. Enough propellant will be available to permit a second rendezvous and re-docking if necessary.

    "Our current estimate for (micrometeoroid) impact that might cause loss of crew and vehicle is about 1-in-210, something on that order," Poulos said. "When we do the late inspection, we're going to improve that number to at least 1-in-280 and as high as 1-in-350, based on the performance of the camera system itself."

    Good imagery, radar and impact sensor data form one leg of Griffin's three-pronged justification for flight. The other two components are the crew's ability to repair minor damage and, in a worst-case scenario, the capability of the space station to support a combined crew of nine until a rescue flight can be mounted.

    It would not be easy. The Russian Elektron oxygen generator has a history of malfunctions, there is only one toilet on board and supplies would be tight. Worse, the only way down in a major emergency would be a single three-seat Soyuz capsule.

    But NASA and the Russians have pre-positioned additional supplies for just such a contingency, including food, water and lithium hydroxide to scrub carbon dioxide from the air, and even if the Elektron failed the day Discovery took off, the station could support the combined nine-member crew for at least 84 days.

    "We're going to have cameras all over the vehicle, inside and outside the vehicle, we'll have ground stations, we'll have radar tracking, we'll have airplanes in the air looking at us and we're going to capture all that data going up," Lindsey said. "Once we get up there on orbit, we're going to separate the tank, we have external tank cameras just like STS-114 did, it's going to image the tank and then of course, we're going to do inspections. So if we have a problem with an ice-frost ramp, we're going to know about it.

    "And if for some reason, in the very unlikely event it hits the orbiter and does damage and we need to do something about that damage, we have limited repair capabilities. And as a final last resort, we also have the safe-haven capability where we stay on station and wait for another vehicle to come get us. So we have a number of ways to mitigate this risk, some certified, some are not certified.

    "We feel pretty comfortable flying as we are with the existing ice-frost ramp design," Lindsey said. "I supported the decision the program made in keeping them the same."

    Until a new ice-frost ramp design is available, NASA engineers have redesigned Discovery's ascent profile to ease stress on the external tank's insulation, changing main engine throttle settings and lofting the shuttle's trajectory.

    Just in case.

    The so-called low-Q ascent profile is not new. NASA used it as recently as 1999 for a Hubble Space Telescope servicing mission.

    But the normally used high-Q profile keeps the shuttle's main engines at a higher throttle setting during a phase of flight when the ship is climbing out of the dense lower atmosphere.

    For Discovery's last mission, which flew high-Q, the shuttle's main engines throttled down to 72 percent power starting 38 seconds after launch. They stayed there for about 14 seconds before throttling back up to 104.5 percent. During the throttled-down phase of flight, the shuttle accelerated through the sound barrier and the ship was subjected to a maximum aerodynamic pressure of about 695 pounds per square foot.

    For Discovery's upcoming flight, the engines will be throttled down to 67 percent power and remain there for about 24 seconds, or 10 seconds longer than the high-Q profile. At the same time, Discovery's trajectory will be lofted slightly to get it out of the lower atmosphere faster. Booster separation will occur at a slightly lower velocity and altitude.

    The net effect is to reduce aerodynamic loads on the liquid oxygen feedline, the ice-frost ramps, the pressurization lines and cable try by about 7 percent at the expense of burning up about 1,180 pounds of additional propellant. The low-Q profile also exposes the crew to slightly greater abort risks.

    For example, an engine failure early in flight could force the astronauts to attempt a risky return-to-launch site abort, or RTLS. During a high-Q flight, the RTLS window of vulnerability is about two minutes and 35 seconds long. For a low-Q ascent, RTLS vulnerability is two minutes and 45 seconds.

    Likewise, vulnerability to aborts to emergency landing sites in Spain and France will be extended some 17 seconds. All in all, the low-Q profile increases a crew's risk of an abort by about 2 percent.

    "What it really means is, as we approach supersonic speeds, when we get the maximum force on the vehicle, we usually throttle the main engines down so we can get through that heavier, thicker part of the atmosphere at a lower speed and accelerate more slowly until really, we're out of the atmosphere and there are no air loads on the vehicle. In the last 10 flights, 12 flights or so, we've been flying what's called a high-Q profile so we don't throttle down as much, we go faster, put more loads on the vehicle.

    "Because our flight had some additional ascent performance - we were light enough we could carry say an extra 1,500 pounds to orbit - if we just gave up about a thousand pounds of that excess performance then we could throttle down sooner, stay throttled down longer and then throttle back up later, which would reduce the loads on the tank by somewhere around 7 to 10 percent.

    "So imagine what it's like if you roll down the window in your car and you're going, say, 40 mph, and you stick your hand out the window you're going to get a certain force on your hand. If you then accelerate to 60 mph and you stick your hand out the window, you can tell there's a big difference. So doing this lower dynamic pressure, low-Q, it's less force on the tank, it buys a little bit more margin to deal with the uncertainties in the ice-frost ramps.

    Pilot Kelly, who will be monitoring Discovery's main engines during the climb to space, said "it's almost transparent for us. The only thing for me that's different, instead of the engines throttling back to the 71 percent range, they throttle back to 67 percent. That's it. It changes abort boundaries, it changes the profile a little bit, it's a little bit more lofted. We've flown a lot more flights at low-Q than we have at high-Q."

    REDUCING RISK BY REDUCING FOAM: HOW MUCH IS ENOUGH?

    In the aftermath of Columbia, NASA engineers learned something they already knew: the foam insulation on the shuttle's external tank flakes away on every flight and poses a threat to the orbiter's heat shield. The phenomenon was not viewed as a major threat, however, and seven astronauts lost their lives.

    The first and most obvious fix was to remove the bipod ramp foam that caused Columbia's destruction. The foam was in place to prevent ice from building up before takeoff on fittings where two struts connecting the shuttle's nose to the tank attach. NASA solved that problem by installing heaters on the fittings and removing the foam altogether.

    Going into Discovery's flight last year, engineers knew foam on another area of the tank - the so-called protuberance air-load, or PAL, ramps - posed another potential risk. The foam is applied by hand, on top of robotically sprayed insulation, and then sculpted to form long wind deflectors. NASA kicked off a program to redesign or eliminate the PAL ramps but decided to launch Discovery last summer with the old design.

    Again, the foam surprised then. During launch last July 26, a one-pound chunk of foam broke away from the hydrogen PAL ramp. While it did not hit anything, it represented a problem that had to be fixed before flights could resume.

    Then came Hurricane Katrina, which devastated New Orleans and damaged Lockheed Martin's Michoud Assembly Facility, where the huge tanks are built. Struggling to help the contractor work force and complete testing and analysis, Hale decided late last year to remove the PAL ramps before the shuttle flew again.

    "We knew the PAL ramps were a hazard and we had a plan that over the course of about two years we were going to do a very orderly, systematic and thorough job and remove the PAL ramps from the external tank," Hale said. "We accelerated that plan. That was the most hazardous piece of foam we had on the outside of the tank. We decided to fix it and we accelerated that work."

    He made that decision on the assumption that computer modeling and wind tunnel data would prove the external brackets, pressurization lines and cable tray could stand up to the expected aerodynamic buffeting in the absence of the protective ramps.

    "There were over 100 different piece parts on that tank, mostly brackets, structural items such as the cable tray, the pressurization lines that run on the outside of the tank, that were affected aerodynamically ... by the removal of the PAL ramp," Hale said.

    In the end, after months of testing and analysis, the results showed the tank was, in fact, structurally strong enough.

    "We have made the largest aerodynamic change to this vehicle that has been made since we started flying 25 years ago, removal of what we call the PAL ramp," Hale said. "We had to verify that the components, the metal components that were protected from the aerodynamic flow by this ramp were still capable of withstanding those loads. We put together an intense campaign of wind tunnel tests, computational fluid dynamic runs and other calculations to provide updated force environments for the structural analysts.

    "The structural analysts have done thousands of calculations in the last two-and-a-half months and were able to report that in all areas they can show that we meet the required factor of safety and we are safe to fly structurally without those two large pieces of foam on the outside of the tank."

    In fact, the structural engineering community "demonstrated conclusively that we met what we call our 1.4 factor of safety," Hale said. "So in the worst case load on the weakest part, we have 140 percent of the strength that you need to ensure that your structure holds together."

    Sensors have been mounted in the cable tray to measure the actual stresses on the external fittings during launch.

    The external tank is covered by some 4,000 pounds of lightweight foam insulation. It's there to prevent ice from forming in the humid Florida weather when the tank is loaded with supercold liquid oxygen and hydrogen. It also helps minimize how much propellant boils off in the tank before launch.

    About 75 percent of the foam is sprayed on robotically in a tightly controlled process. NASA's flight history shows that foam tends to stay in place. But about 25 percent is manually applied, including the 35 pounds or so that made up the now-removed PAL ramps and the still-in-place ice-frost ramps. It is that manually applied foam, sprayed on top of existing foam, that appears to be the most dangerous.

    The most significant concentration of manually applied foam left on the tank after removal of the bipod and PAL ramps is the foam insulating the 37 brackets used to hold the pressurization lines and cable tray in place.

    At first blush, the IFR foam would not appear overly dangerous. In flights where photography of the tank is available, the largest piece of missing IFR foam weighed an estimated .09 pounds. But analysis indicates pieces weighing up to .2 pounds could come off and if one did, at the worst possible time and from the worst possible place, catastrophic impact damage could result.

    Complicating the picture is analysis of a tank that was dissected last year in the wake of Discovery's first return-to-flight mission. Engineers found underlying cracks in the insulation where foam was applied on top of pre-existing insulation. That means there is a possible failure mechanism in place with the ice-frost ramps on Discovery's tank.

    "We have data that shows we have potentially cracks underneath large foam, or foam that's put on top of other foam," said Bill Gerstenmaier, NASA's associate administrator for space flight. "And we have flight history that doesn't show that we lose a lot of foam. ... So the dilemma is how can we not rule out that at some point in the future we're not going to have some larger foam loss with this underlying problem? And therein lies the debate.

    "We can't figure out the theory that can explain to us why we haven't had larger foam loss with this underlying crack. Obviously, there's something we think that's protecting us in the physics of the situation but we don't know what that is."

    And so, while engineers believe .2 pounds is the upper limit on IFR debris, they cannot prove larger pieces are not possible. As a result, NASA kicked off a program to redesign the ice-frost ramps and briefly considered modifying Discovery's tank before flight.

    But during a wind tunnel test, a large chunk of the redesigned ramp blew off. The old design, subjected to similar worst-case conditions in the wind tunnel, came through with only minor shedding. Griffin, Hale and other senior managers approved shipping Discovery's tank to Florida with the old design.

    O'Connor and Scolese, however, opposed the move then and registered a more formal complaint when they voted no-go for launch during a flight readiness review at the Kennedy Space Center earlier this month. The IFR foam remains classified as "probable/catastrophic."

    "One of the things I think that was wrong before Columbia is we didn't pay enough attention to some of the problems we had, in particular foam problems," Hale said. "We pay a lot of attention to those problems today and we're not making any decisions on an ad hoc or a schedule-driven basis. We're taking a very hard engineering look at these things. I've said it before and I'll say it again, if we could go back 25 or 30 years and change the design of the shuttle, the number one thing I would say we needed to do was not put our fragile heat shield in an area where debris can come off during the first three minutes of flight and cause us catastrophic damage.

    "But it's the vehicle we've got and it's the only vehicle we're going to have for the next several years. So if we intend to be a space-faring nation and put Americans into space on an American-flagged vehicle, it's going to be the space shuttle. Our job is to make that as safe as we practically can. It's not going to be perfectly safe."

    Hale agrees NASA should redesign the ice-frost ramps. He even agrees with the "probable/catastrophic" classification. But he believes NASA should test the PAL-free tank in flight before making another major change to the insulation.

    "We think we could lose up to two tenths of a pound of foam," he said. "Off Columbia, we lost a pound and a half, 1.6 pounds. Off the PAL ramp off STS-114, we lost a pound. We've eliminated both of those. The next largest piece we can lose, the biggest we've ever seen is .09, less than a tenth of a pound. We think statistically we might lose two tenths of a pound even though we've never seen that. So you're looking at smaller and smaller pieces of foam that come off less and less frequently. We're on a continuous improvement path.

    "The real question is on this particular flight, why would we not stand down and fix all the ice frost ramps? There are a couple of good reasons. One is we don't have a good design in hand today. But secondly, there is a principle in flight test that says when you have made a major aerodynamic change and you have studied it in the wind tunnel and you've studied it with computer simulations and you think it's good to go fly with, you go fly with that one change. Because all those wind tunnels and all that analysis and all those computer models are never quite as good as real life. You really need to go fly it and see whether it works like you think it was going to and get that data before you proceed to change anything else.

    "It's that flight test principle that we're resting on here today," Hale said. "It is nice to say you ought to stand down and fix all your problems. If we adopted that philosophy we would never fly. We think we have identified the most critical problem, we've fixed that, we need to go flight test to that. We have additional sensors this time, we have additional cameras this time that will bring us back information on how well that worked, and once we feel comfortable that we have accommodated the PAL ramp successfully, we're going to move onto the ice-frost ramp redesign."

    Engineers are hopeful they can eliminate most, if not all, of the IFR foam by replacing the aluminum brackets with a different material, one less susceptible to thermal effects. Titanium is one candidate. For tanks already in the pipeline, different ramp designs might improve safety.

    Gerstenmaier said he hopes to have a new IFR design ready to fly by the end of the year. But that depends on the results of more analysis and wind tunnel testing.

    Despite the controversy generated by the objections raised by O'Connor and Scolese, many current and former space agency officials agreed with the decision to press ahead.

    "I trust the judgment of shuttle program leaders Bill Gerstenmaier and Wayne Hale," legendary Apollo flight director Gene Kranz wrote in an op-ed piece carried by Florida Today. "I brought them into the business of mission control, trained them and watched them grow to shoulder great responsibilities. I have trusted these men for more than a decade and found their risk judgment superior. I trust that they made the proper risk judgment when they committed to the Discovery launch."

    Time will tell.

    A BUSY MISSION TO REPAIR AND SERVICE THE SPACE STATION

    The seemingly endless debate about the external tank foam insulation has shifted attention away from the actual goals of Discovery's mission. But STS-121 is an exceedingly complex flight as such missions go, with three major objectives: space station resupply; repair of the stalled mobile crane transporter; and delivery of Reiter as a third full-time crew member.

    Even if no obvious signs of foam shedding or damage show up in the ascent video, one of the recommendations of the Columbia Accident Investigation Board requires NASA to "provide a capability to obtain and downlink high-resolution images of the underside of the orbiter wing leading edge and forward section of both wings' thermal protection system."

    The Discovery astronauts are going to spend their second day in space carefully inspecting the leading edges of both wings, along with the reinforced carbon carbon nose cap of the shuttle, using the orbiter boom sensor system, or OBSS.

    First, the shuttle's 50-foot-long robot arm will lock onto the OBSS, which is stowed on the right side of the cargo bay. Nowak and Wilson then will spend the entire day maneuvering the boom back and forth along the leading edges of both wings, using an OBSS television camera and the new laser sensor to inspect every square inch of the RCC panels. The astronauts also will use the boom to inspect the nose cap. Maximum speed of the boom survey: 2 inches per second.

    The shuttle's nose cap and wing leading edge panels, all made of heat-resistant reinforced carbon carbon - RCC - endure temperatures of more than 3,000 degrees during re-entry. It was a breach in an RCC leading edge panel that triggered Columbia's destruction in 2003 and it is concern about the integrity of the system that has prompted the flight day two inspections.

    And it doesn't take a major, Columbia-class hole to threaten disaster. Ground tests show impacts that wear away the outer coating of an RCC panel, coupled with internal delamination of the carbon composite layers making up the material, could lead to catastrophic damage.

    But the laser sensor on the end of the OBSS should be able to detect any potentially dangerous damage.

    "The first couple of flights we'll do a lot of inspections to make sure that we really understand the changes that have been made to the external tank, and that the sensing system that we're adding to the leading edge of the wing are really working properly and telling us what we need to know," Fossum said in a NASA interview. "After we get more comfortable with that, with the tank, with the modifications that we've made, my understanding is that we'll be backing off on some of these inspection requirements. But a lot of them are here to stay because we understand how important it is."

    DAY.ET.........DD...HH...MM...EVENT
    
    07/01/06
    Sat 03:49 PM...00...00...00...STS-121 Launch
    Sat 03:58 PM...00...00...09...Main engine cutoff
    Sat 04:26 PM...00...00...37...OMS-2 rocket firing
    Sat 07:24 PM...00...03...35...Shuttle arm (SRMS) powerup
    Sat 07:49 PM...00...04...00...Umbilical camera download
    Sat 08:16 PM...00...04...27...NC1 rendezvous rocket firing
    Sat 08:34 PM...00...04...45...Group B computer powerdown
    Sat 09:49 PM...00...06...00...Crew sleep begins
    
    07/02/06
    Sun 05:49 AM...00...14...00...Crew wakeup
    Sun 07:35 AM...00...15...46...NC2 rendezvous rocket firing
    Sun 08:14 AM...00...16...25...SRMS checkout
    Sun 08:29 AM...00...16...40...Centerline camera installation
    Sun 08:59 AM...00...17...10...Middeck transfer preparations
    Sun 08:59 AM...00...17...10...OBSS unberthing
    Sun 09:49 AM...00...18...00...OBSS starboard wing leading edge survey
    Sun 10:59 AM...00...19...10...OMS pod survey from flight deck
    Sun 11:19 AM...00...19...30...Ergometer setup
    Sun 11:19 AM...00...19...30...OBSS nose cap survey
    Sun 11:49 AM...00...20...00...Crew meals begin
    Sun 01:04 PM...00...21...15...Docking ring extension
    Sun 01:44 PM...00...21...55...NPC rendezvous rocket firing
    Sun 02:04 PM...00...22...15...Spacesuit checkout
    Sun 02:04 PM...00...22...15...OBSS port wing leading edge survey
    Sun 03:34 PM...00...23...45...OBSS berthing
    Sun 04:39 PM...01...00...50...SRMS survey
    Sun 06:04 PM...01...02...15...NC3 rendezvous rocket firing
    Sun 06:09 PM...01...02...20...Rendezvous tools checkout
    Sun 08:49 PM...01...05...00...Crew sleep begins
    
    Docking is targeted for flight day three. Lindsey will guide Discovery through a standard rendezvous profile, approaching the lab complex from behind and below. The terminal phase of the rendezvous procedure begins about three hours before docking with the shuttle trailing the station by about 9.2 miles.

    On final approach, at a distance of about 600 feet directly below the station, with Discovery's nose facing forward and its open payload bay facing the station, Lindsey will carry out the slow 360-degree rotational pitch maneuver, or RPM, that will point the belly of the shuttle at the station.

    As the shuttle's underside rotates into view, Expedition 13 commander Vinogradov and flight engineer Williams, shooting through windows in the Zvezda service module, will photograph Discovery's belly with handheld digital cameras equipped with 400mm and 800mm lenses.

    "The 800 millimeter gives them one-inch resolution, which is what we're looking for around (landing gear) door seals," Hill said. "400 millimeters gives three inches, which is what they're looking for everywhere else."

    Imagery from the station will be downlinked to Houston for detailed analysis.

    After completing the RPM maneuver, Lindsey will position Discovery about 400 feet directly ahead of the space station with the shuttle's nose facing deep space and its cargo bay facing the lab complex. He then will guide the spacecraft to a docking with a pressurized mating adaptor attached to the Destiny laboratory module. Assuming an on-time launch, docking is expected around 11:25 a.m. on July 3.

    After leak checks, Vinogradov and Williams will welcome the shuttle crew aboard the station and provide a safety briefing before all nine astronauts get down to work.

    DAY.ET.........DD...HH...MM...EVENT
    
    07/03/06
    Mon 04:19 AM...01...12...30...ISS crew wakeup
    Mon 04:49 AM...01...13...00...STS crew wakeup
    Mon 06:04 AM...01...14...15...Group B computer powerup
    Mon 06:13 AM...01...14...24...NH rendezvous rocket firing
    Mon 06:19 AM...01...14...30...Rendezvous timeline begins
    Mon 06:58 AM...01...15...09...NC4 rendezvos rocket firing
    Mon 08:34 AM...01...16...45...RPM photo setup verification
    Mon 08:30 AM...01...16...41...TI rendezvous rocket firing
    Mon 09:54 AM...01...18...05...Approach timeline begins
    Mon 10:19 AM...01...18...30...RPM photo documentation
    Mon 11:25 AM...01...19...36...ISS docking
    Mon 11:49 AM...01...20...00...Leak checks
    Mon 12:19 PM...01...20...30...Group B computer powerdown
    Mon 12:19 PM...01...20...30...Orbiter docking system preps for ingress
    Mon 12:39 PM...01...20...50...Hatches open; welcome aboard!
    Mon 01:39 PM...01...21...50...Safety briefing
    Mon 02:04 PM...01...22...15...Russian seat liner installation
    Mon 02:04 PM...01...22...15...SSRMS: OBSS grapple
    Mon 02:24 PM...01...22...35...SSRMS: OBSS unberthing
    Mon 02:59 PM...01...23...10...SSRMS: move to OBSS handoff position
    Mon 03:19 PM...01...23...30...ROOBA leak check
    Mon 04:09 PM...02...00...20...OBSS handoff from SSRMS
    Mon 04:34 PM...02...00...45...Reiter officially joins ISS crew
    Mon 04:39 PM...02...00...50...Spacewalk tools transfer
    Mon 04:39 PM...02...00...50...SRMS positioned to support MPLM install
    Mon 08:19 PM...02...04...30...STS/ISS crew sleep begins
    
    One of the first items on the agenda is to transfer a Soyuz seat liner from Discovery to the station and to check out Reiter's re-entry pressure suit. Once those tasks are accomplished, about four hours after docking, the European astronaut will become an official member of the Expedition 13 crew. He is scheduled to remain aboard the outpost until late December, returning to Earth with the crew of the year's third shuttle mission.

    While Reiter's equipment is being transferred, Wilson and Nowak will use the station and shuttle robot arms to redeploy the OBSS boom for additional inspection work and photo support of the upcoming spacewalks. Because of clearance issues after the shuttle is docked, Discovery's robot arm cannot unberth the OBSS on its own. Instead, the space station's arm - the SSRMS - will pluck the sensor boom from the shuttle's cargo bay and hand it off to Discovery's arm about five hours after docking.

    The astronauts also will begin moving station equipment stowed in the shuttle's middeck area over to the space station, along with tools that will be used in the upcoming spacewalks.

    Flight day four - the July Fourth holiday in the United States - will be devoted to attaching a 21,000-pound cargo module to the Unity module's downward-facing, or nadir, port. Known as Leonardo, the Italian built multi-purpose logistics module is loaded with about 5,100 pounds of supplies and equipment, including a high-tech laboratory freezer, a European plant biology experiment rack and a U.S.-built oxygen generator that ultimately will help support a crew of six.

    In addition, more than 1,000 pounds of fresh water, a by-product of the shuttle's electricity producing fuel cells, will be transferred to the station while Discovery is docked.

    DAY.ET.........DD...HH...MM...EVENT
    
    07/04/06
    Tue 04:19 AM...02...12...30...STS crew wakeup
    Tue 04:49 AM...02...13...00...ISS crew wakeup
    Tue 06:29 AM...02...14...40...SSRMS grapples MPLM
    Tue 06:59 AM...02...15...10...MPLM unberthing
    Tue 07:49 AM...02...16...00...MPLM installation
    Tue 08:59 AM...02...17...10...MPLM bolt torquing; crew meals begin
    Tue 10:09 AM...02...18...20...SSRMS ungrapples MPLM
    Tue 10:24 AM...02...18...35...SSRMS grapples mobile transporter
    Tue 11:04 AM...02...19...15...MPLM vestibule pressurization
    Tue 11:09 AM...02...19...20...SSRMS ungrapples lab module
    Tue 11:39 AM...02...19...50...SSRMS moves to survey support position
    Tue 11:59 AM...02...20...10...SRMS/OBSS heat-shield survey
    Tue 01:19 PM...02...21...30...MPLM activation
    Tue 02:49 PM...02...23...00...MPLM vestibule ingress
    Tue 03:34 PM...02...23...45...MPLM ingress
    Tue 04:50 PM...03...01...01...EVA-1: Procedures review
    Tue 08:19 PM...03...04...30...STS/ISS crew sleep begins
    
    "We're re-supplying them with some rack experiments, a lot of food, clothing, things like that, hardware replacements - there's a whole laundry list of things that we're supplying to the space station," Lindsey said in a NASA interview. "The other purpose, of course, of the MPLM is to bring things down. And so, we're going to bring back a whole bunch of stuff that they don't need anymore. That includes experiment samples, used articles they're not using anymore, and trash - you name it.

    "One of the issues with space station since we've lost Columbia is we've been putting things on board, but we haven't been able to get very many things off. So, one of the goals will be to help them with their stowage issues and logistics issues by bringing a bunch of things off the space station as well."

    Once Leonardo has been robotically bolted in place, the astronauts will perform leak checks to make sure the MPLM is firmly mated to Unity and pressurize the vestibule between Unity and the supply module. Then they'll open the module, float inside and begin the process of moving supplies into the space station.

    At roughly the same time, yet another shuttle tile survey will begin using the RMS-OBSS boom, with additional TV views provided by the SSRMS.

    The tools that will be used for the upcoming spacewalks will be configured for use and the crew will spend an hour reviewing the procedures that will be used in the first spacewalk.

    TESTING A NEW SHUTTLE WORK STATION

    The fifth day of the mission is highlighted by the first of at least two planned spacewalks, a six-and-a-half-hour excursion by Sellers and Fossum to test Discovery's robot arm/OBSS combination as a potential platform to make heat shield repairs down the road.

    "The question we want to answer is, can you use the boom as a worksite, as a platform to repairing underneath the orbiter?" Lindsey said in a NASA interview. " So, the scenario is you have a problem, you want to go repair a tile or a leading edge (panel) or something like that. Can you put (one or two spacewalkers) out on the end of this boom, maneuver them underneath the vehicle, and is the platform stable enough to allow them to do repairs?"

    The shuttle's robot arm is 50 feet long as is the OBSS extension.

    "If an EVA crewmember puts a load or pushes at the end of the boom, how much flex do you get in that boom, how much flex do you get in the arm? Do the joints on the arm back drive? How much do they back drive? And, is it stable enough to be able to do work, precise work, where you have to be careful in how you do it?

    "We're going to put one and then two crewmembers on that boom, go to a couple of positions, and they're going to do some typical EVA-type maneuvers. For example, they'll lean back aggressively while they're standing at the end of the arm to see what kind of drive you get on the joint. They might reach back for a tool and just kind of simulate those kinds of motions.

    "And then, one of the test points will go actually to structure, where they're pushing against a truss structure in the payload bay, and see what kind of flex you're doing. So, we're going to get two things out of that. We're going to get loads information; in other words, how much force you're putting into the arm, how much do the joints move? And we're going to get an operational assessment, if you will. The EVA crewmember will simulate doing a repair and say, 'Can I do a repair with the arm in this configuration?' So, the goal is to be able to figure out at what points underneath the Orbiter do we need a further way to stabilize the crew, like some, putting something to stabilize them on the bottom of the vehicle itself? Or, can we get away without doing that at all?"

    DAY.ET.........DD...HH...MM...EVENT
    
    07/05/06
    Wed 04:19 AM...03...12...30...STS crew wakeup
    Wed 04:49 AM...03...13...00...ISS crew wakeup
    Wed 05:34 AM...03...13...45...EVA-1: Pre-breathe with ISS oxygen
    Wed 08:24 AM...03...16...35...EVA-1: Spacesuit purge
    Wed 08:24 AM...03...16...35...MPLM transfers
    Wed 08:39 AM...03...16...50...EVA-1: Spacesuit prebreathe
    Wed 09:34 AM...03...17...45...SSRMS ungrapples lab module
    Wed 09:39 AM...03...17...50...EVA-1: Crew lock depressurization
    Wed 10:24 AM...03...18...35...EVA-1: Airlock egress; tool setup
    Wed 10:44 AM...03...18...55...EVA-1: Zenith IUA replacement
    Wed 11:14 AM...03...19...25...EVA-1: Tool setup
    Wed 11:54 AM...03...20...05...EVA-1: OBSS setup (part 1)
    Wed 11:59 AM...03...20...10...MELFI transfer
    Wed 12:44 PM...03...20...55...EVA-1: 1 EV position 1 evaluation
    Wed 01:24 PM...03...21...35...EVA-1: OBSS setup (part 2)
    Wed 01:54 PM...03...22...05...EVA-1: 2 EV position 3 evaluation
    Wed 02:29 PM...03...22...40...EVA-1: 2 EV push evaluation
    Wed 02:59 PM...03...23...10...EVA-1: OBSS cleanup
    Wed 03:49 PM...04...00...00...EVA-1: Tool cleanup
    Wed 04:39 PM...04...00...50...EVA-1: Airlock ingress
    Wed 04:54 PM...04...01...05...EVA-1: Airlock repressurization
    Wed 08:19 PM...04...04...30...STS/ISS crew sleep begins
    
    Sellers and Fossum will exit through the station's Quest airlock module, first moving up to the lab's main solar array truss to install a device designed to prevent a cable cutter from inadvertently severing critical video and data cables leading to a rail car used to move the station's robot arm (see the discussion of spacewalk No. 2 below for complete details).

    Making their way down to the shuttle's payload bay, Sellers and Fossum will rig safety tethers and attach a foot restraint to the end of the OBSS along with sensors to record how much force is imparted to the boom when they move about. Sellers then will climb onto the OBSS, connected to the shuttle's robot arm by a long tether and to the sensor boom by another, shorter tether. Fossum said they refer to the latter as "our sissy tether."

    Safely tethered, Sellers will be moved to a point just above the starboard sill of the cargo bay, about 14 feet from any other structure. This is considered a "strong" configuration for the boom. After moving about to impart various forces, he will be moved to a point high above the port wing for another round of "bouncing the boom" tests. Extended some 60 feet from the shuttle, the boom is expected to exhibit a slow back-and-forth sway as Sellers moves about.

    "The idea is to see if you could do a repair while standing on the end of this," Sellers said in a NASA interview. "The problem is, of course, that it's a very long, bendy fishing pole with somebody standing on the end, so it's not a completely stable platform. It sways around a bit; we've tested it in virtual reality, we've tested it on an air-bearing floor. We know that it has some motion, some sway, associated with it."

    In an interview with CBS News, he likened it to painting the side of a boat while standing in a raft bobbing up and down.

    "It will have a long, slow sway, about four to eight seconds period," he said. "So I want you to imagine that you're standing in a little row boat that's going up and down in the swell, slowly, and you're trying to paint the side of a ship that's not moving, or the side of a dock next to you. You have to put quite a lot of compensation in, you have to be careful, but it's not impossible. You just have to think about what you're doing."

    After the first two tests, the arm will be maneuvered back into the cargo bay and Fossum will climb aboard. The boom then will take both spacewalkers back out over the port wing and finally, to a cargo truss in the payload bay that Fossum will push against to mimic actual repair work.

    "After we test it out with one person, we'll bring the boom back down to the payload bay and I'll get into the foot restraint," Fossum said. "Piers will be hanging on to the boom. This is to simulate the kind of situation where we'll actually (be) doing a repair, where I would be the one in the foot restraint, with both hands free so I can do the repair, and Piers will be moving around the outside.

    "We'll have kind of a tool stanchion and some other support equipment set up, so he'll act as if he's getting tools out and handing them to me. We'll be able to evaluate the stability of the system with both of us moving around and putting force into the whole boom and arm just to make sure that it's stable enough. We'll be doing some basic maneuvers in free space.

    "And then, we'll go down to some structure and I'll actually put force into the structure as if I'm tamping down, the repairs, like for a tile repair that requires a continuous tamping motion to push all of the repair material down into the patch site. We'll just do that to see if it holds us stable enough to accomplish those kinds of basic tasks."

    The work could help clear the way for an eventual mission to service the Hubble Space Telescope. The observatory circles the globe in a different orbit from the space station and the crew of any proposed servicing mission would not be able to take advantage of the safe haven option.

    As a result, NASA needs credible ways to make repairs if any impact damage is seen and with the OBSS, the astronauts would have a potential way to work on the belly of the shuttle.

    Ground testing indicates the robot arm/OBSS combination will be relatively sturdy and the astronauts said they had no concerns about the possibility the OBSS - and the astronauts - could somehow break free of the shuttle's robot arm.

    "We've thought about that and all the different ways to get ourselves out of trouble," Sellers said. "We'll still be tethered, by the way, to the main shuttle arm so if we came off, that's our first recourse. So the first thing you've got to do is get off the boom, then you've got to stabilize yourself (and) use the tether to get back to the arm. So a multi-step process, but I think pretty safe."

    The astronauts will focus on equipment transfers from the logistics module the following day - flight day six - review plans for their second spacewalk and hold a traditional joint crew news conference.

    DAY.ET.........DD...HH...MM...EVENT
    
    07/06/06
    Thu 04:09 AM...04...12...20...STS crew wakeup
    Thu 04:49 AM...04...13...00...ISS crew wakeup
    Thu 07:04 AM...04...15...15...MPLM transfers
    Thu 08:54 AM...04...17...05...EVA tools configured
    Thu 10:24 AM...04...18...35...Spacesuit checkout
    Thu 11:19 AM...04...19...30...SAFER checkout
    Thu 11:49 AM...04...20...00...Joint crew meal
    Thu 12:49 PM...04...21...00...Joint crew news conference
    Thu 01:29 PM...04...21...40...Joint crew photo
    Thu 01:49 PM...04...22...00...MPLM transfers resume
    Thu 03:49 PM...05...00...00...EVA-2: Procedures review
    Thu 07:49 PM...05...04...00...STS/ISS crew sleep begins
    

    CRITICAL REPAIR WORK PLANNED FOR SECOND SPACEWALK

    The most critical task planned for Discovery's mission is arguably the one that must be accomplished to permit continued assembly of the international outpost: repair of the stalled mobile transporter.

    The transporter is an ingenious robotic cart designed to creep along rails on the front face of the station's unfinished solar array truss, carrying the station's Canadian-built robot arm from one work station to another. At each work station, the transporter and arm can be locked down to provide stability. The long truss eventually will sport four huge sun-tracking solar array panels that will generate the electrical energy needed to support a six-member crew and a full suite of scientific experiments.

    But the outer segments of the truss cannot be built without the station's robot arm and the arm cannot be moved from point to point unless the transporter is operational and has redundant power, video and data cables.

    As the transporter moves along the truss it plays out or rolls up ribbon-like power and data cables. To provide redundancy, two trailing umbilical system - TUS - reel assemblies play out and rewind separate cables. The transporter was launched with powerful cable cutters in devices on the transporter itself, called interface umbilical assemblies, in case of a jam in either TUS reel that might otherwise strand the work platform.

    On Dec. 16, TUS cable No. 1 on the Earth-facing, or nadir, side of the transporter was severed when the cable cutter in the nadir interface umbilical assembly suddenly fired for no apparent reason, slamming down with 960 pounds of force. Engineers still do not know why the spring-driven cutter fired.

    But the incident left the mobile transporter with just one set of power and data cables and NASA flight rules forbid its movement along the truss unless full redundancy is available. The concern is that a second failure could leave the transporter stranded between work sites and unable to be safely latched down. That, in turn, would pose a risk during shuttle dockings or other events when unwanted movement could prove dangerous.

    "We have rules in place that say we do not base the (station's robot) arm on the mobile transporter during that time and we do not maneuver the mobile transporter," Shireman said. "It's very important for us to restore full functionality before we continue assembly. That's because to continue assembly, we have to move the mobile transporter out on the truss, base the arm out there to actually install the next piece of truss. That's a very important piece of this mission for us, to return to full functionality."

    Said Sellers: "Basically it killed itself just before Christmas. It's a complicated task. If we don't get this thing fixed, we can't move this truck that moves up and down the front face of the station and we can't continue with assembly. So we absolutely have to get it fixed before the next mission.

    "And it's a complicated business because it's a large, difficult-to-handle object, it sits inside a bay and it's got multiple, multiple electrical connections. So there are a number of significant obstacles to getting this done. We've thought about it a lot. I think we'll manage to do it OK, the engineering team has put an enormous amount of effort into this and I think it's going to work out. But it's one of the more daunting tasks."

    Earlier this year, worried that the cable cutter on the upward facing, or zenith, side of the transporter might fire, Expedition 12 commander William McArthur and flight engineer Valery Tokarev attempted to disable the zenith cable cutter during an already planned spacewalk. But they were unable to drive in a "safing" bolt and rather than leave the cable in place, they removed it from the cutting mechanism and tied it off. That had the effect of stranding the mobile transporter at work site 4.

    Sellers and Fossum will attempt to fix the zenith cable system during the first of two planned spacewalks when they will insert a wedge-like blade blocker designed to prevent any damage to the cable even if the cutter fires later. If the blade blocker fits properly, they will re-insert the zenith cable in the interface umbilical assembly and thus restore the transporter to single-cable operation.

    That's important because the crew needs to move the transporter from work site 4 to work site 5 to get the access needed to repair the nadir cable system during a second spacewalk.

    Assuming the zenith blade blocker works, Sellers and Fossum will venture back out to the truss during their second spacewalk and replace the interface umbilical assembly and its deployed cable cutter with a new unit carried up aboard Discovery.

    DAY.ET.........DD...HH...MM...EVENT
    
    07/07/06
    Fri 03:49 AM...05...12...00...STS crew wakeup
    Fri 04:19 AM...05...12...30...ISS crew wakeup
    Fri 05:04 AM...05...13...15...EVA-2: Preparations with ISS oxygen
    Fri 07:54 AM...05...16...05...EVA-2: Spacesuit purge
    Fri 07:54 AM...05...16...05...MPLM transfers
    Fri 08:09 AM...05...16...20...EVA-2: Spacesuit prebreathe
    Fri 09:09 AM...05...17...20...EVA-2: Crew airlock depressurization
    Fri 09:54 AM...05...18...05...EVA-2: Airlock egress
    Fri 10:09 AM...05...18...20...EVA-2: EV1: FGB retrieval
    Fri 10:09 AM...05...18...20...EVA-2: EV2: APFR setup
    Fri 10:49 AM...05...19...00...EVA-2: Pump module retrieval
    Fri 11:09 AM...05...19...20...EVA-2: EV1: Nadir IUA replacement
    Fri 11:09 AM...05...19...20...EVA-2: EV2: APFR reconfig and TUS setup
    Fri 11:59 AM...05...20...10...EVA-2: Pump module installation
    Fri 12:39 PM...05...20...50...EVA-2: Nadir TUS replacement
    Fri 03:24 PM...05...23...35...EVA-2: TUS cable routing
    Fri 04:09 PM...06...00...20...EVA-2: Airlock ingress
    Fri 04:24 PM...06...00...35...EVA-2: Airlock repressurization
    Fri 07:49 PM...06...04...00...STS/ISS crew sleep begins
    
    But first, they will move a large liquid ammonia pump module to a spare parts depot on the station. The pump module, part of a complex system that circulates ammonia coolant through external trusses and the U.S. laboratory module, will be installed during an assembly flight now targeted for launch in December.

    With the pump module safely stowed, Sellers and Fossum will install the new interface umbilical assembly and then remove the 334-pound trailing umbilical system reel assembly. Fossum, riding on the end of the station's robot arm, will hand-carry it down to the shuttle cargo bay. Sellers will hand him the new reel assembly and both astronauts will move back up to the truss for its installation. After routing the cable back though the IUA, Sellers and Fossum will be done and the mobile transporter will be restored to normal, fully redundant operation.

    If the zenith blade blocker cannot be installed for some reason during the first spacewalk, the spacewalkers will remove the zenith IUA and replace it with the new unit, restoring the transporter to single-cable operation.

    In that scenario, they would take the old IUA back inside the station, remove its blade and install it on the nadir side of the transporter during the second spacewalk.

    "I'm excited by the TUS task," Fossum said in an interview. "It failed in December and within weeks, when we came back after ... Christmas, they had one in the (training) pool all wrapped up with a big bow on it. And we started working on this task.

    "It's very important to get that redundancy in the mobile base system, the mobile transporter that moves up and down the truss. If anything was to go wrong with that remaining one we would not be able to move it to a different location. Finishing assembly, adding on pieces of the truss, the solar arrays out on the ends, requires this mobile transporter to be mobile. And so it's been a big effort."

    The next day, the astronauts will once again focus on transferring equipment and supplies from the logistics module to the space station.

    DAY.ET.........DD...HH...MM...EVENT
    
    JULY 8
    Sat 03:49 AM...06...12...00...STS crew wakeup
    Sat 04:19 AM...06...12...30...ISS crew wakeup
    Sat 06:19 AM...06...14...30...MPLM transfers
    Sat 08:39 AM...06...16...50...Middeck transfers
    Sat 10:09 AM...06...18...20...Nitrogen transfer terminated
    Sat 10:29 AM...06...18...40...PAO event
    Sat 10:49 AM...06...19...00...Joint crew meal
    Sat 11:49 AM...06...20...00...MPLM, middeck transfers resume
    Sat 07:19 PM...07...03...30...STS/ISS crew sleep begins
    
    NASA originally planned to baseline a third spacewalk Sunday, July 9, to test heat shield repair techniques. But that excursion later was removed from the pre-launch flight plan when mission managers added late, post-undocking inspections to look for micrometeoroid impact damage. Those inspections would have eliminated planned time off for the astronauts and, worried about over-working the crew, managers declared the third spacewalk optional.

    If the mission extension is not granted, the astronauts will take most of the day off following the second spacewalk. The day after that, Monday, July 10, the Leonardo cargo module, now loaded with about two tons of no-longer-needed equipment and trash, will be unbolted from the station and restowed in the cargo bay for return to Earth. Nowak and Wilson then would begin the late inspection work, using the OBSS to examine Discovery's port wing.

    Undocking would be targeted for around 7:43 a.m. on July 11, followed by OBSS inspections of the shuttle's nose cap and starboard wing leading edge panels. Lindsey and company would spend their last full day in orbit packing up and reviewing landing procedures before firing their braking rockets around 9:45 a.m. on Thursday, July 13, to set up a landing back at the Kennedy Space Center about 10:46 a.m.

    Here is the flight plan for the remainder of a non-extended mission:

    DAY.ET.........DD...HH...MM...EVENT
    
    07/09/06
    Sun 03:19 AM...07...11...30...STS crew wakeup
    Sun 03:49 AM...07...12...00...ISS crew wakeup
    Sun 06:04 AM...07...14...15...ISS CEVIS removal
    Sun 06:19 AM...07...14...30...ISS message window R&R
    Sun 06:24 AM...07...14...35...STS crew off duty time begins
    Sun 10:19 AM...07...18...30...ISS PAO event 1
    Sun 10:39 AM...07...18...50...ISS PAO event 2
    Sun 10:59 AM...07...19...10...ISS meals
    Sun 11:09 AM...07...19...20...STS meals
    Sun 12:09 PM...07...20...20...STS off duty time resumes
    Sun 12:29 PM...07...20...40...ISS CPA installation
    Sun 03:04 PM...07...23...15...MPLM cleanup
    Sun 03:49 PM...08...00...00...MPLM racks configured for entry
    Sun 07:19 PM...08...03...30...STS/ISS crew sleep begins
    
    07/10/06
    Mon 03:19 AM...08...11...30...STS crew wakeup
    Mon 03:49 AM...08...12...00...ISS crew wakeup
    Mon 05:59 AM...08...14...10...MPLM egress
    Mon 06:14 AM...08...14...25...MPLM deactivation
    Mon 06:19 AM...08...14...30...PAO event
    Mon 07:24 AM...08...15...35...Middeck transfers
    Mon 08:04 AM...08...16...15...MPLM vestibule depressurization
    Mon 09:24 AM...08...17...35...Crew meals begin
    Mon 10:24 AM...08...18...35...SSRMS grapples MPLM
    Mon 10:34 AM...08...18...45...MPLM bolts backed out
    Mon 11:19 AM...08...19...30...MPLM pulled away from Unity
    Mon 12:54 PM...08...21...05...MPLM berthed in shuttle bay
    Mon 01:34 PM...08...21...45...SSRMS ungrapples MPLM
    Mon 01:49 PM...08...22...00...SSRMS grapples MBS
    Mon 02:39 PM...08...22...50...SSRMS ungrapples lab
    Mon 03:29 PM...08...23...40...OBSS port survey
    Mon 05:14 PM...09...01...25...Rendezvous tools checkout
    Mon 07:19 PM...09...03...30...STS/ISS crew sleep begins
    
    07/11/06
    Tue 03:19 AM...09...11...30...STS crew wakeup
    Tue 03:49 AM...09...12...00...ISS crew wakeup
    Tue 05:24 AM...09...13...35...Farewell ceremony
    Tue 05:39 AM...09...13...50...Hatch closure
    Tue 06:14 AM...09...14...25...Centerline camera installation
    Tue 06:24 AM...09...14...35...Group B powerup
    Tue 06:24 AM...09...14...35...ODS leak check
    Tue 06:59 AM...09...15...10...Undocking timeline begins
    Tue 07:43 AM...09...15...54...ISS undocking
    Tue 08:12 AM...09...16...23...Separation rocket firing No. 1
    Tue 08:40 AM...09...16...51...Separation rocket firing No. 2
    Tue 09:29 AM...09...17...40...Group B computer powerdown
    Tue 09:29 AM...09...17...40...Crew meals begin
    Tue 10:44 AM...09...18...55...OBSS starboard survey
    Tue 11:19 AM...09...19...30...ISS: PMA-2 depressurization
    Tue 01:24 PM...09...21...35...OBSS nose survey
    Tue 01:59 PM...09...22...10...OBSS berthing
    Tue 02:54 PM...09...23...05...Laptop post-undock reconfig
    Tue 03:04 PM...09...23...15...RMS powerdown
    Tue 04:28 PM...10...00...39...NC-5 rocket firing
    Tue 06:49 PM...10...03...00...STS crew sleep begins
    
    07/12/06
    Wed 02:49 AM...10...11...00...Crew wakeup
    Wed 05:04 AM...10...13...15...FCS checkout
    Wed 05:49 AM...10...14...00...Cabin stow begins
    Wed 06:14 AM...10...14...25...RCS hotfire
    Wed 06:58 AM...10...15...09...NC-6 rocket firing
    Wed 08:49 AM...10...17...00...PILOT landing training
    Wed 10:09 AM...10...18...20...Crew meal
    Wed 11:29 AM...10...19...40...Deorbit briefing
    Wed 11:59 AM...10...20...10...L-1 communications check 1
    Wed 12:19 PM...10...20...30...PAO event
    Wed 12:39 PM...10...20...50...Wing leading edge gear stow
    Wed 12:39 PM...10...20...50...Entry video setup
    Wed 01:24 PM...10...21...35...L-1 communications check 2
    Wed 03:09 PM...10...23...20...PGSC stow (part 1)
    Wed 03:24 PM...10...23...35...Orbit adjust rocket firing
    Wed 03:29 PM...10...23...40...KU antenna stow
    Wed 06:49 PM...11...03...00...Crew sleep begins
    
     
    07/13/06
    Thu 02:49 AM...11...11...00...Crew wakeup
    Thu 05:04 AM...11...13...15...Group B computer powerup
    Thu 05:19 AM...11...13...30...IMU alignment
    Thu 05:24 AM...11...13...35...GIRA stow; PGSC stow (part 2)
    Thu 05:59 AM...11...14...10...Deorbit timeline begins
    Thu 09:44 AM...11...17...55...Deorbit ignition (rev 186)
    Thu 10:46 AM...11...18...57...Landing
    
    THIRD SPACEWALK IF MISSION EXTENDED

    Ever since Columbia went down, NASA and contractor engineers have been struggling to come up with reliable techniques for repairing minor damage to the shuttle's thermal protection system - TPS - tiles and the reinforced carbon carbon panels protecting the nose and wing leading edges from the extreme heat of re-entry. Repairing Columbia-class damage is not considered possible.

    During Discovery's last flight, the astronauts tested modest techniques for repairing tile damage and while those procedures are not yet officially certified for use, the equipment and repair material will be on board again in case it's actually needed.

    This time around, assuming a mission extension is granted, the crew will focus on techniques for repairing small cracks and damage to wing leading edge panels and nose cap material mounted in a special carrier at the rear of Discovery's cargo bay. The spacewalk would be inserted into the flight plan two days after the crew's second spacewalk. All subsequent activity would simply shift one day to the right.

    "The main focus is to evaluate repair techniques for cracks in the carbon carbon material that makes up the leading edge of the shuttle," Sellers said in a NASA interview. "This is hard, black material; it's laid down a bit like fiberglass layers of carbon matting with resin, then matting, then resin built up in layers. This was the material that got damaged during Columbia's launch. So obviously we're very interested in trying to find a fix for it.

    "We're going to take up some materials and plugs and test different techniques for repairing these on a special set of samples in the back of the payload bay of the shuttle. That's going to be the bulk of the content of that EVA. But we're also testing an infrared camera which, basically, sees heat or the disturbing of heat flows in materials. We can see how well that does at picking up cracks in the carbon carbon.

    Small cracks in the RCC material might not be visible to the human eye, Sellers said, "but the heat will have to flow around the crack, it can't jump across the crack. So, the surface temperature is distorted. And, hopefully this infrared camera that detects heat will be able to see some changes in heat flow around crack fields."

    To repair a small crack in an RCC panel, an astronaut would use a special material dubbed "the black goo" by Fossum and Sellers.

    "We have a special space caulking gun that we'll use to squirt out a small amount of this repair material," Fossum explained. "In the vacuum of space, the stuff boils. It's just amazing to see it in a vacuum. The black goo literally, it boils and sputters. We work it with a putty knife until it settles down and becomes more workable. We'll then use that to make repairs, filling small cracks and holes in the sample tiles."

    Another potential repair technique, one that would be useful for larger holes in an RCC panel, calls for the astronauts to bolt RCC plugs down over an impact site much like band aid.

    "We've got some plugs that have been designed to go into the hole and then there's a surrounding kind of a cap area on this, and it's literally a toggle bolt kind of setup just like you might install a towel rack in your bathroom with," Fossum said. "We'll use a space drill to tighten this thing up. The toggle part opens up on the backside to hold it flush. We'll use feeler gauges to make sure that the gap is right, and then we'll use some of the same black goo to kind of seal up the edges."

    NASA manaqgers eventually hope to certify at least some of the techniques for possible use repairing minor damage by the end of the year.


    06:30 p.m., 06/21/06, Update: O'Connor, Scolese oppose launch on technical grounds but don't object to flight; Gerstenmaier says flight is first with system classified as posing 'unacceptable risk'

    NASA's top safety official and the agency's chief engineer said today they opposed the shuttle Discovery's launch July 1 because of concern about so-called ice-frost ramps on the ship's external tank that could shed foam and cause catastrophic impact damage. In fact, Discovery's flight will be the first in shuttle history with a system formally classified in the "unacceptable risk" category.

    Bryan O'Connor, director of Safety and Mission Assurance at NASA headquarters in Washington, and Chris Scolese, the agency's chief engineer, both declined to concur with the decision to launch when signing an official Certificate of Flight Readiness, or CoFR, following a flight readiness review that ended Saturday.

    But both men said today they viewed the issue as a threat to the vehicle - not a direct threat to the crew - and as such, they accepted NASA Administrator Mike Griffin's decision to press ahead with launch.

    Griffin's decision raised concern in some quarters that NASA might not be paying enough attention to two of its top officials and repeating at least some of the management miscues that led to the 2003 Columbia disaster.

    But Griffin and other senior managers insisted that was not the case and that O'Connor and Scolese presented their arguments in great detail and accepted the administrator's decision. In fact, when signing the CoFR document, both men wrote in by hand that they were officially no-go for launch but, since the issue did not threaten the crew, they did not object to proceeding with the flight.

    O'Connor today acknowledged a perception problem with the seemingly contradictory positions, but said it was the result of the flight readiness review process and the engineering community's classification of the ice-frost ramps as "probable/catastrophic" in NASA's integrated risk matrix.

    "When this first came up, most folks were pretty concernd about it," he said. "That concern level has been going down as we learn more about it, as we refine the models, we look at the data. We haven't changed the design, but there's a little bit of a shift toward more comfort than the other direction.

    "I think we're just barely into the unacceptable risk area. I think it's unacceptable to the program to go fly in this condition. But I also believe if it's elevated to the right authority, an administrator (Griffin) who looks at it and with his understanding and his position in the agency who can accept it, then I felt like I was not going to lie down in the flame trench or throw my badge down."

    But for purposes of the certification of flight readiness, "I was no go. Period," O'Connor said. "Now there's a second (hand-written) statement that says something to the effect that given this technical issue has already been elevated to the agency (Griffin) level and the risk has been accepted at the appropriate level by the agency as opposed to the program, I do not plan to appeal that.

    "The reason that's a little strange is normally, if you just follow the rule book on how you have these reviews, you'd have your review and if there were a dissent there, then you'd have to go have another review to elevate it to agency level. The administrator attended the review, he was the appeal level, he attended it and we discussed this issue the day before we all signed the CoFR statements. We got his acceptance of the risk formally, right there in the review. That's why I put two statements in there."

    Said Scolese: "When it all came out, the view of myself was no-go for the flight because I believe we should repair it. But given the decision, and given the fact that we do have many options available to us to protect the crew - and the orbiter if we can effect a repair - the (engineering) community is not against the decision to fly."

    Hand-written notes by O'Connor, Scolese taking exception to Discovery's launching

    Bill Gerstenmaier, NASA's associate administrator for space flight, put it like this:

    "We think it's extremely unlikely we're going to have any kind of problem on the orbiter. We're definitely going to lose foam, there's no question foam will come off these ice-frost ramps. This foam will be of a small enough mass it won't be a concern to us. ... We think this is an extremely remote possibility that it could come back and cause damage to the orbiter such that we would not be able to return that orbiter. If we thought it was different, we'd be doing something different.

    "I'm just as concerned about protecting the hardware as I am the crew and we want to make sure we're not taking a risk or taking an unnecessary gamble. We've looked at this as hard as we can, we understand what could happen, we understand what could come off, we've looked at our history very carefully, we've looked at models, we've looked at other worst-case assessments and when we put it all together we have reasonable risk to go do this. But it's acceptable and I think we're ready to go fly. If we had real concerns, we would not be flying."

    But Gerstenmaier said later, in answer to a question from CBS News, that Discovery's flight will be the first in shuttle history with a system officially classified as probable/catastrophic, that is, one that poses a technically unacceptable risk.

    The shuttle Columbia was destroyed during re-entry Feb. 1, 2003, when super-heated air entered the ship's left wing through a hole that was caused by impact of a suitcase-size 1.67-pound piece of foam that broke away from a so-called bipod ramp 82 seconds after liftoff.

    NASA eliminated the bipod ramps in the wake of the disaster but during Discovery's launch last July on the first post-Columbia mission, a one-pound chunk of foam broke away from a wind deflector known as a protuberance air-load - PAL ramp on the side of the external tank. Two PAL ramps made up of about 35 pounds of foam were in place to shield externally mounted pressurization lines and a long cable tray from aerodynamic buffeting during the shuttle's climb out of the dense lower atmosphere.

    NASA added the PAL ramps late in the shuttle's design phase as a safeguard, in large part because engineers did not have the computer horsepower or wind tunnel capability to fully understand the forces acting on the huge tank during launch.

    Late last year, shuttle program manager Wayne Hale decided to eliminate the PAL ramps based on computer modeling and the assumption that extensive wind tunnel testing would prove the tank and its external fittings were tough enough to stand up to the rigors or launch.

    Wind tunnel data and additional computer modeling did, in fact, show the tank has the required 1.4 factor of safety with the PAL ramps. But engineers remained concerned about insulation covering 37 metal fittings that hold the pressurization lines and cable tray in place.

    Worried about potentially catastrophic foam shedding, engineers tested a new ice-frost ramp design in the wind tunnel but the design failed. Griffin, Hale and other senior managers then decided to stick with the old ice-frost ramp design for Discovery's mission and at least the next few flights while a better design is developed.

    The largest piece of ice-frost ramp foam known to have come off in flight weighed an estimated .09 pounds. Computer modeling indicates pieces up to .2 pounds could break away and, if it happened at the worst possible time and worst possible place on the tank, such debris could trigger catastrophic damage.

    As a result, NASA's engineering directorate classified the ice-frost ramp foam as "probable/catastrophic" in the risk matrix. That means that over 100 flights or so, if NASA stuck with the current ice-frost ramp design, it's now considered probable that ice-frost ramp foam will break away and cause catastrophic damage. NASA only plans 17 or so more flights, but the classification stands.

    O'Connor said foam debris has been falling off the ice-frost ramps "for quite some time. As we learned more about it, we found there's actually a new kind of a failure mechanism here, cracks and delamination under this thick foam on thick foam that we have at these ice-frost ramps. And as we looked at it, the teams realized that the potential here was higher than we had thought before for damage to the orbiter."

    With the PAL ramp now gown, the ice-frost ramps were deemed "higher risk than any of the other foam areas when you look at the potential for loss of the vehicle," O'Connor said.

    "It was high enough that the technical community reviewing the risk, using their modeling and conservative approach to those areas where there are uncertainties, this got into the area of what we would say is unacceptable risk for the program to be taking. Although it's a close call, there are some engineers who think it doesn't quite meet that margin and there are others that do, there was enough engineering and safety and mission assurance concern about this being in the unacceptable level that the program actually classified it formally as unacceptable risk."

    That classification triggered widespread debate among space engineers. Griffin said he did not believe the ramps should be so classified and that in any case, they do not pose a direct threat to the crew. Even a "catastrophic" impact would not affect the shuttle's ability to reach orbit or carry out its mission. In a worst-case scenario, the astronauts could attempt repairs or, if necessary, move into the international space station to await rescue by another shuttle crew. NASA is preparing the shuttle Atlantis for launch on such a rescue mission if necessary.

    O'Connor said he agrees with that logic. But he voted to stand down in the FRR process to make sure the issue was decided at the highest possible level.

    "When I sized all this up, I kind of came down on the thought that the ice-frost ramp failure case, should it actually develop, a piece that would put a real bad hole in one of the tiles or the special tiles around the (landing gear) doors, we might not be able to fix it to the point where we'd be suitable for entry," he said. "Now in a case like that, that's pretty much the definition of loss of vehicle.

    "But the crew does have another option, that is to stay on the space station and then wait for a combination of shuttle/Soyuz (capsules) to retrieve the crew and bring them back. We have plenty of that capability. ... They've done a lot on space station with logistics planning and so on to make sure you could keep nine crew members up there in good shape with relatively good redundant systems available for quite a while to give us time to get the next vehicle ready to go up and bring them down.

    "That's the difference between loss of vehicle and loss of crew. And I thought when I sized all this up that if we were in the red area, in other words, the unacceptable risk area for loss of vehicle, I did not consider us to be there for loss of crew. By the end of our meeting, by the way, even if I disagreed with some on loss of vehicle, I think everybody in that room agreed the loss-of-crew risk for this mission is acceptable. So I didn't see anybody saying that was a piece of the story. And that's why I made that distinction."

    It was that very distinction, along with NASA's pressing need to resume space station assembly to get the job finished before the Bush administration's 2010 deadline for retiring the shuttle, that prompted Griffin to clear Discovery for flight.

    "There is a programmatic risk, without doubt," Griffin said Saturday. "If we have another major incident in launching the space shuttle, I would not wish to continue with the program. We're going to use this flight and the subsequent flights to complete the space station, that's what we want to do with the shuttle, within the next three years we're going to complete the space station. We believe it is possible to do so. But if it is going to be possible to do so, we're going to have to take some programmatic risks because the shuttle will be retired in 2010.

    "This president's budget will not carry funding for shuttle vehicles beyond 2010. So if we're going to fly, we need to accept some programmatic risk and get on with it. Again, I'll point out, for me to accept programmatic risk to do this is not the same as accepting a crew risk, which we believe we're not doing."

    But the "safe haven" option, in which the crew of a damaged space shuttle moved into the space station to await rescue is not without considerable risk itself. A major question mark has been how NASA would justify launching a rescue shuttle - a mission designated as STS-300 - that could fall victim to the same problem. O'Connor agreed it would be a tough call.

    "We would not have time to change the design (of the ice-frost ramps) before STS-300," he said. "But we would have to sit down and feel very comfortable about the concept of going with another flight with that same design. That's why the nature of a lot of the questions in our readiness reviews dealt with, is there anything new about the PAL ramp redesign that makes the environment on these ice-frost ramps different? In other words, we're looking for something unusual about this new configuration that we're flying that would be liable to fool us on this flight and cause something unknown or unexpected to happen on these ice-frost ramps.

    "We really scratched our heads on that, the engineers really worked it, they really looked at the data from analysis and wind tunnels and came back with we don't expect this environment where the PAL ramps are gone to pose anything unusual in the way of an environment on these ice-frost ramps. And so that leads us to believe if we were to have an ice-frost ramp problem on this next flight, it would most likely be in an area where we are already accepting risk. We're accepting the risk that some pieces may come off, knowing that the risk assessment says some of those may be fairly large and there's some low chance that a fairly large piece would hit in a critical area. And that's an acceptance of risk.

    "If we think we're within that engineering knowledge space on the first flight, then that would make it easier to justify flying the second one," he said. "At the very least, there would be a big discussion about whether we're ready to go do that. The third part of the discussion would be what are our alternatives? ... When you're in an emergency situation like this, where you're going to rescue people, it makes people work harder, think harder and really address the risks in ways that tend to focus your attention. We would have people we'd need to bring back. So I'm sure that would color our discussions as well."


    08:30 p.m., 06/20/06, Update: NASA releases 'certificate of flight readiness' document with 'no-go' from chief engineer, top safety manager

    NASA safety director Bryan O'Connor and chief engineer Chris Scolese both voted "no-go" for the shuttle Discovery's launch July 1 because of concerns foam loss could, in a worst-case scenario, lead to loss of the shuttle. But both men, in hand-written notes scribbled on NASA's official Certificate of Flight Readiness, said they did not oppose Administrator Mike Griffin's decision to proceed with launch because the crew of a damaged shuttle could move into the space station to await rescue.

    The Certificate of Flight Readiness, or CoFR, was posted on NASA's web site today. The document is NASA's official stamp of a approval on plans to proceed with launch and top managers from across various shuttle disciplines must sign, saying they concur with the decision.

    The words "I concur with proceeding with this mission" were crossed out by O'Connor and Scolese. Scolese replaced that wording with "I remain no go based upon potential loss of vehicle. However for this mission I have no intention to appeal the decision based upon ISS capability to provide CSCS."

    CSCS refers "contengency shuttle crew support," or safe haven, the option for the crew of a damaged shuttle to move into the space station while awaiting rescue. For at least the next two flights, NASA is preparing a second shuttle for launch an emergency rescue mission if needed.

    O'Connor's hand-written remarks on the CoFR were: "I am no go based on loss of vehicle risk (ice frost ramps). Based on appeal to administrator I have no intention to appeal his risk acceptance and concur with proceeding with mission."

    Both men declined requests for interviews Monday by CBS News.

    The issue hinges on the classification foam insulation around external brackets on the shuttle's external tank known as ice-frost ramps. NASA had hoped to redesign the foam ramps to minimize foam shedding, but engineers were unable to come up with a good alternative in time to support Discovery's flight.

    The agency already had removed so-called protuberance air-load - PAL - ramps from the tank in the wake of a major foam shedding incident during Discovery's last flight a year ago.

    The PAL ramps were in place to shield external pressurization lines and a critical cable tray from aerodynamic buffeting as the shuttle climbs out of the dense lower atmosphere. The pressurization lines are held in place by 34 brackets that are covered in foam insulation - ice-frost ramps - to prevent potentially dangerous ice formation before launch.

    Wind tunnel testing and computer modeling have convinced managers the tank and its external lines and fittings are tough enough to stand up to the stresses of launch without the PAL ramps. But NASA does not yet have a redesign in place for the ice-frost ramps, which now represent the most potentially dangerous concentrations of foam on the tank.

    Engineers had hoped to implement a redesign before Discovery's flight, but wind tunnel testing showed the proposed change fared worse than the old design. As a result, NASA Administrator Mike Griffin, shuttle program manager Wayne Hale and other senior agency managers agreed earlier this spring to stick with the old design for the next few shuttle flights while another redesign is perfected.

    Even so, the ice-frost ramps were officially classified as "probable/catastrophic" in NASA's risk matrix, meaning that over the life of the shuttle program - if not redesigned - it's probable foam debris from the ice-frost ramps would cause catastrophic impact damage on a shuttle.

    Griffin said he did not believe the foam ramps posed such a high level of risk and in any case, the problem does not pose a direct threat to crew safety. Given broader programmatic issues, including the need to complete station assembly before the shuttle is retired in 2010, he said he decided to press ahead with launch.


    12:10 p.m., 06/20/06, Update: Hale defends launch decision; says no undue schedule pressure because of 2010 deadline

    Shuttle program manager Wayne Hale played a direct role in classifying ice-frost ramps on the shuttle's external tank as "probable/catastrophic," but he told CBS Radio today his primary intention was to elevate the issue to a level that would ensure it received the proper attention.

    During a two-day flight readiness review Friday and Saturday, NASA's office of Safety and Mission Assurance and the office of the chief engineer voted to delay Discovery's July 1 launch until the ice-frost ramps could be redesigned to minimize foam shedding.

    A classification of probable/catastrophic in NASA's risk matrix means that over the remaining life of the shuttle program, it is probable foam will separate from an ice-frost ramp and cause catastrophic impact damage to the shuttle's heat shield.

    NASA Administrator Mike Griffin, saying he did not believe the foam ramps posed such a high level of risk, decided to press ahead with space station assembly while a tiger team of engineers works on a new design.

    The decision has generated attention because of Griffin's acknowledgement that schedule pressure - or more properly the threat of schedule pressure later in the station assembly sequence - played a role in his decision to clear Discovery for flight. All sides agreed the ice-frost ramps did not pose a direct threat to the astronauts.

    "We had a full, open and public debate, airing all the opinions, looking at all the data," Hale told CBS Radio today. "Part of the story that perhaps hasn't been quite widely reported is how many folks came forward and said this is not as critical a hazard as you might think it is and we certainly have a good safety margin to go fly.

    "As program manager, I listened to all sides of this and came down with the decision that we should rate this as a (probable/catastrophic) hazard, perhaps more dangerous than it actually is, in order to remind ourselves that we need to go continue to make improvements on the external tank.

    "So that part got widely reported, I'm happy to hear, but the other side, that we are making steady improvements, that this is widely, much better understood than it was before and it has been widely aired and debated without any suppression of evidence or discussion, is a sign that the new NASA is willing to engage in these debates and, in fact, face problems head on rather than sweeping them under the rug."

    Hale said he personally did not feel under any sort of pressure to launch Discovery or any other shuttle because of a looming 2010 deadline to finish station assembly and retire the shuttle fleet.

    "Frankly, I do not feel the schedule pressure that everyone's speculating about," he said. "We have clearly demonstrated in the past that we've been able to fly the kind of flight rate that would lead us to assemble the international space station by 2010 with comfortable margin. So I feel very low schedule pressure to get off the pad, at least from that standpoint."

    But Hale said the public should understand the risks involved with any shuttle flight. Even though the ice-frost ramp concern is not a direct threat to crew survival - the astronauts could move into the space station to await rescue in a worst-case scenario - NASA is "betting the program" every time the shuttle flies.

    "We gamble the program every time we launch the vehicle in a thousand ways, many of which may be obscure to folks, but we take a calculated risk," he said. "I think NASA, by the way, is about the only federal agency that does sort of put the whole agency on the line every time we do our normal business. And we do it in public and we do it with a great deal of discussion with the public.

    "But we do recognize the fact, and always have, that we bet the entire agency, the entire space program, every time we try to launch a rocket."


    08:40 a.m., 06/20/06, Update: NASA updates launch windows

    Flight controllers have updated the shuttle Discovery's launch windows by a few seconds. For July 1, the updated time for an in-plane launch is 3:48:37 p.m., 22 seconds later than previously published. NASA will round up to the nearest minute - 3:49 p.m. - in Public Affairs Office documents. NOTE: The shuttle's launch window on any given day is 10 minutes long. But Discovery's countdown will be timed for launch when Earth's rotation carries the pad 39B into the plane of the international space station's orbit. See the CBS News STS-121 Quick-Look page for additional details.

    DATE..........WINDOW OPEN......IN PLANE.........WINDOW CLOSE.....ISS DOCKING
    
    07/01/06......03:43:37 PM......03:48:37 PM......03:53:37 PM......Flight Day 3
    07/02/06......03:21:05 PM......03:26:05 PM......03:31:05 PM......FD-3
    07/03/06......02:55:23 PM......03:00:23 PM......03:05:23 PM......FD-3
    07/04/06......02:32:51 PM......02:37:51 PM......02:42:51 PM......FD-3
    07/05/06......02:07:09 PM......02:12:09 PM......02:17:09 PM......FD-3
    07/06/06......01:44:37 PM......01:49:37 PM......01:54:37 PM......FD-3
    07/07/06......01:18:55 PM......01:23:55 PM......01:28:55 PM......FD-3
    07/08/06......12:56:23 PM......01:01:23 PM......01:06:23 PM......FD-3
    07/09/06......12:30:41 PM......12:35:41 PM......12:40:41 PM......FD-3
    07/10/06......12:08:09 PM......12:13:09 PM......12:18:09 PM......FD-3
    07/11/06......11:42:27 AM......11:47:27 AM......11:52:27 AM......FD-3
    07/12/06......11:19:55 AM......11:24:55 AM......11:29:55 AM......FD-3
    07/13/06......10:54:12 AM......10:59:12 AM......11:04:12 AM......FD-3
    07/14/06......10:31:41 AM......10:36:41 AM......10:41:41 AM......FD-3
    07/15/06......10:05:58 AM......10:10:58 AM......10:15:58 AM......FD-3
    07/16/06......09:43:27 AM......09:48:27 AM......09:53:27 AM......FD-3
    07/17/06......09:17:44 AM......09:22:44 AM......09:27:44 AM......FD-3
    07/18/06......08:55:13 AM......09:00:13 AM......09:05:13 AM......FD-3
    07/19/06......08:29:30 AM......08:34:30 AM......08:39:30 AM......FD-3
    


    05:00 p.m., 06/19/06, Update: NASA releases statement by O'Connor and Scolese on Discovery launch decision

    NASA's safety chief and the agency's top engineer said today in a joint statement they did not oppose launching the shuttle Discovery July 1 despite serious concern about so-called ice-frost ramps on the ship's external fuel tank.

    Discovery was cleared for launch Saturday after a two-day flight readiness review in which Bryan O'Connor, chief of Safety and Mission Assurance, and the agency's chief engineer, Chris Scolese, voted to delay launch until the ice-frost ramps could be redesigned.

    NASA Administrator Mike Griffin said he did not agree that the ice-frost ramp foam posed "probable/catastrophic" threat to the shuttle and cleared Discovery for flight. A "tiger team" of engineers is working on an ice-frost ramp redesign the agency hopes to implement within a few flights.

    Griffin said even if ice-frost ramp foam did cause damage during Discovery's launching, it would not directly threaten the crew. In a worst-case scenario, he said, the astronauts could either attempt repairs or move aboard the space station to await rescue by another shuttle crew.

    O'Connor and Scolese said today in a statement that they agreed crew safety was not at issue.

    "Crew safety is our first and most important concern," the statement said. "We believe that our crew can safely return from this mission.

    "We both feel that there remain issues with the orbiter - there is the potential that foam may come off at time of launch. That's why we feel we should redesign the ice/frost ramp before we fly this mission. We do not feel, however, that these issues are a threat to safe return of the crew.

    "We have openly discussed our position in the Flight Readiness Review - open communication is how we work at NASA. The Flight Readiness Review board and the administrator have heard all the different engineering positions, including ours, and have made an informed decision and the agency is accepting this risk with its eyes wide open."


    08:50 p.m., 06/17/06, Update: Griffin clears Discovery for July 1 launch over objections from chief engineer and safety office

    NASA Administrator Mike Griffin, overruling objections from the agency's chief engineer and safety office, cleared the shuttle Discovery for launch July 1 on a mission to service and resupply the international space station. The flight also will clear the way for the resumption of station assembly later this fall and deliver a third full-time crew member to the international outpost.

    The objections centered on the risk posed by launching Discovery with foam buildups around brackets on the ship's external tank that are now formally classified as "probable/catastrophic" in NASA's integrated risk matrix. That means it is probable that the so-called ice-frost ramps will shed debris with catastrophic results over the life of the program.

    Griffin told reporters today he did not agree with the probable/catastrophic classification and added that even in a worst-case scenario, the astronauts would not be in immediate danger. Because of new cameras and other sensors, any damage would be seen and the crew could either attempt repairs or move aboard the space station to await rescue by another shuttle crew.

    Throwing in broader programmatic issues, including a presidential directive to finish the station and retire the shuttle fleet in 2010, Griffin said he decided it made more sense to resume shuttle flights now, with the current ice-frost ramps, and to implement a redesign as soon as possible.

    Insisting safety remains his top priority, Griffin left no doubt about the stakes involved. Losing another space shuttle - even if the crew survived - will mean the end of the program.

    "If we were to lose another vehicle, I would tell you right now that I would be moving to figure out a way to shut the program down," he said. "I think at that point, we're done. I'm sorry if that sounds too blunt for some, but that's where I am. We're trying to navigate some very difficult waters ... to get the station assembled. I think that's worth doing. I've stated that on multiple occasions, but it's not easy."

    Griffin's comments came at the end of a two-day flight readiness review at the Kennedy Space Center where top agency managers and engineers gathered to review Discovery's flight processing. The debate about the classification of the ice-frost ramps in NASA's integrated risk matrix stirred a fair amount of debate. NASA's chief engineer and safety manager both said that if the ice-frost ramps were classified "probable/catastrophic" they were no-go for launch. The majority of those attending the FRR disagreed and voted to proceed with the flight. The final decision was Griffin's.

    Because of the unique nature of this debate, and because of the high stakes involved, here is Griffin's complete answer to a question from CBS News to explain his rationale:

    "I'm not concerned with what box in the matrix we're in because that's a matter of terms and definitions," he said. "In point of fact, I don't agree with the way that we categorized that risk as being 'probable.' Because if it's going to be 'probable,' then that means that over some reasonable span of flights I would expect to see evidence of that behavior. We can as statisticians go off and argue about what percentage of the time you expect to see it, but if we say 'probable,' we mean that over some reasonable span of activity we should see it. And I won't at this point refine it further.

    "Now, in fact, we have 113 flights (sic) with this vehicle with these ice-frost ramps under our belt. And while we've had two loss of vehicle incidents, they've not been due to ice-frost ramps. So I have a great deal of trouble believing that a statistically sound statement would be to say that this is a 'probable' event to be seen over the next 16 flights. I just have trouble with that.

    "Now without regard to the label, getting past the label, the concern then is do we, in fact, think that if we fly this ice-frost ramp the way it is for some very small, not 16, but some very small number of flights, a few, until we have a better design - and let me be the first to lead the parade saying we've got to have a better design, we want to know that it's a better design and we want to take our time with it - so the question is, can we fly a few times with this ice-frost ramp without probably incurring a hazard? And based on the data I have seen, I believe that we can.

    "I believe that our models are quite conservative, I believe that our models have a huge variance in them, we really don't know as much about these phenomena as we would like to. Because if we believed our models, we would believe that we had a worse problem than our flight data is showing, which is a red flag to indicate that we don't understand as much as we would like to understand. We need to continue to be hungry, we need to continue to dig out the information the vehicle is telling us. But we need to fly it to dig it out.

    "So how do I justify that? With as much uncertainty as we have, I ... certainly would have to think harder about putting a crew on this vehicle if I thought they didn't have the space station safe haven option and the launch-on-need (rescue flight) option and for that matter, if push came to shove, to call up Russian Soyuz spacecraft for rescue. I do not see the situation we're in as being a crew-loss situation.

    "If we are unlucky and we have a debris event on ascent, it will not impede the ascent, the crew will arrive safely on orbit and then we will begin to look at our options, whether those include repair, launch on need, extended safe haven on the station, asking our Russian partners for help, maybe some or all of the above. We will have decisions to make, but we will have time to make those decisions. We are not in the situation that we were in with Columbia where we didn't know that we had a problem. We'd know we have a problem, we have elected to take the risk, we do not believe we are risking crew.

    "There is a programmatic risk, without doubt. If we have another major incident in launching the space shuttle, I would not wish to continue with the program. We're going to use this flight and the subsequent flights to complete the space station, that's what we want to do with the shuttle, within the next three years we're going to complete the space station. We believe it is possible to do so. But if it is going to be possible to do so, we're going to have to take some programmatic risks because the shuttle will be retired in 2010.

    "This president's budget will not carry funding for shuttle vehicles beyond 2010. So if we're going to fly, we need to accept some programmatic risk and get on with it. Again, I'll point out, for me to accept programmatic risk to do this is not the same as accepting a crew risk, which we believe we're not doing."

    In shuttle program manager Wayne Hale's view, NASA already is accepting a fair amount of risk based on an earlier decision to remove so-called protuberance air-load - PAL - ramps from the tank in the wake of a major foam shedding incident during Discovery's last flight a year ago.

    The PAL ramps were in place to shield external pressurization lines and a critical cable tray from aerodynamic buffeting as the shuttle climbs out of the dense lower atmosphere. The pressurization lines are held in place by 34 brackets that are covered in foam insulation - ice-frost ramps - to prevent potentially dangerous ice formation before launch.

    Wind tunnel testing and computer modeling have convinced managers the tank and its external lines and fittings are tough enough to stand up to the stresses of launch without the PAL ramps. But NASA does not yet have a redesign in place for the ice-frost ramps, which now represent the most potentially dangerous concentrations of foam on the tank.

    Engineers had hoped to implement a redesign before Discovery's flight, but wind tunnel testing showed the proposed change fared worse than the old design. As a result, Griffin, Hale and other senior agency managers agreed earlier this spring to stick with the old design for the next few shuttle flights while another redesign is perfected.

    After an extensive debris verification review May 31, Hale said he agreed the ice-frost ramp foam should be listed in the risk matrix as probable/catastrophic. But he said NASA was justified in pressing ahead with near-term shuttle flights while engineers devise a bracket redesign that eventually will allow them to remove the ice-frost ramp foam altogether. While the IFR foam represents a clear long-term threat, the risk on any given flight is in line with dangers posed by other systems.

    Hale said today the "probable/catastrophic" classification reflected his belief "as program manager those issues need to be elevated to senior NASA management for their review and disposition. I believe they are at an unacceptable level for the program manager to take that risk on by himself."

    Even so, Hale said he believes the ice-frost ramps are "an acceptable risk" when viewed from a broader agency perspective.

    "I recommended to the administrator and (spaceflight chief) Bill Gerstenaier that even though we did rate these very high, I think it is acceptable for a number of reasons to go fly for a limited number of flights while we come up with the redesign," Hale said. "So that's where we rated it. I will tell you that it was an interesting discussion."

    Gerstenmaier said the debate marked "a difficult situation because we have data that shows we have potentially cracks underneath large foam or foam that's put on top of other foam. And we have flight history that doesn't show that we lose a lot of foam. ... So the dilemma is, how can we not rule out that at some point in the future we're not going to have some larger foam loss with this underlying problem? And therein lies the debate.

    "We can't figure out the theory that can explain to us why we haven't had larger foam loss," he said. "Obviously, there's something we think that's protecting us in the physics of the situation, but we don't know what that is. What we discussed as an engineering team are what the pros and cons of that are, we looked at statistical models, we looked at transport models, we looked at all of this as a team. ... There wasn't a united engineering position on this.

    "We laid out our rationale for the decision to go fly and really, no one objects to the decision to go fly," he said. "Both the safety office and the chief engineer, their point was they recommend being no-go but they don't object to us going to fly. ... The problem is, without understanding this underlying failure phenomenon, any fix we put on has some risk associated with it of losing foam or generating ice. We can control that as much as we can through design, but we can't eliminate that. So in a sense, we almost need to go fly to gain some more data."

    Asked again by CBS News to explain how senior managers could cast a no-go vote in the FRR and yet say they agreed with launching Discovery anyway, Griffin made another attempt to explain the flight rationale.

    "Some of the senior NASA individuals responsible for particular technical areas expressed that they would rather stand down until we had fixed the ice-frost ramp with something better whereas many others said no, we should go ahead," Griffin said. "So we didn't have unanimity. Therefore, a decision had to be made.

    "We annunciated a careful rationale for flying that I believe mitigated the concerns that were expressed by the Office of Safety and Mission Assurance and by the office of the chief engineer. And in fact, they agreed with that. I don't want to say there's no ascent risk. There's plenty of ascent risk on the shuttle. Debris shed from the tank does not pose an ascent risk for the shuttle. OK? It poses a risk for entry.

    "Since we have inspection methods, we are beginning to converge on some rudimentary repair methods, since we have the station for a safe haven, since ... we've got an excellent capability for launch on need and we have the Russian partners, we have a number of mitigation strategies should the unlikely occur and we have a debris strike. Subject to those conditions, the chief engineer and office of safety and mission assurance were OK with launch.

    "Looking at their specific discipline areas, they would recommend that we stand down. But there are larger considerations. If we stand down, now we back up station assembly flights. One of the areas that surfaced during the CAIB (Columbia Accident Investigation Board) investigation was the issue of schedule pressure on NASA. Now schedule pressure for us is a fact of life, but it has to be balanced. I do not want to make decisions today which are going to result in having all the schedule pressure in creating station assembly in the last year or two. I don't want to get us into a situation where by being more cautious than I think technically necessary today, we wind up having to execute six flights in the last year or something. That's not smart.

    "So I'm willing as administrator, looking at the whole picture, I'm willing to take a little bit of programmatic risk now - and notice I did not say crew risk - I'm willing to take some programmatic risk now in order to prevent an excessive buildup of programmatic risk later on. This is, in fact, what you pay me to do. The chief engineer and the Office of Safety and Mission Assurance are not paid to worry about schedule risk four years in the future, they're paid to worry about what is the situation with this particular flight. We had their input. In fact, both of them are long and valued friends of mine and people whom I have nothing but the greatest technical respect for. That goes without saying. But I cannot possibly accept every recommendation which I am given by every member of my staff, especially since they don't all agree.

    "I don't know how to say it any more clearly, I'm sorry. I'm really doing the best I can here."

    Discovery's countdown to launch on the 115th shuttle mission is scheduled to begin at 5 p.m. on June 28. Liftoff is targeted for 3:48:15 p.m. on July 1.


    04:40 p.m., 06/16/06, Update: NASA reviews flight readiness; debates risk classification of ice-frost ramps

    NASA managers met at the Kennedy Space Center today to formally review the shuttle Discovery's flight processing and its readiness for launch as early as July 1. One major item on the agenda is a discussion of the threat posed by foam making up so-called ice-frost ramps on the shuttle's external tank.

    The engineering community believes it should be classified as "probable/catastrophic," meaning that over the remaining 17-flight life of the shuttle program, it's probable that foam will break away from the ice-frost ramps with catastrophic results.

    Other engineers disagree, arguing a designation of probable/catastrophic overstates the actual threat. All agree the ice-frost ramps should be modified to minimize foam shedding.

    Shuttle program manager Wayne Hale believes it's acceptable to launch a few missions while the ramps are redesigned, arguing the threat on any given launch is comparable to what the program already accepts for other critical systems.

    However it plays out, a probable/catastrophic classification is problematic in the post-Columbia environment, especially when measured against the recommendations of the Columbia Accident Investigation Board.

    Discovery commander Steve Lindsey downplayed the debate, saying "no matter how heated the argument may or may not get in there today, they're all passionate about (manned spaceflight), they all believe in it, they're all going after the same goal. They just may have a different view on what technically is the best way to accomplish that."

    Lindsey introduced his crew to the flight readiness review participants early today before flying back to the Johnson Space Center for final preparations. The astronauts just finished three days of launch site training, including a dress-rehearsal countdown Thursday.

    Speaking to reporters before departing, Lindsey said the debate over how to technically classify the ice-frost ramps in a risk matrix would not change his belief that Discovery is ready for flight.

    "Yesterday they had a meeting about it and I'm sure they're going to talk about it today," he said. "I don't know exactly where it's going to be classified. I think one of the things, though, that the managers especially wanted to do was make sure that everybody in the program recognizes this is our top risk. And I think they wanted to put it up there (in the risk matrix) to annunciate that hey, this thing is something we have to fix and this thing is something we really have to watch. They're kind of (breaking it out) to separate it from all the other risks that are out there to make sure everybody's aware of that."

    The risk matrix is simply a box three rectangles across and four down. The vertical axis lists the likelihood of an event - improbable, remote, infrequent and probable - and the horizontal axis lists the severity of a failure, from marginal to critical and finally, catastrophic. The matrix covers the range from "improbable/marginal" to "probable/catastrophic."

    "In terms of the actual risk of flying with the ice-frost ramp, just because you put it in that category doesn't change the risk at all," Lindsey said. "Technically, it's the same situation we had before."

    Even so, he said, "there's a significant amount of debate in the community as to where that (risk) really should be. There's a group that thinks it should be up there (probable/catastrophic), there's a group that thinks it should be one block down, a little less amount of risk. For us, with the ice frost ramps, we've flown with them, we've seen pieces come of off them but not large pieces that would cause damage to the orbiter."

    In a worst-case scenario, however, catastrophic damage could, in fact, occur. So why not fix the problem before Discovery flies?

    In Hale's view, NASA already is accepting a fair amount of risk based on an earlier decision to remove so-called protuberance air-load - PAL - ramps from the tank in the wake of a major foam shedding incident during Discovery's last flight a year ago.

    The PAL ramps were in place to shield external pressurization lines and a critical cable tray from aerodynamic buffeting as the shuttle climbs out of the dense lower atmosphere. The pressurization lines are held in place by 34 brackets that are covered in foam insulation - ice-frost ramps - to prevent potentially dangerous ice formation before launch.

    Wind tunnel testing and computer modeling have convinced managers the tank and its external lines and fittings are tough enough to stand up to the stresses of launch without the PAL ramps. But NASA does not yet have a redesign in place for the ice-frost ramps, which now represent the most potentially dangerous concentrations of foam on the tank.

    Engineers had hoped to implement a redesign before Discovery's flight, but wind tunnel testing showed the proposed change fared worse than the old design. As a result, NASA Administrator Michael Griffin, Hale and other senior agency managers agreed to stick with the old design for the next few shuttle flights while another redesign is perfected.

    After an extensive debris verification review May 31, Hale said he agreed the ice-frost ramp foam should be listed in the risk matrix as probable/catastrophic. But he said he believes NASA is justified in pressing ahead with near-term shuttle flights while engineers devise a bracket redesign that eventually will allow them to remove the ice/frost ramp foam altogether. While the IFR foam represents a clear long-term threat, the risk on any given flight is in line with dangers posed by other systems.

    Lindsey agreed with that assessment and said he agreed with Hale that removing the PAL ramps - the biggest change ever made to the tank's aerodynamics - was enough for one mission.

    "There's this thing in the flight test world and the engineering world called the law of unintended consequences," Lindsey said. "When you make a change, you often influence other things. Every time we make a big change, we're taking that risk and you can't drive it to zero.

    "I'm pretty content we've done everything we can in the wind tunnel with these ice-frost ramps as well as the PAL ramp changes. ... We can't know more about these ice-frost ramps and instrument them and get data on how to change them unless we go to flight test. And I think that's where we are right now."

    The flight readiness review is not expected to be wrapped up until midday Saturday. A news conference is planned to announce the results and, presumably, an official launch date. The current target is July 1 at 3:48:15 p.m.

    "They have a long day ahead of them," Lindsey told reporters today. "We, like you, are looking forward to hearing the results of that review."


    03:30 p.m., 06/14/06, Update: Astronauts review emergency procedures; field questions at launch pad

    The Discovery astronauts reviewed emergency procedures at the launch pad today and geared up for a dress-rehearsal countdown Thursday that will set the stage for a major management review Friday and Saturday to set an official launch date.

    Discovery's launch window opens July 1 and if commander Steve Lindsey has anything to say about it, that's the date management will pick.

    "I've been telling the crew that I'm guaranteeing July 1," he joked today at the base of launch pad 39B. "Seriously, looking at technically what's going on with the vehicle, the issues we've been working through, the issues that are coming up for the flight readiness review, I don't know of anything out there right now.

    "There are a couple of controversial issues that could push it a couple of days maybe, but I don't really know of anything out there that would preclude a July 1 launch. So I'm very optimistic that we're going to shoot for early July, as early in that window as we can get."

    In recent days, flight planners have debated whether it might make sense to delay launch a few days to get better lighting to photograph the shuttle's external tank as it separates in orbit.

    Since Discovery's last flight nearly a year go, NASA has removed foam wind deflectors from the tank to minimize the chances for large pieces of debris to break away during ascent. But agency managers decided to delay making changes to ice/frost ramp foam used to insulate external fittings on the tank.

    The shuttle's launch window is defined, in part, by a requirement to launch in daylight to ensure good photography of the tank and any potential impact sites on the orbiter itself; and by a desire to make sure the external tank can be photographed when it separates in orbit half a world away. Orbital lighting is marginal at best on July 1, but it will improve as one moves deeper into the window.

    As it turns out, getting good separation footage is not considered mandatory by NASA management and given the uncertainties involved, shuttle program manager Wayne Hale decided last week not to give up July 1. A final decision will be made at the upcoming flight readiness review, but Lindsey said the crew agrees with the preliminary decision not to hold the flight up for a possibly minimal improvement in lighting.

    "It's my understanding the lighting issue that came up, to say delay a couple of days to get better lighting of the ice frost ramps, is not a done deal that that would improve things," Lindsey said. "The lighting analysis was done with the external tank separating and being in perfect orientation with no tip-off rates, in other words it's not going to tumble at all.

    "But every flight I've ever been on, when the ET comes off it starts tumbling, usually slowly, but it starts tumbling because you get a little bit of venting that comes off the tank as you separate. So just because you delay three or four days is no guarantee you're going to get good lighting on those ice/frost ramps.

    As far as what the crew might actually see on launch day, "I don't think anybody really knows," Lindsey said. "So I think it was a good decision. There was no guarantee that waiting two or three days would yield us any better results than if we go on the first."

    Lindsey, pilot Mark Kelly, flight engineer Lisa Nowak, Stephanie Wilson, spacewalkers Piers Sellers and Mike Fossum, along with European Space Agency astronaut Thomas Reiter, reviewed emergency procedures today in a standard pre-launch exercise. All seven will don 70-pound pressure suits and strap in aboard Discovery early Thursday for the dress rehearsal countdown, known as a terminal countdown demonstration test, or TCDT.

    "The vast majority of our training happens at the Johnson Space Center in Houston where we're in simulators," Lindsey said. "Well, this is definitely not a simulator! The training we get here is invaluable. We learn to drive (a NASA armored personnel carrier) in an emergency, we learn how to operate the slidewire (pad escape) baskets ... and the bunker system."

    For the practice countdown Thursday, "we'll go through the entire process just like we would on a normal launch day. We'll get up in the morning, have a quick breakfast, have a weather brief, get into our suits, get our suits checked, come out to the pad and get strapped into the vehicle, which is the only time we ever get to do that prior to launch.

    "So to get out, get in the vehicle in the vertical, get a feel for what the vehicle looks like - it's close to the simulator, but it's not exactly like the simulator - and then get a chance to egress out of there and see what that feels like, it's really invaluable training for us.

    "The TCDT is a real enjoyable week for us, because it's not quite as intense as a normal training week in Houston," he said. "But then when we go back from TCDT, we know that we're really, really close and we're getting close to the end. So this event more than any other probably makes it feel like to us that it's real, it's really time to go and that we're really about ready."


    05:45 p.m., 06/13/06, Update: Astronauts fly to KSC for practice countdown

    The shuttle Discovery's crew, running a day late because of tropical storm Alberto, flew to the Kennedy Space Center today to practice emergency procedures and take part in a dress rehearsal countdown Thursday.

    NASA managers plan to hold a two-day flight readiness review Friday and Saturday to assess the status of Discovery's launch processing and to set an official launch date. The target date for the second post-Columbia shuttle mission is July 1 at 3:48:15 p.m.

    "It's good to be here," commander Steve Lindsey told reporters after the crew landed on Kennedy's shuttle runway. "We've re-arranged our schedule, we're going to stay an extra day to get everything done down here.

    "As far as I know, everything's OK (with Discovery)," he said. "At the end of this week we have flight readiness review going on. Hopefully at the conclusion of that on Saturday, we'll set an actual launch date. We're all pretty optimistic that early July looks good."

    The goal of the 115th shuttle mission is to resupply the international space station, to deliver a third full-time crew member - German astronaut Thomas Reiter - and to repair a critical external cart used to move the lab's robot arm along the front of an unfinished solar array truss. The cart must be fixed before station assembly can proceed.

    Lindsey and company will review launch pad emergency egress procedures Wednesday and field questions from reporters at the pad before donning pressure suits and strapping in Thursday for the terminal countdown demonstration test - TCDT - practice countdown.

    TCDT is a major milestone in launch processing, giving the astronauts and launch control center personnel a chance to review procedures before attempting the real thing.

    NASA Administrator Mike Griffin, shuttle program manager Wayne Hale, NASA spaceflight chief Bill Gerstenmaier and launch director Mike Leinbach plan to participate in a news conference Saturday to discuss the outcome of the flight readiness review.


    07:00 p.m., 06/07/06, Update: NASA managers certify external tank for flight

    NASA managers today formally certified the shuttle Discovery's external fuel tank for flight based on wind tunnel data and computer modeling that show the huge tank can stand up to the aerodynamic rigors of launch despite the recent removal of long foam wind deflectors. Launch currently is targeted for July 1, at 3:48 p.m., but the long-awaited flight could slip another day or so to ensure better lighting for critical photography of the tank after Discovery reaches orbit. NASA managers are expected to discuss the lighting issue during a weekly review Thursday.

    Discovery's launch window is defined, in part, by a requirement to launch in daylight and to have the external tank separate from the orbiter in daylight, half a world away. The goal is to obtain good photos of the tank's redesigned foam insulation as well as the shuttle's heat-shield tiles and wing leading edge panels to spot any potential impact damage.

    As it turns out, a new analysis of orbital lighting conditions shows a camera mounted in the belly of the shuttle will not have enough light for good photography if Discovery takes off July 1. Conditions improve on July 2 and subsequent days.

    Even then, lighting is not expected to be acceptable for crew handheld still and video photography until around July 5. But the critical driver is the umbilical camera, which is positioned to provide good views of foam ramps around external fittings on the tank that carry pressurization lines.

    Those so-called ice/frost ramps have not been modified. But long protuberance air-load - PAL - ramps that provided some aerodynamic shielding for the pressurization lines and a critical cable tray, were removed in the wake of major foam shedding during Discovery's launch last July on the first post-Columbia mission.

    Shuttle program manager Wayne Hale approved removal of the PAL ramps on the assumption wind tunnel data and computer modeling would show the pressurization lines, cable tray and other fittings will stand up to increased aerodynamic buffeting during the climb out of the lower atmosphere.

    During a meeting at Lockheed Martin's external tank assembly facility near New Orleans today, shuttle managers concluded the PAL ramp-free tank has enough of a margin of safety to endure even worst-case aerodynamic loads.

    The results of the meeting, which focused on the removal of the PAL ramps and modifications to prevent foam shedding near the bipod that attaches the shuttle's nose to the tank, will be presented at a formal flight readiness review June 16-17 at the Kennedy Space Center.

    Discovery's crew, meanwhile, flies to the Florida spaceport June 12 for launch site emergency drills and a dress-rehearsal countdown June 15.


    08:00 p.m., 05/31/06, Update: Debris review finds no 'show stoppers' for July launch; ice/frost ramp foam still deemed dangerous

    After a "spirited" two-day review, NASA managers today concluded the agency has reduced the threat of catastrophic damage from external tank foam and other debris to an acceptable level, a major milestone on the road to clearing the Discovery for launch July 1 on the second post-Columbia shuttle mission.

    "We have found no show stoppers. We believe we have made significant improvements since last year in the elimination of many of the hazards from foam," said shuttle program manager Wayne Hale.

    "But one of the things I don't want to hear when I go home and turn on the TV tonight is that we've fixed the tank and no foam is going to come off. Because that is not the case. ... There will continue to be foam coming off the external tank. What we have done in a very systematic manner is eliminate the largest hazards." But an earlier decision by NASA Administrator Michael Griffin, Hale and other senior agency managers not to change the way foam is used to insulate 34 critical brackets on the skin of the tank means Discovery will be launching with insulation that could, in a worst-case scenario, cause the very sort of catastrophic damage NASA has been struggling to prevent.

    While today's Debris Verification Review, or DVR, did not generate any formal probabilities regarding the actual threat posed by ice/frost ramp "foam shedding," Hale said he believes the IFR foam should be listed in a threat matrix as "probable/catastrophic," meaning that over the life of the shuttle program, debris from the bracket insulation, in a worst-case scenario, could lead to a disaster.

    Even so, Hale believes NASA is justified in pressing ahead with near-term shuttle flights while engineers devise a bracket redesign that eventually will allow them to remove the ice/frost ramp foam altogether. While the IFR foam represents a clear long-term threat, the risk on any given flight is in line with dangers posed by other systems.

    "With the very worst-case assumptions, there were some numbers down as low as 1-in-75 and for some of the better-case assumptions, you're talking about numbers on the order of 1-in-400 for ice/frost ramp foam losses," Hale said.

    "I hate to quote probability numbers without context because it depends so much on what the assumptions were and how conservative or how fine the calculations were that went into the case. But we're talking, basically, something on the order of 1-in-a-few hundred, or 1-in-100, which is consistent with the entire overall risk we fly with the space shuttle."

    During Discovery's launch last year on the first post-Columbia mission, a one-pound chunk of foam insulation broke away from a long wind deflector known as a protuberance air-load - PAL - ramp on the tank. The PAL ramps, one on the oxygen section and one on the hydrogen section of the tank, were designed to shield two pressurization lines and a cable tray from aerodynamic buffeting.

    While the PAL ramp debris lost during Discovery's flight didn't hit anything, NASA managers ultimately decided to remove the ramps on the assumption computer modeling and wind tunnel tests would show the pressurization lines and cable tray are tough enough to endure the ascent environment.

    A design certification review to formally assess the results of testing and to officially sanction the flight worthiness of the new design should be finished in time for Discovery's flight readiness review June 16 and 17.

    This week's DVR was concerned primarily with foam debris and any other sources of potential impact damage to the orbiter.

    The external tank pressurization lines are supported by 34 brackets on the skin of the tank that are insulated by up to two pounds of foam each. The insulation is needed to prevent ice from building up on the brackets when the tank is loaded with supercold rocket fuel. Any such ice would pose an impact threat during launch.

    Along with removing the PAL ramps, engineers wanted to reduce the amount of foam used on the brackets, and thus minimize the debris impact threat from that quarter.

    But during wind tunnel testing earlier this year, an ice/frost ramp redesign option fared worse than the original design. Rather than race to make yet another major change in the tank, NASA managers opted to accept the risk and to fly the ramps as is until a more robust redesign could be developed.

    "We think they are a hazard, I want to make that very clear, they are an area of foam insulation that we very definitely need to deal with," Hale said today. "But the principle that we have to remember, however, is that in a flight test, you want to make one major change at a time, instrument it, fly it and see how that performs before you make another major change.

    "So we're going to fly this flight with a major improvement - the elimination of the PAL ramp - but we know we have another hazard that we also need to eliminate, and that will be the elimination of the ice/frost ramps as quickly as we can come up with a good design option. So we put them right at the top of our risk matrix. That's the number one thing we have to work on next."

    No such risk matrix has been formally approved for Discovery's flight.

    "Basically, this vehicle, and you can take this to the bank, is about a 1-in-100 vehicle," he said. "It is a risky vehicle to fly. And nobody should mistake that, there are a number of things that can cause bad outcomes in this vehicle. What we've tried to do is take a very serious look at every one of the areas that we think are higher risk and do our best to mitigate those."

    Columbia was brought down in 2003 by a 1.6-pound piece of foam insulation from an area of the tank known as a bipod ramp. The PAL ramp foam that broke free during Discovery's launching last July weighed about one pound. The largest documented piece of ice/frost ramp foam shedding amounted to about 0.09 pounds. Engineers believe, however, up to 0.2 pounds - about three ounces - is possible.

    Removing the PAL ramps eliminated about 34 pounds of foam. Engineers hope to implement an incremental ice/frost ramp upgrade, first using insulators to allow the removal of some foam and ultimately by using different bracket material, possibly titanium, to achieve the same insulating effects without any foam at all.

    Hale said the interim fix using insulators might be available three or four tanks down the road. Complete elimination of foam will take longer.

    "Today we have a tank on the pad that has lost 34 pounds, the largest amount of foam that we've ever taken off the tank, to reduce the hazard," Hale said. "We have put on a special set of sensors, both accelerometers and force measurements on that tank, as well as a suite of six new cameras on the solid rocket boosters that will be monitoring the performance of the vehicle during ascent to ensure that we have done our job properly in the removal of that protuberance air-load ramp. But we do expect to see foam come off."


    04:15 p.m., 05/19/06, Update: Discovery hauled to pad; Hale says 'preliminary' look at wind tunnel data positive

    Shuttle program manager Wayne Hale, on hand for Discovery's rollout to launch pad 39B today, said a preliminary look at complex wind tunnel data shows the ship's redesigned external fuel tank should be safe to fly in July. While stressing that a detailed analysis of the data is ongoing and saying new problems could always crop up, "the preliminary loads indications are good, but we have to wait until they get to the bottom line."

    "You don't know until you add up the last column of numbers and that's going to come in just before the design certification review for the external tank here in about three weeks," Hale said, standing in a field surrounded by reporters just a few dozen yards from the shuttle crawlerway.

    NASA has conducted extensive wind tunnel testing and computer modeling to better understand the aerodynamic loads, or forces, acting on the redesigned external tank as the shuttle climbs out of the dense lower atmosphere.

    Long foam air deflectors, originally put in place to shield external pressurization lines and electrical cables from buffeting, were removed in the wake of Discovery's launch last July on the first post-Columbia mission when a large chunk of foam broke away from a protuberance airload - PAL - ramp.

    In recent briefings, Hale declined to give any hints about the nature of the wind tunnel data. But he told reporters today a first look at the structural loads data was positive.

    "It's kind of like doing your taxes," he said. "The first time through, you kind of do a rough cut and see if you're going to get a refund or not. ... That's what we've got from the structural guys, they've got their first rough cut. It looks good, but you really don't know what you've got until you work through the entire analysis and look at all the cases - there are something like 34,000 loads cases they have got to look at - and the job's not done till it's done.

    "We've very hopeful and I feel a good degree of confidence it'll all come out good, else we wouldn't have rolled the vehicle out here today. But you can't say it's done until it's done."

    Wind tunnel testing is complete, he said, and the design certification review is scheduled to begin in earnest in early June. No more major modifications to the tank are expected. Engineers plan to continue an analysis of possible changes to so-called ice-frost ramps along the side of the tank - foam-covered fittings that carry the pressurization lines - but any changes will be deferred until the next flight in late August or the flight after that in mid December.

    NASA managers originally hoped to implement ice-frost ramp changes before Discovery's flight but Hale decided one major tank change - elimination of the PAL ramps - was enough for one flight.

    "For the record here, folks, I expect we will lose foam, two to four or more pieces off the ice-frost ramps," Hale said. "I also expect they'll be small. We have got a suite of six cameras on both the solid rocket boosters plus the camera on the external tank, we're going to try to understand the mechanism of when those things come off, how big they are. ... So after this flight, all the instrumentation we've got on this vehicle ... will make us a lot smarter."

    Discovery began the 4.2-mile trip to pad 39B at 12:45 p.m. Hale rode atop the shuttle's mobile transporter as the "stack" slowly inched its way out of the Vehicle Assembly Building under a brilliant cloud-streaked sky. He then climbed off and fielded questions while Discovery continued its slow trek to the pad (the trip was interrupted at least once because of an overheated bearing).

    "It was great, you know? It's better than going on a cruise ship," Hale exclaimed. "It's a fabulous feeling to say we're rolling Discovery to the launch pad for our next launch attempt on July 1. It's just a great feeling being here. Folks have worked really, really, really hard. We still have some work ahead of us, but I think we're on a really good path to make July 1."

    Asked if NASA had a realistic shot at launching three missions this year, Hale said "it will be tight, particularly the third flight, which right now we've got penciled in on our schedule for Dec. 14. It's going to be a lot of work."

    The problem is moving up completion of external tank No. 123 in time to support a possible rescue mission if major problems develop during the August-September flight of shuttle Atlantis.

    "Right now the tank folks are struggling to deliver the tank, there's about a week that they're looking at taking out of their schedule, putting more resources in to try to deliver that tank earlier than they would normally like. But given that, we have a really good shot at making three flights this year."

    Discovery's tank was recently equipped with a fresh set of critical engine cutoff - ECO - sensors after questions were raised about reliability. Hale initially favored a fueling test in early June to verify the performance of the new sensors, but he decided last week to forego such a test.

    "We've got good ECO sensors in this tank, the best that we know how to make, and we have screened all the engine cutoff sensors out of the 50 plus that we had on hand," he said. "We picked the best four and installed them in the tank out here. I have a high degree of confidence that they'll all work right.

    "We reviewed all that stuff, there could be a bogey man hanging out there that we could find out on the launch pad. I really tried to talk my team into doing a tanking test and they talked me out of it. We'll find out on launch day and I believe we're probably going to find out there are four good sensors and they'll all work as advertised."

    Asked when he might begin to feel "home free" about Discovery and all the work that's been done since the last flight, Hale said "when the wheels stop rolling on the runway."

    "It's an uphill job to fly a vehicle in space, every minute of every day between now and that wheels stop. You're never home free. The day you think you're home free, you are screwing up and you're looking to run into trouble. This is a tough business and it requires attention every day."

    But Hale looked relaxed and confident, clearly buoyed by watching Discovery make its way to the pad. Asked if he did, in fact, get a tax refund this year, Hale laughed and said, "I already got it. My wife spent it."


    02:30 p.m., 05/12/06, Update: Discovery moved to VAB

    Under a brilliant spring sky, the shuttle Discovery took a major step toward the launch pad today, moving from its processing hangar to the Vehicle Assembly Building for attachment to its redesigned external tank and booster rockets.

    Mounted atop a squat multi-wheel transporter and cheered on by scores of engineers and technicians, Discovery took about an hour to complete the short trip to the cavernous VAB. Rollout to launch pad 39B is targeted for May 19 with launch on tap July 1.

    "This is our second big milestone in the flow," said Stephanie Stilson, director of Discovery's ground processing. "Obviously, the first one was when we mated the tank to the solid rocket boosters. Now, this is milestone No. 2 and huge for us, especially for the folks working on the orbiter. They've been spending the last 200-or-so days ... getting that orbiter ready to fly. They're happy to get it out of the bay. That means we're moving forward and we're going to launch very soon."

    After attachment to a huge sling, overhead cranes will rotate Discovery into a vertical orientation before slowly moving it into high bay 3 Saturday for attachment to its external tank. Leak checks, continuity tests and other unfinished work will be completed in the high bay next week before rollout to the launch pad.

    An updated processing schedule is available on the CBS News STS-121 Quick-Look page, along with a detailed flight plan, a "mission walkthrough," personnel assignments and the latest launch windows through July 19.


    11:30 p.m., 05/11/06, Update: ECO swap ordered for STS-115 tank; Hale sticks with 4-of-4 launch rule

    NASA managers today decided to swap out engine cutoff - ECO - sensors inside the liquid hydrogen section of an external fuel tank slated for use with the shuttle Atlantis in late August. Because of lingering questions about subtle failure modes, engineers at the Kennedy Space Center earlier installed a fresh set of hydrogen ECO sensors in the tank that will be used on the next flight in July.

    Engineers were never able to determine the exact cause of those earlier problems, and many favored changing a launch rule to permit a flight if three of the four sensors were working properly. While that might seem like an undue risk, the redundancy built into the system assures safe operation in certain narrowly defined failure scenarios.

    But in a bit of a surprise, shuttle program manager Wayne Hale today decided to stick with the four-of-four ECO sensor launch rule, meaning Discovery will be delayed if one or more sensors misbehaves when the tank is loaded with fuel on launch day.

    The launch team left open the possibility of revisiting the three-of-four rationale if a failure is actually observed. A similar rationale was in put in place before Discovery's launch last July on the first post-Columbia mission, but the sensors worked normally and the rule was never put to the test.

    In any case, Hale told the assembled engineers and managers today that he is confident the carefully screened ECO sensors recently installed in external tank 119 will work properly.

    "We have a great deal of confidence we're not going to see any issues," an official said (a detailed description of ECO sensor location and operation is available from CBS News and Spaceflightnow.com

    Now, based on today's discussion, ET-118, the tank that will be used by Atlantis in late August, will get a new set of ECO sensors as well. The tank is scheduled to be shipped from Lockheed Martin's Michoud Assembly Facility near New Orleans on May 30, arriving at the Kennedy Space Center June 5. The new sensors will be installed at Kennedy, although engineers have not yet decided whether to do the invasive work with the tank in a horizontal or vertical orientation.

    NASA managers are protecting the option of launching rescue flights for the next two missions. Assuming Discovery takes off July 1 as currently planned, a "launch-on-need" rescue by Atlantis, using ET-118, could be staged as early as Aug. 11. If Atlantis takes off Aug. 29, a rescue flight by Discovery could be launched around Nov. 11 using the next tank in the sequence, ET-123.

    But because resources have been focused on getting the next two tanks in the sequence ready for flight, preparations have lagged for ET-123. Current processing schedules show shipment to Florida could be delayed from around Aug. 12 to as late as Sept. 17.

    It typically takes about three months to process a tank for launch at Kennedy but the external tank project recently concluded a 62-day flow is achievable. If ET-123 really is delayed to mid September, processing for a Nov. 11 rescue flight would end up, on paper at least, being about a week down.

    Hale today told external tank managers to "scrub" the schedule as much as possible to make up for lost time and offered help from other centers if needed.

    The concern here is that if Atlantis' crew ran into problems that forced the astronauts to seek "safe haven" aboard the international space station, ET-123 might not be ready to support a rescue flight before station supplies started running short.

    This all assumes Discovery could be "turned around" after its July flight in time to support a rescue mission.

    The launch window for mission STS-115 - the fight after Discovery's - opens Aug. 29 and closes Sept. 13. The next window opens Oct. 26 and closes Oct. 29. Those launch windows are based on a requirement to launch the next two flights in daylight and to have good orbital lighting to photograph the external tank after separation half a world away.

    Another constraint is the angle between the sun and the plane of the station's orbit, which determines how hot or cold the shuttle-station combination will get during docked operations. Because of payload temperature constraints, NASA may only have two launch days in October due to beta angle issues if Atlantis misses the August-September window.

    Foam insulation issues aside, the next two external tanks in the sequence - ET-119 and ET-118 - should be ready to support launchings in July and late August or early September, although the ECO sensor swap out planned for ET-118 will be difficult. More important, both launch dates assume NASA ultimately concludes the decision late last year to remove long foam air deflectors from the tank was sound and that external fittings are tough enough to stand up to increased aerodynamic buffeting.

    But any major delays getting ET-123 ready to support a rescue mission could prevent NASA from launching Atlantis in the August-September window. While the schedule is currently out of synch, NASA managers are hopeful they can pull it back in when all is said and done.


    04:30 p.m., 05/04/06, Update: NASA nixes tanking test

    NASA managers today ruled out a June 1 fueling test with the shuttle Discovery, deciding there was no clear-cut technical justification for a complex exercise that would put unwanted stress on the tank's foam insulation and use up valuable contingency time.

    Shuttle program manager Wayne Hale ordered engineers to make tentative plans for a tanking test earlier this spring as a way to make sure recently replaced engine cutoff - ECO - sensors would work properly on launch day.

    The test would not have included any so-called "drag on" instrumentation in the shuttle's aft compartment and its sole purpose would have been to verify the ECO sensors changed state from dry to wet and back again as expected. In the absence of additional instrumentation, no detailed operational insights would be possible.

    During a weekly program meeting today, the management team unanimously decided not to run the test, officials said, because any major problems with the ECO sensors almost certainly would preclude a launch in the July window anyway and because loading the tank with supercold propellant would subject its foam insulation to unwanted thermal stress.

    Shuttle tanks are certified for 13 fueling cycles. When a countdown proceeds past the point where the tank is pressurized for launch - part of the plan for the June test - it counts as two cycles.

    Discovery's launch on the second post-Columbia mission is targeted for July 1. The ECO sensors will be checked, as usual, when the tank is loaded with liquid hydrogen and oxygen on launch day.

    The ECO sensors are part of a backup system intended to make sure the shuttle's three main engines don't shut down early or run too long. All four hydrogen ECO sensors are required to be operational for launch, but NASA managers could waive that requirement in certain narrowly defined cases depending on whether a given sensor failed in the wet or dry state.

    But any major ECO sensor problems, whether they occurred June 1 or July 1, almost certainly would rule out a launch before the window closes July 19. The engineering community believes all four sensors currently installed will work properly.

    Engineers currently plan to move Discovery from its processing hangar to the Vehicle Assembly Building for attachment to the tank and its twin solid-fuel boosters on May 12. Rollout to the launch pad is targeted for May 19.

    Rollover could be briefly delayed if engineers decide to correct a subtle timing problem with a recently installed jet thruster control assembly. But with the elimination of the tanking test, the Kennedy Space Center launch team has 17 days of contingency time available to handle unexpected problems.

    The engineering community is still assessing the overall safety of the external tank without foam wind deflectors called protuberance air load - PAL - ramps. The ramps were removed following the loss of foam debris from the hydrogen PAL ramp of the tank used by Discovery during the first post-Columbia mission last July.

    A final analysis of the tank's ability to withstand aerodynamic buffeting without the ramps in place, based on wind tunnel testing and complex computer modeling, is expected next month.


    03:00 p.m., 04/28/06, Update: NASA decides against ice-frost ramp changes; analysis of PAL-less tank enters final stages

    NASA managers have decided not to make any major, last-minute changes to the foam insulation that prevents ice from forming around fittings that hold pressurization lines and a cable tray to the space shuttle Discovery's external fuel tank. Work to minimize the amount of foam used on the fittings will continue but in the near term, wind tunnel testing shows the so-called ice/frost ramps should stand up to the aerodynamic buffeting of launch as is, without shedding large, potentially dangerous pieces of insulation.

    But with just two months to go before the July 1 opening of Discovery's launch window, engineers do not yet know whether the tank is safe to fly without larger foam air deflectors that were removed after a big chunk of insulation fell off during the first post-Columbia flight last July.

    At issue is whether the higher aerodynamic buffeting expected in the absence of the deflectors can cause the pressurization lines, cable tray or brackets to fail during the first minute or so of flight as the shuttle climbs out of the dense lower atmosphere.

    A decision is not expected until NASA's formal flight readiness review, a two-day discussion that begins June 16. At that point, shuttle program manager Wayne Hale said today, the engineers studying the issue will say "yes, this structure will hold together or no, it won't. And if the answer is 'no, it won't,' well, we're not going anywhere. We have some confidence that it will, but you don't know until you do the math and get the numbers."

    The air dams, known as protuberance air-load - PAL - ramps, were in place primarily to protect the pressurization lines and cable tray from buffeting during the region of maximum aerodynamic pressure, which occurs during the first minute of flight.

    NASA managers decided to remove the long ramps late last year - eliminating 37 pounds of foam that could be a source of potentially dangerous launch debris - based on computer modeling that indicated the external pipes and fittings were tough enough to stand up to launch turbulence on their own. The decision was made on the assumption wind tunnel testing this spring would confirm the computer modeling and because engineers were unable to come up with reliable techniques to ensure the ramp foam stayed in place.

    "That change constitutes the largest aerodynamic change that we have made to the space shuttle launch system since it first flew," Hale said. "And we're approaching that with a great deal of care, doing the work necessary to prove the aerodynamics will still be good, that we have not introduced an aerodynamic loads problem that will cause the structure underlying to come to grief. That's an intricate process."

    He said a final analysis of the aerodynamic forces acting on the tank in the absence of PAL ramps is due for completion May 5. That data will be folded into an on-going structural analysis intended to determine whether or not the tank can meet NASA's standard safety factor of 1.4, where 1 represents worst-case conditions. The results will be presented at the flight readiness review in June.

    As of today, however, Hale would not say whether preliminary indications are favorable or not.

    "The aerodynamics loads are higher without the PAL ramp than they were before with the PAL ramp," Hale told reporters at the Kennedy Space Center. "It's not an absolute number they talk about, I don't have a nice number I can give you that says it's, you know, 1.3 times higher than it was before. I don't have a number like that.

    "I will tell you at the end of the day, the structural analysis folks, when they look across all the scenarios, all the Mach numbers, all the angles of attack, all the potential vibratory cases that they look at, (after) thousands of computer runs, will have to come back and tell me that we have the space-shuttle-standard 1.4 factor of safety or better for us to be able to launch. So we'll have to be able to withstand 140 percent of whatever the maximum load case is."

    The shuttle program faces retirement in 2010 as NASA transitions to a new spacecraft and a new exploration mandate that calls for a return to the moon by 2018 or so.

    Some in the shuttle program worry the program could be terminated early if NASA fails to get Discovery off the ground this summer or fall at the latest. But Hale dismissed those concerns, saying "look, if we go fly and have another accident, THAT will be the end of the program."

    "I would rather not fly and say we couldn't get our act together and if people in high places think that's fine for us to quit, that's OK, than to rush to some ill-advised launch where we have a catastrophe. That would be worse. So I don't think about those kind of things. I'm going to keep working on this program until they tell me to quit working on this program and I'm not worried about whether July is the end of the program or not."

    Here is the latest launch processing schedule (a more detailed schedule that runs through the end of the year and includes critical space station launches and milestones is available on the CBS News STS-121 Quick-Look page):

    NASA managers at a program requirements change board meeting Thursday agreed not to make any more major changes to the ice-frost ramp foam around 34 pressurization line attachment fittings. Some, including NASA safety chief and former shuttle commander Bryan O'Connor, argued in favor of delaying Discovery's launch until a new ramp design, one that eliminated additional foam, could be certified through testing.

    While initial test data were positive, "when we came right down to it, the recommendation I came to is we're in a flight test program, classical flight test," Hale said. "When you make a major change (like removing the PAL ramps), you should fly that major change without other major changes to see how it performed. And if you have subsequent changes to be made, you make those in subsequent flights."

    The current ice-frost ramp design performed well during recent wind tunnel testing, but Hale said small pieces of foam almost certainly will come off during Discovery's launch.

    "It is not without risk to fly these ice/frost ramps as they exist," he said. "There was a strong, concerted opinion from several folks that we should wait until we have a good design on these pieces of foam and then change them as well before we go fly. That not without merit and we considered it very strongly.

    "However, at the end of the day, we came back to the fact that it is more appropriate to make one change at a time to take care of the biggest problem we have and then work our way to the next situation we'd like to improve.

    Bill Gerstenmaier, NASA's chief of spaceflight at headquarters in Washington, agreed with that approach, saying the agency is "really kind of pushing the state of the art of our analysis and wind tunnel capabilities throughout the country."

    "There's not really one wind tunnel where you can simulate all the proper conditions that are going on with the tank," he said. "There's not really one test facility where you can simulate all these things that come together in a shuttle launch.

    "The tank expands when it's pressurized, it contracts when it's cooled down, the vibration from the solid rocket motors cause vibration through the tank structure, which goes through this bracketry, those press lines have gases flowing through them, they're moving up and down, they're dynamically moving in and out. All of that is tremendously difficult to simulate in our test facilities and to put together in computational flight dynamics.

    "So at some point, you really need to go to flight ... with some instrumentation so you can monitor that performance and see how the design you put together with the best of your engineering capabilities actually performs in flight. And that's exactly what we're doing here."

    In other recent developments, NASA managers have decided to replace one of two electronics boxes in Discovery's aft compartment - a maneuvering jet control unit - because of concern about so-called "tin whiskers." in recent weeks, engineers have been concerned about a metallurgical phenomenon in which thin, hair-like whiskers of tin can extrude from circuit card guides in a certain type of chassis. Should a whisker break off and fall on an exposed electrical component on a circuit card, a short could result.

    The boxes in question are used in a variety of critical shuttle systems to control the movement of the vehicle's main engine nozzles, wing flaps and to fire maneuvering jets. But the components are redundant - there are four for each system - and managers decided the chances of multiple whisker-related shorts was negligible. One reaction jet driver box, however, was replaced with a pristine unit.

    Engineers also have replaced main engine No. 2 because of concern about solder defects in an attached control computer and completed the replacement of critical low-level fuel sensors in the hydrogen section of Discovery's external tank. The engine cutoff - ECO - sensors were replaced because of electrical indications of a potential failure mode in one of the four. The sensors are part of a backup system used to make sure the engines don't shut down early or run too long because of other problems.

    NASA managers will meet next Thursday to decide whether or not to carry out a tanking test June 1 to verify the performance of the ECO sensors. Some engineers have questioned the value of a tanking test given that thermal stresses caused by the super-cold rocket propellent apparently contribute to foam cracking and, potentially, to debris during launch.

    Shuttle tanks are certified for 13 fueling cycles, Hale said today. A fill-and-drain without tank pressurization counts as one cycle but countdowns in which the tank is pressurized for launch count as two. A tanking test, in which the countdown would be taken down to its final minutes to test the ECO sensors and the pressurization system, would count as two cycles on the tank.


    01:45 p.m., 04/17/06, Update: One of three baselined spacewalks eliminated; will be added after launch if power conservation permits mission extension

    Because of an over-loaded crew timeline and new heat-shield inspection requirements, shuttle flight planners have decided to eliminate one of three previously planned spacewalks from Discovery's upcoming mission - a spacewalk devoted to testing heat-shield repair techniques - in order to give the crew more time off in orbit, officials say. If the astronauts can conserve enough power, however, and if Discovery doesn't tarry on the launch pad, the mission will be extended one day and the spacewalk will be put back in the flight plan.

    The goals of Discovery's mission are to carry supplies and equipment to the international space station; to repair a robot arm carrier on the station's main solar array truss; and to perform a variety of other tasks to ready the complex for resumption of assembly later this year.

    Three spacewalks, carried out by Piers Sellers and Michael Fossum, were planned:

    1. EVA-1: Preliminary repair work on the robot arm mobile base station; and tests to determine the stability of the shuttle's robot arm when it is equipped with a 50-foot extension. The extension is used to inspect the shuttle's tiles, nose and wing leading edges for signs of impact damage. NASA planners want to know if the arm-boom combination can carry an astronaut on the end for possible repair work in the future.

    2. EVA-2: Station robot arm mobile base station repair. The mobile base station moves along rails on the main solar array truss to position the lab's robot arm for assembly work as required. Two ribbon-like power/data cables unreel or wind up in front and behind the cart as it moves along. One of the two cables was inadvertently cut by an on-board safety system last year. During Discovery's mission, Fossum and Sellers will replace the cut cable and its reel and make sure the cables cannot be inadvertently severed in the future. They also will move a new pump module to the station.

    3. EVA-3: Tests of repair techniques that could be used someday to fix relatively minor damage to the shuttle's tiles, reinforced carbon carbon wing leading edge panels, and RCC nose cap.

    The flight plan calls for the crew to carry out an extensive heat-shield inspection, as usual, on the second day of the mission using the robot arm boom extension. The station crew will examine the ship with high-powered cameras during final approach and additional inspections will be done the next day. Similar inspections were carried out during the first post-Columbia mission last year.

    In recent weeks, however, NASA added additional post-launch heat-shield inspection work to Discovery's flight the day before undocking from the station and also shortly after it departs. Those additional inspections, designed to look for micrometeoroid or space debris impacts, reduced the crew's off-duty time to a single half day over the duration of the mission.

    Here is the flight plan with all three spacewalks:

    Concerned about allowing the crew just a half-shift of rest and relaxation in a busy flight, NASA managers considered simply extending the mission one day up front. But in the end, they decided to replace the third spacewalk with crew off-duty time on flight day nine.

    NASA is holding open the possibility of reinserting the tile-repair demonstration spacewalk on flight day 10 if the astronauts can conserve enough electrical power for a one-day mission extension.

    They also will need.

    The shuttle's on-board supplies of hydrogen and oxygen, used to generate electricity, diminish with every day the ship stays on the ground after loading. To have a chance for a mission extension, Discovery needs to get off the pad within three days of its eventual target launch date. Otherwise, the flight will be put on hold for 72 hours so the hydrogen and oxygen supplies can be topped off.

    In more "routine" launch campaigns, the shuttle can make three attempts over four to five days before a stand down to reload ground tanks and on-board fuel cell supplies.

    The flight plan posted on the CBS News STS-121 Quick Look page still reflects a full three-spacewalk mission. An updated timeline will be posted as soon as it's available.


    05:50 p.m., 04/13/06, Update: Foam loss incidents studied; NASA managers assess shuttle tanking test; possible engine swap on tap

    During wind tunnel tests earlier this week, NASA subjected a full-scale mockup of a shuttle external tank section to the kind of aerodynamic forces a real tank would experience during launch. In one series of tests, unmodified foam insulation used to prevent ice buildups around external fittings suffered only minor damage while a redesigned "ice/frost ramp" suffered major foam loss.

    The redesign is being considered in a bid to remove as much insulation as possible from the tank to minimize the threat of debris shedding during launch. The old ice/frost ramps, which insulate the fittings used to hold two pressurization lines and an electrical cable tray in place, featured long, sloping ramps to smooth the flow of air.

    But those very ramps, it was believed, were susceptible to cracks and failure, providing a potential source of debris that could strike a shuttle during launch. The redesigned ramps are much more blunt. But in initial wind tunnel tests at the Arnold Engineering Development Center in Tullahoma, Tenn., the old design fared much better than the redesign. During two sets of test runs this week, the new design suffered major foam loss.

    "That's exactly what testing is all about," said one official. "This is where you want to find a problem, not on launch day."

    More tests are planned and other design changes are under consideration, along with the option of flying the ramps "as is." But a decision on how to proceed is needed by the end of the month to give engineers time to make any required changes before NASA's planned July launch of the shuttle Discovery on the second post-Columbia mission.

    In other developments, shuttle program manager Wayne Hale has told project engineers to begin planning for a shuttle fueling test around June 1 to verify performance of new low-level fuel sensors in the tank scheduled for use by shuttle Discovery in July. The test has not yet been formally approved and is opposed by some - including, sources say, William Gerstenmaier, NASA's chief of space operations - because of concern about putting unnecessary thermal stress on the tank's foam insulation.

    But Hale strongly favors the test in the wake of recent, unprecedented work to replace four engine cutoff - ECO - sensors, which are part of a critical backup system used to make sure the shuttle's main engines shut down on time. Problems with ECO sensors before Discovery's launch last July on the first post-Columbia mission were never fully resolved and a tanking test would give engineers confidence the new sensors will work properly on launch day. A tanking test also would provide an opportunity to monitor the performance of a relief valve used to maintain proper tank pressurization during flight. A valve in a tank last year cycled more often than usual.

    Discovery remains targeted for launch at 3:48 p.m. EDT on July 1 (a detailed flight plan and a calendar of upcoming space station/shuttle milestones are available on the CBS News STS-121 Quick-Look page.

    To make the July 1 launch target, however, the shuttle team must overcome several challenging hurdles, including completion of wind tunnel testing and analysis to confirm recent changes to the external tank's foam insulation are safe.

    During Discovery's flight last July, a large piece of foam insulation broke away from an air deflector called a protuberance air-load - PAL - ramp running down the outside of the hydrogen section. The PAL ramp was in place to smooth the flow of air across two externally mounted pressurization lines and an electrical cable tray as the shuttle rockets out of the dense lower atmosphere.

    Shuttle managers decided late last year to simply remove the ramps based on computer modeling that indicated the pressurization lines, cable tray and attachment fittings - and the foam ice/frost ramp insulation used to prevent ice formation on the brackets - were tough enough to withstand the expected aerodynamic buffeting.

    Discovery's tank, without PAL ramps, was shipped to the Kennedy Space Center in March on the assumption wind tunnel testing would confirm the computer modeling. Tests using a scale model of the shuttle and others using a larger scale section of the tank have been completed at NASA's Glenn and Ames research centers. Those tests were focused on learning more about the acoustic environment the tank is subjected to during launch as well as the aerodynamic "loads" to make sure the tank and its external lines and fittings can stand up to ascent forces.

    Those data have not yet been fully analyzed. Despite initial concern about somewhat ambiguous results, engineers in recent days have expressed optimism the end result will support the decision to remove the PAL ramps.

    NASA currently is carrying out wind tunnel tests at the Arnold Engineering Development Center using a full-scale model of a tank segment that can be equipped with ice/frost ramps of various shapes. A turntable allows engineers to properly orient the mockup to ensure the wind strikes it at the proper angle to reflect the forces acting at any given moment during ascent. The testing is designed to collect data on all aspects of the PAL ramp-free tank design.

    The ice/frost ramps were partially shielded from aerodynamic buffeting by the now-removed PAL ramps and questions were raised about whether the old ramp design could stand up to launch forces. In one set of runs at Tullahoma, the original design suffered only minor damage, sources said. But in two sets of tests using the redesigned ice/frost ramps, large chunks of foam blew off. It's not yet clear what caused the failures and more tests are planned.

    In the meantime, the launch team at Kennedy is pressing ahead for July. A team from the Michoud Assembly Facility near New Orleans, where the external tanks are built, is refoaming the bottom of the tank following the ECO sensor swap out work. The tank is scheduled to be attached to a pair of already assembled solid-fuel booster rockets on April 24 and if all goes well, Discovery will be attached to the tank around May 12. Roll out to the launch pad is targeted for May 19.

    The proposed fueling test would not prevent a July 1 launch, engineers say, because of contingency time built into the schedule following a March 15 decision to delay launch from May 10 to July 1. But the concern about subjecting the tank to unnecessary thermal stresses by loading it with super-cold rocket fuel remains.

    Engineers now believe the expansion and contraction of the tank during multiple fueling cycles contributes to the formation of tiny cracks and other defects that can lead to foam loss during flight. Opponents of the fueling test believe the health of the ECO sensors can be confirmed through electrical testing without the need for a fueling cycle.

    This issue raises thorny questions about how NASA will conduct future launch campaigns. In the past, the agency routinely fueled space shuttles for flight even when forecasters predicted bad weather. In some cases, the forecasters were wrong and the shuttle was able to fly. But in others, they were right and NASA was forced to drain the tank and try again another day.

    If thermal stress can, in fact, lead to cracks and other issues with the foam insulation, as now seems probable, NASA may be forced to rethink its long-standing policy of fueling a shuttle when bad weather is expected. And that could have a bearing on how long it takes to get Discovery off the ground in July given the frequency of afternoon thunderstorms along the Florida Space Coast.

    Weather aside, the fragility of the foam also could force NASA managers to consider putting limits on how many times a tank can be loaded with liquid oxygen and hydrogen. But at this point, that is speculative and no such discussions have been held or are currently planned.

    Other issues still on the table include the possible swap out of main engine No. 2 because of a computer controller issue; completion of a complex debris verification review, showing the tank won't shed large pieces of foam or allow dangerous ice buildups around external fittings; and completion of a design review of the tank modifications in general.

    Another wild card is the potential threat posed by so-called "tin whiskers" that can form on circuit card guide rails in various electrical components. While the precise causes are not known, small whisker-like extrusions can form in tin and other metals under certain stress conditions. The concern is that a whisker could break off, fall on a circuit board and cause a short.

    Whiskers recently were found during inspection of an ascent thrust vector control box, used to control the system that moves the shuttle's main engines for steering. Discovery has numerous electrical boxes with a common design that are susceptible to such whiskering. Sources say engineers believe Discovery can safely fly as is based on redundancy in the systems involved. But a final decision on how to proceed has not yet been made.


    08:00 a.m., 03/29/06, Update: July 1 target for STS-121 faces threats; shuttle managers mull downstream launch targets; engineers assess electrical issue UPDATED at 6:15 p.m. to clarify nature of electrical concern

    Initial wind tunnel tests indicate recent modifications to the foam insulation on the shuttle's external tank may not be as easily analyzed as initially hoped, sources say. While additional testing may resolve the matter, showing the removal of wind deflectors called PAL ramps from the tank will not compromise safety, other ongoing technical issues, including a new concern about possible circuit board problems, threaten the July 1 target date for the next shuttle mission.

    Shuttle program managers, meanwhile, are studying proposed launch dates for subsequent missions in the wake of a March 15 decision to delay Discovery's launch on the second post-Columbia mission from May 10 to July 1. Managers plan to meet Thursday to review the following proposed "no-earlier-than" launch targets:

    The schedule hinges on Discovery's processing flow and while the recent delay to July 1 gives engineers some much needed time to fix known problems and resolve open issues, it's not yet clear whether it will be enough. Here is the schedule as it currently stands (readers are advised to take these dates with a grain of salt; they are targets only and almost certainly will change as processing continues):

    Discovery's launch delay from May 10 to July 1 was ordered by program manager Wayne Hale to give engineers time to replace suspect engine cutoff sensors in the hydrogen section of Discovery's external fuel tank. One of the four hydrogen ECO sensors in the tank showed a slight shift in electrical resistance that indicated a possible failure mode. Multiple failures in flight could lead to a premature engine shutdown or fool the ship's flight computers into running the engines long enough to suck the tank dry. Both scenarios are potentially catastrophic.

    The ECO sensor swap out requires engineers to remove foam insulation at the base of the tank and to open a large manhole cover to permit workers to climb inside. Once the sensors are replaced, the tank must be closed up, refoamed and retested.

    That three-week process provides an umbrella of sorts for engineers working other issues that also threatened the original May 10 target date.

    Ongoing wind tunnel tests using scale models to assess the acoustic and aerodynamic forces acting on the tank during launch still represent the long pole in the tent.

    After a large piece of foam insulation fell away from the hydrogen protuberance air-load - PAL - ramp on Discovery during launch last year, NASA managers decided to simply remove the wind deflector from future tanks. The ramps were in place to smooth the flow of air across an external cable tray and two pressurization lines as the shuttle rockets through the region of maximum aerodynamic pressure during the climb out of the dense lower atmosphere.

    Managers decided to remove the ramps based on preliminary results from sophisticated computer models and on the assumption that wind tunnel testing would confirm the pressurization lines and cable tray were strong enough to withstand whatever buffeting they might experience in the absence of the PAL ramps.

    NASA has not revealed what the wind tunnel testing has shown to date, but sources say the initial results were not as clear cut as engineers had hoped. The ambiguous results, however, could be the result of scaling issues - problems making sure data collected with sub-scale mockups correctly reflects full-scale reality - and a NASA spokeswoman cautioned that testing and analysis are far from complete.

    The worst-case scenario would be unambiguous data showing the tank does not have the desired safety margin without the PAL ramps, a result that would derail plans to launch Discovery this summer and raise questions about the future of the program. The best-case scenario would be confirmation that the tank and its external fittings were conservatively designed, as many hope, and more than tough enough to withstand the expected environment.

    As of this writing, it's not clear how this issue might play out.

    On another, more positive front, engineers now believe they have a good understanding of the behavior of foam insulation around brackets running up the side of the tank that hold the pressurization lines in place. The so-called ice/frost ramp foam, in place to prevent ice from forming on the brackets prior to launch, was once partially protected from aerodynamic buffeting by the now removed PAL ramps. Engineers believe they have a handle on what sort of changes are needed to minimize foam loss from the ice/frost ramps.

    Another tank issue is the replacement of a gaseous oxygen vent valve that helps maintain the proper pressure for main engine operation. During initial work to replace the valve, a light fixture contacted foam insulation in the area, but a NASA spokesman said the incident caused only minor, easily-repaired damage.

    Of more pressing concern, engineers have discovered a potential electrical issue, this one involving the ascent thrust vector control - ATVC - system used to move the shuttle's main engine nozzles during launch.

    During ground tests, sources said, an ATVC control box suffered a malfunction. The failure may have been due to a phenomenon known as "whiskering," in which certain metals - like the tin used in circuit card guides - develop crystalline extrusions that pose a short-circuit threat should they break off and fall across unprotected circuit components. In this case, the concern focuses on tin whiskers possibly growing from circuit board guides found in ATVC boxes and others that share a common chassis design.

    This may be the result of a change in the way Honeywell built the boxes in question or, more worrisome, an age-related or stress-related phenomenon, officials say. It's not yet known how extensive the whiskering might be or what impact it might have on Discovery's launch. But the ATVC system in question is critical for flight safety and if hardware must be replaced aboard Discovery, the July launch target could be in jeopardy.

    In other developments, two of Discovery's cockpit windows have been replaced because they were not tested properly and engineers are now discussing whether to replace two others.

    At the same time, engineers studying the results of a new analytical technique for assessing the structural "loads" on the external tank have been surprised by results suggesting brackets near the base of the tank might not have the expected safety margin.

    More tests are planned and engineers stress the picture almost certainly will change as additional data come in. Even so, some have suggested modifying the flight profile for Discovery's next mission to lower aerodynamic stress on the tank as the shuttle climbs out of the lower atmosphere.

    A so-called "low-Q" flight profile was developed to reduce loads on the cockpit windows. The windows in question are being replaced, but the modified ascent profile could be used, some have suggested, to lower stress on the tank and its fittings if necessary.

    At this point, such talk is just that - talk - and the issue has not been formally discussed by program managers.

    One other issue appears to have been resolved. Engineers now believe a small fragment of metallic contamination seen in a mesh filter just above the point where a liquid oxygen propellant line attaches to one of Discovery's main engines does not pose an ignition threat. But the debris cannot be removed without breaking into the main propulsion system, a complex process that engineers want to avoid unless absolutely necessary. As such, it appears NASA managers will agree to simply leave the contamination in place for Discovery's launching.

    In addition, work to repair the shuttle's robot arm, dinged in a hangar incident earlier this month, is ahead of schedule. The arm should be re-installed next month with no impact on the July launch target.


    12:30 a.m., 03/15/06, Update: Launch delayed to July for ECO sensor swap; robot arm assignment uncertain; propulsion system issues still under discussion; initial wind tunnel runs begin

    The shuttle Discovery's launch on the second post-Columbia mission has been delayed to at least July 1 because of work to replace suspect engine cutoff - ECO - sensors in the ship's external tank. Shuttle program manager Wayne Hale made the decision Tuesday, after two days of detailed engineering discussions, even though the issue was not an open-and-shut case and even though the sensor in question may be good enough to fly. In the end, Hale decided to err on the side of caution in a bid to resolve, once and for all, questions about the sensors that have lingered since Discovery's launch on the first post-Columbia mission last July.

    "This was not an easy decision," Hale told reporters late today. "We had quite an interesting debate, pros and cons, looked at every possible way around this and finally concluded it was far smarter for us to be conservative and to take the safe route and replace the sensors that are in the tank.

    "That will take us about three weeks of work and that, of course, will move us out of the May launch window for STS-121. So today, we are proposing that the no-earlier-than launch date, the earliest possible launch date, would be July 1."

    Discovery should be ready to fly well before the target date, but program managers want to launch the next two missions in daylight to make sure they can document how the foam insulation on the external tank performs.

    It was the loss of a large piece of insulation that doomed Columbia in 2003 and the loss of another large piece of foam during Discovery's launch last July that has held up subsequent flights. NASA currently is conducting wind tunnel tests to make sure changes to the tank's insulation are safe and Hale said today he does not yet have enough data to make a final decision.

    But assuming the foam modifications are good to go, Discovery must be launched in daylight for photo-documentation to verify the insulation's performance. Because the shuttle is flying to the space station, it must launch into the plane of the lab's orbit and that, coupled with a daylight launch constraint and other factors, limits when NASA can make a launch attempt. The next "window" opens July 1 and closes July 19.

    "We, in fact, will be ready, we think, with the vehicle before July 1, but we are dedicated to launching in the daylight so we can watch what happens to the external tank and the rest of the flight vehicle during the daylight for at least two more flights, STS-121 and the subsequent STS-115," Hale said. "So we are aiming now for July 1."

    The new launch date will give NASA time to resolve a variety of other challenging issues, including analysis of the foam modifications, what to do about main propulsion system contamination, what to do about MPS seals that may not meet specifications and recent damage to the shuttle's robot arm that could force NASA to use one taken from Endeavour. Given the launch delay, however, NASA may be able to fix Discovery's arm in time for launch in July.

    The ECO sensors are located at the base of the hydrogen section of the shuttle's huge external tank. The sensors are part of a backup system intended to make sure the shuttle's three main engines shut down before they completely drain the tank. Running the tank dry could cause powerful turbopumps to cavitate and fail, with potentially catastrophic results.

    The sensors use platinum wires whose electrical resistance depends on temperature. When the sensors are submerged in ultra-cold liquid hydrogen, resistance is extremely low. As the fuel level drops and the sensors become exposed, the temperature - and resistance - goes up. The change in resistance is monitored by a so-called point sensor box that, in turn, sends data to the shuttle's flight computers.

    Sensors can "fail wet" or "fail dry." Failing in the wet state is considered relatively benign because the shuttle is launched with more propellant than it actually needs and because the sensors are, in essence, a backup system. If sensors fail wet, the engines would continue to run and the shuttle's computer system presumably would shut them down on time based on meeting orbital requirements. But if two sensors failed in a dry state, the computers would be misled into believing the tank was nearly empty and the main engines would be ordered to shut down early. Unless it happened extremely late in the climb to space, that could trigger a dangerous, untried abort scenario.

    "Just like your car, you don't want to run it out of gas, that's not a good thing," Hale said. "You'd like to get where you want to go before the tank is completely empty. So the normal planning for a mission allows us to achieve the right orbital conditions - altitude, speed, direction of travel - without running out of propellant. In fact, we load extra fuel on board to make sure that even if we have small variations in the performance of the vehicle during launch, a small reserve is there to make sure we get to that point in the sky without running out of gas.

    "The sensors are there in case we have some kind of performance problem, which we have had twice in the history of the program."

    In one case - the launch of Challenger on mission STS-51F in July 1985 - a main engine shut down early because of an engine sensor problem, triggering an abort to a lower-than-planned orbit. As a result, the two remaining engines had burn longer than usual to make up the shortfall and the shuttle essentially ran out of gas below the desired altitude. The ECO sensors performed normally and forced engine shut down before the tank was completely dry.

    The only other instance of ECO sensors playing a role in a flight came in 1999 during launch of the Chandra X-ray Observatory aboard the shuttle Columbia. Because of a hydrogen leak and an electrical short circuit, Columbia's tank was nearly drained and the ECO sensors, once again, came to the rescue.

    "In both cases, the sensors, through the on-board computers, correctly told us that the tank was dry, we were out of fuel and we should shut the engines down," Hale said. "You like to shut the engines down with just a little bit of gas left in the lines to make sure those pumps, that pump the hydrogen and the oxygen into the engines, don't cavitate as they spin down. That's not good for the engines and it can lead to a number of problems, so we have in place these sensors on both the fuel side and the oxygen side."

    During Discovery's launch campaign last year, however, the ECO sensor system experienced a variety of subtle problems. Engineers were never able to trace the issue to an obvious fault and in the end, shuttle managers opted to replace the fuel tank. Even then, problems remained, but engineers believed the only likely worst-case result would be one sensor failing wet. After a detailed analysis, they approved a plan to launch Discovery with three of four working sensors for a limited set of circumstances. As it turned out, all four sensors worked normally on launch day and Discovery's ascent was uneventful from an ECO sensor standpoint.

    But NASA launched an extensive engineering evaluation that ultimately made a tentative connection between changes in the resistance of a sensor and possibly loose wiring leading to the detectors. And as it turned out, one sensor in Discovery's current tank - ECO-3 - showed a small two-ohm resistance shift during a test prior to shipment to the Kennedy Space Center.

    The tank was shipped anyway because a sensor swap-out, if one was ordered, would be easier to carry out with the tank in a vertical position, something not possible at Lockheed Martin's Michoud Assembly Facility near New Orleans.

    "During the course of this investigation over the last several months, they found that there may be a problem in the manufacturing of these sensors and that problem is in the way the wires are attached to these low-level sensors," Hale said. "There is a place that the wires attach to the sensors called a swage fitting. That swage fitting in some sensors that have been removed some time back in the history of the program have been noted to be a little loose and that's caused intermittent readings, varying resistance, in the sensor, which of course is how the sensor tells you whether it's reading a dry or a wet signal.

    "Last year, when we prepared to launch STS-114, we had a high degree of confidence the sensors would only fail, if they were to fail, in the wet reading condition. There is now some body of evidence that would indicate it's possible for the sensors to read erroneously dry when the tank is not, in fact, dry. A predecessor indication that something may be going on in the sensors is a shift in the resistance over time, particularly after the tank has been transported, vibrated, rattled around a little bit.

    "We, in fact, have a sensor in the external tank slated for the next flight that's showing a very small shift in its resistance reading, well within any previously established specification. However, because of the new knowledge we have this year and the ongoing engineering work that's looking at how these sensors work and how they may potentially have problems, we are taking the step of removing the external tank sensors from the bottom of the liquid hydrogen tank, from the tank we're going to use for the next space shuttle flight."

    The current ECO sensors were manufactured in 1996. The new sensors were built in 2002 and are believed to be immune to the loose wiring/swage fitting phenomenon. Ultimately, Hale said, the ECO sensor decision was driven by safety and the need for engineering forensics, not schedule.

    "This is what we call a criticality 1 (system), life-or-death kind of situation that you want those sensors to work properly, either way," he said. "They can prevent bad things from happening if they work properly and certainly, if they work badly they can cause bad things to happen. So we need to have a good set."

    To replace the sensors, engineers from the Michoud Assembly Facility, working in the Kennedy Space Center's Vehicle Assembly Building, will remove foam insulation from the very bottom of the tank, unbolt a large manhole cover and get inside the cavernous hydrogen section. Once the new sensors are in place, the manhole cover will be bolted back in place and, after lowering the tank to a horizontal orientation, foam insulation will be re-applied.

    "We hope to take the four sensors that we take out and put them in extensive tests," Hale said. "We want to see if the one sensor that's got this slightly elevated resistance reading really has this problem that the engineering tests say it could potentially have and then, of course, we will look at the other three sensors which were manufactured about the same time in the same facility.

    "We have a number of these sensors in tanks that are still slated to fly. The sensor in question was made 10 years ago, in 1996, and passed all its acceptance tests."

    The additional six weeks of work "should provide us plenty of time" to wrap up ongoing analysis of foam modifications, as well as a variety of other issues, including what to do about contamination on a liquid oxygen filter screen leading to one of the ship's main engines and questions about critical seals between the engines and the main propulsion system plumbing.

    "I think we'll be in good shape to look forward to a launch about the first of July," Hale said. "I remain optimistic we'll still be able to get three missions in this year, but I don't have the details on where we will fly the next two missions. Later in the fall, I'm sure."


    12:15 p.m., 03/08/06, Update: Robot arm undergoes ultrasound inspection; engineers assess tile damage on Endeavour's body flap

    The shuttle Discovery's robot arm is undergoing ultrasound inspections after a weekend mishap in which a moveable access bucket bumped into the arm during work to clean up broken glass. Two small indentations were found underneath the arm's insulation blankets and NASA wants to make sure the underlying structure wasn't damaged. At the same time, engineers are assessing tile damage to the shuttle Endeavour's body flap caused by equipment that slipped off a tray used by workers inspecting the ship's rudder/speed brake.

    The Endeavour incident happened Tuesday morning in Orbiter Processing Facility Bay 2 while technicians were carrying out an X-ray inspection of the rudder and speed brake system in the shuttle's vertical stabilizer.

    "While they were doing that, they dropped some equipment off the tray," said Jessica Rye, a NASA spokeswoman. "What they dropped was a film processor, it struck the left hand side of the body flap. There was some tile damage on the body flap, which they're addressing. They're looking, of course, at structural inspections to evaluate if there is any structural damage to the body flap."

    In Discovery's hangar (OPF Bay 3), meanwhile, engineers are continuing inspections of the shuttle's 50-foot-long robot. Friday night, engineers servicing the shuttle's heat shield tiles broke a light fixture. During work to vacuum up the fragments, a telescoping bucket used to move technicians from point to point in the cargo bay bumped into the robot arm.

    Insulation blankets were removed and engineers spotted apparent damage to an aluminum grounding strap that runs the length of the arm. In addition, there are two small indentations in the arm's so-called outer bumper, an epoxy honeycomb material that protects the arm's underlying carbon composite structure. One indentation is .115 inches deep and 1 inch long and the other is .035 inches deep and a half-inch long.

    During Discovery's upcoming mission, the shuttle arm will be used to pick up a long boom equipped with cameras and laser sensors to inspect the shuttle's heat-shield system after launch. In addition, two astronauts will ride about on the end of the boom during the first of three planned spacewalks as part of an engineering study to evaluate the extended arm-boom system's stability. The idea is to find out if the system could be used for heat-shield repair work if such work is ever needed.

    To help evaluate the loads on the arm-boom system, Discovery's robot arm has been instrumented and engineers want to make sure the arm itself and the instrumentation were not damaged by the work bucket incident.

    As of this writing, the arm damage does not appear to be a threat to the shuttle schedule, but engineers won't know for sure until the ultrasound tests are complete.


    02:45 p.m., 02/07/06, Update: NASA assesses unexpected reading from fuel tank sensor

    Shuttle engineers are studying what, if anything, to do about an unexpected reading from one of four liquid hydrogen main engine cutoff - ECO - sensors in Discovery's external fuel tank, officials said today. The sensors play a critical role during the climb to space by ensuring a shuttle's main engines shut down normally before draining the ship's external tank. A malfunction could trigger an early engine shutdown or let the powerplants run too long.

    ŹŹ Discovery's launch last year was delayed because of ECO sensor problems that cropped up during pre-flight fueling tests. While engineers were never able to conclusively resolve the issue, data showed the problem was not generic and NASA managers approved a rule change that would have permitted Discovery to fly with three of four operational ECO sensors if the same problem showed up again. As it turned out, the rule change was not needed. On launch day, the sensors behaved normally.

    This time around, a possible problem was noticed before external tank No. 119 - the one Discovery will use on its next flight - was shipped to Florida from Lockheed Martin's Michoud Assembly Facility near New Orleans. The tank arrived at the Kennedy Space Center last week.

    During an all-systems electrical check at Michoud, a NASA spokesman said, liquid hydrogen ECO sensor No. 3 showed a 2-ohm shift from what engineers expected. The test was carried out again and ECO-3 showed the same reading.

    "They haven't done anything since," said a NASA spokesman at the Johnson Space Center in Houston. "They're down there (at the Kennedy Space Center) processing the tank (for launch) and they're still talking about it."

    The unexpected reading is within or very close to design specifications and it's not yet clear if anything will need to be done. If the sensors have to be replaced, engineers will need between one and three weeks to get inside the tank and make the swap.

    "But you don't know if you've corrected the problem because you don't know if it's in the sensors or the connector and wiring behind it," the NASA spokesman said.

    In the meantime, engineers are developing flight rationale to fly with three of four sensors much like the agency was prepared to do with Discovery's last launch.

    NASA Spaceflight.com, a web site that covers NASA operations, first reported the ECO sensor issue today, saying launch would be delayed for a sensor swap out. But no such decisions have been made, according to shuttle program manager Wayne Hale. The issue has not yet even been elevated to Hale's level and it is far from clear what, if any, impact it might have on plans to launch Discovery during a 12-day window starting May 10. The next window opens July 1.

    But Discovery's processing schedule has no built-in contingency time, and an ECO sensor swap-out would clearly pose an additional threat to the May window.

    Hale told the shuttle team Monday, sources said, that the May launch target is threatened on a variety of fronts and that figuring out whether it makes sense to reshape foam insulation making up so-called ice/frost ramps on the exterior of the tank remains a long pole in the tent (see earlier status reports for details). But Hale said he plans to stick with May 10 while engineers collect additional data.

    A discussion on whether to modify the shape of the ice/frost ramps is planned for March 23. Background on the ECO sensor problems that cropped up during Discovery's STS-114 launch campaign last year can be found in the CBS News Space Archive. A description of the sensors and how they work is available from CBS News and Spaceflight Now.


    09:00 p.m., 03/06/06, Update: Engineers look into shuttle robot arm 'bump'

    Engineers are looking under the insulation on the shuttle Discovery's robot arm to make sure an inadvertent "bump" by a moving servicing bucket didn't cause any damage.

    The incident began when a light in the shuttle's Orbiter Processing Facility hangar broke during tile servicing, raining a small amount of glass into Discovery's open cargo bay. During work over the weekend to vacuum up the fragments, the safety rail around the top of a telescoping bucket used to move workers from point to point in and around the shuttle's cargo bay bumped the 50-foot-long robot arm mounted along the left side of the bay. Sources said it did not appear the incident caused any major damage, but the results of a detailed inspection are not yet known, according to a NASA spokeswoman.

    During Discovery's upcoming mission, the shuttle arm will be used to pick up a long boom equipped with cameras and laser sensors to inspect the shuttle's heat-shield system after launch. In addition, two astronauts will ride about on the end of the boom during the first of three planned spacewalks as part of an engineering study to evaluate the extended arm-boom system's stability. The idea is to find out if the system could be used for heat-shield repair work if such work is ever needed.

    To help evaluate the loads on the arm-boom system, Discovery's robot arm has been instrumented and engineers want to make sure the arm itself and the instrumentation were not damaged by the work bucket incident.


    06:30 p.m., 02/28/06, Update: Hale 'optimistic' about three shuttle flights in '06, but no contingeny time in schedule for May launch

    If NASA can get the shuttle Discovery off the ground on the second post-Columbia mission this spring or summer, the agency will have a realistic shot at launching three flights this year, program manager Wayne Hale told reporters today.

    But the shuttle program faces a wide variety of complex technical challenges as it readies Discovery for launch as early as May 10, including critical wind tunnel tests to prove external tank modifications will work as expected; engineering studies to determine whether additional changes are needed; resolution of main engine seal and contamination concerns; and a success-oriented processing schedule that assumes no major problems develop between now and then.

    Even so, Hale said he remains "very optimistic that if we can fly in May or July, that we'll get three flights, three shuttle flights, up in this calendar year."

    That assumes, of course, that no large pieces of foam insulation break away from shuttle fuel tanks during launch and that whatever debris does fall off doesn't cause any serious damage.

    "It does depend on what happens with those flights because when we get back from a mission, we have to review what happened and see if there's anything that affects the next flight," Hale said.

    "We have been holding a series of management meetings to make sure we have the right resources staged to be able to look at any in-flight anomalies and come a resolution on them in the 10 or so weeks we'd have between flights. That is going to be a challenge to change from this kind of interregnum period, where we've had lots and lots of time to work on anything and everything to the maximum extent possible down to something that says well, we need to kind of turn the crank here and do what is reasonable and proper, surely, but probably not guild the lily. ... I remain optimistic that if we fly this summer, we'll be able to get three flights off this calendar year. But time will tell."

    Discovery's revamped external tank, which departed Lockheed Martin's Michoud Assembly Facility near New Orleans by barge on Saturday, is expected to arrive at the Kennedy Space Center Wednesday afternoon, 70 days before the proposed May 10 target launch date. The tank was shipped with up to 10 days of potential work left to sculpt foam insulation around brackets carrying external pressurization lines. Engineers are still debating whether the so-called ice/frost ramps need additional modification or whether they're good to go as is.

    "The real tough question is, will we come to a reasonable consensus that we have done enough to mitigate foam loss once again," he said. "And there are probably a dozen other issues that we're looking at on a daily basis. One of those could turn out to be a speed bump. But as of today, I see no reason to say anything other than we are progressing toward May. I remain optimistic. There's a lot of work to be done. I will commit to you and to the team and to the crew that we won't proceed until we have done the work that we need to do to prove it's safe to fly."

    Hale will chair a program requirements control board - PRCB - meeting Thursday that will consider making the following dates "no-earlier-than" launch targets:

    Because of photo-documentation requirements to launch the next flight in daylight, and to ensure external tank separation in daylight half a world away, NASA has to deal with limited launch windows. The next three useable windows are May 3-22; July 1-19; and Aug. 29-Sept. 14. NASA would give up the daylight launch constraint for an emergency mission and may give it up for flights after May if the upcoming mission suffers no major foam loss and if ongoing analysis shows new cameras and radar systems could detect debris shedding in darkness.

    As it now stands, NASA will be extremely hard pressed to make May 10. Launch director Mike Leinbach said the processing schedule has no built-in contingency time to handle unexpected problems.

    "External tanks typically are not in the critical path for a launch," he said. "That's not the case this time. This time, when the tank shows up it is in the critical path to get to a May launch attempt. ... We used to provide on the order of 25 to 30 days of contingency in the whole processing flow, from the tank, through the SRBs, the orbiter processing and the vertical flow out at the launch pad. What we've done this time is, we've put together a schedule that has no contingency in it.

    "Some people could call that an aggressive schedule. I like to call it an exciting schedule. It has a reasonable chance of success. If we run into a significant technical issue, we don't have much time to resolve it, obviously. But barring the big 'gotcha' in the processing, we feel pretty good about making that schedule."

    An official launch date will not be set until much later in the processing flow and "we will run right down to the wire to whatever the launch date turns out to be," Hale said of the ongoing work and analyses. "Right now, I have asked, we've put in a request for the team to evaluate a May 10 launch date. We're going to review the response to that request on Thursday. I expect, and already have been given some hints, that there are going to be some poke outs. The question is not are there poke outs, the question is how many and can we mitigate them. ... We're going to have a very interesting discussion Thursday."

    The major change to the shuttle's external fuel tank is removal of two protuberance air-load - PAL - ramps that ran up the lower hydrogen section of the tank and the upper oxygen section. The ramps were in place to shield two external pressurization lines and a critical cable tray from potentially damaging aerodynamic buffeting as the shuttle rockets through the sound barrier shortly after launch.

    But during Discovery's launch on the first post-Columbia mission last July, a large piece of the hydrogen PAL ramp broke off. In the wake of that incident, NASA managers decided to re-evaluate the engineering justification for the PAL ramps and tentatively concluded, based on computer modeling, that the design was overly conservative and that the ramps weren't needed.

    The ramps were then removed from ET-119 and the huge tank was shipped to Florida on the assumption upcoming high-speed wind tunnel tests using mock ups of tank hardware will confirm computational fluid dynamics modeling. If they don't, all bets are off.

    "The computer simulations and the paper analysis indicates that the structure should be able to take the aerodynamic loads that we generate on the cable tray, particularly after we removed the PAL ramp. But the proof is in the wind tunnel testing. We've got a series of wind tunnel tests, the first kicks off in just a couple of weeks at the Glenn Research Center, and we hope to get the data that will confirm what we hope is conservative engineering analysis on paper. If we find a surprise in the wind tunnel ... then we'll go deal with that.

    "When we look forward to the launch date, the thing that is going to pace getting Discovery off the ground is not the work that we're doing at the Kennedy Space Center, because we believe we have that well in hand and know what to do, but it is the engineering analysis and tests that go toward proving that what we have assembled on the launch pad is safe to fly."

    Overall, NASA engineers believe changes to the tank in the wake of Discovery's last mission will limit the size of any foam debris to small one-ounce chunks the size of a matchbox or smaller. The chunk of foam that came off during the July mission weighed more than a pound. Other areas of foam loss also have been addressed.

    "Just to make it perfectly clear to you, foam will still come off the tank after we have done all of these mitigation efforts," Hale said. "What we have done is worked off all the large pieces and we believe the pieces that come off will be small. ... Our task ahead of us is to ensure that all of these very small pieces of foam, most of them less than an ounce, will be of a size that they cannot have enough energy to do damage if they strike the orbiter. So that is work ahead of us.

    "I wanted to make sure everyone understands we are trying to eliminate critical foam loss, but we will expect to see foam coming off this next tank. As we go forward in the manifest for the next several flights, we'll continue to make improvements so we can eliminate even smaller and smaller pieces of foam loss."

    Along with final tank modifications, the wind tunnel testing and on-going analysis of the launch debris environment, NASA also faces additional work to complete servicing of Discovery's heat shield tiles and resolution of concern about out-of-specification main engine seals and metallic debris trapped in a main propulsion system oxygen propellant line.

    Hale said he is optimistic the seal issue will not hold up the launch even though at least some of the six seals in question do not meet printed specifications. The propulsion system has passed a helium signature leak test and engineers currently are evaluating whether the fact that some of the seals are slightly too thin could cause any problems. If worse comes to worse, the current seals can be replaced - even at the launch pad - but it's not clear if such work could be done in time to support a May 10 launch attempt.

    The other propulsion system issue - debris trapped in a main engine liquid oxygen inlet filter - is less clear cut. At issue is the nature of the debris. If it is made of titanium, it could pose an ignition threat during engine operation. There is no titanium in the liquid oxygen system and engineers say it's probably a metal that poses no threat. But they can't prove it. The debris cannot be removed without breaking open the propulsion system, which engineers don't want to do out of fear the fix might cause additional problems.

    "We can't get it out," said Leinbach. "To open up the system, to clean the screen, is an extensive job. It still fits the processing flow, but it's an extensive job, one that we don't want to do. But if the program decides it's a risk to flying and we need to pull it out, we'll do it."


    05:30 p.m., 02/27/06, Update: NASA awaits external tank; unfinished work could threaten May 10 target; shuttle/station manifest proposal

    The shuttle Discovery's modified external tank may arrive at the Kennedy Space Center Wednesday, a day early, to kick off the final push toward launch of the second post-Columbia shuttle mission. But agency officials say unfinished foam work, testing and resolution of other on-going issues will make it extremely difficult for NASA to meet its May target launch date.

    Even so, shuttle program manager Wayne Hale, chairing an external tank shipment review last week at the Marshall Space Flight Center in Huntsville, Ala., opted to stick with a May 10 target date pending additional discussions at this Thursday's program requirements control board - PRCB - meeting in Houston.

    Hale will participate in a shuttle program update news conference Tuesday at the Kennedy Space Center.

    External Tank 119 departed Lockheed Martin's Michoud Assembly Facility by barge on Saturday, nearly a week ahead of schedule. But engineers face up to 10 days of additional foam closeout work in Florida as the space agency gears up for normal launch processing.

    NASA planners have been baselining an accelerated 62-day processing flow that typically includes five days of contingency time to handle unexpected problems. Depending on how much post-shipment foam work is actually required for ET-119, that contingency time could shrink to zero or even go negative, i.e., push the launch to later in May. As it now stands, a full 10 days of post-shipment work would drive the launch date to around May 12 with no contingency time. A meeting to discuss tank processing issues is planned for Tuesday.

    Other "long poles" in the launch processing schedule include positive results from upcoming wind tunnel tests to verify recent tank modifications will work as advertised; a launch ice/debris analysis; and final design reviews associated with the tank work.

    Engineers are also working two issues with the shuttle's main propulsion system that must be resolved before flight.

    After two helium leak test failures, replacement seals were installed between two of the ship's three main engines and propellant feed lines. The propulsion system is now leak free. But three of the four seals in question do not quite meet printed specifications and engineers are conducting an analysis to show the seals will work as required. NASA also is working with the vendor to ensure compliance with specifications in the future.

    Another open issue involves small metal fragments trapped on a filter screen above a liquid oxygen main engine inlet. Similar debris was seen in a filter screen in the main propulsion system aboard the shuttle Endeavour and engineers are trying to figure out whether the material represents an ignition threat. If the debris must be removed before flight, Discovery would not be able to meet the May launch window, officials said. See the Feb. 17 status report for additional details.

    That said, here is the latest near-term launch schedule. Readers are advised that recent discussions of long-term manifest options on this page and other sites have been superceded by a new space station assembly sequence (see below); the following target dates are topics on the agenda at Thursday's PRCB meeting and thus subject to change:

    STS-116 is officially slated for the shuttle Endeavour. But Endeavour, currently undergoing a major inspection and overhaul, will not be ready to fly before February and NASA almost certainly will switch that flight to Discovery. And that, in turn, would delay implementation of a major modification planned for Discovery that will permit it to use space station electrical power when docked to the orbital outpost.

    As it now stands, the shuttle can transfer its own 28-volt power into the station's 120-volt system, but it doesn't work the other way around. Using a new Boeing-supplied Power Converter Unit, the shuttle will be able to augment its own fuel cell-generated power with station electricity, allowing future crews to remain docked for nine to 12 days. That's a high-priority upgrade to maximize the time available for assembly work, but modifications to Discovery will be deferred one flight if Discovery does, in fact, stand in for Endeavour.

    The space station, of course, is the major manifest driver. All but one of the 17 flights remaining between now and the end of the shuttle program in 2010 are devoted to space station assembly, resupply and maintenance. The lone exception is a possible flight to service and upgrade the Hubble Space Telescope.

    While that mission carries a high scientific priority, it is not yet clear how NASA will conduct a flight that cannot take advantage of the international space station if the orbiter suffers any significant damage during launch or in orbit.

    Space station-bound shuttle crews can use the lab complex as a "safe haven" in the event of major problems, but that option isn't available to a Hubble crew because the shuttle does not have the ability to move from one craft's orbit to the other. A decision on how to proceed ultimately could play a role in when NASA turns over one of its two shuttle launch pads for modifications to support the new Crew Exploration Vehicle.

    Shuttle managers would like to keep pad 39B available in case the agency ultimately decides a second shuttle must be prepared for a quick-launch emergency mission to protect the Hubble crew. All of that remains up in the air as of this writing, but it is a factor in manifest planning and CEV test flight scenarios.

    NASA had been hoping to launch a Hubble servicing mission eight or nine flights into the new sequence. But the agency is expected to move up launch of two key European and Japanese space station modules, at the request of the international partners, pushing a Hubble flight to early 2008 on the 11th mission in the latest proposed manifest.

    NASA Administrator Mike Griffin and his international counterparts plan to discuss the station assembly sequence at a "heads of agencies" meeting Thursday at the Kennedy Space Center. A news conference is planned Thursday afternoon.

    The European and Japanese space agencies, sources say, have been adamant about moving up the launch of ESA's Columbus research module and the Japanese Kibo module. NASA planners initially resisted the idea because it complicated logistics and sequential assembly work.


    02:30 p.m., 02/17/06, Update: Astronauts optimistic about May launch; NASA studies engine seals, contamination issues; fuel tank to ship ahead of schedule

    NASA now plans to ship the next external fuel tank to the Kennedy Space Center ahead of schedule and the shuttle Discovery's commander said today the astronauts remain optimistic about launching in May on the second post-Columbia mission. But a variety of technical issues remain on the table, including wind tunnel tests to show fuel tank changes will work as expected, an ice and debris analysis and, most recently, main engine seal leaks and metallic contamination in the main propulsion system.

    The latter issue appears to be a generic problem in that metallic debris, estimated to weigh just 0.08 milligrams, has been found in the liquid oxygen prevalve filter screen used by Discovery's main engine No. 1 and also in an oxygen prevalve screen in the shuttle Endeavour. In the latter case, the debris is estimated to weigh 1.1 milligrams. The concern is that such debris, depending on its composition, could trigger a catastrophic fire during engine operation.

    It is not yet known whether the shavings detected by boroscope inspections represent a real ignition threat, whether the shuttle can safely fly as is or whether time-consuming work to disassemble the system and remove the debris will be necessary. If so, NASA could be hard-pressed to launch Discovery before the next launch window closes May 22.

    In a separate issue, Discovery's main propulsion system failed a helium leak test after engine installation and then failed it again after engineers detached the engines, installed different seals (two per engine) and reattached the powerplants. Engineers now plan to install the best seals in the shuttle inventory and carry out a third helium signature test to verify the integrity of the system.

    If the system passes, NASA will press ahead with Discovery's processing for a launch as early as May 10. But the issue will remain open until engineers figure out what caused the original sealing problem or, if the problem involves hardware that does not meet specifications, whether the shuttle can fly safely with any such out-of-spec components.

    At Lockheed Martin's Michoud Assembly Facility near New Orleans, meanwhile, engineers are readying external tank No. 119 for shipment to the Kennedy Space Center as early as next Friday, Feb. 24, a week ahead of schedule.

    During Discovery's launch last July on the first post-Columbia mission, a large piece of foam insulation broke away from the liquid hydrogen section of the external tank's protuberance air-load - PAL - ramp. In the wake of that incident, NASA managers decided to remove the PAL ramps on all subsequent tanks, starting with ET-119.

    The PAL ramps were added to the external tanks before the first shuttle mission to act as aerodynamic dams, shielding two external pressurization lines and a critical cable tray from buffeting as the shuttle rockets out of the dense lower atmosphere. Computer modeling now indicates the ramps aren't needed and that the pressurization lines and cable try are tough enough to endure whatever buffeting they might experience.

    But wind tunnel tests are needed to confirm the computer results and that work will not be finished until next month.

    "We resisted taking the PAL ramps off," shuttle program manager Wayne Hale told Kennedy Space Center workers today during an "all hands" briefing. "We were looking at taking the PAL ramps off eventually and we had this nice program, we were going to do a lot of wind tunnel tests, do all this analysis, instrument a couple of tanks and fly a couple of tanks and get the data that would prove without a shadow of a doubt we didn't need these PAL ramps. ... Clearly, supersonic aerodynamics, the forces that are imposed on the pressurization lines and the cable tray that run up the side of the tank on the outside, you don't want to fool around with that because you can't stand for those things to come loose. So we've got to do it right. That was in the plan."

    But in the wake of Discovery's launch last July and inspections of a tank originally scheduled for the next mission, "we knew the PAL ramp had to go," Hale said. "So the big discussion was how can we prove this is safe to do?"

    "We've done some very conservative kinds of analyses ... and that indicates we are probably OK to take it off," Hale said. "But it also has big uncertainty factors. And if you put the big uncertainty factors on it, it's not what you'd like. So we've got an expedited set of wind tunnel tests that we're running, first at the Glenn Research Center coming up in March and secondly, at the Arnold Engineering Development Center in Tullahoma, Tenn., in June. You might detect that June is kind of after when we'd like to fly."

    But Hale said by around April 1, engineers should have "some numbers that we can at least hang our hat on and if we pass go at that point, which is to say the structure will hold together as we go supersonic on the tank, then life is good. We're not really sure that's going to happen, that's why we've got the Glenn Research Center wind tunnel tests, which has a full-scale part of the tank with these lines and cable trays. Putting that model together and getting it into a wind tunnel is not something they do overnight."

    Wind tunnel testing will run through March. Data will be compared to the engineering analysis and "hopefully say, you know, we were too conservative and the loads are actually less than this conservative analysis, we can reduce the uncertainty."

    But if the March testing generates less definitive results, additional higher-fidelity tests will be conducted at Arnold in June and Discovery's flight will slip into the July launch window and possibly even later.

    "This is a success-oriented schedule," Hale said. "We are betting, as we do frequently, that we will be smart enough to say we're good to go. But if the answer comes out bad, we'll put the red flag out and we'll say we've got to wait until the July launch window to get the AEDC wind tunnel test results back.

    "We're all assuming the analysis will show the structure as it stands is good to fly, that it's got the strength necessary to withstand the aerodynamic loads. But I won't kid you, if the answer comes back and says, you know, the cable tray will come off, that's not something we're going to fly with. And then we'll have to sit down and scratch our heads.

    "So here's the story," Hale concluded. "We are working towards, as we always seem to in this business, an optimistic (schedule for a May launch). The data has got to prove it is safe to go fly. If the data doesn't come in in time, or the data says it's not safe to fly, then we'll stop what we're doing and go to plan B. I have a great deal of confidence the data will show we are safe to go fly, but it's going to be what it's going to be. ... Welcome to our world."

    Other long poles in the processing tent include completion of a detailed ice and debris threat analysis; possible work to replace additional "gap fillers" between heat shield tiles on the orbiter's belly; and work to confirm a long boom that will be used to carry out post-launch heat shield inspections in orbit can withstand launch forces.

    Discovery commander Steven Lindsey and five of his six crewmates - pilot Mark Kelly, Michael Fossum, Lisa Nowak, Stephanie Wilson and Piers Sellers - spoke with reporters today at the Kennedy Space Center and expressed confidence about getting off in May.

    "The foam problem, obviously we're working on it," Lindsey said. "Everybody knows what happened on 114 (Discovery's last flight). The PAL ramp foam problem, I think we have solved since we've taken the PAL ramp foam off the tank and it won't be there. The data that I've seen ... I'm pretty confident that's the right decision and we're going to be OK on that."

    Lindsey said "the program has never advertised that we will never lose any foam. And we'll lose foam on this flight."

    "The key is, to make sure the foam we do lose is small enough that it can't hurt us if it hits the vehicle," he said. "And that's what we're working towards. So I feel pretty confident that the decisions we're making based on the information we have and the engineering analysis and wind tunnel testing, we're going in the right direction."

    Even so, he cautioned, "this is a test flight and part of the purpose of this test flight is to test the changes we've made to the tank. And so obviously, we won't know for sure until we fly it."

    During Discovery's flight last summer, spacewalker Stephen Robinson, riding on the end of the space station's robot arm, ventured under the nose of the shuttle to remove two protruding gap fillers that had shaken loose during launch. The gap fillers provide a sort of protective cushion between tiles during launch and re-entry. Gap fillers that protrude into the airstream during re-entry can cause excessive localized heating.

    In the wake of Discovery's last flight, engineers have replaced gap fillers in critical areas.

    "The gap fillers, we're in the process of replacing a bunch of them and making sure they're secure," Lindsey said. "As everyone knows, we had one come loose and had to pull it out on the last flight. We've got the primary zones done on the gap fillers, there are some more zones that we just signed up to do that still supports May. There is still some debate going on over another section and whether we need to pull those.

    "As far as I know, I don't think that in particular is threatening the May launch date. There is a lot of work going on to get the tank ready, to get the tank shipped on time, to do a good tank flow here to get us all ready to go. There are a whole bunch of things out there. Right now, we're still holding to May, we're training to May and the program is marching toward May. We'll see.

    "The only kind of risk we want to take here is a schedule risk, not a technical risk. Nothing technically is being eliminated for the May launch date. We're doing everything technically that we would normally. If we get to a point where, from a schedule standpoint it doesn't make May, then we're going to slip. But we're not going to skip any technical steps."


    03:30 p.m., 02/16/06, Update: NASA prepares tank for shipment; launch date assessment in work

    NASA managers plan to meet early next month to discuss launch dates for the next space shuttle mission. The launch window opens May 3 and closes May 22, but the agency's current "no-earlier-than" planning date is May 10.

    The May 10 date assumes the shuttle Discovery's revamped external fuel tank, ET-119, leaves the Michoud Assembly Facility near New Orleans by around March 3. The tank may actually ship as early as Feb. 24, but Discovery will not be ready to fly until at least May 10 because of time need to process the shuttle stack and complete required tests and analyses.

    The May 10 date assumes upcoming wind tunnel tests show NASA's earlier decision to remove a foam ramp from the tank will not impact flight safety and that engineering studies show a long boom needed to inspect the shuttle's heat-shield tiles in space can withstand launch forces and other loads. Other required studies include a mission-specific launch debris threat analysis.

    A launch on May 10 would occur around 1:08 p.m. EDT. The goals of the 115th shuttle mission include delivery of spare parts and supplies to the international space station and delivery of a European astronaut to join the station's long-term crew. Three spacewalks are planned to A) show the robot arm inspection boom can be used to move astronauts to various heat shield repair points; B) to demonstrate reinforced carbon carbon repair techniques; and C) to service a mobile cart used to move the station's robot to work sites on the lab's solar array truss.

    While the STS-121 launch date may well change, here's is a summary timeline of mission highlights to give readers a feel for when major events will occur (this summary timeline is available on the CBS News STS-121 Quick-Look page and in one of the worksheets making up SpaceCalc):

    DAY.ET.........DD...HH...MM...EVENT
    
    05/10/06
    Wed 01:08 PM...00...00...00...STS-114 Launch
    Wed 01:17 PM...00...00...09...Main engine cutoff
    Wed 01:46 PM...00...00...38...OMS-2 rocket firing
    Wed 01:58 PM...00...00...50...Post-insertion timeline
    Wed 07:08 PM...00...06...00...Crew sleep begins
    
    05/11/06
    Thu 03:08 AM...00...14...00...Crew wakeup
    Thu 07:08 AM...00...18...00...TPS survey begins
    Thu 05:08 PM...01...04...00...Crew sleep begins
    
    05/12/06
    Fri 01:08 AM...01...12...00...Crew wakeup
    Fri 06:13 AM...01...17...05...TI rendezvous rocket firing
    Fri 08:57 AM...01...19...49...ISS Docking
    Fri 10:03 AM...01...20...55...Hatch opening
    Fri 05:08 PM...02...04...00...Crew sleep begins
    
    05/13/06
    Sat 01:08 AM...02...12...00...Crew wakeup
    Sat 04:43 AM...02...15...35...MPLM installation
    Sat 08:48 AM...02...19...40...OBSS RCC survey
    Sat 05:08 PM...03...04...00...Crew sleep begins
    
    05/14/06
    Sun 01:08 AM...03...12...00...Crew wakeup
    Sun 06:28 AM...03...17...20...EVA-1: Airlock depressurization
    Sun 07:13 AM...03...18...05...EVA-1: Airlock egress (boom loads
    test; removal of damaged cable system on station cart)
    Sun 01:28 PM...04...00...20...EVA-1: Airlock ingress
    Sun 05:08 PM...04...04...00...Crew sleep begins
    
    05/15/06
    Mon 01:08 AM...04...12...00...Crew wakeup
    Mon 10:28 AM...04...21...20...Crew news conference
    Mon 04:38 PM...05...03...30...Crew sleep begins
    
    05/16/06
    Tue 12:38 AM...05...11...30...Crew wakeup
    Tue 05:58 AM...05...16...50...EVA-2: Airlock depressurization
    Tue 06:43 AM...05...17...35...EVA-2: Airlock egress (mobile cart
    repair work)
    Tue 12:43 PM...05...23...35...EVA-2: Airlock ingress
    Tue 04:38 PM...06...03...30...Crew sleep begins
    
    05/17/06
    Wed 12:38 AM...06...11...30...Crew wakeup
    Wed 09:38 AM...06...20...30...Crew off-duty time
    Wed 04:38 PM...07...03...30...Crew sleep begins
    
    05/18/06
    Thu 12:38 AM...07...11...30...Crew wakeup
    Thu 05:58 AM...07...16...50...EVA-3: Airlock depressurization
    Thu 06:43 AM...07...17...35...EVA-3: Airlock egress (RCC crack repair
    demonstration)
    Thu 01:13 PM...08...00...05...EVA-3 ends
    Thu 04:38 PM...08...03...30...Crew sleep begins
    
    05/19/06
    Fri 12:38 AM...08...11...30...Crew wakeup
    Fri 10:38 AM...08...21...30...MPLM berthing
    Fri 04:38 PM...09...03...30...Crew sleep begins
    
    05/20/06
    Sat 12:38 AM...09...11...30...Crew wakeup
    Sat 04:48 AM...09...15...40...Undocking operations begin
    Sat 05:33 AM...09...16...25...ISS undocking
    Sat 07:08 AM...09...18...00...Final separation rocket firing
    Sat 09:23 AM...09...20...15...Crew off-duty time begins
    Sat 04:08 PM...10...03...00...Crew sleep begins
    
    05/21/06
    Sun 12:08 AM...10...11...00...Crew wakeup
    Sun 03:08 AM...10...14...00...FCS checkout
    Sun 03:08 AM...10...14...00...Cabin stow begins
    Sun 04:18 AM...10...15...10...RCS hotfire
    Sun 12:48 PM...10...23...40...KU antenna stow
    Sun 04:08 PM...11...03...00...Crew sleep begins
    
    05/22/06
    Mon 12:08 AM...11...11...00...Crew wakeup
    Mon 03:18 AM...11...14...10...Deorbit timeline begins
    Mon 07:18 AM...11...18...10...Deorbit ignition
    Mon 08:21 AM...11...19...13...Landing
    
    NASA has not provided a detailed briefing on STS-121 launch processing since mid December, but program manager Wayne Hale may address the media before the end of the month. In the meantime, here is a calendar of upcoming events as provided by a variety of sources. This calendar is available on the STS-121 Quick-Look page and in the CBS Space News Space Calendar. Launch dates are planning/processing targets only and are thus subject to change:

    DATE.......EVENT
    
    03/03/06...19 Progress undocks from Zvezda aft port; 5 a.m. ET.
    03/03/06...STS-121: external tank ET-119 leaves Michoud Assembly
    Facility (possible move to Feb. 24; if so, KSC arrival 3/1)
    03/08/06...STS-121: ET-119 arrives at KSC
    03/29/06...Soyuz TMA-8 launch with ISS-13 crew (9:29 p.m. EST)
    03/31/06...Soyuz TMA-8 docks with ISS at Zvezda aft port (11:11 p.m. EST)
    
    04/08/06...ISS-12 crew aboard Soyuz TMA-7 undocks from Zarya nadir
    port and lands (landing at 7:40 p.m. EST)
    04/14/06...STS-121: Discovery rollover to VAB
    04/17/06...STS-121: Payload to launch pad
    04/18/06...Soyuz TMA-8 moves to Zarya nadir port
    04/21/06...STS-121: Rollout to launch pad
    04/23-25...STS-121: Terminal Countdown Demonstration Test
    04/24/06...21 Progress launches
    04/26/06...21 Progress docks at Zvezda aft port
    
    05/03/06...Shuttle launch window opens
    05/10/06...STS-121: Launch (1:08 p.m.; "no-earlier-than" date)
    05/22/06...STS-121: Landing (8:21 a.m.)
    05/22/06...Shuttle launch window closes
    05/31/06...STS-115: ET-118 shipped from MAF
    
    06/19/06...20 Progress undocks from Pirs module
    06/28/06...22 Progress launches
    06/30/06...22 Progress docks at Pirs
    
    07/01/06...Shuttle launch window opens
    
    (NOTE: if STS-121 gets off in the May window, no shuttle flight
    will be attempted in July because of ET/orbiter processing issues)
    
    07/19/06...Shuttle launch window closes
    07/24/06...STS-115: Rollover
    07/27/06...STS-115: Payload (P3/P4 truss elements) to launchpad
    07/31/06...STS-115: Rollout to launch pad
    
    08/04/06...STS-300: Launch (rescue flight; if needed)
    08/08/06...STS-115: TCDT
    08/28/06...STS-115: Launch (if analysis of lighting permits)
    08/29/06...Shuttle launch window opens
    08/30/06...STS-115: Docking with ISS (if launched 08/28)
    
    09/08/06...STS-115: Landing (if launched 8/28)
    09/12/06...21 Progress undocks from Zvezda aft
    09/14/06...Soyuz TMA-9 with ISS-14 crew launches (expected to
    slip until after STS launch window closes)
    09/14/06...Shuttle launch window closes
    09/16/06...Soyuz TMA-9 docks at Zvezda aft port
    09/24/06...Soyuz TMA-8 with ISS-13 crew undocks from Zarya port
    
    10/18/06...23 Progress launches
    10/26/06...Shuttle launch window opens (based on lighting)
    10/30/06...Shuttle launch window closes
    
    12/20/06...24 Progress launches
    12/23/06...Shuttle launch window opens (based on lighting)
    12/25/06...Shuttle launch window closes
    


    12:40 p.m., 02/09/06, Update: Adding processing milestones; updating summary timeline

    A revised summary flight plan has been posted on the STS-121 Quick-Look page and major hardware processing milestones have been added to the sidebar of this page. The summary flight plan is based on a May 10 target launch date and a launch time of 1:08 p.m. This is NASA's current internal target, but it is not an official date and it likely will change as NASA's processing schedule matures. Likewise, the summary flight plan will change as well as planning continues and readers should take it with a grain of salt. It is posted here primarily to provide a general feel for when major mission events will take place.


    03:15 p.m., 02/06/06, Update: NASA budget supports up to 17 shuttle flights; agency still hopeful about May launch

    By sharply reducing the growth of space science and other NASA programs over the next five years, NASA managers hope to erase a projected multi-billion dollar shortfall in the shuttle budget, permitting up to 17 missions between now and the program's retirement in 2010, including a possible flight to service the Hubble Space Telescope. Only two flights are expected this year, one in May and the other late this summer, as NASA struggles to complete its recovery from the Columbia disaster and finish a major overhaul of the shuttle Endeavour.

    Unveiling NASA's fiscal 2007 budget, Administrator Mike Griffin said today the Bush administration is requesting $16.8 billion for the civilian space agency, a 3.2 percent increase over fiscal 2006. The 2007 budget includes $5.3 billion for space science; $4 billion for development of a new manned spacecraft and other technologies for the president's moon-Mars exploration initiative; and $6.2 billion for the space shuttle and international space station projects.

    To help make up a projected $3 billion to $5 billion shortfall in the shuttle budget between now and 2010, NASA plans to limit the growth of the space science budget to just 1.8 percent in 2007 and 1 percent per year thereafter. Doing so will defer the development of several major unmanned projects, including one to search for planets around other stars and another to detect Earth-like extra-solar worlds.

    "Leadership means setting priorities," Griffin said today. "And leadership means making difficult decisions based on the best facts and analysis available. And one plain fact is NASA simply cannot afford to do everything that our many constituencies would like us to do. We must set priorities and we must adjust our spending to match those priorities."

    To make up the projected shuttle shortfall, "we took a couple of billion out of science and a billion and a half out of the exploration line and made up what we needed to make up," Griffin said.

    During a news conference last month, Griffin said NASA's space science budget would not be cut to fund the shuttle, the space station or the Bush administration's moon-Mars initiative. But growth would be reduced, he said.

    "We are not whacking the space science program to pay for human exploration," he said in response to a question from CBS News. "This is not the 'Sopranos,' we don't whack people or programs here. We have, of course, in this nation, I do not need to be the one to tell you this, this is a difficult budgetary environment. NASA is not looking forward to any gifts of robust growth from either the administration or the Congress. We expect to keep approximately the funding we have, which will essentially be a very low growth funding profile and therefore, all of the components, each separate component of what NASA does can expect to have, at best, only modest growth.

    "The difference between cuts and modest growth, I guess, needs to be explained to people. I think we're doing well and within NASA, the space science program is doing well and will continue to do well." Today, a reporter asked the administrator, "last September you said that not one thin dime would be taken away from the science programs for human spaceflight and exploration. Is what you just said, that that's exactly what has been done, not just one thin dime but two billion dollars taken away from space science to complete the ISS?"

    "Yep, that's right," Griffin said with his usual candor. "I wish we hadn't had to do it, I didn't want to, but that's what we needed to do."

    The Planetary Society, an international space interest group, said today the president's 2007 budget request for NASA "shortchanges space science in order to fund 17 projected space shuttle flights."

    "Despite recent spectacular results from NASA's science programs, this budget puts the brakes on their growth within the agency," the society said in a statement. "It seriously damages the hugely productive and successful robotic exploration of our solar system and beyond."

    Society president Wesley Huntress, a former associate administrator for space science at NASA headquarters, said the agency is "essentially transferring funds from a popular and highly productive program into one scheduled for termination."

    In January 2004, President Bush announced a new direction for NASA, telling the agency to complete the international space station and retire the shuttle by 2010; to develop a new crew exploration vehicle to replace the shuttle; and to use that spacecraft and other technologies to return astronauts to the moon by the end of the next decade. Returning to the moon is seen as a first step toward eventually launching humans to Mars.

    NASA has been struggling to complete post-Columbia safety upgrades, which have cost far more than initially envisioned, and to come up with a space station assembly sequence that can meet long-standing international commitments and research objectives by the 2010 deadline. Twenty eight flights were required to meet the program's original objectives, but that number was whittled down to 18 last year and now, to 16, assuming two resupply flights are ultimately cancelled and replaced by commercial missions. NASA's 2007 budget includes money, however, to continue preparations for an additional flight to service the Hubble Space Telescope.

    In the near term, NASA still hopes to launch the shuttle Discovery on the second post-Columbia mission, STS-121, during a window that opens May 3 and closes May 22. Because of hardware processing issues, NASA insiders say mid to late May is the current best guess as to an eventual launch date.

    NASA's launch windows are limited because of a post-Columbia directive to launch the first few shuttle flights in daylight and to make sure external fuel tank separation occurs in daylight half a world away. NASA engineers want to make sure the tank's foam insulation doesn't break away during launch and good lighting is required for detailed ground- and space-based photo documentation.

    Those requirements, along with the nature of the international space station's orbit, limit NASA to relatively infrequent windows. The next three are as follows:

    During the first post-Columbia mission last July, a large chunk of foam insulation broke away from a so-called protuberance air load - PAL - ramp on the side of Discovery's external fuel tank. The ramp, made of hand-applied foam insulation, was in place to smooth the flow of turbulent air over two external pressurization lines and a critical cable tray.

    Late last year, NASA managers decided to simply eliminate the ramp after detailed computer analysis indicated the pressurization lines and cable tray are tough enough to withstand the expected buffeting as the shuttle breaks through the region of maximum aerodynamic pressure shortly after launch.

    On the assumption upcoming wind tunnel tests in March will verify the earlier analyses, external tank No. 119, sans PAL ramp, will be shipped to the Kennedy Space Center from Lockheed Martin's Michoud (La.) Assembly Facility on March 3.

    External tank No. 118, slated for use by the shuttle Atlantis for the third post-Columbia mission, STS-115, is not scheduled to arrive in Florida until late May. Atlantis and ET-118 will be on call for rescue duty in the event of a major problem during Discovery's upcoming flight that might force the crew to seek "safe haven" aboard the international space station.

    Given ET-118's late arrival in Florida, a stranded crew would have a fairly long wait for a ride home. Assuming a mid-May launch for Discovery on mission STS-121, Atlantis would not be ready for rescue duty until around Aug. 4.

    But space station managers say the orbital lab complex will have enough oxygen and other supplies on board by the time of Discovery's launch to support a combined crew for almost six months.

    If Discovery does, in fact, get off in May and no major problems develop, NASA will process Atlantis for a launching in late August on mission STS-115.

    At that point, if all goes well, NASA almost certainly will relax the daylight launch requirement. Even so, agency officials say, a third flight appears unlikely this year because the shuttle Endeavour, currently undergoing a major overhaul, won't be ready to fly mission STS-116 until early 2007.


    06:00 p.m., 12/15/05, Update: NASA decides to remove PAL ramps; engineers gain insights into foam loss; May launch still 'viable'

    NASA engineers and managers have recommended the removal of a protective foam air deflector from the shuttle's external tank to eliminate a major source of potentially dangerous launch debris, a top agency official said today. While NASA has not given up launching the next flight in May, additional work to implement and certify other changes required by the deflector removal could push the launch to later next summer.

    Bill Gerstenmaier, NASA associate administrator for space operations, would not discuss possible launch targets during an afternoon teleconference with reporters, saying such talk was premature and put unnecessary "schedule pressure" on the team. Instead, he said, engineers were going to focus on thoroughly assessing the possible causes of foam shedding based on recent insights into cracks found in a tank slated for the flight after next.

    "We're going to do the right thing and let the data drive us where we need to go," he said.

    During a Program Requirements Control Board meeting at the Johnson Space Center in Houston today, engineers recommended removing the external tank protuberance air-load - PAL - ramps from the shuttle's external tank. Last month, shuttle program manager Wayne Hale said engineers did not believe NASA would be ready to launch a PAL-free tank until the third mission in the upcoming sequence.

    But computer modeling now shows the structures the ramps were designed to protect - two pressurization lines, support brackets and a critical cable tray - are beefy enough to withstand any expected aerodynamic forces, or loads, they might encounter during ascent. Wind tunnel tests are planned for February to verify the results of the computer modeling.

    But engineers are still assessing what changes will be required to so-called ice-frost ramps, areas of foam around the brackets supporting the pressurization lines that are intended to prevent ice formation before blastoff.

    "Based on the data we've reviewed, we don't need to do any redesign of the cable tray or the press lines," Gerstenmeir said. "So there's no redesign of the basic bracketry or the basic tank structure. That all looks fine. We'll confirm that with the wind tunnel tests. The margins look very good in that region. ... So that's a very positive thing, it takes a lot of that work out of the critical path.

    "From an overall standpoint, depending on what engineering solution gets picked (to address the ice-frost ramp issue), May is still very viable. Some of the other engineering solutions that would require a more detailed certification process of foam applications, etc., may move us somewhere else."

    The shuttle's external tank is made up of a large hydrogen tank, a so-called intertank section and an upper oxygen tank. Gaseous hydrogen and oxygen, used to pressurize the tanks, are diverted from the propellants feeding the shuttle's main engines and routed up the tops of the respective tanks in externally mounted pipes. The pressurization lines run next to a long cable tray that carries electrical lines routing data and commands between the shuttle and various tank and booster subsystems.

    When the shuttle was designed in the 1970s, engineers believed shock waves during the vehicle's transition to supersonic speeds could cause potentially catastrophic damage to the pressurization lines and/or the cable tray. As a result, the tank was equipped with two PAL ramps, one running along the upper section of the hydrogen tank and the other along the outside of the oxygen tank.

    During Discovery's launching last July on shuttle mission STS-114 - the first post-Columbia flight - a one-pound chunk of foam ripped away from the hydrogen PAL ramp just after the ship's solid-fuel boosters were jettisoned two minutes and five seconds into flight.

    Earlier this fall, Hale ordered all existing PAL ramps dissected and removed. Engineers were assessing new fabrication techniques as a possible solution when numerous small cracks were discovered prior to the removal of the PAL ramp of a tank slated for the third post-Columbia mission.

    Engineers now believe the cracks almost certainly are related to the thermal stress the tank undergoes when it's loaded with super cold rocket fuel. The tank in question - ET-120 - originally was to be flown by Discovery last July and it was fueled for two pre-launch tests. The tank later was replaced for unrelated reasons, but the cracks could have been caused by thermal stress.

    If that theory is correct, cracks would be a constant threat for shuttles that were fueled for launch and then delayed for other reasons. Whether similar cracks played a role in the foam loss experienced by Discovery's tank in July is an open question.

    But given the small size of the cracks, the difficulty in detecting them at the launch pad and the lack of any on-pad repair procedures, NASA managers opted to forego attempting to fix the PAL ramps and to recommend their removal instead.

    "They've done a tremendous job of chasing the cracks," Gerstenmaier said. "We saw the cracks in the non-destructive testing, in the X-rays and in the terahertz radar data. What they've done now is, they've carved out the cracks and they've followed the crack as it goes down into the foam and then they see the crack actually break into smaller cracks, into some delamination layers down internal to the foam. Then we see some of the cracks progress slightly underneath the cable tray, we see some of the cracks actually (branch) out into the acreage foam. So we know where the cracks are running.

    "What we don't know is really why they're initiating. We have some theories. ... There are two different types of foam. There's the foam that's on the acreage of the tank that's about an inch thick and then we spray this PAL ramp foam on top of it. Those two types of foam have different thermal expansion coefficients, so we now have a math model of the stress field between those two foams as they chill down. That's a key driver. Where we put one type of foam on top of another type of foam, it causes that lower layer of foam to be colder, it's not as strong at cold temperatures so the cracks can initiate down there and then carry up into the upper piece of foam."

    Gerstenmeir said a major unrsolved question is how temperature changes and tank pressurization interact to cause cracks. "Exactly how they fit together, we haven't had a chance to pull together," he said. But he provided a relatively detailed summary of how a crack might lead to foam shedding.

    "The tank has a one-inch layer of foam all around and then the PAL ramp is about, probably an eight- to 10-inch foam layer (is) sprayed on top of that," he said. "What happens is that foam that's sprayed on top, it provides an insulating layer that allows that one-inch piece of foam to get cold through its entire length, so it is now cold from the surface of the tank all the way to the top of that one-inch layer of foam.

    "The fact that that foam is cold, when it gets cold it loses some strength, or it's more brittle, and easier to crack. And then the fact that the foam on top is expanding at a different coefficient of thermal expansion, it causes a shear, or a stress layer, on top of that one-inch layer of foam as well as there's a shear layer, or a stress layer, down where the foam attaches to the tank.

    "So then, that can cause a crack to initiate somewhere in that underlying one-inch piece of foam and then that crack can then propagate on up into the foam on top of it. If that crack goes all the way to the surface, that's where the outside air is, and it goes all the way down to the tank, then that provides a path for air to come in, liquefy in that lower region next to the tank."

    As the super cold hydrogen in the tank is drained and the structure warms up, "that liquid air then expands, pushes out on the foam and can cause a large piece of foam to come off," Gerstenmaier said. "So that's kind of the theory we're looking at."

    Removing the PAL ramp will eliminate the problem with differential contraction and expansion based on the use of two different types of foam. But engineers still must decide what will be needed to eliminate foam shedding around the ice-frost ramp brackets that support the pressurization lines.

    "The ice frost ramp sticks under the cable tray a little bit and it sticks into that region where the PAL ramp was and we saw some cracking in that ice frost ramp right next to the cable tray, or actually maybe a little bit under the cable tray," Gerstenmaier said. "What we need to do is understand what caused that cracking and will it be prevented by just removing the PAL ramp? Do we need to do something in that area, do we need to put some kind of other foam over that (to prevent) ice formation in that area? That's the kind of work we need to go understand.

    "The engineering teams have many solutions for that. We'll check some of those out analytically over the next couple of weeks, we'll pick an engineering solution, probably in the next week or two, then schedule a little bit of confirmation tests or analysis in the early part of January. And then if we need to make a physical fix on the tank by spraying foam, we would do that in the middle part of January to the later part of January and then we would ship the tank around the first part of February."

    If that schedule holds up, NASA would have a theoretical shot at launching the shuttle Discovery in May. Because of a post-Columbia decision to launch at least the first two return-to-flight missions in daylight - and to ensure the external tank separates in daylight half a world away - NASA can only launch during relatively short "windows." The next three such launch windows are:

    Whatever engineers decide to do to Discovery's tank, they will also have to upgrade a tank for use in a possible emergency rescue mission. Assuming Discovery's flight goes well, that tank and shuttle then would be used for the next normal flight in the sequence.

    The tank currently slated for use in that mission, ET-120, has so many small cracks, many of them penetrating all the way to the aluminum skin of the tank itself, it may make more sense to process another tank, ET-118, in its place. Gerstenmaier said today a second tank will, in fact, be ready in time to support Discovery's mission whenever it is cleared to fly.


  • 04:30 p.m., 12/08/05, Update: NASA managers debate PAL ramp removal

    NASA managers plan to meet next week to discuss whether to ship a shuttle external fuel tank to Florida in early February without so-called PAL ramp wind delectors in hopes wind tunnel tests and computer modeling will prove the ramps aren't needed to shield external pressurization lines and a cable tray from aerodynamic buffeting.

    If the tank is shipped without the ramp, and if the upcoming tests confirm it's not needed to prevent a catastrophic failure, NASA will be clear to launch the shuttle Discovery next spring as planned on the second post-Columbia mission. In so doing, the agency will eliminate a potential source of impact debris and put to rest recent concern about cracks in the foam ramps.

    But PAL ramps cannot be added at the Florida spaceport and if the tests show the pressurization lines and cable tray do, in fact, need shielding, the tank would have to be shipped back to Lockheed Martin's Michoud Assembly Facility near New Orleans for additional work. And that would put the next shuttle flight on indefinite hold.

    In that case, engineers would have to reapply the long ramp, either manually or robotically spraying on foam insulation to build a sort of dam to smooth the flow of supersonic air over the externally mounted components.

    More important, and potentially time consuming, they also would have to develop new application techniques or change the composition of the foam - or both - to prevent hard-to-see cracks from forming after the tank is loaded with supercold rocket fuel.

    And those issues will be present in the near term if shuttle managers decided to ship a tank with PAL ramps in place.

    "I am fairly convinced that we're going to make a decision to build the first tank one way or the other before the end of the year and proceed at some schedule risk while we do the engineering," shuttle program manager Wayne Hale said in an interview with CBS News. "We wouldn't fly until we had a good solid engineering story to back up what we did, but we may ship a tank that we're at some risk we could get surprised and have to turn it around.

    "The one thing I keep coming back to, and I keep telling the team is, whatever we do we're going to prove it's safe to go fly or we're not going to fly. So, the rest of it is just kind of how do we maximize the potential to fly as quickly as we can? We're going to do it right, we're going to make sure it's safe to the best of our abilities, and the schedule will wind up being whatever it is."

    The protuberance air-load - PAL - ramps have been under the microscope and the center of attention since a 1-pound chunk of foam broke off the hydrogen PAL ramp on Discovery's tank during the first post-Columbia flight last July. The debris did not strike the shuttle, but upcoming flights were put on hold while engineers studied what could be done to prevent such foam shedding in the future.

    So far, engineers have been unable to come up with a definitive explanation for the foam loss and, consequently, a fix. Hale ordered all existing PAL ramps removed and engineers were assessing new fabrication techniques as a possible solution when small cracks were discovered prior to the removal of the PAL ramp of a tank slated for the third post-Columbia mission.

    While engineers have not come to a formal conclusion on what caused the cracks, the consensus is that it likely is related to the thermal stress the tank undergoes when it's loaded with super cold rocket fuel. The tank in question originally was to be flown by Discovery last July and it was fueled for pre-launch tests. The tank later was replaced for unrelated reasons, but the cracks could have been caused by thermal stress.

    "That is clearly their thinking, but that's a preliminary (conclusion)," Hale said. "Where I have to play the bureaucrat in all this is we haven't completed the analysis. Until you get the engineering done, you can't put the stamp on it and say certainly. But I can say that is what everybody is inclined to believe is the cause of the problem, where the preliminary work is leading us to believe, that it's thermally induced cracking, which may have been there for a long time."

    If that theory is correct, cracks would be a constant threat for shuttles that were fueled for launch and then delayed for other reasons. Whether similar cracks played a role in the foam loss experienced by Discovery's tank in July is an open question.

    "The cracks, most of them, don't show up at the surface and the ones that do you have to be really right up (on them) to (see) them," Hale said. "It's not something you can see from several feet away or with the operational TV cameras the pad. So it's not something you would necessarily detect if you went and tanked and scrubbed."

    During a November news conference, Hale said engineers were looking into whether the ramps could simply be removed, eliminating the potential source of debris. At that time, he said it would be difficult to complete the required testing in time for Discovery's May launch window and that it more likely would take until the third flight in the upcoming sequence. That was due in large part to scheduling conflicts delaying the start of wind tunnel testing.

    But he said his thinking changed - and the issue became more urgent - when the crack issue surfaced Thanksgiving week, indicating "we've got a more severe problem in that PAL ramp foam than we had initially thought."

    Since then, NASA has been able to book wind tunnel time in February to find out, one way or the other, if the ramps can be safely eliminated.

    "Getting rid of (the ramp), if you can afford to get rid of it from the structural standpoint, that is clearly a way forward," Hale said. At the same time, he added, "the folks are off working very hard to come up with some options to change the way the foam is sprayed on, to prevent these cracks."

    But if the cracks are, in fact, caused by thermal stress and if the upcoming tests show the ramps can't be eliminated, NASA will be stuck with a thorny problem: developing a new PAL ramp and then proving it will not shed debris.

    "The way to get around that is if we have some 'eureka' that says we know why we had cracks and we circumvent that with a processing change at MAF (Michoud Assembly Facility)," said LeRoy Cain, manager of launch processing at the Kennedy Space Center. "For flying with the PAL ramps, to get to that point, we're going to have to have confidence that we understand how we got the cracks in these cases and that we have mitigated that."

    Said Hale, "that kind of becomes then the operative question, is not only can you come up with a fix and apply it, but how do you prove that the fix to the foam did what you wanted it to do, which is to prevent these cracks from occurring?"

    As a result, engineers are hopeful the upcoming tests will allow the ramps to be eliminated.

    "I think we all would like to have them gone," Cain said. "On the other hand, the jury's still out on these cracks."

    Cracks aside, a "tiger team" of experts and engineers looking into the PAL ramp foam loss during Discovery July flight concluded in October that "in the future, the only way to ensure no foam will be lost from the PAL ramps is to eliminate ramps altogether."

    "A wind tunnel test program has been completed for both the LO2 (liquid oxygen) and LH2 (liquid hydrogen) cable trays without the PAL ramps, and initial results indicate the PAL ramps are not required to protect the cable trays from aeroelastic instabilities," the report said.

    "STS-114 LO2 tank cable tray data collected to validate test program results is under analysis, but initial results appear to confirm the test program conclusion that the PAL ramp can be eliminated. Wind tunnel limitations did not permit testing to continue beyond the flight envelope required to establish a 32 percent margin for the LH2 tank cable tray as required. ... Additional testing is required before the LH2 PAL ramp can be removed.

    "The ET Tiger Team recommends the SSP (space shuttle program) undertake whatever additional testing is required to substantiate wind tunnel results, including instrumentation of flight cable trays if necessary, and that the PAL ramps be eliminated at the earliest opportunity."

    The shuttle's external tank is made up of a large hydrogen tank, a so-called intertank section and an upper oxygen tank. Gaseous hydrogen and oxygen, used to pressurize the tanks, are diverted from the propellants feeding the shuttle's main engines and routed up the tops of the respective tanks in externally mounted pipes. The pressurization lines run next to a long cable tray that carries electrical lines routing data and commands between the shuttle and various tank and booster subsystems.

    When the shuttle was designed in the 1970s, engineers believed shock waves during the vehicle's transition to supersonic speeds could cause potentially serious damage to the pressurization lines and/or the cable tray. As a result, the tank was equipped with two protuberance air-load, or PAL, ramps, one running along the upper section of the hydrogen tank and the other along the outside of the oxygen tank.

    The PAL ramp "was put on there in the old days as what I would characterize as a suspenders and belt approach," NASA Administrator Mike Griffin told CBS News last month. "The analysis (of the forces involved) is very difficult to do. Most folks, if you asked them, would say I don't really think we need that (but) It was the kind of thing that was technically very difficult to prove because it's a complex aerodynamic flow field, multi-mach number range, yada, yada, yada. So the suspenders and belt approach is, I don't think I really need (the PAL ramp) but I'm going to put it on there anyway because what can it hurt? Well, what it can hurt is if it falls off!

    "Now we no longer take the attitude well, I'll put some foam on there, what can it hurt? If we're going to put foam on something it better be that we really need the foam to be there. On the last flight, STS-114 ... we went to the trouble ... to calculate aerodynamically the very complex flow field surrounding the bipod structure and we concluded we don't need a bipod ramp and we don't need bipod ramp foam. That's what we hope to do with the PAL ramp. We're not there yet."

    The PAL ramps are built up by workers at Michoud, who manually spray on foam and then sculpt it, making ramps that smooth the flow of supersonic air over the pressurization lines and cable tray.

    "As you go from subsonic to supersonic through the max Q (maximum aerodynamic pressure) region, the shock waves off the top of the SRBs (solid-fuel rocket boosters) cause the flow to cross the cable tray and the press lines at about an 80-degree angle," Hale said. "The important region is just through Mach 1 or maybe 1.2."

    To find out whether the pressurization lines and cable tray can withstand the buffeting without suffering a catastrophic failure, a scale section of a tank will be tested in a supersonic wind tunnel in February. At the same time, computer modeling based on computational fluid dynamics (CFD) will be carried out to get a better understanding of the aerodynamics in the region.

    Because the testing should be complete before Discovery's launch window opens, shuttle managers can consider the option of shipping the next tank to Florida without a PAL ramp on the assumption the upcoming tests will show it's not needed.

    "The thing that I'm keenly interested in is the actual test data," Cain said. "The CFD, it will either confirm or not confirm whatever the test data says is right. But that flow field is non intuitive. It's extremely complex."

    Hale agreed, saying "there's a lot of work to be done. We're going to get together before the end of the year to make a decision."

    The topic is expected to be discussed - and possibly resolved at the program level. - next Thursday at a Program Requirements Control Board meeting at the Johnson Space Center in Houston. Another topic on the agenda is deciding what sorts of foam and wing leading edge repair techniques are worth pursuing.

    "If you're going to reapply PAL ramps to the tank, because we're taking them off all the tanks, they're going to go back on at the first of the year," Hale said. "So we would like to decide before the end of the year whether or not to do that.

    "So folks are thinking very hard about how we would get the aerodynamic data to make sure we're in good shape, number one, if we take the ramps off. Or, we have a large group that is still off analyzing why these cracks occur and what changes we might make to the foam application to prevent the cracks from happening.

    "The one thing that is crystal clear to me is that we cannot launch with these cracks. We just can't."

    The PAL ramp foam shedding during the July shuttle mission was the first known case of such debris since the early days of the shuttle program. But NASA only has post-separation photographs of about half the shuttle tanks launched and it's possible more PAL ramps suffered shedding that went unnoticed. Engineers are reviewing photography from past missions to look for any such signs of damage.

    "It's interesting, we went back to the history, we dug into the history of how they got on (the tank)," Hale said. "They were actually a late addition before STS-1. And it came in because some of the wind tunnel testing was not as conclusive as they wanted it to be and it was put on, in the words of the report I have in my hand, to ensure that we have margin structurally. Once they put 'em on, and it was cheap and it took care of the problem, we just kind of kept doing it. So there has always been a question from the first flight whether or not they were actually necessary.

    "Over the course of time, we've made a lot of changes to the tank," he said. "We've eliminated one of the lines that used to go up there called the anti-geyser line, it's not there any more. The cable tray itself, which is a rectangular metal box, has shrunk to about half its original size and the structure that attaches that to the tank and the underlying tank structure is all different. We've gone from the standard weight tank, to the lightweight tank to the super lightweight tank, all that stuff has changed.

    "The question of the day is, is the structure capable of withstanding the aerodynamic loads, some of which are transient - you know, the flag off the flag pole flapping in the breeze kind of effect - and some of which are what the aerodynamicists call steady state. And so we are off to do some computational fluid dynamics work. We thought we were going to have to wait to get into the wind tunnel until May and we have identified a wind tunnel opportunity in early February."