08:45 p.m., 12/22/06, Update: Shuttle Discovery glides to smooth Florida landing; NASA managers thrilled with success of flight
Dropping out of an overcast sky, the shuttle Discovery glided to a picture-perfect one-orbit-late landing today at the Kennedy Space Center, closing out a complex space station assembly mission and avoiding a feared diversion to New Mexico.
With commander Mark Polansky and pilot William Oefelein at the controls, Discovery flew through a sweeping left overhead turn, lined up on runway 15 and swooped to a smooth touchdown on the broad concrete landing strip at 5:31:24 p.m.
Barreling down the runway with the shuttle's nose still elevated, Oefelein fired Discovery's red-and-white braking parachute, the nose landing gear rotated to the pavement and the orbiter slowly rolled to a stop.
"Houston, Discovery, wheel stop," Polansky radioed.
"Roger, wheel stop, Discovery," astronaut Ken Ham replied from mission control. "You've got a building full of thrilled folks back here in Houston that are thrilled to have you in Florida. Roman, to you and your crew ... congratulations on what was probably the most complex assembly mission to date."
"Thanks for the words," Polansky replied. "You've got seven thrilled people right here and we're just really proud of the entire NASA team that put this together. So thank you, and I think it's going to be a great holiday."
Mission duration was 12 days 20 hours 44 minutes and 24 seconds spanning 5.3 million miles and 203 complete orbits.
"The crew on orbit and the crew on the ground could not have done better," said NASA Administrator Mike Griffin. "I mean, I think when you look back at this mission, they just could not have done better. They did four EVAs (spacewalks) instead of three planned EVAs, accomplishing some additional tasks to get past a stuck solar array that teaches us once again we have a lot to learn about spaceflight and how our hardware performs in spaceflight.
"But we did learn and in the learning we made it better. So it was a wonderful day, it was a wonderful end to a great mission and I'm proud to be here."
Already running one orbit late because of low clouds and threatening rain showers, Polansky, Oefelein and their crewmates awaited a down-to-the-wire decision on whether to attempt a landing at California's Edwards Air Force Base or whether to press ahead for a final chance to make it home to Kennedy.
The only alternative was a landing at White Sands Space Harbor, N.M., a backup site only used once in shuttle history and one that is not equipped to rapidly prepare a shuttle for return to Florida.
Entry flight director Norm Knight, overseeing his first shuttle landing, initial held out hope of going to Edwards when forecasters told him Kennedy appeared to be "no go." But as the time approached for the rocket firing needed to reach Edwards, crosswinds picked up at the Mojave Desert test flight facility and Polansky was told to reset the shuttle's flight computers for a possible Kennedy landing.
With less than seven minutes to go until the critical rocket firing, forecasters with the Spaceflight Meteorology Group at the Johnson Space Center in Houston predicted Kennedy would be "go" at landing time and chief astronaut Steve Lindsey, flying a NASA training jet near the runway, gave a thumbs up, saying rain showers were clearly dissipating.
Knight then gave Polansky clearance to proceed with re-entry.
"On behalf of the Kennedy Space Center, Christmas came three days early for us," said Mike Leinbach, launch director at the Kennedy Space Center. "We, uh, a great, great mood to have Discovery out on our runway.
"As you know, we did deploy some folks out to White Sands Space Harbor for a potential landing out there because at certain points late in the mission, it looked like we might have to land out there. So we were fully prepared to do that. We sent 52 folks out there, along with some special equipment, backup equipment we have here at the Kennedy Space Center in case we had to land out there. And we always have a backup crew out at (Edwards) in case we have to go out to California.
"But all that didn't have to happen," Leinbach said. "We came here today, it was a great call by Norm Knight and the flight team. And so it's great to have Discovery home."
Flying upside down and backward over the Indian Ocean, Polansky and Oefelein fired the shuttle Discovery's twin orbital maneuvering system rockets for three minutes and 46 seconds starting at 4:26:30 p.m. to lower the far side of the ship's orbit and set up a landing on runway 15.
The burn went normally and a half hour later, Discovery dropped into the discernible atmosphere 400,000 feet above the south Pacific Ocean.
The sky at Kennedy remained overcast throughout the descent, but the ceilings were well above NASA's 5,000-foot safety limit and the prevailing winds were pretty much right down the runway. Lindsey reported light turbulence just above the runway threshold, but said it posed no problem for Polansky.
Getting Discovery back to Florida was a welcome surprise to the astronauts, their waiting families and NASA managers who feared a diversion to Northrup Strip in White Sands.
Concerned about the threatening weather on both coasts, NASA managers rushed equipment and personnel to White Sands Wednesday and Thursday to assist the astronauts and protect the space shuttle from the elements if it had to land there.
Because NASA does not have the cranes and other equipment stationed at White Sands needed to service the shuttle and lift it up onto a 747 carrier jet for transport back to Florida, engineers estimated it could take a month or more to get Discovery home.
That would have thrown a major wrench into NASA's plans to launch Discovery next fall on a critical mission to deliver a European research module to the space station. But as it turned out, the fears were groundless and Discovery made it home without any major problems.
Polansky, Oefelein, flight engineer Robert Curbeam, Nicholas Patrick, Swedish astronaut Christer Fuglesang, Joan Higginbotham and European Space Agency astronaut Thomas Reiter plan to fly back to Houston Saturday.
For Reiter, launched to the station aboard Discovery last July, today's return marks a return to gravity for the first time in some six months. A team of flight surgeons was standing by to assist the veteran space flier, who faces weeks of physical therapy to regain his "land legs."
Reiter was replaced aboard the station by NASA astronaut Sunita "Suni" Williams, who was ferried to the lab complex by Polansky and his crewmates. Williams, who joined Expedition 14 commander Mike Lopez-Alegria and flight engineer Mikhail Tyurin, plans to remain aboard the station until next spring.
Discovery's mission was the most complex flight yet in the space station assembly sequence, a challenging mission to switch the outpost from interim power to its permanent electrical system.
During two spacewalks, Curbeam and Fuglesang added a spacer segment to the station's main solar array truss and rewired two of the lab's four major power channels. Curbeam and Williams then re-wired the other two channels during a third spacewalk.
The astronauts also had to retract one wing of a huge solar panel in the system that provided the station's interim power. The array is scheduled to be moved to the far left end of the solar array truss next September.
But initial attempts to retract the panel were unsuccessful as the folding slats in the solar blankets repeatedly hung up on guide wires. Curbeam and Fuglesang eventually staged a fourth, unplanned spacewalk last Monday to successfully stow the balky blankets. But the addition of the spacewalk, and a decision to retain a final heat shield inspection Wednesday, pushed landing from Thursday to today.
Along with re-wiring the space station, the astronauts also transferred 69 pounds of oxygen, 47 pounds of nitrogen, delivered 4,800 pounds of equipment and supplies to the station and brought 4,900 pounds of trash and no-longer-needed gear back to Earth.
They also installed a camea on the station's solar array truss, delivered space debris shields for the Russian Zvezda command module, upgraded the U.S. carbon dioxide removal system and delivered a new charcoal bed for an air cleaner.
"This was a tremendous way to end this year, I think it's great to be back here in Florida, it's great to see the teams work and operate together," said Bill Gerstenmaier, NASA's chief of space flight. "It was just a great, great day."
04:30 p.m., 12/22/06, Update: Shuttle braking rockets fired
Flying upside down and backward over the Indian Ocean, commander Mark Polansky and pilot William Oefelein fired the shuttle Discovery's twin orbital maneuvering system rockets for three minutes and 46 seconds starting at 4:26:30 p.m. to lower the far side of the ship's orbit and set up a landing on runway 15 at the Kennedy Space Center.
The sky at Kennedy is overcast, but chief astronaut Steve Lindsey, flying a NASA training jet that mimics the handling of the shuttle on final approach, says approaching showers appear to be dissipating and forecasters are predicting "go" conditions at touchdown.
Here is a rough timeline of upcoming events (in EST):
EST...........EVENT 05:00:03 PM...Shuttle reaches discernible atmosphere; altitude: 400,000 feet 05:05:01 PM...1st roll command to right 05:21:57 PM...1st right-to-left roll reversal 05:25:55 PM...Velocity less than mach 2.5 05:28:02 PM...Velocity less than mach 1 05:28:13 PM...330-degree left overhead turn to line up on runway 15 05:32:22 PM...Landing
04:20 p.m., 12/22/06, Update: Discovery cleared for Florida landing With approaching showers dissipating, entry flight director Norm Knight cleared the shuttle Discovery's crew to press ahead with a deorbit rocket firing at 4:26:30 p.m., setting up a landing on runway 15 at the Kennedy Space Center around 5:32:22 p.m.
"We have worked this one about as hard as we can," astronaut Ken Ham radioed the crew from Houston. "And believe it or not, we're going to offer you a 'go' for the deorbit burn. We're pretty confident we're going to keep you clear of clouds and rain."
02:05 p.m., 12/22/06, Update: NASA passes up first Florida landing opportunity; Discovery crew will try again one orbit later
With the weather in Florida deteriorating, entry flight director Norm Knight has ordered the Discovery astronauts to pass up their first attempt to make it back to the Kennedy Space Center today. Landing opportunities at Edwards Air Force Base, Calif., White Sands Space Harbor, N.M., and the Kennedy Space Center are available one orbit later, around 5:30 p.m.
"We are officially now waving off this opportunity at the Cape," astronaut Ken Ham radioed from mission control in Houston. "The weather there continues to be unstable and we're pretty sure we're going to have precip within 30 miles at landing time. To further cloud your mood on Florida, the second rev doesn't look muych different. However, we're going to keep it as an option. So procedurally, we're going to keep you in the deorbit prep checklist."
Landing at the Kennedy Space Center originally was targeted for 3:56 p.m. The next landing opportunities are around 5:30 p.m. at Edwards, White Sands or Kennedy. A final set of opportunities is available around 7 p.m. at Edwards and White Sands.
The forecast for White Sands remains "go," while high crosswinds are expected at Edwards. Forecasters are hoping the winds will die down a bit as the afternoon wears on. But Knight cannot pass up White Sands if Edwards remains "no go."
12:30 p.m., 12/22/06, Update: Payload bay doors closed for entry
The Discovery astronauts closed the shuttle's payload bay doors today around 12:15 p.m. to ready the ship for a landing at the Kennedy Space Center, weather permitting, at 3:56 p.m. A microswitch initially indicated one of the latches needed to lock the back of the right-side door in place was not engaged and the astronauts powered up television cameras for a visual inspection. But by the time they looked, the microswitch finally changed, indicating no problems, and the astronauts quickly confirmed that.
"It looks like it's going to be just fine," said Commander Mark Polansky.
The decision to close the doors and press on for a possible Florida landing on the crew's first opportunity was made after chief astronaut Steve Lindsey, flying a NASA jet over the Kennedy Space Center, reported generally acceptable landing conditions as of noon.
Forecasters are continuing to predict low clouds and possible showers later in the day that would violate NASA's flight rules in Florida and high crosswinds at Edwards Air Force Base, Calif. The forecast for NASA's only other shuttle landing site - Northrup Strip at White Sands Space Harbor, N.M, remains "go."
For now, entry flight director Norm Knight is sticking with his original strategy, which called for an initial attempt to land at Kennedy and, failing that, to circle the globe one more time for additional shots at Edwards and Kennedy 90 minutes later. If conditions still aren't acceptable, Discovery's crew will go around again and then land at either Edwards or Northrup Strip.
There are no technical problems aboard Discovery and the astronauts are on track readying the shuttle for a possible deorbit rocket firing at 2:49 p.m., weather permitting.
10:00 a.m., 12/22/06, Update: Astronauts ready shuttle for re-entry
The Discovery astronauts are rigging the shuttle for re-entry today, hoping bad weather will hold off long enough to permit a Florida landing this afternoon to close out a successful space station assembly mission.
But the latest forecast from the Spaceflight Meteorology Group at the Johnson Space Center in Houston calls for a good chance of low clouds and showers within 30 nautical miles of the Kennedy Space Center runway. High crosswinds are expected at Edwards Air Force Base, Calif., leaving Northrup Strip at White Sands Space Harbor, N.M., as NASA's only landing site with a "go" forecast.
Discovery only has enough liquid oxygen for its electricity generating fuel cells to stay in orbit until Saturday. With just two days of power remaining, NASA flight rules call for bringing the ship down today if at all possible even if that means the agency's first New Mexico landing since 1982.
The astronauts were awakened for their last day in space by a recording of "(There's No Place Like) Home for the Holidays" beamed up from mission control.
"Good morning, Discovery," astronaut Shannon Lucid radioed from Houston. "We hope you agree with us that thre's no place like home for the holidays because we hope to see you back here on Earth later this afternoon."
"Shannon, we can't agree more," said shuttle commander Mark Polansky. "So thanks for that. Thanks for all the morning music and we'll be looking forward to seeing you and everyone else ... when we get back to Houston."
NASA is rushing critical ground support equipment to White Sands to protect the orbiter's water lines, rocket thrusters and fuel cell systems from from sub-freezing weather in case of a landing on the 17,000-foot hard-packed gypsum runway. Discovery would be exposed to the elements at White Sands for up to two months while engineers ready the ship for a ferry flight back to Florida atop a 747 jumbo jet. The turnaround time at Edwards is about a week to 10 days.
The runway at White Sands is one of the widest, flattest and longest available to the space shuttle and Polansky and Discovery pilot William Oefelein have trained there extensively, flying NASA training jets rigged to handle like space shuttles on final approach.
"If we land there, I feel like we're going to be in great shape on the vehicle but the turnaround is going to take a little bit longer," said John Shannon, chairman of NASA's mission management team. "I would not be surprised if we were out at White Sands for 45 to 60 days."
But NASA managers are hoping the weather in Florida or California will prove the forecasters wrong and permit a landing on the East or West Coast.
Entry flight director Norm Knight, overseeing his first shuttle landing, said Thursday his strategy will be to press ahead for the first landing opportunity in Florida, which calls for a deorbit rocket firing at 2:49 p.m. and a touchdown at 3:56 p.m.
If the weather doesn't cooperate, Polansky and company will circle the globe one more time and try to land in Florida or California 90 minutes later, weather permitting. If not, they will go around again and if the weather at Edwards hasn't improved, Discovery likely will be cleared for NASA's first New Mexico landing since Columbia swooped to a touchdown to wrap up the third shuttle mission in March 1982.
"Just another standard landing," Polansky joked Thursday after hearing Knight's re-entry strategy.
While a final Edwards landing opportunity is available one orbit later - and winds are expected to die down a bit later this evening - NASA managers are reluctant to approve that many attempts in a row due to crew fatigue and other issues.
Here is a summary of NASA's end-of-mission landing weather flight rules (source: NASA):
Here are all of today's landing opportunities (in EST throughout; deorbit burn durations for orbits 203-205 are estimates; times subject to minor changes):- Cloud coverage of 4/8 or less below 8,000 feet and a visibility of 5 miles or greater required.
- Wind (Peak): Daylight crosswind component may not exceed 15 knots (12 knots at night). Headwind may not exceed 25 knots. Tailwind may not exceed 15 knots. Peak winds must not be greater than 10 knots over the average wind. Turbulence must not be greater than moderate intensity.
- No thunderstorms, lightning, or precipitation within 30 nautical miles of the runway. The 30 nautical mile standoff from the runway approximates the 20 nautical mile standoff along the approaches to both ends of the runway.
- Detached opaque thunderstorm anvils less than three hours old must not be within 20 nautical miles of the runway or within 10 nautical miles of the flight path when the orbiter is within 30 nautical miles of the runway.
- Consideration may be given for landing with a "no go" observation and a "go" forecast if at decision time analysis clearly indicates a continuing trend of improving weather conditions, and the forecast states that all weather criteria will be met at landing time.
EST...........EVENT Rev. 202 deorbit to KSC Runway 15 12:13:00 PM...Payload bay doors closed 12:19:00 PM...Mission control 'go' for OPS-3 entry software load 12:29:00 PM...OPS-3 transition 12:54:00 PM...Entry switchlist verification 01:04:00 PM...Deorbit parameters update 01:09:00 PM...Crew entry review 01:24:00 PM...Commander, pilot don entry suits 01:41:00 PM...Inertial measurement unit alignment 01:49:00 PM...CDR/PLT strap in; mission specialists don suits 02:06:00 PM...Shuttle steering check 02:09:00 PM...Hydraulic power system prestart 02:16:00 PM...Toilet deactivation 02:24:00 PM...Vent doors closed for entry 02:29:00 PM...Mission control 'go' for deorbit burn 02:35:00 PM...Mission specialists seat ingress 02:44:00 PM...Single APU start 02:49:05 PM...Deorbit ignition 02:52:22 PM...Deorbit burn complete 03:24:19 PM...Entry interface 03:29:19 PM...1st roll command to right 03:36:33 PM...1st left-to-right roll reversal 03:49:46 PM...Velocity less than mach 2.5 03:51:53 PM...Velocity less than mach 1 03:52:40 PM...253-degree left overhead turn to line up on runway 03:56:12 PM...Landing on runway 15 Rev. 203 Deorbit to EDW Runway 04 04:19:40 PM...Deorbit ignition 04:22:57 PM...Deorbit burn complete 04:55:00 PM...Entry interface 05:00:00 PM...1st roll command to left 05:16:15 PM...1st left-to-right roll reversal 05:20:42 PM...Velocity less than mach 2.5 05:22:52 PM...Velocity less than mach 1 05:23:14 PM...Shuttle on the HAC 05:27:07 PM...Landing Rev. 203 Deorbit to NOR Runway 17 04:20:45 PM...Deorbit ignition 04:24:02 PM...Deorbit burn complete 04:55:49 PM...Entry interface 05:00:49 PM...1st roll command to left 05:10:13 PM...1st left-to-right roll reversal 05:21:14 PM...Velocity less than mach 2.5 05:23:27 PM...Velocity less than mach 1 05:24:18 PM...Shuttle on the HAC 05:27:26 PM...Landing Rev. 203 Deorbit to KSC Runway 15 04:26:10 PM...Deorbit ignition 04:29:27 PM...Deorbit burn complete 05:00:03 PM...Entry interface 05:05:01 PM...1st roll command to right 05:21:57 PM...1st right-to-left roll reversal 05:25:55 PM...Velocity less than mach 2.5 05:28:02 PM...Velocity less than mach 1 05:28:13 PM...Shuttle on the HAC 05:32:22 PM...Landing Rev. 204 Deorbit to EDW Runway 04 05:54:35 PM...Deorbit ignition 05:57:52 PM...Deorbit burn complete 06:28:54 PM...Entry interface 06:33:54 PM...1st roll command to right 06:41:54 PM...1st right-to-left roll reversal 06:54:25 PM...Velocity less than mach 2.5 06:56:25 PM...Velocity less than mach 1 06:56:26 PM...Shuttle on the HAC 07:00:47 PM...Landing Rev. 204 Deorbit to NOR Runway 17 05:57:05 AM...Deorbit ignition 06:00:22 AM...Deorbit burn complete 06:30:54 PM...Entry interface 06:35:54 PM...1st roll command to right 06:48:19 PM...1st right-to-left roll reversal 06:56:15 PM...Velocity less than mach 2.5 06:58:29 PM...Velocity less than mach 1 06:59:04 PM...Shuttle on the HAC 07:02:28 PM...Landing Rev. 205 Deorbit to EDW Runway 04 07:32:20 PM...Deorbit ignition 07:35:37 PM...Deorbit burn complete 08:04:36 PM...Entry interface 08:09:35 PM...1st roll command to right 08:24:20 PM...1st right-to-left roll reversal 08:30:10 PM...Velocity less than mach 2.5 08:32:17 PM...Velocity less than mach 1 08:32:23 PM...Shuttle on the HAC 08:36:31 PM...Landing
08:40 p.m., 12/21/06, Update: 07:00 p.m., 12/21/06, Update: Astronauts set for Friday landing; weather predicted 'no-go' i Florida, California; NASA downplays turnaround concerns with possible White Sands landing
The Discovery astonauts tested the shuttle's re-entry systems today and packed up for a trip back to Earth Friday to close out a successful space station re-wiring mission. Results from a final heat shield inspection, carried out Wednesday, show Discovery's nose cap and wing leading edge panels are in good shape and the crew has official clearance to press ahead with re-entry. The only question is where the seven astronauts will land.
Because of an earlier decision to add a spacewalk to Discovery's mission, the shuttle only has enough supplies to remain in orbit until Saturday at the latest. To provide a safety cushion in case of unexpected problems with the spacecrat, NASA flight rules call for a return to Earth Friday, weather permitting, at one of the agency's three landing sites - the Kennedy Space Center in Florida, Edwards Air Force Base, Calif., or Northrup Strip at White Sands Space Harbor, N.M.
With marginal to bad weather expected in Florida and California, NASA may be facing its first New Mexico shuttle landing since 1982. Because White Sands is NASA's lowest-priority landing site, equipment needed to prepare the shuttle for a ferry flight back to Florida is not readily available and Discovery's return to Kennedy would be delayed up to two months.
That would throw a wrench into NASA's overall processing schedule and likely delay Discovery's next flight in October. But from a crew safety standpoint, "landing at White Sands is of no concern to us at all," said John Shannon, chairman of NASA's Mission Management Team. "The crew gets the bulk of their training in the shuttle trainer aircraft at White Sands."
The hard-packed gypsum runway is level to one inch every 1,000 feet and measures 17,000 feet long and 300 feet wide.
"The concern out at White Sands is not with the runway facility, but with the turnaround," Shannon said. "We don't have the large mate-demate device that we use to lift up the orbiter and put it on the back fo the shuttle carrier aircraft (for transport back to Florida). Also, we don't have as much equipment there to service the vehicle. Basically, you power it down and wait for the cavalry to arrive."
Just in case, two C-17 cargo jets were called up to ferry backup equipment from Kennedy to White Sands, including a purge unit to pump nitrogen gas through the shuttle's plumbing and a power system to run various heaters and other systems to defend against expected freezing weather Saturday night. Rocket nozzle covers also are being sent to keep out gypsum dust, which caused major contamination problems after Columbia landed at White Sands in 1982.
"If we land there, I feel like we're going to be in great shape on the vehicle but the turnaround is going to take a little bit longer," Shannon said. "I would not be surprised if we were out at White Sands for 45 to 60 days."
He said a team of 50 to 60 Kennedy Space Center engineers and technicians are being dispatched to New Mexico to support a possible landing. If Discovery does, in fact, land there, several hundred more workers will fly out the day after Christmas.
Shannon and company are hoping the forecast changes and that the weather will permit a landing in either Florida or California. The astronauts have landing opportunities at all three sites on four successive orbits Friday starting with a deorbit burn on orbit 203 at 2:49 p.m. for a landing on KSC runway 15 at 3:56 p.m.
Edwards, Northrup and Kennedy are available on the next orbit, for landings around 5:30 p.m. EST, and two more opportunities, at Edwards and White Sands, are available the orbit after that around 7 p.m. EST. A final Edwards opportunity is available one orbit later, around 8:36 p.m. EST. But That opportunity would only be available if entry flight director Norm Knight calls off the first Kennedy oppotunity well in advance.
Ground track charts: http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts116/news/landing.html Entry data: http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts116/news/dol_pad.html Here are all the landing opportunities for Friday (in EST):
02:49 PM...12...18...02...Orbit 203 deorbit burn (TIG) for KSC landing 03:56 PM...12...19...09...202 KSC landing 04:19 PM...12...19...32...203 Edwards Air Force Base TIG 05:27 PM...12...20...40...EAFB landing 04:20 PM...12...19...33...203 Northrup Strip TIG 05:27 PM...12...20...40...Northrup landing 04:26 PM...12...19...39...203 KSC TIG 05:32 PM...12...20...45...KSC landing 05:54 PM...12...21...07...204 EAFB TIG 07:00 PM...12...22...13...EAFB landing 05:57 PM...12...21...10...204 Northrup TIG 07:02 PM...12...22...15...Northrup landing 07:32 PM...12...22...45...205 EAFB TIG 08:36 PM...12...23...49...EAFB landingThe forecast for the Kennedy Space Center calls for scattered clouds at 2,000 and 5,000 feet and a broken deck at 10,000 feet. But there is a chance for a broken deck at 5,000 feet and a chance for showers within 30 nautical miles, both flight rule violations. Winds will be gusting to 22 knots, but the crosswind component for a landing on runway 15 is just 2 knots or so.
At Edwards, clouds are no problem but winds out of 290 degrees gusting up to 22 knots will result in a crosswind of about 20 knots for a landing on runway 22/04. The crosswind limit for a shuttle commander returning to Earth is 15 knots in daylight, 12 knots in darkness.
The outlook for Northrup Strip at White Sands calls for light winds and broken cloud decks at 15,000 and 20,000 feet. It is "go" for landing.
"OK, Roman, shoot, you could probably look out the window and see some of the weather we're talking about here," astronaut Ken Ham radioed shuttle commander Mark Polansky late today. "But the big picture regarding the Cape, there's a front that's kind of pushing through the panhandle that you've been reading about for the last couple of days, it's on its way over toward the Cape. What that means in the local area there is some areas of low clouds in the vicinity as well as some convergence and showers if you will, which are more or less very light and streaming in sporadically if you will from the southeast to the northwest across the runway, which results in winds pretty much right down the runway.
"The official forecast is few (clouds) at 2,000, scattered at 5,000, broken at 10,000 with the winds 150 (degrees) at 15 knots peaking at 22. However, we're carrying a chance of broken at 5 and rain showers within 30. So it's going to be just playing the game realtime at the Cape tomorrow and see how that pans out for us. Over."
"Copy all," Polansky replied. "Just another standard landing."
"You pretty much read right through that," Ham said. "Now where it gets interesting is looking out west. Edwards, there is a front more or less extending southwest to northeast, it's essentially in northern California right now, pushing southeast. ... That is predicted to be through the area of Edwards tomorrow, resulting in clear skies. The actual forecast is few (clouds) at 10,000 (feet), seven-mile vis. However, it's going to carry with it some real strong winds that are essentially perpendicular to the runway. Currently it's forecast at 290 (degrees) 15 peak 22, which is a peak crosswind of 20 knots. And along with that, some moderate turbulence in the middle altitudes.
"However, over at Northrup, that will still be ahead of that front tomorrow," Ham said. "The forecast there is broken at 15, broken at 20,000, good visibility, light winds. So Northrup right now is a go forecast. But as time progresses, that front may push into Northrup, making Northrup worse and making Edwards better as we move into Saturday. Do you have any questions there?"
"No, no questions at all on the weather."
"OK. So the big picture for tomorrow regarding strategy is, we're going to try for the Cape on the first rev. And second rev, we're looking predominantly at the Cape and Edwards. And then the third rev we'll be looking mostly at Edwards and Northrup. ... Having said that, you pretty much have an equal chance to land at any given site there. if it turns out tomorrow that Northrup is our only 'go' site, that's where we'll be sending you."
"OK. That's what we've been reading in the messages and what we've been expecting, so we will be prepared to go wherever and we've got our betting pools on board, we'll go ahead and talk about them after we land," Polansky said.
Assuming the weather provides any chance at all, Polansky, pilot William Oefelein and their crewmates will shoot for a landing in Florida on the first opportunity. That would require a three-minute 17-second rocket firing on orbit 202, lowering the shuttle's velocity by about 222 mph. After a half-hour free fall, the shuttle would enter the discernible atmosphere at an altitude of 400,000 feet - entry interface - at around 3:24 p.m. At that point, the orbiter would be 5,100 miles from runway 15 at the Kennedy Space Center with touchdown expected at 3:56:12 p.m.
Here are preliminary numbers for a KSC entry on orbit 202 (in EST; minor changes expected):
EST...........EVENT 10:49:00 AM...Begin deorbit timeline 11:04:00 AM...Radiator stow 11:14:00 AM...Mission specialists seat installation 11:20:00 AM...Computers set for deorbit prep 11:24:00 AM...Hydraulic system configuration 11:49:00 AM...Flash evaporator checkout 11:55:00 AM...Final payload deactivation 12:09:00 PM...Payload bay doors closed 12:19:00 PM...Mission control 'go' for OPS-3 entry software load 12:29:00 PM...OPS-3 transition 12:54:00 PM...Entry switchlist verification 01:04:00 PM...Deorbit parameters update 01:09:00 PM...Crew entry review 01:24:00 PM...Commander, pilot don entry suits 01:41:00 PM...Inertial measurement unit alignment 01:49:00 PM...CDR/PLT strap in; mission specialists suit don 02:06:00 PM...Shuttle steering check 02:09:00 PM...Hydraulic power system prestart 02:16:00 PM...Toilet deactivation 02:24:00 PM...Vent doors closed for entry 02:29:00 PM...Mission control 'go' for deorbit burn 02:35:00 PM...Mission specialists seat ingress 02:44:00 PM...Single APU start 02:49:05 PM...Deorbit ignition 02:52:22 PM...Deorbit burn complete 03:24:19 PM...Entry interface 03:29:19 PM...1st roll command to right 03:36:33 PM...1st left-to-right roll reversal 03:49:46 PM...Velocity less than mach 2.5 03:51:53 PM...Velocity less than mach 1 03:52:40 PM...253-degree left overhead turn to line up on runway 03:56:12 PM...Landing
01:15 p.m., 12/20/06, Update: Hale discusses late inspection vs landing day debate; says flight safety was deciding factor; schedule risk not a player
The decision earlier this week to add a spacewalk to Discovery's mission and still preserve a final heat shield inspection today forced NASA managers to delay re-entry one day to Friday and in so doing, give up one of three end-of-mission landing opportunities. With only two available landing days - Friday and Saturday - NASA flight rules require a landing attempt Friday, even if that means diverting the shuttle to California or New Mexico. The latter option is a worst-case scenario that could expose the orbiter to sub-freezing weather for two days, possibly damaging thruster seals and water lines, and delay the ship's return to Florida by four to six weeks.
The latest forecast from the Spaceflight Meteorology Group at the Johnson Space Center in Houston calls for a chance of showers and low clouds at the Kennedy Space Center on Friday and high crosswinds at Edwards Air Force Base in California's Mojave Desert. The forecast for Northrup Strip at White Sands Space Harbor, N.M., where only one shuttle has ever landed, calls for acceptable conditions.
The weather improve at Edwards Saturday and deteriorates in New Mexico. The weather at Kennedy is expected to remain no-go. But NASA flight rules preclude waving off Friday if any one of the sites is acceptable because of the possibility of a mechanical or electrical problem that might require troubleshooting. That means a landing in New Mexico Friday, NASA's first since 1982, is a possibility, depending on how the weather plays out.
Even so, shuttle Program Manager Wayne Hale said the decision to retain today's heat shield inspection was a no brainer.
"I have to tell you there are a lot of folks who think this is really extraordinarily critical," Hale told CBS News in an interview Monday at the Johnson Space Center. "I haven't quite gone to that level, but we're evolving in our thinking. The crew office has been very strong in desiring a late inspection."
A detailed heat shield inspection was conducted earlier in the mission to look for any damage that might have been incurred during launch. The goal of the late inspection is to look for signs of micrometeoroid and orbital debris damage - MMOD - that might have occurred since the first inspection was completed.
NASA engineers currently put the odds of an MMOD impact that could cause entry-critical damage at around 1-in-200 to 1-in-250. That's roughly equivalent to the same level of risk faced by the astronauts during launch.
"There is a pretty good statistical database now on this debris that is too small to be tracked by the Space Command radars and yet large enough to cause a serious problem," Hale said. "And in fact, we do see a number of MMOD hits on the orbiter every time we fly, small stuff that does maintenance-type, non-critical damage, which is consistent with all these statistical models."
To help improve the odds, NASA now re-orients the station-shuttle complex during docked operations to turn the orbiter's heat shield away from the direction of motion.
"Attitude plays a big role," Hale said. "We changed the attitude to more or less shield the shuttle, we're flying 180 degrees around from where we used to fly, which helps. And the numbers, it's something on the order of a 1-in-200 chance of incurring critical damage if you did nothing. If you do a late inspection and you assume a certain probability of detection, which the guys have studied, and then you say we have this repair technique that we have a high degree of confidence in - not 100 percent, so you put a knock-down factor in that - gets the odds down to around 1-in-320-ish if all that's effective."
Discovery's reinforced carbon carbon nose cap and RCC wing leading edge panels experience the most extreme heating during re-entry - more than 3,000 degrees Fahrenheit. Earlier in the mission, after the initial inspection was completed, sensors in the outboard left wing detected what many engineers believe was an MMOD impact. The astronauts took a look with a robot arm television camera and no obvious signs of damage were spotted. But the incident seems to have played a role in the ensuing debate about retaining the late inspection.
"This flight in particular has been somewhat complicated by this report we have off the wing leading edge sensor that said we probably, not guaranteed but probably, had an MMOD strike somewhere on that outboard lower left wing. And we've looked at it with the camera views that we could, which give you some kind of resolution but not the best resolution. There's a large portion of the community, by the way, that feels that's a closed issue, that we had the resolution we would have needed to see critical damage. But like all these things, there is a debate. ... I think we'd all like to take another look. And the question is, how hard do you want to take that extra look?"
NASA's options are limited by the amount of hydrogen and oxygen Discovery is carrying to generate electricity and a pre-launch decision to add a docked day to the flight because of the mission's complexity and the possibility a day would be needed to correct problems activating the lab's permanent power system.
As such, Discovery's flight is classified as a 12-plus-zero-plus-two-day mission, i.e., a 12-day flight with two weather contingency days. There is not be enough hydrogen and oxygen on board to extend the mission itself beyond 12 days and still preserve two backup landing days.
Going into Discovery's mission, late inspection was not listed as a major mission objective and managers agreed up front to take it off the board if the astronauts ran into problems with the station's electrical and cooling systems that might require an additional day for troubleshooting or an unplanned spacewalk.
When NASA did, in fact, add a spacewalk to the mission to retract a balky solar panel, many shuttle observers assumed late inspection would be taken out of the timeline. Late inspection, in fact, did not even show up on a list of pre-flight mission priorities. But NASA's Mission Management Team opted to retain late inspection and give up a landing day instead.
"We knew when we wrote the rules pre-flight that there was a large part of the community that believes late inspection is absolutely mandatory to provide safety to the crew," Hale said. "It's a priority, it was just written down differently than what we're talking about today. It was always a priority."
It was not an issue under the original flight plan, which called for undocking Monday, late inspection Tuesday and a landing Thursday at the Kennedy Space Center, with Friday and Saturday as weather backups. But the flight plan was thrown into disarray when the astronauts ran into problems retracting a solar array on the international space station.
By adding a spacewalk to the mission, NASA managers had to make a difficult decision.
"I think our thinking is evolving," Hale said of the late inspection turn around. "That's what you're seeing, our thinking is evolving here. One of the things I'm very interested in is to get some ground truth, to get Discovery back home ... look at the whole wing and say was there really something that happened out there or was this just a thermal creaking of the joints kind of thing? So we're trying to understand the whole process."
Depending on what the engineers find, NASA's thinking about MMOD and the relative priority of future late inspections might be altered. But in the near term, Hale said, there was no real choice.
"Our thinking is evolving and I've got to tell you from where I sit, if MMOD is going to be our number one risk, or number two, we have to do whatever we can to mitigate that risk," he said. "And so you look at the other side and say OK, what (does) having that weather day buy me? It buys me another day or another certain percentage chance to get back to the Kennedy Space Center, principally.
"It's not so much that we won't find a safe place to land, it's can I get back to the Kennedy Space Center as opposed to being out west somewhere where I've got a longer turnaround? It's a schedule thing. So when I see it's a safety versus a schedule (thing), then the preponderance of evidence has got to be on the safety. I'm not here to tell you that this is necessarily where we're going to wind up for the long term, but I am telling you that we are still weighing this and our thinking is evolving on the late inspection."
But by keeping late inspection in Discovery's flight plan, NASA managers had to extend the flight a day and give up one of the three end-of-mission landing days. And with just two landing days available, that means an attempt to get Discovery down - somewhere - on Friday.
The fact that NASA is even willing to consider a landing in New Mexico to ensure late inspection is an obvious indicator of NASA's post-Columbia willingness to put safety first.
That point is driven home when one considers what a landing in New Mexico would mean to the space agency.
The only pre-positioned equipment at White Sands is a shuttle tow bar, a tractor for towing the orbiter to a servicing area, a set of stairs to position by the ship's side hatch and a motor home to serve as an "astrovan."
After landing on the gypsum runway, the crew would power down the shuttle's electrical systems, exit and depart the area. Discovery would be towed to a concrete pad that is somewhat out of the wind to minimize damage cause by blowing gypsum dust.
And then the shuttle would simply sit, awaiting equipment and personnel from Kennedy and Edwards. With no power or heated purge air, Discovery would be exposed to sub-freezing temperatures for two days, possibly causing thruster seals to rupture. That would require time-consuming repairs back at Kennedy should that actually occur.
Once power and purge air are available, engineers would service the shuttle's hydraulic system and rocket engine valves and position the ship's three main engines for attachment of an aerodynamic cone required for the ferry flight back to Florida. The cone itself would have to be disassembled at Edwards, shipped to White Sands and then re-assembled.
Likewise, engineers would have to move and re-assemble a huge harness-like device to eventually pick the shuttle up for attachment to its 747 transport jet. The huge cranes required to do the heavy lifting would have to be shipped in and assembled on site.
It typically takes a week to 10 days at Edwards, where all the equipment is pre-positioned, to ready a shuttle for shipment back to Florida. The work costs about $1 million. At White Sands, engineers would need four to six weeks to get the job done, roughly the same time that would be needed to get a shuttle back from Spain or France after an emergency landing during launch. The cost of a New Mexico turnaround is not known, but officials say it would be "significantly more" than $1 million.
"The back-of-the-envelope turn-around time based on bar charts and schedules is 45 days," Hale said. "They have a convoy that will get the astronauts off safely and the vehicle powered down and they can tow the vehicle off the gypsum lakebeds to a concrete pad in an area that is protected from the winds. And they can put covers on to keep gypsum dust out, which is what happened on STS-3 (in March 1982). But then we've got to get everybody out there to do all the normal turnaround and most of all, the lift to put it on the 747.
"We have a contract that we've kept alive out there so we know what it takes to go get the cranes and all of that. But it would be a considerably longer operation than at Edwards. Again, that's just a schedule thing."
Discovery already was scheduled to be taken off flight status after this mission for a major inspection and overhaul. The shuttle Endeavour, coming out of its own orbiter maintenance and down period, or OMDP, will serve as the emergency rescue vehicle for the next shuttle flight in March.
But Discovery's next flight is STS-122, a high-priority mission scheduled for launch next October to carry the European Space Agency's Columbus research module into orbit. While NASA likely could make up any lost time getting Discovery back to Florida, the schedule is tight and the Columbus launch date would be in clear jeopardy if Discovery ends up in New Mexico.
"I haven't reviewed those schedules in detail ... but I would tell you it doesn't matter," Hale said. "If we need to go to Edwards or we need to go to White Sands and it's the day we need to land, we'll do it and then we will deal with the consequences and change our plans accordingly."
Based on historical weather data, there is just a 1 percent chance of bad weather closing all three landing sites in late December. There is only an 8 percent chance of Kennedy and Edwards both being down at the same time due to weather.
One wild card in the discussion about Discovery's eventual landing site may be a new set of tires installed on the space shuttle. NASA flight rules currently forbid landings in crosswinds greater than 15 knots. That limit can be raised to 17 knots if there is no turbulence.
But Discovery is equipped with a new type of landing gear tire that is capable of handling the stress of 20-knot crosswind landings. It's not yet clear whether the Mission Management Team might reconsider the crosswind landing limit Friday. The current forecast calls for a crosswind of 18 knots.
A landing at Edwards, however, still poses a major problem for Hale.
"My concern about extending the flight a day and potentially landing at Edwards is a workforce morale issue because we worked very hard to get this vehicle off early so we could get it down on the ground to give everybody off Christmas," he said. "And now by extending a day, and certainly if we land out west, we're going to have about 350 folks that are not just going to have to work Christmas but be 3,000 miles away from their families for a couple of weeks around Christmas.
"I really wanted to give folks the holiday with their families and I sure hope it works out that way because of workforce morale, the tension, you know, esprit de corps kind of thing. When I tell my wife I'm going to have to go to California to be with them on Christmas day, I may be looking for a new place to live!
"Having said that, that is all secondary to safely wrapping up this flight," Hale added. "We'll do what we've got to do."
06:05 p.m., 12/20/06, Update: Shuttle Discovery undocks from space station
The space shuttle Discovery undocked from the international space station today after a successful four-spacewalk visit to re-wire the outpost and prepare it for arrival of European and Japanese research modules over the next two years.
Sailing through space at five miles per second 220 miles above the Indian Ocean, hooks and latches locking the shuttle's docking system to the station disengaged at 5:10 p.m. and Discovery eased away from the lab complex.
"Discovery. Departing," station commander Mike Lopez-Alegria, a Navy captain, said as the shuttle moved away, ringing a ship's bell in the Destiny laboratory module.
With pilot William Oefelien at the controls, Discovery moved out in front of the station and then looped up to a point 600 feet directly overhead before thruster firings to depart the area.
"We have completed the sep one burn," shuttle commander Mark Polansky radioed. "And for (space station) Alpha from the crew of Discovery: we wish you smooth sailing. Thank you for the hospitality and hard work and we hope you enjoy the new electrical system on board station."
As the shuttle slowly separated, observers in the eastern United States saw the two as "a fast-moving, bright, white star" in the early evening sky, according to an observer in Chappaqua, N.Y. "It was as bright as Venus but looked larger," he said.
Considered the most complex shuttle mission ever flown, Discovery's crew added an extension to the station's main solar array truss and activated the lab's permanent electrical system. They also staged a dramatic, unplanned spacewalk Monday to complete the retraction of a balky solar array.
"This mission, which I think we will all declare successful, was very much the result of the hard work that was put i by the teams on the ground," Lopez-Alegria told flight controllers during a brief farewell ceremony earlier today. "I think we acted as your 'end effectors,' if you will. You guys did all the thinking and we just did it. And we want to thank you for letting us participate in what we think was a great step forward in human space flight."
Said Polansky: "It's always a goal to try and leave some place in better shape than it was when you came and I think we've accomplished that due to everyone's hard work. And so with that, I hope we're really on our way to a great start for assembly completion."
After a final round of hugs and handshakes, the Discovery astronauts floated out of the Destiny module and the last hatch between the shuttle and the station was closed at 2:42 p.m. Here is the schedule for the rest of the day (in EST and mission elapsed time):
EST........DD...HH...MM...EVENT 05:10 PM...09...20...22...UNDOCKING 06:12 PM...09...21...25...Crew meals begin 06:42 PM...09...21...55...Station docking port depressurized 07:12 PM...09...22...25...Group B computer powerdown 07:37 PM...09...22...50...Undocking video playback 08:00 PM...09...23...13...Mission status briefing on NASA TV 11:47 PM...10...03...00...Shuttle crew sleep begins 12:00 AM...10...03...13...Daily video highlights reel on NASA TV 07:47 AM...10...11...00...Crew wakeupJoining Polansky, Oefelein, Robert Curbeam, Christer Fuglesang, Nicholas Patrick and Joan Higginbotham for the trip home is Thomas Reiter, a European Space Agency astronaut who was launched to the station aboard Discovery last July. He was replaced aboard the station by Sunita "Suni" Williams, a NASA astronaut who was ferried to the outpost by Polansky and company.
"I just want to say to Thomas, I hope Discovery takes you home as smoothly and safely as it brought me here," Williams said before the shuttle crew departed.
Lopez-Alegria captured the moment for the combined crews, saying "So with that we bid a bitter-sweet farewell to Discovery. We had a wonderful time with you guys, it was really a pleasure, I can't think of a motto that describes the way we did things other than 'work hard and play hard,' although there wasn't very much play time.
"It's now time to turn the page and with that, we'd like to welcome aboard Suni to our crew. I want to keep it brief because most of her runway is still way out in front of her and as we like to say, it's good to pace yourself. Suni is going to add a completely different dimension but I'm sure we'll continue in Thomas' tradition of professionalism."
Discovery's crew plans to carry out a final heat shield inspection Wednesday before packing up Thursday for a landing attempt Friday afternoon.
The shuttle only has enough hydrogen and oxygen for its electricity producing fuel cells to stay in orbit until Saturday at the latest. When only two landing days are available, NASA's flight rules require a landing attempt on the first day, if possible, at either the Kennedy Space Center in Florida, Edwards Air Force Base, Calif., or White Sands Space Harbor, N.M.
The preliminary forecast calls for a chance of low clouds and rain in Florida and slightly high crosswinds at Edwards on Friday. While White Sands is currently "go" Friday, NASA wants to avoid a New Mexico landing if at all possible because the equipment needed to ready the ship for its ferry flight back to Florida would have to be shipped in.
While it typically takes a week to 10 days to get a shuttle back from Edwards, engineers estimate up to 45 days or so would be needed to return Discovery from White Sands.
Discovery originally was scheduled to land Thursday, but the docked portion of the flight was extended one day to add the solar array retraction spacewalk. Given the extra day, the only way to get Discovery down on Thursday was to eliminate the final heat shield inspection. But NASA's Mission Management Team decided to stick with the inspection and landing was pushed to Friday.
Shuttle Program Manager Wayne Hale said in an interview with CBS News on Monday he agreed with the importance of conducting the so-called late inspection of the heat shield. But he hopes it won't result in a landing in California or New Mexico.
"We worked very hard to get this vehicle off early so we could get it down on the ground to give everybody off Christmas," he said. "And now by extending a day, and certainly if we land out west, we're going to have about 350 folks that are not just going to have to work Christmas but be 3,000 miles away from their families for a couple of weeks around Christmas.
"I really wanted to give folks the holiday with their families and I sure hope it works out that way because of workforce morale, the tension, you know, esprit de corps kind of thing. When I tell my wife I'm going to have to go to California to be with them on Christmas day," Hale joked, "I may be looking for a new place to live.
But, he said, "that is all secondary to safely wrapping up this flight. We'll do what we've got to do. ... I have to tell you there are a lot of folks who think (late inspection) is really extraordinarily critical. I haven't quite gone to that level, but we're evolving in our thinking. The crew office has been very strong in desiring a late inspection."
10:00 a.m., 12/18/06, Update: Weather outlook uncertain for Friday landing
An early landing forecast predicts a possibility for clouds and rain at the Kennedy Space Center for the shuttle Discovery's planned landing Friday. Slightly high crosswinds are expected at Edwards Air Force Base in California's Mojave Desert but conditions at Northrup Strip near White Sands, N.M., are expected to be acceptable. Conditions in California are expected to improve on Saturday, but Florida remains questionable.
Discovery only has enough hydrogen and oxygen on board for its electricity producing fuel cells to remain in orbit until Saturday at the latest. A decision to add a spacewalk to Discovery's mission Monday - and a decision to retain a final heat shield inspection Wednesday - pushed landing from Thursday to Friday. When just two landing days are available, NASA flight rules require a landing attempt at one of the agency's three sites on the first day to preserve the final landing opportunity for use in the event of mechanical problems or more bad weather.
NASA wants to avoid a landing in New Mexico if at all possible because it would take an estimated 45 days to bring in cranes and other equipment needed for mounting the shuttle atop a transport jet for return to Florida.
The heat shield inspection now planned or Wednesday is one of NASA's post-Columbia safety upgrades. It is intended to spot any micrometeoroid damage that might have occurred after the heat shield was inspected earlier in the mission. The threat of an entry-critical impact is believed to be in the neighborhood of 1-in-250. As such, many in the shuttle community believe the so-called "late inspection" is a high-priority objective.
But it is not officially listed as a high mission priority in NASA's flight documentation and agency officials earlier left open the option of reconsidering the late inspection and moving landing back to Thursday depending on the forecast. As of this writing, however, no such discussions have been held and managers said Monday it was unlikely the landing target would change.
Historically, based on actual weather in late December, there is only a 1 percent chance of bad weather that would preclude a landing at all three of NASA's three sites on the same day. There is only an 8 percent chance of bad weather at both Kennedy and Edwards.
08:00 a.m., 12/19/06, Update: Shuttle crew gears up for undocking
The Discovery astronauts, wrapping up one of the most complex space station assembly missions yet attempted, plan to undock from the outpost today after a four-spacewalk visit to re-wire the lab complex, setting the stage for the eventual attachment of European and Japanese research modules.
All that's left is to complete a final few equipment and supply transfers between the shuttle and the station before hatches are sealed around 2:30 p.m.
"We're about 94 percent complete with all the transfers from the shuttle to the ISS, which amounts to about 3,500 pounds," Kirk Shireman, deputy space station program manager, said late Monday. "We're 90 percent complete with the transfers from the ISS back to the shuttle, which puts us at about 3,300 pounds of cargo that's back in the shuttle. So overall, we're about 92 percent complete.
"We've transferred about 49 pounds of nitrogen to our high pressure airlock tanks from the shuttle and we transferred earlier about 69 pounds of oxygen. We also transferred 86 liters of water (23 gallons) from the shuttle to the ISS. So again, transfers are going extremely well. The rest of the mission's going extremely well and we've finished all but the undock of our major mission objectives. We're very pleased."
A brief farewell ceremony is planned a few minutes before 2 p.m. and if all goes well, a final hatch between Discovery and the space station will be closed just before 2:30 p.m. Undocking is targeted for 5:09 p.m.
Joining Discovery commander Mark Polansky, pilot William Oefelein, Nicholas Patrick, Robert Curbeam, Christer Fuglesang and Joan Higginbotham will be European Space Agency astronaut Thomas Reiter, who was launched to the space station in July. He was replaced by astronaut Sunita "Suni" Williams, who took off aboard Discovery to join Expedition 14 commander Mike Lopez-Alegria and flight engineer Mikhail Tyurin as a member of the lab's full-time crew.
Because the docked phase of Discovery's mission was extended one day to accommodate an unplanned spacewalk Monday to retract a balky solar array, the astronauts will not carry out a photo-documentation fly around of the station after undocking.
Instead, Oefelein will move Discovery out in front of the U.S. Destiny laboratory module and then fly a quarter loop up to a point directly above the lab complex before dropping behind the station and departing the area.
Here is an updated timeline of today's activities (in EST and mission elapsed time; includes revision G of the NASA television schedule):
EST........DD...HH...MM...EVENT 08:47 AM...09...12...00...STS crew wakeup 09:17 AM...09...12...30...ISS crew wakeup 10:00 AM...09...13...13...Video file on NASA TV 11:17 AM...09...14...30...Logistics transfers resume 01:22 PM...09...16...35...Oxygen transfer system tear down 01:37 PM...09...16...50...Final transfer tagup 01:57 PM...09...17...10...Farewell ceremony 02:22 PM...09...17...35...Hatch closing 02:47 PM...09...18...00...Orbiter docking system leak checks 02:52 PM...09...18...05...Centerline camera installation 03:52 PM...09...19...05...Group B computer powerup 04:04 PM...09...19...17...Noon 04:17 PM...09...19...30...Undocking timeline begins 04:32 PM...09...19...45...Sunset 05:08 PM...09...20...21...Sunrise 05:09 PM...09...20...22...TDRS-West acquisition 05:09 PM...09...20...22...UNDOCKING 05:10 PM...09...20...23...Initial orbiter separation 05:11 PM...09...20...24...ISS holds current attitude 05:14 PM...09...20...27...Range: 50 feet; reselect -X jets 05:16 PM...09...20...29...Range: 75 feet; low-Z jets 05:36 PM...09...20...49...TDRS-East acquisition 05:36 PM...09...20...49...Noon 05:38 PM...09...20...51...Separation burn No. 1; STS directly above ISS 06:03 PM...09...21...16...Sunset 06:06 PM...09...21...19...Separation burn No. 2 06:12 PM...09...21...25...Crew meals begin 06:39 PM...09...21...52...Sunrise 06:42 PM...09...21...55...PMA-2 depressurization 07:12 PM...09...22...25...Group B computer powerdown 07:37 PM...09...22...50...Undocking video playback 08:00 PM...09...23...13...Mission status briefing on NASA TV 11:47 PM...10...03...00...STS crew sleep begins 12:00 AM...10...03...13...Daily video highlights reel on NASA TV 07:47 AM...10...11...00...Crew wakeup
08:40 p.m., 12/18/06, Update: Spacewalk No. 4 ends
Astronauts Robert Curbeam and Christer Fuglesang began repressurizing the space station's Quest airlock module at 8:38 p.m. to officially end a successful six-hour 38-minute spacewalk to fully retract a set of balky solar blankets.
This was the 77th spacewalk devoted to station assembly and maintenance since construction began in 1998, pushing the cumulative EVA total to 469 hours and 59 minutes. It as the fourth spacewalk for Discovery's crew, pushing the mission total to 25 hours and 45 minutes, and a shuttle-record fourth for Curbeam. Including three 2001 spacewalks, Curbeam now ranks fifth on the spacewalk endurance list with 45 hours and 34 minutes of EVA time over seven spacewalks.
07:40 p.m., 12/18/06, Update: Solar array successfully retracted
Perched on the end of the space station's robot arm, astronaut Robert Curbeam, assisted by Swedish flier Christer Fuglesang, finally coaxed a set of balky solar blankets to fully retract today after repeatedly clearing guide wire hangups. The successful retraction of the huge array, which finally folded up like pleated window blinds, was the final objective of the shuttle Discovery's mission to re-wire the international space station.
"Robert Curbeam, you do good work," astronaut Stephen Robinson radioed from mission control when a final guidewire snag was pulled free.
NASA managers were ecstatic.
"'Wow' is about the only thing I can say," said Kirk Shireman, deputy manager of the space station program at the Johnson Space Center in Houston. "What a day. ... It was really an emotional roller coaster today."
Said John Curry, lead space station flight director: "I've been training for this flight for over six years. And so, I can't even begin to explain to you what it feels like to finally accomplish what we set out to do. That's cathartic, I guess. I've been scared of this flight for a long time, so to be given the opportunity to accomplish what we were asked to do, to actually be given the extra EVA to meet all the objectives, I'm very relieved right now. ... I'm very, very proud and relieved and thankful that things worked out the way they did."
The P6 solar array, made up of two wings known as 2B and 4B, was attached to the station six years ago to provide interim power during the initial stages of assembly. Construction has now reached the point where the arrays need to be moved to the station's main solar array truss and wired into the lab's permanent power system.
To do that, the two wings are being folded up one at a time, with 4B scheduled for retraction during Discovery's mission and the still fully extended 2B wing during a shuttle mission next March. In September, another crew plans to move the stowed arrays to the left end of the main truss and re-extend both wings.
The Discovery astronauts attempted to retract the 4B wing on Wednesday but they were only able to pull it in about half way. Several of the slats in the folding blankets, held in alignment by guide wires similar to the cords in pleated blinds, failed to fold evenly, stopping the process in its tracks. Repeated attempts to free a presumably jammed grommet and guide wire were unsuccessful.
On Saturday, during a spacewalk by Curbeam and Sunita "Suni" Williams to finish the Discovery crew's goal of re-wiring the space station, NASA's Mission Management Team approved a fourth spacewalk to help get the P6-4B wing retracted. Curbeam and Williams, meanwhile, finished their electrical work early and ventured up to the stalled array for an up-close inspection.
The spacewalkers then repeatedly shook the solar array storage box, setting up ripples in the hinged slats of the solar cell blankets, freeing up stuck grommets and permitting their crewmates inside to retract the central mast an additional six bays. But they eventually ran out of time and had to call it a day, leaving 11 of the mast's 31 open-framework bays still extended.
For today's spacewalk, Curbeam and Fuglesang were equipped with a variety of tools, all insulated with non-conducting tape, to free grommets and guide wires as needed. The solar array will be shunted to lower its electrical potential. In addition, the station's robot arm was available to position Curbeam as required.
Once in position, Curbeam spotted a frayed guidewire that was preventing the solar array slats from folding up smoothly. Using an insulated tool similar to a windshield ice scraper, he gently flipped the slats, one at a time, to work the frayed section of guide wire through a series of grommets. That allowed the blanket panels to line up properly, much like the slats in a pleated blind. Commands were then sent to pull the array's central mast in about 40 inches, the length of one of its open-framework bays.
"OK, and Houston, we're ready to go one bay retract," shuttle skipper Mark Polansky radioed. "OK. Here we go. Ready, ready, retract."
After one bay, the retraction was halted. Curbeam reported "I have a grommet that's caught on the outboard guidewire of the aft blanket."
Fuglesang, free floating near the base of the array, shook the blanket storage box, setting up ripples in the still-exposed slats in hopes of freeing the guide wire. It moved somewhat, but did not pop free. Fuglesang shook it again, to no avail.
"Can I get one more shake?" Curbeam asked.
"You're go for another three-cycle shake."
"OK," Fuglesand said. "One, two, three..."
But the shaking didn't work and Curbeam, on the end of the robot arm, was moved up to the panel to try some additional slat flips with his scraper tools. To his surprise, guidewire was moving freely and Curbeam could not see anything obviously amiss. But the guidewire was slack, indicating a problem somewhere.
He then pulled out an improvised wire-puller tool, snagged the loose guidewire and gently pulled to take up the slack. But the cable pulled in freely, resulting in a loop of free line.
"Here we go... yes, and all that's doing is kind of pulling the outboard looseness."
He reported the guidewire was sliding through the grommets smoothly, raising questions about whether a takeup reel at the base of the blanket box was winding properly.
"Our concern is, either the reel isn't doing its job or that snag is trying to roll down until it gets very close to the reel," Robinson said.
Flight controllers then asked Curbeam what he thought about using a set of needle nose pliers to pull the frayed wire back out manually to get a feel for the motion. Then he could, perhaps, cut the fray away. Fuglesang was asked to look at the base of the blanket box and report whether he could spot the guidewire where it entered a takeup reel.
He saw no problems and Curbeam used the needlenose pliers to pull the guidewire out of the takeup mechanism on the theory that, like pulling on a stuck safety tether, that might clear up whatever was causing the problem.
"OK, here we go, I'm going to pull it out about five inches," Curbeam called. "Now I'm going to let go. And it is, tensioned, all the way out!"
"Good work!" someone said.
"The tension was very light. I pulled it out to five inches estimated and let it go and it retracted very smartly, I mean immediately."
"LIke a safety tether real," Robinson observed.
"Exactly. It took in quite a bit of line."
The astronauts then attempted another one-bay retraction. The mast pulled in smoothly, but another grommet appeared to hang up on a guidewire. Fuglesang gave the storage box two more shakes to jerk it free and the astronauts ordered another one-bay retraction.
And again, the grommet hung up. After using a longer "cheater bar" to reach the area, Curbeam cleared the snag and another one-bar retraction was ordered.
"Ready, ready, retract."
Again, a grommet appeared to hold up but this time, it freed itself.
"The aft solar array looks good," Curbeam reported. "And the forward is good," said Fuglesang.
"You are go for a single bay retract," Robinson said.
The blankets rippled a bit and seemed to hang up briefly, but as the motion damped out the slats lined back up. Another retraction was ordered, but this time, the slats hung up again.
From that point, it was retract one bay, manually clear hang ups, retract again.
Finally, four hours and 20 minutes into the retraction, only one bay remained extended from the mast canister. The spacewalkers spent a half hour inspecting the blanket boxes to make sure the slats were lined up and ready for final retraction.
"You are go for final retract per step 17.6," Robinson radioed around 6:50 p.m.
"OK, copy that. We're going to go ahead and set up for the final retract," Polansky replied. "OK guys, here comes the final retract command. Ready, ready, retract."
"Good motion," the spacewalkers said in unison as the central mast pulled in the final few feet. As the top of the array box moved down into place over the lower section, smoothly sandwiching the array slats between them, flight controllers burst into applause.
But the celebration was premature. Curbeam reported the center guidewire on one of the blankets apparently didn't fully retract and a short loop was left exposed. After closer inspection, Curbeam used needlenose pliers and attempted to gently pull the looped wire out through an exit port to permit a takeup reel to pull it in. But the wire didn't budge.
After using his pliers to pull the wire out from between two slats - and a folded over grommet as well - Curbeam was asked to pull on the guidewire again in a bid to pull out the slack.
"OK, all loop's gone, no wire down between the glass panel," he replied. "It is in tension."
"Beamer, we don't have TV," Robinson said a moment later. "Do you feel the guidewire is now not looped and completely clear and the way it should be?"
"Most definitely," Curbeam replied.
"Robert Curbeam, you do good work," Robinson said.
After a final inspection, commands were sent to engage latches, firmly locking the solar array blanket boxes closed to complete the retraction.
"Step 31, we are go for SABB latching," Robinson said at 7:30 p.m., five-and-a-half hours into the spacewalk.
"OK, the forward blanket box is completely latched," Curbeam reported. Houston then confirmed both boxes were latched, saying "Great job by everybody up there and down here on the ground. "We do have confirmed latch."
In the end, it took 71 mast motor activations over four days to fully retract the P6-4B solar array.
"This was very big for the space station program," Shireman said. "We had to have this array retracted in order to relocate this element, the P6, out to the port end of the truss. ... As you also know, our plan is to retract the 2B array on the next shuttle flight, 13A, in March of next year. So we needed to not only get this array retracted, but we needed to learn how to do it so we could get prepared for the next shuttle flight. So today, was a very, very big day for the station program."
Today's spacewalk began at 2 p.m., but by the time the astronauts got up to the array and ready to work, they were in orbital darkness. Coming back into sunlight around 3:15 p.m., Curbeam outlined his plan of action.
"And Houston, what I plan to do, just looking at this, it looks like if I push just a little on the hinge panel that should free up that grommet. Just a little on that outboard hinge panel ... and I think you'll see this whole thing loosen. Then I'll give a little back bend just to make sure the wave doesn't come out and get too close to me."
"We copy that. Sounds like a good plan. Tell us what tool you plan to use, Beamer," astronaut Stephen Robinson called from Houston. "And just to let you know, that guide wire is a three-strand wire."
"Oh great," Curbeam said. "I think you've got two left. I'm going to start off with the scraper tool then I'm going to do a knee bend just to get away from any resulting wave. ... And here we go."
He flipped a slat and then saw the frayed section catch in the next grommet.
"The guidewire is catching on every single grommet," Curbeam said. "Now it's caught on the next inboard grommet. I'm going to lift that one up. Here we go on the next grommet. ... I'm going to have to loosen each one individually because like I said, each grommet is catching up on that part. So the next grommet's coming with your concurrence."
"Houston concurs."
"OK, got two grommets that time," Curbeam said. "Yeah, you can see probably on (my helmet camera) now that part right there, that I'm pointing to, that part of the guidewire is frayed and that's what it's hanging up on."
He then released one grommet after another.
"As soon as that frayed part gets in the reel, though, we should be OK," he reported. "One more grommet... and another... and another... yeah, the tensioning reel is taking in the frayed part."
A few moments later: "OK, it is past all the grommets and well clear of anything it should hang up on. I am putting away the scraper tool... the scraper tool is stowed... and I'm as low profile as I can be. If you guys want to leave me here, that's fine or if you've gotta take me clear, that's fine."
The robot arm then moved Curbeam a few feet away while his crewmates inside prepared to send the first retraction command.
"And Houston, just so you know, it was only one strand that was popped," he reported.
"OK, Beamer, it's great to have an explanation for why it was hanging up," Robinson replied from mission control.
Curbeam said he did not expect the wire to cause any problems during the array's re-extension after it is moved to the end of the station's main solar truss next September.
02:00 p.m., 12/18/06, Update: Spacewalk No. 4 begins
Astronauts Robert Curbeam and Christer Fuglesang switched their spacessuits to internal battery power at 2 p.m. to officially begin a planned four-hour spacewalk to complete the retraction of a balky solar array. It will take the spacewalkers about a half hour to set up their safety tethers and make their way up to the P6-4B solar array.
EST........HH...MM...EVENT 02:00 PM...00...00...Spacesuits to battery power 02:05 PM...00...05...Airlock egress 02:30 PM...00...30...P6-4B retraction .....................SSRMS (station robot arm) setup and ingress .....................SSRMS GCA to worksite .....................Solar array blanket box survey .....................Solar array wing (SAW) retraction troubleshooting ........................SAW panel problem correction ........................SAW retraction .....................Blanket box closure .....................SSRMS GCA to egress .....................SSRMS cleanup 05:30 PM...03...30...Payload bay cleanup 06:00 PM...04...00...Airlock ingress 06:25 PM...04...25...Repressurization
12:00 p.m., 12/18/06, Update: Astronauts suit up for solar array repair spacewalk
Astronauts Robert Curbeam and Christer Fuglesang, Sweden's first man in space, are preparing for a fourth spacewalk today to help coax a recalcitrant solar array to fully retract. The astronauts are running a few minutes ahead of schedule and the spacewalk, the 77th devoted to station assembly and maintenance since construction began in 1998, is scheduled to begin around 2 p.m.
This will be Curbeam's fourth spacewalk during this mission - a space shuttle record - and his seventh overall. He currently ranks 13th on the list of most experienced spacewalkers with 38 hours and 56 minutes of EVA time.
"This is the first time that one crew member has been asked to do four spaceswalks in one (shuttle) mission," said lead EVA planner Tricia Mack at the Johnson Space Center. "And really, if anyone can do it, it's Beamer. He is rock solid. ... he's calm under pressure, he is just a machine, he is an EVA machine. He does everything right, he says all the steps and he can do other people's tasks, he works quickly and effectively, he reacts well to change."
Curbeam, call sign EV-1, will be wearing a suit with red stripes around the legs. Fuglesang, call sign EV-2, will wear an unmarked suit. Here is a timeline of today's activity (in EST and mission elapsed time; includes items from rev. F of the NASA TV schedule):
EST........DD...HH...MM...EVENT 09:17 AM...08...12...30...STS crew wakeup 09:47 AM...08...13...00...ISS crew wakeup 09:52 AM...08...13...05...EVA-4: 14.7 airlock repress 10:12 AM...08...13...25...EVA-4: Hygiene break 10:37 AM...08...13...50...EVA-4: 10.2 airlock depress 11:02 AM...08...14...15...EVA-4: Campout preps 12:32 PM...08...15...45...EVA-4: Spacesuit purge 12:47 PM...08...16...00...EVA-4: Spacesuit oxygen pre-breathe 01:37 PM...08...16...50...EVA-4: Airlock depress 02:12 PM...08...17...25...EVA-4: Spacesuits to battery power 02:17 PM...08...17...30...EVA-4: Airlock egress 02:42 PM...08...18...00...EVA-4: P6-4B troubleshooting/retraction 05:42 PM...08...21...30...EVA-4: Payload bay cleanup 06:12 PM...08...23...25...EVA-4: Airlock ingress 06:37 PM...08...23...50...EVA-4: Airlock repress 08:47 PM...09...00...00...Rendezvous tools checkout 10:30 PM...09...01...43...Mission status briefing on NASA TV 12:47 AM...09...04...00...STS/ISS crew sleep begins 01:00 AM...09...04...13...Daily video highlights reel on NASA TV 08:47 AM...09...12...00...STS crew wakeupThe P6 solar array, made up of two wings known as 2B and 4B, was attached to the station six years ago to provide interim power during the initial stages of assembly. Construction has now reached the point where the arrays need to be moved to the station's main solar array truss and wired into the lab's permanent power system.
To do that, the two wings are being folded up one at a time, with 4B scheduled for retraction during Discovery's mission and the still fully extended 2B wing during a shuttle mission next March. In September, another crew plans to move the stowed arrays to the left end of the main truss and re-extend both wings.
The Discovery astronauts attempted to retract the 4B wing on Wednesday but they were only able to pull it in about half way. Several of the slats in the folding blankets, held in alignment by guide wires similar to the cords in pleated blinds, failed to fold evenly, stopping the process in its tracks. Repeated attempts to free a presumably jammed grommet and guide wire were unsuccessful.
On Saturday, during a spacewalk by Curbeam and Sunita "Suni" Williams to finish the Discovery crew's goal of re-wiring the space station, NASA's Mission Management Team approved a fourth spacewalk to help get the P6-4B wing retracted. Curbeam and Williams, meanwhile, finished their electrical work early and ventured up to the stalled array for an up-close inspection.
The spacewalkers then repeatedly shook the solar array storage box, setting up ripples in the hinged slats of the solar cell blankets, freeing up stuck grommets and permitting their crewmates inside to retract the central mast an additional six bays. But they eventually ran out of time and had to call it a day, leaving 11 of the mast's 31 open-framework bays still extended.
For today's spacewalk, Curbeam and Fuglesang will be equipped with a variety of tools, all insulated with non-conducting tape, to free grommets and guide wires as needed. The solar array will be shunted to lower its electrical potential. In addition, Curbeam will work from the end of the station's robot arm, allowing him to access possible trouble spots that otherwise might be beyond his reach.
NASA has budgeted three hours for the repair work, but the spacewalk can be extended several hours if necessary.
01:30 p.m., 12/17/06, Update: Spacewalk decision highlights shuttle risk trades; heat shield inspection remains top NASA priority
Faced with an unforgiving space station assembly sequence, NASA managers were forced to shoehorn an additional spacewalk into Discovery's mission to complete the retraction of a recalcitrant solar array. The spacewalk came at the expense of a landing weather contingency day but it was either that or give up a post-undocking heat shield inspection, an option many shuttle engineers were reluctant to consider.
The issue illustrates the difficulty NASA managers may face balancing flight safety with schedule pressure resulting from the Bush administration's 2010 deadline for completing the international space station and retiring the shuttle. That somewhat arbitrary deadline leaves NASA little maneuvering room when it comes to dealing with unexpected problems like the partially retracted solar array that has disrupted the Discovery crew's schedule.
In this case, NASA's options are limited by the amount of hydrogen and oxygen the shuttle can carry to generate electricity and a pre-launch decision to add a docked day to the flight because of the mission's complexity and the possibility a day would be needed to correct problems activating the lab's permanent power system.
As such, Discovery's flight is classified as a 12-plus-zero-plus-two-day mission, i.e., a 12-day flight with two weather contingency days. There is not be enough hydrogen and oxygen on board to extend the mission itself beyond 12 days and still preserve two backup landing days.
NASA went into Discovery's flight with an understanding that the post-undocking heat shield checkout could be taken off the table if the astronauts had problems with the space station electrical work that might require an additional spacewalk. Late inspection, in fact, did not even show up on a list of pre-flight mission priorities.
This was not an issue under the original flight plan, which called for undocking Monday, late inspection Tuesday and a landing Thursday at the Kennedy Space Center, with Friday and Saturday as weather backups. But the flight plan was thrown into disarray when the astronauts ran into problems retracting a solar array on the international space station.
NASA engineers concluded the P6-4B solar array could be safely left in its partially deployed state for several months, but it had to be dealt with eventually. The P6 array, which provided interim power during the lab's initial assembly, is scheduled to be moved to the left end of the station's main solar power truss in September and it cannot be moved with either of its two wings even partially extended. Only three options were available:
- Adding a spacewalk to Discovery's mission to complete the retraction
- Deferring any repair attempt to the station crew after the shuttle's departure
- Deferring the work to the next shuttle mission, assembly flight 13A, in March
At the same time, station managers were not keen to add a spacewalk to the three-person Expedition 14 crew's already busy schedule. Spacewalks use the buddy system and a single astronaut would be required to stay inside and operate the retraction system as well as the space station's big robot arm.
"We're choreographed pretty tightly now to get from here to assembly complete," station Program Manager Mike Suffredini told reporters Saturday night. "And the next step for us as a program is to go into this stage where (the Expedition 14 crew has) three EVAs where we have to finish the reconfigurations ... and hook up the lab to the central cooling system."
Adding a solar array repair spacewalk would require "arm operations, two crew outside, commanding the solar array," Suffredini said. "That right there is at least four crew and you still haven't talked about your (spacewalk coordinator) crew person we normally have for each EVA."
Station planners also were reluctant to add solar array repair work to the next shuttle assembly mission scheduled for March. During that flight, the other wing of the P6 array must be retracted and a new set of arrays installed.
In the end, the MMT, chaired by John Shannon, decided Saturday to add a spacewalk to Discovery's mission to resolve the matter sooner rather than later. To the surprise of many shuttle observers, however, the MMT opted to retain the late inspection, giving up one of the two available landing weather contingency day instead.
NASA has three shuttle landing sites in the United States: The Kennedy Space Center in Florida, Edwards Air Force Base, Calif., and Northrup Strip in White Sands, N.M. Landings at Edwards add more than a week to a shuttle's turnaround time. Only one shuttle mission ever ended at Northrup, in 1983, and it's not clear how much time would be needed to get Discovery back from New Mexico.
As it turns out, the landing site is not as much of an issue for Discovery as it might normally be. Whenever the orbiter gets back to Kennedy, it will be taken off flight status for a major inspection and overhaul. The shuttle Endeavour, coming out of its own orbiter maintenance and down period, or OMDP, will serve as the emergency rescue vehicle for the March shuttle flight.
But Discovery's next flight is STS-122, a high-priority mission scheduled for launch next October to carry the European Space Agency's Columbus research module into orbit. While NASA likely could make up any lost time getting Discovery back to Florida, the schedule is tight and program managers don't like to lose time on the front end of such an important processing flow.
In any case, when only two landing days are available NASA flight rules require all three landing sites to be staffed and for the shuttle to come home on the first available opportunity.
"With that day (Friday) being the day before the last opportunity - we have to be on the ground by Saturday - that means we're going to call up all three landing sites, Edwards, KSC and Northrup, and our intent will be to put the vehicle on the ground somewhere that day at one of those sites," said Phil Engelauf, a senior manager in the mission operations directorate at the Johnson Space Center.
Engelauf said the unusual decision to give up a landing day turned on the importance many engineers attach to the late inspection, regardless of how it is officially classified. At orbital velocities, a 0.05-inch-wide piece of aluminum carries the kinetic energy of a 22-caliber long rifle bullet. The overall threat of a potentially catastrophic micrometeoroid strike, or an impact with space debris, is believed to be on the order of 1-in-250.
The heat shield is photographed during launch and inspected in excruciating detail before docking. The late inspection is designed to spot any damage that might have occurred after that point, during the normal course of the mission.
"It was a very complicated discussion and there were a lot of issues put on the table," Engelauf said. "Since return to flight, we've spent a lot of time talking about MMOD (micrometeoroid/orbital debris), which is one of the top risks in the program. We have wing leading edge sensors and we've signed up to add late inspection to the missions. We do go through a process before the mission, placing the mission activities in relative priority and the late inspection is usually placed below those activities that would cost us reflight."
That means, he said, that NASA would give up late inspection in cases where a spacewalk or some other crew action could resolve a situation that otherwise might require another shuttle mission. That logic also would apply for an event that "might have a significant impact on the assembly sequence such that the next mission could not happen in its proper order or that we would have to change the sequence of the assembly because we had to redo an EVA task."
"Trading that particular element, the importance of MMOD risk and the importance of the inspection and the relative newness of that topic in the program ... folks still believe that the priority to do that is extremely high," Engelauf said.
He agreed that NASA has never before "given up a landing opportunity for routine payload operations or other objectives."
"But this is not a routine objective," he said. "This is a fairly significant impact to the subsequent flights that puts it back up into that regime of whether or not it falls above late inspection to do the solar array work. When we added all of those things up, MMOD risk is eventually a safety discussion. And talking about the probability of safely getting the vehicle back on the ground.
"When you compare that to the landing-site-opportunity discussion, it's a schedule risk issue, whether or not you're going to get to a preferred landing site and whether there's going to be a schedule implication. The program managers spent a lot of time thinking real hard about this decision and the ultimate conclusion was we wanted to protect the safety issue of late inspection over the schedule issue."
Against that backdrop is the overriding drive to complete the station by 2010. Given a tight schedule and limited resources, NASA does not have the leeway it once did to handle unexpected problems. But Engelauf said safety would always trump any perceived schedule pressure.
"There is a constant awareness and people are continuously on the lookout for situations where we could feel like there's pressure to do something that might be not in the best interest of safety of the program," he said. "I think in this particular case, all of those decisions were, in fact, put on the table, all of those decisions were talked about and there was pretty unanimous support for the decision we came up with. I don't recall anybody bringing up a dissenting opinion."
As for the 2010 deadline, "that's not worth debating from my perspective," he said. "It is what it is. We are charged with executing this program with the tools that we have and I think the community is really doing an outstanding job of vigilance, of making good, safe and well-considered decisions independent of the other deadline issues."
In the end, he said, "I think we've got a good workable plan, we think we've minimized the risk to both programs. We have incurred, I think, some programmatic schedule risk that we're going to put the orbiter at a landing site that might cost us a little bit more turnaround time. But we think the bigger picture trade warrants that, given the significance of getting this array retracted for station and what that means to the rest of the sequence."
10:00 p.m., 12/16/06, Update: Astronauts shake solar array, coax additional retraction; 11 bays still extended; spacewalk Monday to complete retraction
Astronaut Robert Curbeam, a weight lifter in his spare time, and fellow spacewalker Sunita "Suni" Williams, a former Navy diver and helicopter pilot, took turns shaking a huge solar array storage box today in a bid to loosen up sticky grommets and fully retract unruly blankets. Despite considerable initial success, the astronauts ran into a particularly stubborn grommet on Williams' side and ran out of time, setting the stage for a fourth spacewalk Monday to complete the array's retraction.
Engineers are confident Curbeam and Swedish astronaut Christer Fuglesang will complete the job Monday, wrapping up the only loose end in an otherwise surprisingly successful mission to re-wire the international space station. Unlike today's excursion, the spacewalkers will be able to take advantage of the station's robot arm to get precisely positioned for the work and will have access to tools that likely will make it easier to reach troublesome areas.
The P6 array features two huge wings stretching 240 feet from tip to tip. Each wing is made up of two flexible solar blankets separated by a telescoping central mast. The blankets are made up of slats designed to fold up like pleated window blinds, using guide wires under tension to keep the slats lined up.
During initial retraction of the left-side 4B wing Wednesday, it appeared that one or more grommets were hanging up on the guide wires, preventing the slats from smoothly folding together. The idea today was for the spacewalks to shake the blanket boxes, causing the blankets to ripple in a wave-like motion and free up the guide wires.
But first, Curbeam and Williams had to complete work to route solar power to the station's central electrical grid. They finished about ahn hour ahead of schedule, floated up to the huge array and took turns shaking the array blanket boxes to loosen guide wires hanging up in several grommets.
"Here we go," Curbeam called, beginning his first shake. "There's five (pushes)."
"OK."
"Yeah, there's three grommets that are kind of grouped together, they're just staying together, they're not moving at all," Curbeam reported. "All the rest of them seem pretty well spaced."
"You're talking the close guide wire?" asked astronaut Stephen Robinson in mission control.
"Yes, I am. That fold seems to be a bit of problem all the way across."
"Standby, we're discussing, Beamer," Robinson called. "We'd like you to try doing the very same thing you just did, only about half that frequency. It's a big structure and this will build up potentially a little closer to its natural frequency."
"OK, at about half the frequency I gave you last time, starboard and port, five cycles... there's five cycles."
"That's great, Beam," Robinson said. "You're the best at this anyone's ever been."
"Easy for you to say."
"Let us know if you see any difference in any of the grommets," Robinson said after the laughter died down.
"No, those three seem to be grouped up," Curbeam said. "I can't tell if they're binding on the two outward guide wires, but on the inside they are stuck together."
"OK."
"Grommets 10, 11 and 12 outside of the blanket box, they're kind of just stuck together at weird angles where it looks like they're going to be together forever. I'm sure that wouldn't be the case when it's extended, but that's what it looks like it."
After additional shakes, Robinson said "that's an impressive amount of motion and very, very effective. Any new observations by the shuttle crew? We did not see anything change but we cannot see the grommets."
"I think we have consensus that the grommet numbers 1 through 11, if the stuck one is 12, are most definitely moving with respect to the guidewire," said station commander Mike Lopez-Alegria. "And our sense is that grommet 12 is also moving slightly away from the inner blanket box so that now it is farther away than it was before. Does that make sense to you guys?"
"Yes, it does," Robinson said.
"And I can tell you grommet 10 inboard is free now," Curbeam said. "I have no doubt you gys are thinking about this, but it sure seems tempting to try a retract while that motion is going on," Lopez-Alegria said. "It just seems like there's some stiction on that grommet that we could do nothing but help."
Flight controllers agreed, but decided to wait until the next daylight pass to make any additional attempts. Coming back into sunlight, Curbeam shook the box two more times before Lopez-Alegria sent commands to retract the mast one bay.
"OK issueing a retract command," he called. "Ready, ready, now."
"It's coming in," Curbeam said.
"Everything looks good on my side," reported Williams.
"Ditto," said Curbeam. "Grommet 12, definitely free." As the mast was retracted a bay at a time, repeated shaking was required to keep the guide wires freely moving in the grommets.
"We're thinking about one more bay retract," Robinson called at one point. "What's your input?"
"I think you should do it," Curbeam said. "If I see bad things happening, I'll call you all."
"Hey guys, I have a little bit of a dissenting vote," Lopez-Alegria said. "I think it would be useful to do a shake now because I'm pretty sure we're headed right down the same path and a shake now would put us in a better position to continue after that one bay."
"And Houston concurs," Robinson said. "Let's do a shake."
Curbeam then shook the array and another retraction cycle was ordered. Then another.
"Stop retract! Stop retract," Curbeam called.
"Abort!" Williams said.
"It's definitely out of plane on this side," Curbeam said. "Something is still hanging up. And guidewires, the outboard guidewires are definitely loose. Inboard seems tight for about a couple of grommets and then it goes loose. It's definitely hooking up on one grommet and I think I can see it."
"A shake may be in order," someone said.
Curbeam shook the box again, and said "OK, it's all lined up for you again. You might want to wait until that wave settles down. But it's definitely not stuck any more."
Additional retraction cycles were commanded and the blankets generally appeared to be folding smoothly. But in the end, a particularly stubborn grommet on Williams side resisted both spacewalker's efforts to shake it free.
"Beamer, you want to come over here and try it?" Williams called after repeated attempts to shake it loose. But Lopez-Alegria said he doubted Curbeam could make a difference and that Williams had induced as much motion in her blankets as Curbeam had in his.
And so, with time running out, Robinson told the spacewalkers to call it a day.
"We really commend you for a tremendous effort, an Olympian effort," he said. "We're ready for you to come back to the airlock."
In the end, Curbeam and Williams shook the array storage boxes 19 and 13 times respectively. Eight retraction cycles were ordered, leaving 11 of the 31 bays making up the mast still extended.
With the completion of today's spacewalk, the 76th devoted to station assembly, astronauts and cosmonauts have logged 463 hours and 21 minutes building the international outpost. The total through three spacewalks for Discovery's mission is 19 hours and seven minutes.
08:00 p.m., 12/16/06, Update: Astronaut shakes solar array; stuck grommets appear to loosen up
Astronaut and part-time weightlifter Robert Curbeam repeatedly shook a stalled solar array today, sending ripples through its partially retracted blankets and apparently loosening up previously stuck grommets and guide wires. Curbeam and spacewalker Sunita Williams are standing by during a night pass while flight controllers discuss making another attempt to retract the array.
07:15 p.m., 12/16/06, Update: Spacewalkers head up to partially retracted solar array
Running about an hour ahead of schedule, astronauts Robert Curbeam and Sunita Williams have finished their planned space station work and are making their way up to the P6 solar arrays for an inspection of the partially retracted 4B wing. Other than a close-up inspection, the only troubleshooting planned is for the spacewalkers to gently shake the array's blanket box in a bid to free a hung-up guide wire. Engineers believe one or more grommets is providing enough friction to prevent the guide wire from moving freely. That, in turn, is preventing the slats making up one of two solar blankets from folding smoothly as the P6 mast is retracted.
06:45 p.m., 12/16/06, Update: Revised mission timeline
NASA flight controllers are revising times for critical mission events due to the addition of a spacewalk Monday to address solar array problems. Assuming spacewalkers Robert Curbeam and Sunita Williams don't fix the trouble today, here are revised times for critical mission events between now and landing Friday (in EST and mission elasped time):
DATE/EST.........DD...HH...MM...EVENT 12/19/06 Tue...05:09 PM...09...20...22...Discovery undocks from space station Tue...05:38 PM...09...20...51...Separation burn 1 Tue...06:06 PM...09...21...19...Separation burn 2 Tue...06:52 PM...09...22...05...Separation burn 3 12/20/06 Wed...07:06 PM...10...22...19...MEPSI microsat deploy Wed...08:37 PM...10...23...50...RAFT microsat deploy 12/21/06 Thu...01:19 PM...11...16...32...ANDE microsat deploy Thu...01:49 PM...11...17...02...ANDE separation 12/22/06 Fri...02:52 PM...12...18...05...Deorbit ignition Fri...03:55 PM...12...19...08...LandingA revised flight plan will be posted as details become available.
06:05 p.m., 12/16/06, Update: 4th EVA approved; additional details
NASA's Mission Management Team today decided to add a fourth spacewalk to Discovery's mission in a bid to full retract an unruly solar array on the international space station. The decision was announced during a spacewalk by Robert Curbeam and Sunita Williams to finish re-wiring the orbital outpost.
"We are go for EVA-4 on flight day 10," astronaut Stephen Robinson radioed from Houston.
Curbeam and Williams plan to inspect the partially retracted P6-4B array later today and to possibly shake its storage box in a bid to free a presumably hung up guide wire preventing the blankets from folding smoothly.
Assuming that doesn't resolve the issue, Curbeam and Swedish astronaut Christer Fuglesang will carry out a fourth spacewalk Monday to attempt some sort of repair.
Under that scenario, Discovery would undock from the station Tuesday and the astronauts would carry out a final heat shield inspection Wednesday. After packing up Thursday, landing at the Kennedy Space Center would be expected around 3:56 p.m. Friday.
Curbeam and Williams successfully wrapped up a complex re-wiring job today, routing solar array electricity through two main bus switching units, transformers and other equipment making up channels 1 and 4 of the space station's electrical power system. Flight controllers then successfuly activated a critical pump to circulate ammonia coolant through cold plates and radiators to keep the electrical components from overheating.
Curbeam and Fuglesang wired in electrical power system channels 2 and 3 during a spacewalk Thursday. Today's work completed the station's switch over from interim to permanent power, a major milestone that clears the way for future crews to build out the station's main solar array truss and, eventually, to add new modules.
Building out the main power truss requires astronauts to fold up and move the P6 solar arrays, which provided interim power to the station. P6 eventually will be moved to the far left side of the power truss where it will joint a set of arrays known as P4 that were attached in September.
The Discovery astronauts attempted to retract the left wing of the P6 array, known as P6-4B, on Wednesday but they were only able to pull it in about half way. Several of the slats in the folding blankets failed to fold evenly, stopping the process in its tracks. Repeated attempts to free a presumably jammed guide wire were unsuccessful.
Engineers initially said the array could be safely left as is, that it had enough structural rigidity in its partially retracted state to withstand shuttle and Russian Progress supply ship dockings and undockings. But there were questions about whether it was up to the jarring from Soyuz crew capsule dockings at a port closest to the array.
NASA managers said earlier an additional spacewalk to deal with the array would force the astronauts to forego a planned final heat shield inspection after undocking because the shuttle only has enough hydrogen and oxygen for its electricity producing fuel cells to stay in orbit until Saturday at the latest.
The original flight plan called for a landing Thursday at the Kennedy Space Center, preserving two weather contingency days. NASA seldom cuts into the weather reserve, prompting speculation that an additional spacewalk would rule out the late heat shield inspection.
NASA went into Discovery's flight with an understanding that a post-undocking heat shield checkout could be taken off the table if the astronauts had problems with the space station electrical work that might require an additional spacewalk.
But during today's Mission Management Team meeting, senior agency managers concluded an additional spacewalk would, in fact, be required to deal with the recalcitrant solar array.
The repair work could have been deferred to the station's three-person crew, but spacewalks use the buddy system and a single astronaut would be required to stay inside and operate the retraction system as well as the space station's big robot arm.
In the end, the MMT, chaired by John Shannon, decided to add a spacewalk to Discovery's mission to resolve the matter sooner rather than later. The P6-2A wing, currently fully extended to the right side of the station, is scheduled to be retracted in March and engineers would like to have experience with P6-4B before attempting a second retraction that might result in the same problem.
The P6 array, with both wings fully retracted, is scheduled to be unbolted and moved to the far left end of the station's solar array truss in September.
Along with adding another spacewalk to Discovery's mission, the MMT also decided to preserve the final heat shield inspection, giving up one of the shuttle's two weather contingency days.
With only one weather contingency day beyond that, NASA likely will activate both of its backup landing sites at Edwards Air Force Base, Calif., and White Sands, N.M., on Friday. Touchdown at the Kennedy Space Center, weather permitting, is scheduled for 3:56 p.m.
05:45 p.m., 12/16/06, Update: MMT approves fourth spacewalk for solar array work
NASA's Mission Management Team today decided to add a fourth spacewalk to Discovery's mission in a bid to full retract an unruly solar array on the international space station. The decision was announced during a spacewalk by Robert Curbeam and Sunita Williams to finish re-wiring the orbital outpost.
The astronauts plan to inspect the P6-4B solar array later today and to possibly shake its storage box a bit to free a hung-up guide wire. Assuming no additional work to retract the array, a fourth spacewalk by Curbeam and Christer Fuglesang will be carried out Monday.
Under that plan, Discovery would undock from the station Tuesday and the crew would carry out a final heat shield inspection Wednesday. After packing up Thursday, the astronauts would head for a Kennedy Space Center landing Friday around 3:56 p.m.
Additional details will be posted here momentarily.
04:45 p.m., 12/16/06, Update: Loop A cooling system successfully activated
Flight controllers today successfully activated a powerful pump on the space station's main solar power truss, pushing ammonia coolant through cold plates and into big radiators to keep critical electrical gear from overheating.
The pump activation was the final major step in a complex two-spacewalk re-wiring job to route solar array electricity through four big main bus switching units, transformers and other components making up the lab's permanent electrical system.
"Discovery, for EVA, not only do you have a good view you have something to celebrate," astronaut Stephen Robinson radioed from Houston. "The pump module activation went great for loop A, so you will not be R-and-R'ing any pump modules."
"Excellent, that's awesome news," drawled spacewalker Robert Curbeam.
"That's good news," agreed fellow spacewalker Sunita "Suni" Williams.
"Good job, guys," Curbeam added.
"And a nice job by the software engineers who did all that work a long time ago," Williams said.
Activation of the loop A cooling system was critical because the two main bus switching units at the heart of the channel 1/4 power circuitry would overheat if left on their own. An independent cooling system - loop B - was activated Thursday after Curbeam and Swedish astronaut Christer Fuglesang wired in the channel 2/3 MBSUs and transformers.
Flight controllers are now in the process of powering up space station systems that were shut down for today's re-wiring work.
04:20 p.m., 12/16/06, Update: Electrical re-wiring complete
Spacewalkers Robert Curbeam and Sunita Williams finished re-wiring space station electrical power system channels 1 and 4, clearing the way for flight controllers to begin flowing solar array electricity through two main bus swithing units, transformers and other critical components. Engineers now plan to activate an ammonia cooling system to complete the station's switch-over from interim to permanent power.
"One hour 46 minutes into the spacewalk today, the task of reconfiguring the power system on the outside of the space station is complete and the ISS flight control team has been giving a go to begin repowering the station," said NASA commentator Kyle Herring in mission control. "And by comparison to EVA-2, that task took one hour and 45 minutes today. That task took one hour and 46 minutes (Thursday) to complete."
The spacewalk Thursday, in which Curbeam and Christer Fuglesang wired in the channel 2/3 circuits, was finished an hour ahead of schedule. If today's spacewalk stays on the same pace, Curbeam and Williams should have plenty of time to inspect a partially deployed solar array high atop the outpost.
"Discovery, Houston, for EVA with some really great news," astronaut Stephen Robinson called from Houston at 4:18 p.m. "We have a good, successful power up, no MBSU or DDCU (transformer) R & R will be required."
"That is great news," replied shuttle pilot William Oefelein. "Boy, you guys are really fast on that. Well done."
"No kidding. That's beautiful," Curbeam drawled.
"Well, it's great to have some good on-orbit electricians working for us," Robinson said.
02:30 p.m., 12/16/06, Update: Spacewalk No. 3 begins
Astronauts Robert Curbeam and Sunita "Suni" Williams switched their spacesuits to internal battery power at 2:25 p.m. to officially kick off the third planned spacewalk of shuttle Discovery's mission. Curbeam and Williams plan to finish a major space station rewiring job and then, if time permits, inspect a partially retracted solar array.
NASA's Mission Management Team, meanwhile, is meeting today to discuss the possibility of adding a fourth, unplanned spacewalk to the mission to complete the solar array's retraction. An additional spacewalk, if approved, likely would be staged Monday.
But a fourth spacewalk would delay the shuttle's undocking from the station by one day and preclude a planned post-undocking heat shield inspection. Some managers believe the inspection should take precedence over any solar array work while others believe the stalled array warrants quick resolution.
Either way, Discovery is expected to return to Earth Dec. 21. A decision on whether to add a fourth spacewalk is expected later today.
10:45 a.m., 12/16/06, Update: Discovery astronauts gear up for final planned spacewalk
Astronauts Robert Curbeam and Sunita "Suni" Williams are gearing up for a critical spacewalk today to finish re-wiring the international space station. If time is available and no major problems develop, they also plan to inspect a balky solar array and perhaps shake it a bit to free up a stuck guide wire that is preventing its full retraction.
NASA's Mission Management Team met early today to debate the possibility of adding a fourth, unplanned spacewalk to Discovery's mission Monday if the spacewalkers are unsuccessful but as of this writing, no final decisions have been made.
Today's spacewalk, scheduled to begin around 2:42 p.m., is the 76th devoted to station assembly and the third for Discovery's crew. Going into today's excursion, 64 U.S., Russian, Canadian, French, German and Swedish astronauts had logged 455 hours and 50 minutes building and maintaining the outpost since assembly began in 1998. Curbeam and Christer Fuglesang logged 11 hours and 36 minutes during the first two spacewalks of Discovery's mission. Today's outing will be Curbeam's sixth over two missions and Williams' first.
During a spacewalk Thursday, Curbeam and Fuglesang re-wired two of the station's four primary circuits - channels 2 and 3 - allowing electricity from the still-extended P6-2B array and the newly installed P4-2A blankets to flow through main bus switching units 2 and 3 at the heart of the station's permanent power system.
With power flowing through MBSUs 2 and 3, flight controllers successfully activated one of two coolant systems - coolant loop B - that use ammonia to carry heat away to a set of big radiators.
Today, Curbeam and Williams will connect the output from the P4-4A solar wing to power channels 1 and 4. Stored electricity in the batteries charged by the partially retracted P6-4B array also will be tied into channels 1/4 to provide eight hours of emergency "parachute mode" battery power if needed. As was the case Thursday, once power starts flowing through MBSUs 1 and 4, flight controllers must activate the second ammonia cooling system - loop A - to prevent the switching units and other equipment from over heating. While flight controllers work through the complex electrical system and cooling loop activation, Curbeam and Williams will move a set of Russian space debris shields to the station, along with a grapple bar needed during future assembly work.
Thursday spacewalk to re-wire channels 2/3 was completed a full hour ahead of schedule. If Curbeam and Williams are just as efficient today, they will have time to move up to the top of the station for an up-close inspection of the partially retracted P6-4B solar blankets.
The problem cropped up Wednesday, when the astronauts attempted to retract the blankets as part of work to switch the space station over to its permanent power system.
The P6 array, which features two wings - 2B extending on the right side of the station and 4B on the left - stretches 240 feet from tip to tip. It was mounted on the station six years ago to provide interim power during the initial stages of assembly.
To activate the station's permanent power system, the Discovery astronauts needed to retract the left wing of P6 to clear the way for the newly installed P4 arrays to begin rotating to track the sun. The right wing of P6, the 2B panel, will be retracted next March and in September, P6 will be moved to its permanent position on the left end of the station's main solar array truss next to P4.
But the P6-4B wing refused to cooperate and despite more than six-and-a-half hours of trying, the astronauts were only able to retract the panel about halfway. That was enough to permit the P4 array to rotate as required, but not enough to provide the desired long-term structural stability.
On Friday, the astronauts attempted to shake the stuck slats loose by rotating the array's central mast to set up oscillations in the flexible blanket. German astronaut Thomas Reiter even tried exercising with bungie cords in a bid to set up vibrations in the station structure that might jostle the unruly array. But the efforts had no discernible effects.
NASA managers are reluctant to add a dedicated spacewalk to Discovery's mission because that would force the astronauts to forego a planned heat shield inspection after undocking from the station. Others argue the array should be fixed now and not deferred to the next shuttle mission or to the station crew's already busy schedule.
(Editor's Note: The following is background on the space station's electrical and cooling systems for readers who might want a quick refresher. This is a shortened version of the electrical system overview that first ran here as part of a more detailed mission preview.)
The space station's solar array truss eventually will stretch the length of a football field, sporting two sets of dual-wing solar arrays on each end. The solar array wings, or SAWs, are numbered based on their position on the station with even numbers assigned to panels on the left, or port, side of the main truss and odd numbers assigned to SAWs on the right, or starboard, side.
The recently installed P4 segment's two SAWs are numbered 2A and 4A while the P6 SAWs are numbered 2B and 4B. The S4 arrays will be designated 1A and 3A while the S6 SAWs will be known as 1B and 3B.
The four sets of solar arrays are essentially identical. In each set, solar power flows from two SAWs into a sequential shunt unit. Power coming into the SSU can vary from 130 to 180 volts DC depending on a variety of factors, including blanket degradation, shadowing, etc.
Electrical power system components
Because each solar array wing powers a separate station circuit, the IEAs in each array include two sets of electronics. A direct current switching unit (DCSU), containing six high power switches, routes SAW electricity from the SSU into battery charge/discharge units that regulate the flow of power to and from six batteries, three for each SAW.
When the array's SAWs are in sunlight, the DCSU sends solar power to the MBSUs, through the SARJ, and also into the batteries to charge them up. As the station moves into Earth's shadow, the DCSU begins adding battery power to the flow going to its MBSU to maintain the proper voltage. When the arrays are completely eclipsed, the DCSU sends battery power alone to the MBSU in a continuous, automatic procedure.
The DCSU, the battery chargers and other components in each array's integrated electronics unit are cooled by ammonia circulated through cold plates and then routed to a single deployable radiator. Each of the four sets of arrays that eventually will be attached to the station include its own ammonia cooling system, which is independent of the main cooling systems in the S1 and P1 truss segments.
Electricity from the solar arrays is known as "primary power." The MBSUs take that primary power and route it to transformers known as DDCUs, which lower the voltage to a precisely controlled 124 volts DC. This so-called "secondary power" is then directed to the station's myriad electrical systems using numerous electro-mechanical switches known as remote power controllers.
The eight solar array wings on the completed space station will feed power through separate lines to the MBSUs. For redundancy, power from four SAWs will flow to a pair of major circuits - 1 and 4 - while power from the other four SAWs will be directed to a second pair of circuits - 2 and 3.
While the MBSUs can be cross tied to route power to different circuits in case of failures, the ammonia systems are independent and not connected to protect against a micrometeoroid impact that might rupture a line and take out the entire system.
But that lack of connectivity means a problem with loop A or B can take out two of the station's four primary electrical circuits.
"This is the one that from a station design perspective I wish they had plumbed it, cross tied it, because the pump and all the ammonia that's on the port side of the vehicle, that cools the 2/3 side, and then the pump and the ammonia tank and all that that's on the starboard side on the S1 truss, cools the 1/4 channel. So if a pump goes down or doesn't ever come up, the way that the guys when they designed the vehicle felt they got away with it, they said hey, I've got four power channels and so it's OK to lose two power channels and still be OK from a redundancy perspective.
"The problem is, that's not exactly the way the station's built, there are certain things that are wired to the 2/3 side and certain things that are wired to the 1/4 side. So they didn't cross tie the plumbing. ... If I can't get (a) pump running within a certain amount of time, I have to save time on the back end of the spacewalk to allow the crew to unwire what they did before and to back out again. If I left the wiring the way it was and the pump never got up to speed and I sent the crew back in, the MBSUs and the DDCUs (transformers) will overheat. It's just a matter of time."
The DDCU limit is 140 degrees Fahrenheit while the limit on the MBSUs is 115 degrees.
"In terms of EVA requirements, it takes about two hours for the crew to get to the point where they're ready for us to power stuff back up again," said station flight director John Curry. "We power all that stuff down so they don't shock themselves, they make the connections and then they tell us they're clear and we're ready for activation."
Lead station electrical officer Dave Crook "then activates a script that powers on a whole bunch of stuff really fast because obviously, we're racing against the clock we talked about earlier. So in the first 20 minutes, I'll know if the copper path worked. If any of those things don't work, I've also got a number that we can check against the limits on the suits, if one of the MBSUs fail or one of the DDCUs fail, we can do an R&R. And that would be during that specific EVA because hopefully, I have enough time for that. We've choreographed how that would work. There's an MBSU spare as well and that could be done in real time."
It will take about 20 minutes for the computer commands to execute, rerouting power to the MBSUs and downstream DDCUs. It will take another 45 minutes to an hour to activate each ammonia cooling system.
"The problem is, we don't want to cavitate the pumps (run them without fluid)," Curry said. "You have to get the ammonia pushed through the system at the proper pressure and the operating pressure of the pump is like 376 psi so we've got to get that pump up to minimum number before we can start trying to activate it so we don't cavitate. So that takes a little bit of time."
Adding up the numbers, Curry's team will know if power and cooling are active within about and hour to an hour and a half. While a spare MBSU or DDCU could be installed during the same spacewalk, trouble with an ammonia pump unit would cause a significant impact on the mission.
"Let's say the pump doesn't come up, or say I got bit by some software feature like what happened (when a SARJ commanding problem cropped up during the September shuttle mission)," Curry said. "If I can't figure that out within a short period of time, then I have to back out because I couldn't get the cooling done and there's not enough time to do the R-&-R of the pump.
"The pump weighs a lot, it's 1,500 pounds, so that's a complex remove-and-replace scenario. That would take an entire dedicated EVA to do that. There's a plan I've got in place where if the pump didn't come up to speed on EVA-2, then we would give the MMT (Mission Management Team) folks a day to think about it and then the next day after that, we would then use (another spacewalk) to R-&-R the pump.
"That's the part that concerns me, infant mortality," Curry said. "Every time you start up a new system you always learn something. Something could come up to bite us. The problem is, I've only got about an hour to figure that out. The pressure's on the ground. That's the difference between this flight and most others. This is a simple task for the crew. All they have to do is hook up a cable."
Because of safety requirements and the toxic nature of ammonia, electrical components inside the station's pressurized modules are cooled by water circulating through cold plates. That water is then routed to heat exchangers tied into external ammonia loops and radiators.
In the near term, the primary external ammonia system will only be used to cool electrical components mounted on the solar array truss.
10:45 p.m., 12/15/06, Update: Solar array inspection, possible repair work added to Saturday spacewalk
NASA managers late this evening told the Discovery astronauts that if enough time is available at the end of an already-planned spacewalk Saturday, two spacewalkers will be asked to carry out an up-close inspection of a partially retracted solar array to help engineers figure out what might be needed to coax the blankets into full retraction.
"We'll plan to execute EVA-3 tomorrow as published," astronaut Stephen Robinson radioed the astronauts late today. "It includes all the (planned) tasks. When we are done, assuming all the power and thermal reconfiguration goes well as it did during EVA-2, then if we have time, we may do a fairly simple task to do an inspection of this solar array wing.
Flight controllers plan to ask one or both spacewalkers to manually shake the array storage box to loosen a presumably stuck guide wire believed to be preventing a cluster of solar blanket slats from evenly folding up like a pleated blind. No other repair work will be attempted, at least according to the latest planning, but engineers are holding open the possibility of staging a fourth, unplanned spacewalk Monday if necessary.
"Right now, there's a lot of discussions going on as to mechanically what really is the hang up," Robinson said. "We're currently envisioning this as an inspection task. How much and what you could touch and what kind of good it could do is still very much under discussion, so we're not ready to really tell you what that could be. That will probably be developing even during EVA-3 tomorrow. So right now, think of it as going up, taking a really close look and telling us what's really going on."
The primary goal of Saturday's spacewalk, scheduled to begin around 2:42 p.m., is to re-wire two of the space station's four major electrical circuits. Power channels 2 and 3 were successfully activated during a spacewalk Thursday along with one of the station's two independent ammonia cooling loops.
Astronauts Robert Curbeam and newly arrived station astronaut Sunita "Suni" Williams plan to re-wire power channels 1 and 4 during Saturday's spacewalk followed by activation of cooling loop A.
As originally laid out, the spacewalk was expected to last about six hours. But during Thursday's excursion, Curbeam and Swedish astronaut Christer Fuglesang completed the channel 2/3 re-wiring a full hour ahead of schedule. Flight controllers say Saturday's spacewalk could be extended to seven hours if necessary, providing time for the solar array inspection.
The problem with solar wing P6-4B cropped up Wednesday, when the astronauts attempted to retract the blankets as part of work to switch the space station over to its permanent power system.
The P6 array, which features two wings - 2B extending on the right side of the station and 4B on the left - stretches 240 feet from tip to tip. It was mounted on the station six years ago to provide interim power during the initial stages of assembly.
To activate the station's permanent power system, the Discovery astronauts needed to retract the left wing of P6 to clear the way for a newly-installed set of arrays, known as P4, to begin rotating to track the sun. The right wing of P6, the 2B panel, will be retracted next March and in the fall of 2006, P6 will be moved to its permanent position on the left end of the station's main solar array truss next to P4.
But the P6-4B wing refused to cooperate and despite more than six-and-a-half hours of trying, the astronauts were only able to retract the panel about halfway. That was enough to permit the P4 array to rotate as required to track the sun, but not enough to provide the desired long-term structural stability.
Today, the astronauts attempted to shake the stuck slats loose by rotating the array's central mast to set up oscillations in the flexible blanket. German astronaut Thomas Reiter even tried exercising with bungie cords in a bid to set up vibrations in the station structure that might jostle the unruly array. But the efforts had no discernible effects.
NASA managers are reluctant to add a dedicated spacewalk to Discovery's mission because that would force the astronauts to forego a planned heat shield inspection after undocking from the station. In addition, work on the arrays poses a variety of risks because of the unknown nature of the problem, sharp edges, lack of training and the potential for electric shock.
Unlike some shuttle missions, Discovery's flight cannot be extended. Before launch, NASA managers decided to add a day to the flight and the shuttle does not have enough hydrogen and oxygen for its electricity producing fuel cells for any additional extensions beyond the two days NASA always keeps in reserve for bad weather.
While some engineers clearly favor a spacewalk repair, others are opposed, arguing the partially retracted panel is stable in the short term and that it makes more sense to defer retraction until engineers understand the problem - and possible solutions - more thoroughly.
The space station crew could carry out a retraction spacewalk, or the work could be deferred until the next shuttle crew arrives.
However the debate plays out, a decision must be made Saturday one way or the other.
"We have a great view of what's going on with the array up there from the shuttle flight deck," station commander Mike Lopez-Alegria told reporters earlier today. "My perspective looking at it from the inside last time was it doesn't need much coaxing. You've probably heard us use the analogy of trying to fold a map. As you know at times when you're folding a map it's helpful to poke it here and there and I think our approach will be not very different from that, although we'll be poking gently."
For his part, Curbeam said "there's a lot of very delicate pieces to the solar array wing and we want to make sure we don't rip one of those blankets or damage any of the hardware that's up there. ... As always, you want to do no harm first."
09:20 p.m., 12/15/06, Update: Retraction test aborted; solar array slats refuse to smoothly fold into storage box
After repeatedly shaking a partially retracted solar array blanket to free a presumably stuck guide wire, the shuttle-station astronauts extended a central mast a few feet as a prelude to possibly attempting a step-wise retraction. But a cluster of about 10 folding slats just above the array's storage box appeared stuck together, possibly because of the guide wire. When the astronauts began retracting the mast, the slats began flopping over to one side as they reached the storage box. The procedure was aborted, leaving the array in generally the same shape it was at the beginning of the test. Flight controllers have ruled out any additional tests tonight but meetings are on-going about whether to add any troubleshooting to an already planned spacewalk Saturday to finish re-writing the international space station.
06:15 p.m., 12/15/06, Update: Solar array wiggle tests continue; astronauts willing to do unplanned spacewalk if managers deem it safe
Flight controllers tried additional "wiggle" tests late today to shake a hung-up guide wire loose and clear the way for full retraction of a partially folded solar array. As with earlier tests, results were inconclusive but the Discovery astronauts said they would be willing to stage a repair spacewalk if mission managers conclude a quick repair is necessary and can be safely carried out.
"We have a great view of what's going on with the array up there from the shuttle flight deck," said station commander Mike Lopez-Alegria. "My perspective looking at it from the inside last time was it doesn't need much coaxing. You've probably heard us use the analogy of trying to fold a map. As you know, at times when you're folding a map it's helpful to poke it here and there. I think our approach will be not very different from that, although we'll be poking gently."
NASA's Mission Management Team met today to discuss a variety of options to fully retract the P6-4B solar array wing. The wing currently is retracted a little more than half way with at least one guide wire hung up on a grommet that seems to be preventing the slats in a solar blanket from folding smoothly.
Earlier today and again late this afternoon, flight controllers sent commands to move the array's mast slightly to trigger a wave-like motion in the folding slats that make up the solar blanket. The idea was to set up enough motion to free the guide wire from the friction believed snagging it in a grommet.
Television views from space showed the blankets rippling gently, but it was not immediately apparent whether the gentle shaking accomplished anything.
It appears unlikely NASA managers will add any solar array tasks to an already-planned spacewalk Saturday to finish a major re-wiring job to switch the international space station's circuitry form an interim to a permanent power system. The station's robot arm likely would be needed on the left side of the complex to provide access to the base of the array and the arm is needed on the right side of the station to support Saturday's spacewalk. But as of this writing, no options have been ruled out.
If a spacewalk is added to the mission, either Sunday or Monday, the Discovery astronauts would have to give up a planned post-undocking heat shield inspection. Commander Mark Polansky told reporters today he would be willing to do that if managers decide retracting the array is the higher priority.
"Certainly we rely a lot on the imagery team on the ground to go ahead and take a look and tell us that they think everything is going well with the orbiter, which we've gotten so far," he said. "There are a lot of risk trades here and we have a mission to accomplish. So I'm sure (we will) take a look at risk versus reward and see what's the best thing to accomplish.
"In a perfect world, I'd like to have everything but it's not quite that perfect. So we'll go ahead and try to find out what's the best thing we could do for overall mission success and safety."
Saturday's re-wiring spacewalk will be carried out by Robert Curbeam and newly arrived station astronaut Sunita Williams. But a solar array repair job would be carried out by Curbeam and Christer Fuglesang, who trained for solar array contingencies before launch.
Working around the array carries some risk because of sharp edges, minimal training and the possibility of arcing that could lead to potentially dangerous electric shocks. But any tools would be insulated and Curbeam said he was not particularly worried.
"I"m really not concerned at all about the shock hazard," he said. "We've got a great team on the ground working on a plan and hopefully it'll work well for us. But if nothing else, I know it will be safe for us so I'm not concerned about the shock hazard at all.
"Of course, we're excited about the possibility of helping out and helping make the house up here a little bit better by fixing that solar array if we can."
NASA managers also are considering deferring any additional work to the next shuttle mission or to the station's crew after Discovery departs. If an unplanned spacewalk is added to Discovery's mission, a decision must be made soon.
"The biggest thing about it is there's a lot of very delicate pieces to the solar array wing and we want to make sure we don't rip one of those blankets or damage any of the hardware that's up there," Curbeam said. "As always, you want to do no harm first."
01:30 p.m., 12/15/06, Update: Astronaut exercise session; no obvious change to solar panel
Trying to succeed where robotic jostling failed, German astronaut Thomas Reiter, wrapping up a six-month stay aboard the international space station, worked out with a resistive exercise device today in a bid to impart enough vibration to shake loose a hung-up solar array.
While past exercise sessions in the Unity module directly below the stalled solar array were known to trigger oscillations in the fragile blankets, Reiter's workout today did not shake the array enough to have any immediately obvious effects.
"I see no change at all in the configuration," shuttle commander Mark Polansky observed.
"Of course, I'm very sorry to hear that," Reiter joked. "I was training for that for half a year."
"We'll give you the Silver Medal for that, Thomas," astronaut Terry Virts radioed from mission control in Houston.
Reiter made several more attempts, but no changes were apparent to the untrained eye.
In a news briefing late Thursday, space station Program Manager Mike Suffredini said Leroy Chiao, a former commander of the outpost, was able to shake the P6 solar arrays doing squats with a bungie cord resistive exercise system mounted in the Unity module.
The shaking was not intentional and the exercise routine was changed to avoid such jostling in the future. But Suffredini thought it was worth a try today on the off chance it might free a hung-up guide wire preventing the P6-4B solar blankets from retracting smoothly.
Earlier today, flight controllers attempted to shake the blankets by rotating a central mast 10 degrees one way, pausing and then returning to the starting point. Again, no obvious improvements were immediately apparent.
The P6-4B solar array currently is retracted about half way and engineers say it can safely remain in that configuration for at least the next three to four months. NASA managers are debating whether to add a fourth, unplanned spacewalk to Discovery's mission to free the blankets or whether to hand the work off to the station astronauts or a future shuttle crew.
If a spacewalk is added to Discovery's mission, it would occur Sunday, after a final re-wiring spacewalk Saturday, or on Monday. Discovery's landing would remain targeted for next Thursday and a planned post-undocking heat shield inspection would be canceled.
10:20 a.m., 12/15/06, Update: Astronauts awakened; initial solar array 'wiggle' tests inconclusive
Flight controllers today began a series of tests to gently shake a partially retracted solar array on the international space station in hopes of freeing an apparently hung up guide wire.
The astronauts attempted to retract the P6-4B array Wednesday, but they were only able to pull it in about half way. That was enough for the crew's space station re-wiring mission to proceed but engineers would like to resolve the issue if at all possible without having to stage an additional spacewalk or deferring the work to next year.
At 8:49 a.m. commands were sent to rotate the array's central mast 10 degrees on one direction and then back to the starting point after a one-minute pause. The idea of the so-called "wiggle test" was to induce enough motion in the flexible blankets to free a guide wire in a grommet that appears held up by friction.
Engineers believe that may explain why the blanket in question did not fold up smoothly during repeated attempts Wednesday.
A second wiggle test was carried out at 9:35 a.m. but in both cases, the results were inconclusive. A third test, which included a 40-second pause between the first and second mast rotations, was carried out shortly after 10 a.m.
Again, the results were inconclusive, at least to the untrained eye. Live television from the space station showed the array slowly turning, but resulting motion in the solar blankets was subtle and difficult to discern in realtime.
NASA's Mission Management Team plans to review the situation this morning and additional tests may be carried out this afternoon. Space station program manager Mike Suffredini told reporters late Thursday it might be possible for an astronaut working out with a resistive exercise device to induce enough motion to achieve results.
If additional tests are ordered, they likely will occur after a lengthy shuttle water dump scheduled to end around 2 p.m.
02:30 a.m., 12/15/06, Update: Solar array 'wiggle' tests on tap; possible retraction attempt; spacewalk options still under study
NASA managers, thrilled with the success of a space station re-wiring spacewalk Thursday, plan to remotely shake and jiggle a partially retracted solar array Friday in a bid to free a hung up guide wire and coax the blankets into full retraction. One proposed test includes having an astronaut work out with a resistive exercise device to impart forces known to shake, or excite, the fragile solar arrays.
Engineers are still assessing the feasibility of a fourth, unplanned spacewalk to manually free the guide wire. But they have ruled out adding any such work to an already planned spacewalk Saturday to finish re-wiring the station. NASA managers would prefer to avoid an additional EVA if at all possible because it would force the Discovery astronauts to forego a final heat shield inspection after undocking next week.
A third option is to simply leave the array as is and attempt retraction later, either by a station crew or during the next shuttle visit in March.
"We're looking at all these options, we haven't made any decisions," Mike Suffredini, space station program manager at the Johnson Space Center, told reporters late Thursday. "Right now, the ISS is in a very good configuration relative to this array. ... We've got plenty of time in this configuration, there's no cause for alarm."
The astronauts Wednesday attempted to remotely fold up one wing of the solar arrays that provided interim power to the space station, the first step in on-going work to switch the lab complex to its permanent power system. The retraction was required to provide the clearance needed for newly installed arrays on the end of the station's main power truss to begin rotating to track the sun.
But the P6-4B array wing refused to cooperate, with its pleated blind-like slats failing to smoothly fold up. After repeated extension-retraction cycles over more than six-and-a-half hours, the astronauts finally managed to retract the blankets about halfway. That was enough to permit the newly installed P4 arrays to rotate as required. At that point, the astronauts were told to shift gears and prepare for Thursday's spacewalk.
Engineers now believe a guide wire is hanging up in a grommet due to friction and that if the array can be shaken a bit, the wire might break loose, permitting the blankets to fold smoothly.
Crew wakeup Friday is scheduled for 9:47 a.m. At some point during the next hour or so, commands will be sent to rock the arrays by rotating a central mast one way and then the other in a motion siimilar to changing the pitch of a propeller.
"If that doesn't work, there's actually another technique that will make you laugh a little bit, we have what we call the IRED (Interim Resistive Exercise Device), it's a resistive exercise device the crew uses," Suffredini said. "We found through experience a few increments ago that if they exercise at the right rate, they can excite the solar arrays. In fact, Leroy Chiao was exercising and we noticed through the camera that the array was really getting a work out."
No word yet on who might be asked to perform the ultimate power squats this time around, but if it happens it will follow a water dump scheduled to end around 1:45 p.m. Friday. First, the team will attempt to shake the arrays by rotating the mast.
"There's a water dump that we've got scheduled tomorrow (and) we didn't want to perturb that, so we wanted to see if this wiggle test will work before 10 a.m. local time (CST) tomorrow," said lead space station flight director John Curry. "So we're going to do that test sometime before 10 a.m. then we'll have a Mission Management Team meeting to discuss the results of that and then go from there."
"If either one of these techniques clears it, then what we will do probably later in the day is try this retraction technique," Curry said. "We'll probably retract it a bay or two at a time and stop and let the whole system settle out ... and see if we can't ease it back into the blanket box that way."
Otherwise, the astronauts plan to hold traditional joint crew news conference at 3:47 p.m. and to make preparations for a third and final spacewalk Saturday to complete the space station's switch over to its permanent power system.
Astronauts Robert Curbeam and Swedish flier Christer Fuglesang re-wired two of the station's four major electrical circuits during a five-hour spacewalk Thursday. Flight controllers also successfully activated a powerful ammonia coolant pump to keep the newly activated electronic gear from overheating.
"Today went as close to without a hitch as you can possibly have a spacewalk go," Curry told reporters. "From a programmatic perspective, and from an ops perspective for this particular spacewalk, this one scared me as one of those that I was worried about, all the potential contingencies that could occur, what if the software doesn't come up right, what if the pump doesn't come up right, what if the power doesn't do what it's supposed to do?
"And all that stuff worked exactly and precisely the way folks designed it and tested it and we executed the EVA and the crew, both of them, they were just machines, couldn't have gone better. ... We've simmed this particular day hundreds of times. And the fact that it went the way it did today gives me a lot o confidence that when we go to do the exact same thing again (on Saturday), that the same thing will happen. I'm hopeful, because obviously we proved a lot of things today."
Curbeam and Fuglesang finished their work an hour ahead of schedule Thursday. But even if Saturday's spacewalk by Curbeam and Sunita Williams goes just as smoothly, no solar array troubleshooting can be added to the excursion because the station's robot arm will not be in position to get an astronaut to the array.
"It just flat doesn't fit," Suffredini said.
07:45 p.m., 12/14/06, Update: Spacewalk ends
Running ahead of schedule, astronauts Robert Curbeam and Christer Fuglesang wrapped up a successful spacewalk today, re-wiring two of the space station's four main electrical circuits so flight controllers could tie them into the lab's permanent power system.
The spacewalk began at 2:41 p.m. - about a half hour early - and ended at 7:41 p.m., a full hour ahead of schedule, when the astronauts began repressurizing the station's Quest airlock module. The five-hour spacewalk was the 75th devoted to station assembly and maintenance and the second for Curbeam and Fuglesang, pushing their total EVA time to 11 hours and 36 minutes.
The total spacewalk time devoted to station assembly now stands at 455 hours and 50 minutes. A veteran of five spacewalks over two missions, Curbeam has now logged 31 hours and 25 minutes walking in space, moving him up to 20th on the list of most experienced spacewalkers.
Curbeam will be joined by station astronaut Sunita "Suni" Williams during a third and final spacewalk Saturday to re-wire the station's other two main circuits and to activate a second ammonia cooling loop.
Curbeam and Fuglesang, Sweden's first astronaut, have been strictly business during the first two spacewalks, barely mentioning anything beyond the work at hand. Today, during a brief pause, they marveled at the northern lights seen from the vantage point of space.
"Wow, is that an aurora?" Fuglesang wondered aloud as the shuttle-station complex sailed through darkness toward northern Europe. "I think it is."
"It certainly is, Christer, that's an aurora. I'm sure you've seen as many as I have," said shuttle pilot William Oefelein, who grew up in Alaska.
"No, I haven't seen many. Someone should turn out all the lights outside the station."
"I'm not thinking that's a good idea, Christer," Williams joked from the Destiny laboratory module.
"It's different when you look down on them instead of up at them," Oefelein mused.
"Yeah. No, I don't see many in Stockholm."
"Gosh, it's beautiful," Curbeam said. "Wow."
05:30 p.m., 12/14/06, Update: Loop B ammonia pump operating normally; good cooling reported
After spacewalkers re-wired two of the space station's four main electrical circuits, flight controllers at the Johnson Space Center in Houston successfully activated a critical cooling system in a major milestone for station assembly.
"Discovery, Hosuton, for EVA. More good news," astronaut Stephen Robinson radioed from Houston.
"Go ahead," replied Discovery pilot William "Billy O" Oefelein.
"Billy O and crew and everybody on board, would like to let you know the pump module powerup has gone just great," Robinson reported. "You will not be doing an R-and-R of a pump module today. We've got good rpm, temperatures and pressures."
"Excellent," spacewalker Robert Curbeam drawled.
"That is great news, great work by Houston all around," Oefelein said. "I know (lead flight director John Curry) has worked on this for a long time. Congratulations to him and his great team there. Well done."
"Ditto," Curbeam drawled.
The station's main power system is equipped with two independent cooling loops, designed to pump ammonia through cold plates to carry heat away from big switching units, transformers and other components. One cooling loop is devoted to equipment on the 2/3 circuits activated today while the other is associated with circuits 1 and 4, scheduled for re-wiring Saturday.
Had the loop B pump module failed to run properly today, Curbeam and Swedish astronaut Christer Fuglesang would have had to reverse their electrical work, switching back to an interim power system, to prevent the main bus switching units from overheating. A spare pump module is available on the station, but with today's successful activation of the loop B pump, no such repair work will be needed.
05:00 p.m., 12/14/06, Update: Electrical work complete; channels 2/3 successfully repowered
One hour and 54 minutes into a planned six-hour spacewalk, astronauts Robert Curbeam and Christer Fuglesang completed their electrical re-wiring work to route electricity from the space station's solar arrays into two of the four main circuits making up the lab's permanent power system.
Flight controllers then successfully powered up the two channels, routing electricity through a pair of big main bus switching units and transformers mounted on the statoin's solar array truss.
"Discovery, Alpha, with some good news from Houston," astronaut Stephen Robinson radioed from Houston.
"We're ready for the good news," an astronaut replied from space.
"It's not good news, it's great news," Robinson said. "MBSU 2 and 3 and the associated DDCUs have powered up successfully. You do not have to do an MBSU or DDCU change out today."
"Excellent," Curbeam drawled.
Flight controllers then turned their attention to activating a large ammonia pump in one of two untried cooling systems to keep the electronics from overheating.
The pump has been in space for four years, but other than aliveness tests, it has never been turned on. But cooling is critical and the pump is needed to push ammonia through cold plates to carry heat away from the electrical components and into large radiators for dissipation in space.
With flight controllers busy activating the power and cooling systems, Curbeam and Fuglesang are in the process of moving two equipment carts from one side of the station's robot arm transporter to the other in preparation for station assembly work next year.
03:00 p.m., 12/14/06, Update: Spacewalk No. 2 begins
Editor's Note:Floating in the Quest airlock module, astronauts Robert Curbeam and Christer Fuglesang, Sweden's first man in space, switched their suits to battery power at 2:41 p.m., officially kicking off a planned six-hour spacewalk to begin re-wiring the international space station.
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As part of today's re-wiring work, the space station's KU-band antenna system will be shut down. In addition, the shuttle's KU-band TV system will be down to avoid radiating the spacewalkers. As a result, little live television from space is expected during today's excursion.
"Well Mike, the time has come," astronaut Stephen Robinson radioed from Houston. "Looking on the flow chart, we are about to implement block 21 on page 4 of 8, the EPS (electrical power system) channel 2/3 powerdown. You're going to lose half the lights in the lab and the node. You will not have comm between the U.S. and the Russian side, the lab aft ATU will be out. We have the big loop through the shuttle air-to-ground only, your space-to-ground (audio loop) will not be there."
"Steve, we copy all," station commander Mike Lopez-Alegria replied. "Thanks for the great big picture words."
This is the 75th spacewalk devoted to station assembly and maintenance since construction began in 1998 and the second for Curbeam and Fuglesang, who spent six hours and 36 minutes outside Tuesday attaching a solar array truss segment. Going into today's spacewalk, 64 U.S., Russian, Japanese, Canadian, German, French and now Swedish astronauts have logged 450 hours and 50 minutes building and working on the lab complex.
09:45 a.m., 12/14/06, Update: NASA debates adding spacewalk to Discovery's mission to retract balky solar array; station re-wiring spacewalks today and Saturday as planned
The Discovery astronauts are gearing up for a critical spacewalk today to begin re-wiring the international space station while engineers debate whether to add an unplanned spacewalk early next week to help coax an unruly solar array into full retraction.
Astronauts Robert Curbeam and Christer Fuglesang, Sweden's first man in space, are scheduled to begin a planned six-hour spacewalk at 3:12 p.m., their second in three days. The goal of this excursion is to switch two of the station's four major electrical circuits over to the lab's permanent power system.
The other two circuits will be re-wired during a spacewalk Saturday by Curbeam and newly arrived station astronaut Sunita "Suni" Williams. Both spacewalks are required to route electricity from the station's main arrays through big switching units and transformers on the solar array truss that make up the lab's permanent power system.
Before activating the permanent power system, the astronauts Wednesday attempted to remotely fold up one wing of the solar arrays that provided interim power. The retraction was required to provide the clearance needed for newly installed arrays on the end of the power truss to begin rotating to track the sun.
But the P6-4B array wing refused to cooperate, with its pleated blind-like slats kinking and failing to smoothly fold up. After repeated extension-retraction cycles over more than six-and-a-half hours, the astronauts finally managed to retract the blankets about halfway. That was enough to permit the newly installed P4 arrays to rotate as required. At that point, the astronauts were told to shift gears and prepare for today's spacewalk.
Flight Director John Curry said the partially retracted array was in a safe configuration and that shuttles and Russian spacecraft could dock and undock without causing any structural problems should engineers decide to postpone any corrective activity.
But flight controllers are studying a variety of options for an unplanned spacewalk by Curbeam and Fuglesang to complete the retraction Monday or Tuesday. They opted not to add any repair activities to today's spacewalk or Saturday's excursion because of the critical nature of the re-wiring work and the possibility of additional problems that might require action.
Kirk Shireman, deputy manager of the station program at the Johnson Space Center in Houston, said the solar array problem was particularly frustrating because it looked so easy to solve. On Earth, that is.
"The hard part, you probably saw it at the very beginning when we had that (blanket) fold problem, you look at it and say, boy, if I could just touch it right there it would fold correctly and retract."
Shireman said engineers are looking "at what are the rules, what things should we be worried about when we go out there and touch it ... whether it's a tool, perhaps modifying some of our tools to prevent damage to the arrays and certainly to protect the astronauts from any hazard. These panels, there is glass, these cells have glass in them, they build up charge, so we want to make sure we don't have a potential shock hazard. ... We're going to go through and do an analysis on all those things before we'll send somebody out to do anything with these arrays."
Curbeam and Fuslegang were trained for several solar array contingencies and Curry said access to the blankets was not an issue.
"The good thing is, all the failures that we had today, if you want to call it a good thing, were all in the area near the base of the blanket box," he said. "So you could position a crew member who could actually position himself at the font of one of these blankets. He could cover that wing, for example. You would probably be talking about putting the second crewman on (a robot) arm, more likely, and doing it from the other side. So it's physically possible. You could physically put two guys there if you had to and then you talk about what you do when you get them there and what they're allowed to do, whether they touch it themselves with a glove or whether they touch it with a tool. But it is possible."
During today's spacewalk, Curbeam and Fuglesang will work on and around the central truss segment in the station's main solar array truss atop the Destiny laboratory module. They will unplug 19 thick electrical connectors and replug 17 to re-route solar power to channels 2/3. They also will reposition two equipment carts that are towed along the truss by the station's robot arm-carrying mobile transporter. The spacewalk is relatively straight forward; the real challenge today is in mission control, where flight controllers will be sending hundreds of computer commands in a precise sequence to activate critical systems without causing problems for the operational circuits.
The main solar array truss is mounted atop the Destiny laboratory module at right angles to the long axis of the station's pressurized modules. The central S0 truss segment sits in the middle atop the lab, flanked by the S1 and P1 truss elements. S0, S1 and P1 house the major electrical components of the permanent electrical system: Four main bus switching units, or MBSUs, and transformers called DC-to-DC converter units - DDCUs - that serve to step down and regulate solar array power to levels needed by station equipment.
S1 and P1 also house the station's two independent cooling systems, each of which include large ammonia tanks, a nitrogen gas pressurization system and a massive pump module to pushes ammonia coolant through cold plates and heat exchangers and out into deployable radiators, three on S1 and three on P1. To maximize heat rejection, the radiators are mounted on a rotating beam that can point them toward the cold of deep space.
In September, the crew of mission STS-115 attached two new truss segments to the left side of the solar array beam. The first, P3 (there is no P2) features a powerful solar alpha rotary joint, or SARJ, while the second, P4, includes a new set of solar arrays that stretch 240 feet from tip to tip.
The solar array truss eventually will feature two SARJ joints, one on each side, to rotate the station's solar arrays like giant paddle wheels as the lab complex circles the Earth. That rotation, 360 degrees every 90-minute orbit, will keep the arrays generally face on to the sun. The orientation of the blankets can be fine tuned by so-called beta gimbal assemblies, or BGAs, that automatically adjust the pitch of each solar array wing like the orientation of an airplane propeller can be adjusted in flight.
The P3 SARJ was successfully activated Wednesday and the P4 arrays are now rotating to track the sun. Flight controllers also pressurized one of the two ammonia coolant loops in preparation for activation later today to provide cooling to the MBSUs and other components.
The space station's electrical system was designed to operate in an interim mode during the initial stages of construction, using the P6 arrays mounted on the end of a short segment known as Z1 that extends upward from the Unity module. Up until now, P6 provided power to six DDCUs and two others in the Z1 truss. An interim cooling system kept the electrical components from overheating.
During today's spacewalk and again on Saturday, the station's main electrical circuits will be powered down, channels 2/3 first and then 1/4. The output from the new P4 arrays and the still-extended P6-2B wing will be routed to the main bus switching units on the solar array truss and the lab will begin drawing power from the MBSUs, downstream DDCU transformers and remote power control modules.
Complicating the work, certain command-and-control computers must remain operational throughout the power switch over, requiring the station crew to install jumpers between components in avionics racks in the lab module to provide redundancy for critical systems when a given power channel is shut down.
After today's spacewalk, all channel 2/3 power, provided by P6-2B and P4-2A, will be routed through MBSUs 2 and 3 on the S0 truss. After the third spacewalk, all channel 1/4 power, provided by P4-4A, will be routed through MBSUs 1 and 4. The retracted P6-4B array also will be tied into channel 1/4 to provide "parachute mode" battery power if needed.
While the electrical system is being reconfigured, the main ammonia cooling system in the truss - the external active thermal control system, or EATCS - must be activated to dissipate the heat that will be generated by the electrical power system as components come on line. Large radiators on the port side of the main solar array truss will begin rotating for the first time to maximize heat rejection.
The space station's solar array truss eventually will stretch the length of a football field, sporting two sets of dual-wing solar arrays on each end of the main truss. The solar array wings, or SAWs, are numbered based on their position on the station with even numbers assigned to panels on the left, or port, side of the main truss and odd numbers assigned to SAWs on the right, or starboard, side.
The recently installed P4 segment's two SAWs are numbered 2A and 4A while the P6 SAWs are numbered 2B and 4B. The S4 arrays will be designated 1A and 3A while the S6 SAWs will be known as 1B and 3B.
The four sets of solar arrays are essentially identical. In each set, solar power flows from two SAWs into a sequential shunt unit. Power coming into the SSU can vary from 130 to 180 volts DC depending on a variety of factors, including blanket degradation, shadowing, etc.
Electrical power system components
Because each solar array wing powers a separate station circuit, the IEAs in each array include two sets of electronics. A direct current switching unit (DCSU), containing six high power switches, routes SAW electricity from the SSU into battery charge/discharge units that regulate the flow of power to and from six batteries, three for each SAW.
When the array's SAWs are in sunlight, the DCSU sends solar power to the MBSUs, through the SARJ, and also into the batteries to charge them up. As the station moves into Earth's shadow, the DCSU begins adding battery power to the flow going to its MBSU to maintain the proper voltage. When the arrays are completely eclipsed, the DCSU sends battery power alone to the MBSU in a continuous, automatic procedure.
The DCSU, the battery chargers and other components in each array's integrated electronics unit are cooled by ammonia circulated through cold plates and then routed to a single deployable radiator. Each of the four sets of arrays that eventually will be attached to the station include its own ammonia cooling system, which is independent of the main cooling systems in the S1 and P1 truss segments.
Electricity from the solar arrays is known as "primary power." The MBSUs take that primary power and route it to transformers known as DDCUs, which lower the voltage to a precisely controlled 124 volts DC. This so-called "secondary power" is then directed to the station's myriad electrical systems using numerous electro-mechanical switches known as remote power controllers.
The eight solar array wings on the completed space station will feed power through separate lines to the MBSUs. For redundancy, power from four SAWs will flow to a pair of major circuits - 1 and 4 - while power from the other four SAWs will be directed to a second pair of circuits - 2 and 3.
During today's spacewalk, flight controllers will power down components on the 2/3 channel and Curbeam and Fuglesang will re-plug cables on the truss to route solar array power to the channel 2/3 MBSUs and associated equipment in S0. DDCUs in the lab module will be disconnected from the interim P6 power system. The output from P6 will be connected to the MBSU inputs and the DDCUs on the truss and in the lab module will be connected to MBSU output. It will take about two hours to reach this point.
Next, flight controllers will power up the MBSUs and DDCUs in the permanent electrical distribution system and verify they are working properly, a procedure that will take about a half hour. Ammonia coolant loop B then will be activated to cool the electronic gear. The same procedures will be carried out for power channels 1/4 during the third and final planned spacewalk when coolant loop A will be activated.
Once the MBSUs are powered up, cooling must be activated within a few hours to prevent potentially serious damage.
"On EVA 2 we're going to turn off the 2/3 channel," Curry said. "Some boxes, it's just a loss of redundancy and on other boxes, the stuff is actually physically off. So when you've got things that are physically off, you've got what we call passive thermal limits, meaning it's stuff getting too cold and how long can it go without breaking the hardware?
"Of course, most of the things like that, you have to go based on analysis because when you turn the thing off, you no longer have telemetry on it to tell you whether it's doing well or doing poorly. So we spent a lot of time trying to figure out what are the things that are the biggest risks. And if you look at the way the EVAs are planned out, we broke up the power downs into two sections, one where we do the first set of wiring, which is for things - the majority of the stuff that can make it without power for the rest of the EVA, meaning five or six hours.
"There were three other things that were not in that category, mostly related to the comm system and to the cameras on the outside of the vehicle. So those ones we (do) late. Comm is obviously very important and you don't want to go a long period of time without the comm stuff. So the S-band antennas and the KU-band system, we do those very late so the amount of time they went without power was less than an hour. That was all passive thermal. So I think we're fine on passive thermal.
"The bigger concern is the active thermal, and it's not just the MBSUs but it's all the truss equipment. There's a whole bunch of boxes that are in line for power, your MBSUs, your DDCUs and then your RPCMs. The DDCUs and the MBSUs are cooled by cold plates that have this ammonia running through them. Right now, on the permanent system the ammonia is still sitting in the tanks, we haven't started pushing it through the system yet because we're waiting until we need it."
While the MBSUs can be cross tied to route power to different circuits in case of failures, the ammonia systems are independent and not connected to protect against a micrometeoroid impact that might rupture a line and take out the entire system.
But that lack of connectivity means a problem with loop A or B will take out two of the station's four primary electrical circuits.
"This is the one that from a station design perspective I wish they had plumbed it, cross tied it, because the pump and all the ammonia that's on the port side of the vehicle, that cools the 2/3 side, and then the pump and the ammonia tank and all that that's on the starboard side on the S1 truss, cools the 1/4 channel. So if a pump goes down or doesn't ever come up, the way that the guys when they designed the vehicle felt they got away with it, they said hey, I've got four power channels and so it's OK to lose two power channels and still be OK from a redundancy perspective.
"The problem is, that's not exactly the way the station's built, there are certain things that are wired to the 2/3 side and certain things that are wired to the 1/4 side. So they didn't cross tie the plumbing. So what that means is, on EVA-2 when I go to activate loop B's pump, if loop B's pump doesn't come up, if I have any kind of glitch - and I want you to know this in case it happens - there's a clock that I will be running for the MBSUs and the DDCUs and just in general and then I have to compare that clock against the crew's (spacesuit) clock, how long they can actually stay out.
"If I can't get that pump running within a certain amount of time, I have to save time on the back end of the spacewalk to allow the crew to unwire what they did before and to back out again. If I left the wiring the way it was and the pump never got up to speed and I sent the crew back in, the MBSUs and the DDCUs will overheat. It's just a matter of time."
Engineers initially concluded the MBSUs would overheat within an hour or so, but a later assessment using a qualification unit showed the devices could operate without cooling for five to six hours.
"So we think we're OK," Curry said. "I have telemetry on the MBSUs and I have telemetry on the DDCUs. So I have numbers in the flight rules that tell me thou shalt not let the temperature of the MBSUs or the DDCUs get above this certain number."
The DDCU limit is 140 degrees Fahrenheit while the limit on the MBSUs is 115 degrees.
"In terms of EVA requirements, it takes about two hours for the crew to get to the point where they're ready for us to power stuff back up again," Curry said. "We power all that stuff down so they don't shock themselves, they make the connections and then they tell us they're clear and we're ready for activation."
Lead station electrical officer Dave Crook "then activates a script that powers on a whole bunch of stuff really fast because obviously, we're racing against the clock we talked about earlier. So in the first 20 minutes, I'll know if the copper path worked. If any of those things don't work, I've also got a number that we can check against the limits on the suits, if one of the MBSUs fail or one of the DDCUs fail, we can do an R&R. And that would be during that specific EVA because hopefully, I have enough time for that. We've choreographed how that would work. There's an MBSU spare as well and that could be done in real time."
It will take about 20 minutes for the computer commands to execute, rerouting power to the MBSUs and downstream DDCUs. It will take another 45 minutes to an hour to activate each ammonia cooling system.
"The problem is, we don't want to cavitate the pumps (run them without fluid)," Curry said. "You have to get the ammonia pushed through the system at the proper pressure and the operating pressure of the pump is like 376 psi so we've got to get that pump up to minimum number before we can start trying to activate it so we don't cavitate. So that takes a little bit of time."
Adding up the numbers, Curry's team will know if power and cooling are active within about and hour to an hour and a half. While a spare MBSU or DDCU could be installed during the same spacewalk, trouble with an ammonia pump unit would cause a significant impact on the mission.
"Let's say the pump doesn't come up, or say I got bit by some software feature like what happened (when a SARJ commanding problem cropped up during the September shuttle mission)," Curry said. "If I can't figure that out within a short period of time, then I have to back out because I couldn't get the cooling done and there's not enough time to do the R-&-R of the pump.
"The pump weighs a lot, it's 1,500 pounds, so that's a complex remove-and-replace scenario. That would take an entire dedicated EVA to do that. There's a plan I've got in place where if the pump didn't come up to speed on EVA-2, then we would give the MMT (Mission Management Team) folks a day to think about it and then the next day after that, we would then use EVA-3 to R-&-R the pump."
In that case, EVA-2 "would end up being a waste of time," Curry said. "That's the part that concerns me, infant mortality. Every time you start up a new system you always learn something. Something could come up to bite us. The problem is, I've only got about an hour to figure that out. The pressure's on the ground. That's the difference between this flight and most others. This is a simple task for the crew. All they have to do is hook up a cable."
In an interview, shuttle commander Mark Polansky agreed, saying flight controllers will be under pressure to make quick decisions if things go wrong.
"You can't just sit there and say, 'I did this and that happened therefore it must have been because of what I did.' It could be because of a lot of things, you've got to be careful not to jump to the wrong conclusion," Polansky said. "And oh by the way, you don't have a day to think about it because people are sucking on their oxygen and using up their (carbon dioxide-absorbing lithium hydroxide). There's a very short fuse here."
Because of safety requirements and the toxic nature of ammonia, electrical components inside the station's pressurized modules are cooled by water circulating through cold plates. That water is then routed to heat exchangers tied into external ammonia loops and radiators.
In the near term, the primary external ammonia system will only be used to cool electrical components mounted on the solar array truss.
NASA planners initially considered having Discovery's crew complete the electrical switch over as well as the plumbing changes necessary to switch the module heat exchangers from interim to permanent cooling. But given the complexity of the electrical work, the cooling system re-plumbing was deferred to early next year when Williams and station commander Michael Lopez-Alegria will tie the module heat exchangers into the primary cooling system during two spacewalks.
10:10 p.m., 12/13/06, Update: Spacewalk timeline unchanged
Despite problems fully retracting a balky solar array, the timeline for Thursday's planned spacewalk by Robert Curbeam and Christer Fuglesang to begin re-wiring the international space station is unchanged and will be carried out as previously published. Here is the integrated timeline, including revision D of the NASA television schedule (in EST and mission elapsed time):
EST........DD...HH...MM...EVENT 10:17 AM...04...13...30...Shuttle crew wakeup 10:47 AM...04...14...00...Statoin crew wakeup 10:52 AM...04...14...05...EVA-2: Crew lock repress to 14.7 psi 10:52 AM...04...14...05...EVA-2: Hygiene break 11:00 AM...04...14...13...Video file on NASA television 11:37 AM...04...14...50...EVA-2: Crew lock depress to 10.2 psi 12:02 PM...04...15...15...EVA-2: EVA preparations 12:27 PM...04...15...40...MCC: Power system channel 2/3 commanding starts 01:02 PM...04...16...15...ISS: Avionics rack 1 jumper installation 01:32 PM...04...16...45...EVA-2: Spacesuit purge 01:47 PM...04...17...00...EVA-2: Spacesuit prebreathe 02:22 PM...04...17...35...Shuttle robot arm (RMS) powerup 02:37 PM...04...17...50...EVA-2: Crew lock depressurization 03:07 PM...04...18...20...Station arm (SSRMS) setup 03:12 PM...04...18...25...EVA-2: Airlock egress 03:22 PM...04...18...45...Station KU comm system off line 03:27 PM...04...18...40...MCC: Power system channel 2B powerdown 03:37 PM...04...18...50...EVA-2: Channel 2/3 power reconfig 04:32 PM...04...19...45...ISS Treadmill vibration control gyro R&R 04:37 PM...04...19...50...EVA-2: EV2: CETA cart 2 relocation 05:07 PM...04...20...20...EVA-2: EV1: CETA cart 2 relocation 06:02 PM...04...21...15...MCC: Power system final activation 06:32 PM...04...21...45...EVA-2: CETA cart 1 relocation 07:42 PM...04...22...55...EVA-2: EV1: Insulation installation 07:52 PM...04...23...05...EVA-2: EV2: EVA bag installation 08:02 PM...04...23...15...EVA-2: EV1: Z1 truss reconfig 08:22 PM...04...23...35...EVA-2: Payload bay cleanup 08:42 PM...04...23...55...EVA-2: Airlock ingress 09:07 PM...05...00...20...EVA-2: Airlock repressurization 09:17 PM...05...00...30...ISS: Avionics rack 1 jumper removal 10:27 PM...05...01...40...RMS powerdown 11:30 PM...05...02...43...Mission status briefing on NASA television 01:47 AM...05...05...00...STS/ISS crew sleep begins
09:00 p.m., 12/13/06, Update: Astronauts gear up for Thursday spacwalk; SARJ rotating, coolant loop primed with ammonia; solar array troubleshooting continues
Space station flight controllers, faced with an unruly solar panel and an increasingly tight schedule, put array troubleshooting on hold late today and pressed ahead with work to ready the lab complex for a critical re-wiring spacewalk Thursday.
In a first for the orbital outpost, flight controllers fired up a massive gear-driven joint on the left side of the station's main solar power truss to begin slowly rotating a new set of arrays like a giant paddle wheel, allowing the panels to track the sun as the station circled the globe.
Engineers then began work to pressurize one of two untried cooling systems in the main truss. If all goes well, a massive pump will begin active cooling Thursday during a spacewalk by Robert Curbeam and Christer Fuglesang to activate one of the station's two main electrical circuits.
Up until now, the U.S. segment of the station has drawn power from an interim system that provided electricity during the initial stages of construction. NASA now needs to switch the station over to its permanent power system to provide the electricity needed by current and future research modules.
The first step in that proces was to retract the left wing of the P6 solar array, the one providing interim power, to clear the way for newly installed arrays on the left side of the main truss to begin rotating as required.
But after more than six-and-a-half hours and repeated attempts to coax the P6 array's two left-side solar blankets to fold up smoothlyl like pleated window shades, the astronauts were only able to retract the central mast about half way, or 17 of 31 40-inch bays.
Some 45 commands were sent to retract and extend the mast in stop-and-start fashion, but the blankets would not fold neatly. Rather than spend any more time on additional cycles, lead flight director John Curry decided to put troubleshooting on hold and to press ahead instead with preparations for Thursday's long-planned spacewalk.
While not an ideal situation, P6 was retracted enough to provide more than 10 feet of clearance between the end of the stalled array wing and the newly installed P4 arrays. That cleared the way for flight controllers to power up the solar alpha rotary joint, or SARJ, to begin rotating the new arrays.
Engineers then began work to pressurize one of two coolant loops on the main power truss with ammonia. Cooling is required to keep big electrical switching units and transformers in the power system from overheating once activated Thursday and drawing power from the P4 arrays and the still-extended right wing of P6.
Another spacewalk is planned Saturday, by Curbeam and new station crew member Sunita "Suni" Williams, to wire in the station's other main circuit and to activate a second ammonia coolant loop.
"The big picture is very simple," astronaut Stephen Robinson radioed the astronauts from Houston. "Flight day 6 (Thursday) will be executed as planned, including EVA-2. We've been practicing a long time, we're ready to do it exactly as written. The solar array is obviously safe for SARJ rotation because it's rotating. The port (cooling system radiator) is on its way to minus 30 degrees and after that, we'll start filling the ETCS (external thermal control system) loops.
"In the background, we're going to call up Team 4 to assemble an EVA plan that would aid in solar array retraction. Now this would be done no earlier than EVA-3 but it could also be EVA-4 or a stage EVA (by the station astronauts). That's what Team 4 will help us work out."
Robinson said even though P6 is not fully retracted, "we are go to execute the rest of the mission as planned, that includes undocking, the Progress (supply ship) docking coming up in a few weeks. So we're actually in a very good config. We appreciate all your hard work today and we're looking forward to a day tomorrow that should be unlike no other on space station."
"We're trying to figure out what 'unlike no other' means," quipped station commander Michael Lopez-Alegria. "In the meantime, we copy everything else you said and we look forward to working with you guys, Team 4's plan. I'm sure that whatever it is we'll be ready to handle it and we'll just stand by for further words."
"Roger that," Robinson replied. "We'll certainly let you know. ... Thanks again for all the hard work on the solar array today."
"Thanks, Steve, we appreciate you taking our participation into account and you know, we all tried as much up here as you guys did on the ground and it just wasn't going to work for us today. But that stuff happens and I'm sure we'll get through it."
"Well Mike, actually we consider it a success," Robinson said. "We're looking at the SARJ rotating on the big screen up there and people are darn happy about that."
"Yeah, Steve, the glass is definitely at least half full," joked the station commander.
07:00 p.m., 12/13/06, Update: Updating extended solar array troubleshooting
Editor's Note...
Due to problems with our automated email delivery system, space updates are being delayed. Please check the STS-116 Current Mission page for realtime updates:
http://www.cbsnews.com/network/news/space/current.html
My apologies for the inconvenience.
Continuing running notes...
A few minutes before 6 p.m., astronaut Stephen Robinson radiod up a revised "big picture" plan, telling the astronauts to re-extend the mast as far as necessary to clear the folding and tension problems and then to retract in stop-and-start fashion one bay at a time.
The mast was re-extended to about 28 bays "and we're ready to retract," astronaut Sunita Williams radioed at 6:02 p.m. "We're going to retract one bay at a time. We're retracting... ready, ready, now."
After one bay, she stopped the motion. Then restarted and stopped again. And again, one blanket slat folded the wrong way. The mast was re-extended to get the fold out and then retracted one bay. That went well, and Williams was cleared to retract two bays at a time after reaching the 23-bay mark without any problems.
Williams then took the mast in to 17-and-a-half bays without any apparent problems and, at 6:24 p.m., continued the retraction. But at 16-and-a-half bays, movement was halted again when the slats at the base of one blanket appeared to be starting to fold the wrong way.
Williams then re-extended the mast about one bay to clear the fold problem and then proceeded to retract one bay at a time. The fold reappeared. The mast was extended then retracted a half bay at 6:37 p.m., more than five hours after the retraction work began. Again, the panel in question began folding over the wrong way.
"We may be converging on a therory here," Lopez-Alegria said. "It looks like the fold between the panels, I don't know the nomenclature, the tabs are called A24 and A25, the fold between those two panels seems more reluctant than the others and that's the one that is apt to fold sort of onto the accordian pile there where we're getting hung up."
"Copy, Mike, thanks for the data. That'll help us," said astronaut Stephen Robinson in mission control.
As a test, the mast was retracted another half bay, to about 16-and-a-half bays, but the astronauts reported the folding slats in question were spilling off to one side. It was the 44th stop or start command issued since the work began earlier in the day.
As Discovery and the station moved back into Earth's shadow, lead station flight director John Curry, deputy space station program manager Kirk Shireman and other top managers huddled near Curry's console in mission control to debate their options.
05:45 p.m., 12/13/06, Update: Astronauts struggle to get balky solar array retracted enough to permit other critical work; troubleshooting continues
Continuing running notes...
Going into their third daylight pass since the retraction work began, the P6-4B solar array wing remained partially retracted with 17.5 40-inch bays of its central mass still extended. Fifteen start-and-stop cycles were needed to get there. Flight controllers ultimately agreed with a suggestion by Discovery commander Mark Polansky to re-extend the mast to 19 bays and then employ a start-and-stop technique to allow any unwanted motion to damp out before it could cause a problem.
By limiting the re-extension to 19 bays, flight controllers were assured of at least 10 feet of clearance between the P6-4B wings and the newly installed P4 arrays on the end of the station's main solar array trust. The goal of Discovery's mission is to re-wire the space station to take advantage of its permanent power system. But to do that, the P4 array must be able to freely rotate to track the sun. And for that to happen, the 4B wings of the P6 array must be retracted at least 40 percent - about 19 bays.
The astronauts told flight controllers they did not believe extending the mast to 19 bays would be enough to clear the problem. But they said in their view there was little risk they would be unable to get back to the 19-bay point. Flight controllers then told them to try it anyway, Williams extended the mast two 19 bays and retracted to 18 before calling an abort.
The same problem developed.
"What we see is the beginning of the same sort of pattern," said station commander Michael Lopez-Alegria. "We stopped at 17-and-a-half bays. And the probelm that we see is simliiar, although not as pronounced. So what we think is indicated is that this problem is, in fact, asociated with this particular spot. I guess that's good news and bad news. Bad news because it's a problem. Good news because it's inside 19 bays.
"What we think we'd recommend is going back out to 19 again and then come back in just to try to gain a little more insight into the repeatability of it. And then if it repeats like we think it will, then reassess at that point. But it may be worthwhile at that point to go beyond 19 and then stop at some point and come back in. We're not clear on how far to go beyond 19 but we can cross that bridge when we come to it."
"That's a great plan, Mike, and we concur entirely with it," said Stephen Robinson from mission control.
The mast was extended to 19 bays and another retraction commanded.
"Retracting, ready, ready, now," astronaut Sunita Williams called at 4:39 p.m. Two and a half bays later, "aborting!"
"Houston, we're just a smidge past 17 bays showing," Polansky said. "It looks like it's very repeatable."
After discussing it further, the astronauts and flight controllers mutually agreed to extend the array until guide wires once again showed the proper tension even if that ultimately meant extending past 19 bays. At that point, wherever it might be, the astronauts would retract in small steps, hoping to maintain the proper tension."
And so, at 4:54 p.m., Williams began re-extending the mast, stopping again at 19 bays. She then retracted a half bay and stopped to evaluate the motion of the slats. After letting the motion damp out, whe restarted retraction. This time, slats on the other panel making up the array wing appeared to fold the wrong way, forcing another abort with 17 and a half bays extended.
The mast was re-extended to 19 bays to clear the folding problem. Another retraction was started and this time, the slats folded the wrong way on the other panel.
Trying a different approach, a decision was made to extend the mast with stop-and-start movements, i.e., to command an extension followed by an immediate abort in hopes the shorter-period, jerkier motion might help.
Lopez-Alegria reported that approach didn't work, saying the modest ripples set up in the blankets was not enough to clear the problems.
At that point, as the shuttle-station complex sailed into Earth's shadow for another night pass, flight controllers told the astronauts the goal was now to get the mast back inside of 19 bays to make sure they could eventually press ahead with plans to start rotating the P4 arrays and priming the solar array truss cooling system with ammonia for the long-planned electrical re-wiring work on tap Thursday.
"We're thinking in terms of EVA solutions we might be able to apply on EVAs 2 or 3, but our near-term goal will be in the next day pass to try to get down to less than 19 bays."
Moving back into daylight around 5:40 p.m., Lopez-Alegria asked for an update.
"The team has made the decision to redeploy beyond 19 until the fold problem has cleared," Robinson said. "Let's hear youyr side and then we'll tell you what we're thinking."
Lopez-Alegria said the array apparently had two problems, one involving random folding issues and the other caused by a tension issue in the guide wires. He suggested repositioning the arrays slightly to provide a better view to help determine if the latter is a cause or an effect.
While engineers thought about that idea, the crew was cleared to re-extend the mast as required to clear the folding problem.
04:10 p.m., 12/13/06, Update: P6 array partially retracted; engineers debate options for coaxing balky array to full retraction
After multiple stop-and-start retractions and extensions, the Discovery astronauts were unable to fully retract a huge solar array. While it eventually retracted enough for another array to start rotating later to track the sun, additional work was needed to coax the balky array into full retraction.
The not entirely unexpected problem threw a wrench into Discovery's tightly choreographed space station re-wiring mission, requiring multiple retraction-extension-retraction cycles to coax the array's venetian blind-like slats to smoothly fold into a storage box at the base of its collapsible central mast.
After several slats folded the wrong way, astronaut Sunita Williams sent commands to redeploy the mast in hopes they would straighten out.
"Going to deploy. Ready, ready, now," Williams called at 2:58 p.m.
The blankets then appeared to unfold normally and the kinks smoothed out as engineers hoped.
"We like that. We'd like you to abort, abort the deploy now," astronut Terry Virts called from mission control.
"OK, aborted."
"Just to let you know, while definitely it's a lot better, it still looks like in that center it's bowed out ... and I'm afraid when we retract it we'll see the same thing," commander Mark Polansky radioed.
"Are you saying you think we need to deploy some more?" Virts asked.
"Our recommendation would be to deploy it a little bit more," Polansky agreed. "We've onely gone one bay so far."
"OK, thanks, give us just one sec while we talk about it."
A few moments later, Virts told the astronauts to continue the extension.
"OK. On three, we're going to deploy," Williams called at 3:01 p.m. "Ready, ready, now."
The panels continued extending. And finally, the two slats that had bowed and folded the wrong way appeared to pop back out and into the right positoin. Williams immediately stopped the extension with 27 of the array's 31 40-inch mast bays extended.
"OK, copy that, we did see it pop in place," Virts said.
After discussing the array's appearence, flight controllers told Williams to attempt another retraction and to collapse the central mast until just two bays remained extended from its storage canister.
"Ready, ready, now," Williams called at 3:09 p.m. "And it looks like that spot, that troublesome spot is folding correctly now."
"Still with a long way to go, that's still good news from Suni Williams, that redeployment of the array cleared the problem," observed NASA commentator Kyle Herring in mission control.
But two minutes later: "Going for an abort," Williams called. "Stand by, we'll get words down to you in a minute. ... We just wanted to check out the tension wires, we saw a little bit of motion. Now that we've stopped everything looks fine. We're happy to continue if you're OK with that."
"OK, Suni, that's good news to hear," Virts said, getting laughs in the control center when he repeated lines made famous during the Apollo 11 moon landing: "You've got a bunch of guys about to turn blue down here. ... You're 'go' to proceed with the retract."
The retraction then resumed, but was aborted again a few moments later when the forward blanket appeared to bow out somewhat. Polansky suggested another re-extension to clear the problem and flight controllers ultimately agreed. "You know, Terry, I kind of think this is going to be one of those things where we're going to go ahead and retract it for a while, and if there's a problem we're going to have to stop and then extend it for a while until it resolves and then maybe retract it again," he said. "It might be just a back-and-forth thing to get it in."
The astronauts then re-extended the array until the blanket slats in question straightened out and then ordered another retraction cycle.
"Retracting. Ready, ready, now," Williams called at 3:28 p.m. A moment later, "Aborting!"
Two slats on one of the blankets folded the wrong way right at the blanket storage box. The mast was re-extended to 27.5 bays, the slats straightened out and Williams tried again.
"Ready, ready, now," she called at 3:33 p.m. Then: "Aborting."
"Houston, Discovery, now the problem's over there on that first panel on the forward, the first panel from the blanket box, right smack dab in the middle, it looks like its bowing out against the fold," Polansky reported. "We thought it had popped out, but I guess not."
Once again, the mast was extended, this time to nearly its full length of 31 bays. And then another retraction cycle began.
"So far, all looks good," Williams radioed as the mast began pulling the blankets back in. A few moments later, "Still looking good..."
But at 3:41 p.m., "Going for the abort," Williams called. "We count about 19 bays and the reason we aborted is that the guide wires looked a little slack."
"OK, copy, about 19 bays," said Virts. "We're going to take a look at it."
He then told Williams to retract one additional bay. There were no folding problems, but the blankets did not appear to be under as much tension as one might expect. In any case, flight controllers told her to resume retraction, saying "Suni, keep on pressing. You're go to retract until you see a problem."
But she had to stop again with 17-and-a-half bays still extended. Again, it appeared critical cables used to keep tension on the blankets were not applying enough force. Polansky was not sure if the panel could be extended enough to clear the problem without passing through the 19-bay point, the minimum amount of retraction required to permit engineers to begin rotating the newly installed P4 solar arrays later today.
As the shuttle-station complex passed from orbital daylight into darkness, engineers told the astronauts to stand by pending additional discussion about what to do.
2:10 p.m., 12/13/06, Update: P6 solar array retraction aborted; engineers assess kinks in solar blankets
In a make-or-break first step in an ambitious mission to re-wire the international space station, the Discovery astronauts today began retracting a huge solar array to clear the way for a complicated electrical job. But the venetian blind-like blankets on one side developed kinks and folds that forced the astronauts to abort the procedure.
Not sure how the array will behave after being fully extended for six years, the astronauts sent commands to retract it just a few feet before a photo survey to assess it's health.
"Houston, Discovery on the big loop," astronaut Sunita Williams called down to mission control in Houston. "Going to retract... ready, ready, now." A few seconds later, she reported "one bay is in... two bays in... three bays, hitting the abort button now."
After stopping the retraction, the astronauts inspected the complex collapsible mast and the folding blankets that make up the P6-4B solar wing to make sure all the linkages in the mast were in good shape and that the blankets were folding as expected.
The P6-4B solar array features two solar blankets to either side of a central mast that fold up like the slats in venetian blinds. The open-framework mast extends 31 40-inch bays and is designed to collapse from the base as a motor pulls the moveable linkages down into a storage canister.
Television views from space showed a slight kink in a crease between to slats of the blanket at one end that appeared to be folding in the wrong direction.
"OK, Terry, the only thing that I see ... is if you look at the zenith most array and from the blanket box you count maybe one, two, three folds, right there in the middle, it kind of looks like it's popped out a little opposite of the way it's going to fold," commander Mark Polansky radioed Houston. "I don't think it's a problem. ... if you want to look further, let me know."
The astronauts continued a detailed photo survey while flight controllers assessed the health of the system.
"So far, it looks great," astronaut Terry Virts radioed a few minutes later from mission control. "We have a small change to the plan. We're going to ask you to retract two more bays and while you do that, keep one of the cameras pointed at that area of interest. We think it's not going to be a problem, we think it's going to retrtact fine. We just want to verify that."
Williams then sent commands to continue the retraction, stopping after two more bays of the mast collapsed into its canister. "That's four bays... five bays, hitting the abort button now," Williams reported. Video showed generally smooth folding in the body of the array, but slats toward the bottom, where the mast retracts into its storage canister, appeared misaligned and not folding smoothly. Engineers did not appear overly concerned, but they wanted to be sure they understood the situation before proceeding.
The array must be retracted at least 40 percent to permit a newly installed set of arrays - P4 - on the left end of the station's main power truss to rotate as required to track the sun. The flight plan calls for that rotation to begin later today, a requirement before the astronauts can stage a spacewalk Thursday to switch the station from it's temporary to its permanent power system.
After discussing the situation, flight controllers gave the astronauts permission to continue the retraction to the point where just two bays extended from the storage canister. The original plan called for retracting all the way to one bay, but engineers decided to double that to provide additional safety margin.
"Ready, ready, now," Williams radioed at 2:05 p.m. Moments later, after three or four more bays retracted, she aborted the procedure.
Video showed major kinking in the aft blanket toward its base, raising questions about whether or not the blanket would, in fact, fold up.
"The part on the forward array cleared itself almost immediately," Polansky reported, referring to one of the two blankets. "On the aft array, however, there was a lot of oscillation going on.
"It looked a couple of times like it was going to fold correctly, but then it started kind of bowing out in a nadir direction and we just got uncomfortable."
Flight controllers told the astronauts to hold off any additional retraction while engineers assess the situation. Polansky suggested re-extending the blankets and then trying another retraction.
"OK, thanks for the words," Virts replied. "The options you were just talking about are exactly what we're talking about on the ground."
"I mean, the best analogy I can give is ... it's kind of like folding a map up," Polansky said. "You have the fold in the paper and if you start folding it and the fold's going the wrong way, you try a little bit but you get to the point where it bows out and there's nothing you can do but pop it back in place or unfold it and try again."
(Editor's note... this story will be updated throughout the day.)
02:50 a.m., 12/13/06, Update: Critical solar array retraction kicks off station re-wiring work
With one successful spacewalk behind them, the Discovery astronauts, the space station's crew and scores of engineers and flight controllers move into the most critical phase of the current station assembly mission today with the planned retraction of a huge solar array wing.
The solar wing, known as P6-4B, has been extended for six years and no one knows if it will retract smoothly or cause problems. But retract it must to permit another set of arrays to begin rotating to track the sun and to clear the way for spacewalks Thursday and Saturday to switch the station over to its permanent power system.
"This is a major milestone for the program," John Curry, lead station flight director, told reporters late Tuesday. "Tomorrow is the beginning, it's a four-day sequence that we have spent a lot of time pursuing.
"Many, many people have spent a lot of time training to do this because the station, for all this time, has been in this infant stage and we need to go to the permanent system so we can add the Japanese module, Kibo, and so we can add (the European Space Agency's) Columbus later in '07 and '08. So how do I feel? I feel anxious. I'm ready to go and my team is ready to go."
The goal of Discovery's mission is to re-wire the station, re-routing power from an interim system, used during the lab's initial assembly, to a much more capable, much more complicated permanent system that will provide the electricity needed to eventually support research in the U.S., European and Japanese laboratory modules.
"All this reconfiguration we have to do on (Discovery's mission), those are big steps," said Paul Hill, mission operations manager at the Johnson Space Center. "It doesn't sound like much. It sounds pretty mundane and nerdy. We're sending a bunch of commands, changing over electrical and thermal controls. (But) when we first came up with this sequence in 1994, we all sat back and said, 'how are we going to figure this one out?'
"Today, the folks who have been leading that effort feel pretty good they've got their arms around it but they're ... keeping their fingers crossed that everything goes well."
Here is a timeline of today's activity (in EST and mission elapsed time):
10:17 AM...03...13...30...Shuttle crew wakeup 10:47 AM...03...14...00...Station crew wakeup 12:47 PM...03...16...00...Shuttle roboar arm (RMS) powerup 01:22 PM...03...16...35...Logistics transfers resume 01:22 PM...03...16...35...P6-4B array retracted 3 bays 01:32 PM...03...16...45...P6 photo survey 02:02 PM...03...17...15...P6-4B retracted to 1 bay 02:57 PM...03...18...10...P3 solar alpha rotary joint begins sun tracking 03:17 PM...03...18...30...SAFER jet backpack checkout 03:22 PM...03...18...35...P6 solar array blanket box unlatched 03:52 PM...03...19...05...EVA-2: Equipment lock preps 04:17 PM...03...19...30...Loop B coolant loop filled with ammonia 04:37 PM...03...19...50...Crew meals begin 06:00 PM...03...21...13...Post-MMT briefing on NTV 06:17 PM...03...21...30...P6 port wing final 1 bay retraction 08:07 PM...03...23...20...PAO Event (audio only) 09:12 PM...04...00...25...P6 solar array blanket box latched 10:02 PM...04...01...15...EVA-2: Procedures review 10:27 PM...04...01...40...RMS powerdown 11:30 PM...04...02...43...Mission status briefing 01:17 AM...04...04...30...EVA-2: Crew airlock to 10.2 psi 02:17 AM...04...05...30...STS/ISS crew sleep beginsThe space station's main solar array truss sits atop the Destiny laboratory module at right angles to the axis made up of the station's pressurized modules.
The S0 truss segment sits in the middle atop the lab, flanked by the S1 and P1 truss elements. S0, S1 and P1 house the major electrical components of the permanent electrical system: Four main bus switching units, or MBSUs, and transformers called DC-to-DC converter units - DDCUs - that serve to step down and regulate solar array power to levels needed by station equipment.
S1 and P1 also house the station's two independent cooling systems, each of which include large ammonia tanks, a nitrogen gas pressurization system and a massive pump module to pushes ammonia coolant through cold plates and heat exchangers and out into deployable radiators, three on S1 and three on P1. To maximize heat rejection, the radiators are mounted on a rotating beam that can point them toward the cold of deep space.
In September, the crew of mission STS-115 attached two new truss segments to the left side of the solar array beam. The first, P3 (there is no P2) features a powerful solar alpha rotary joint, or SARJ, while the second, P4, includes a new set of solar arrays that stretch 240 feet from tip to tip.
The solar array truss eventually will feature two SARJ joints, one on each side, to rotate the station's solar arrays like giant paddle wheels as the lab complex circles the Earth. That rotation, 360 degrees every 90-minute orbit, will keep the arrays generally face on to the sun. The orientation of the blankets can be fine tuned by so-called beta gimbal assemblies, or BGAs, that automatically adjust the pitch of each solar array wing like the orientation of an airplane propeller can be adjusted in flight.
Discovery docked with the space station on Monday. That same day, the astronauts used the shuttle's robot arm to pull a short spacer segment - P5 - from the orbiter's cargo bay. The 4,110-pound tress segment was attached to P4 during a spacewalk Tuesday by Robert Curbeam and Christer Fuglesang.
The space station's electrical system was designed to operate in an interim mode during the initial stages of construction, using a set of arrays known as P6. Those arrays currently are mounted on the end of a truss segment known as Z1, which extends upward, toward zenith, from the Unity connecting module. P6 provides power to six DDCUs and two others in the Z1 truss. An interim cooling system keeps the electrical components from overheating.
Before the station's power system can be reconfigured - the major goal of Discovery's mission - the left wing of the P6 array, known as the 4B wing, must be retracted to permit the newly installed P4 panels to rotate as needed to track the sun. The right wing of P6 - the 2B wing - will be retracted during the next shuttle flight in March. If all goes well, P6 will be moved, bolted to the P5 spacer truss and its 2B/4B solar blankets re-extended during a shuttle flight next fall.
"Until now, P6 has been parked in an interim location in the middle of the truss on top of Unity," said Hill. "Not only has it provided electricity, but it used a smaller, temporary cooling system for the U.S. segment until the MBSUs and the more robust permanent cooling system were installed and activated.
"This set up has worked very well, but it also means we have many electrical and cooling lines connected to the early or temporary systems, rather than the permanent or assembly-complete architecture.Ê In order to finally connect all of the powered equipment to the their permanent power and cooling sources, the vast majority of the U.S. equipment must be powered down, the connections physically switched by spacewalking astronauts, then powered back up.
"This is a long, choreographed activity in order to ensure at least one of every critical component remains powered throughout the reconfigurations," he said. "The important element in all of this is that the additional power provided by the new solar arrays and the additional cooling the permanent cooling system provide are necessary before we can install the Japanese and European research laboratories which are also coming in the next year."
Early today, flight controllers are scheduled to begin moving critical station operations from hardware powered by the 4B solar array (through channels 1 and 4) over to hardware powered by the 2B solar array (through channels 2 and 3). The goal is to get the total load on the 4B array to around 6.5 kilowatts. That work will begin around 9 a.m.
Later in the morning, flight controllers plan to execute a procedure known as "seamless power channel handover," which will move the 6.5-kilowatt load remaining on the P6-4B wing to the newly installed P4-4A wing on the left end of the main solar array truss. Once the handover is complete, the still-extended P6-2B wing will be providing power to station channels 2 and 3 while P4-4A will be powering channels 1 and 4.
At that point, shortly before 1:30 p.m., the astronauts will send commands to retract the left side P6-4B solar array wing. The wing must be retracted at least 40 percent to provide the clearance needed for the new P4 array to rotate as needed to track the sun. But from a structural loads standpoint, the array must be retracted to the point where no more than one of the 31 bays making up the central mast remains extended.
"Flight directors always worry about the worst case," Curry said in an interview. "These wings have been out there for six years now, taking thermal cycles and those kinds of things. The mechanism is relatively complicated. There's a chance that we might have a problem with that."
Working in a step-by-step fashion, the astronauts first will send commands to retract the mast the length of three 40-inch bays. If that goes well, retraction will resume and continue to the point where only one bay remains extended. All of that will happen during a single 45-minute-long daylight pass.
"We're going to retract to three bays, stop, survey, make sure everything looks good then start back up again," Curry said. "Then we're going to go from three bays all the way down to one bay, which is about 40 inches. I think there's a good chance that we could end up staying at that location for a long time. I've gotten the loads people to tell me that from an attitude control perspective, from a shuttle undocking perspective, those kind of things, I could go ahead and do the rest of the mission and still keep the array not fully retracted, keep the array at one bay."
The reason that might be needed is because the solar blankets, which were packed up like venetian blinds for launch, might not fold up smoothly during retraction."
"What I'm telling you is there's a decent chance that won't happen during the 116 mission, or that day, and I don't particularly care because it doesn't stop me from doing the rest of the flight," Curry said. "Why would I think we might stop at one bay? The analogy I always give people, when we buy a map at the store it's nice and compressed. But when you start using your map for six years and you decide it's time to fold it back up again, it doesn't fold as tightly as when it was bought at the store. That's what's going to happen here. There's definitely going to be some waves on those folds even if it comes back perfectly.
"So I think there's going to be some concern with compressing that last 40 inches because you could potentially be breaking glass, damaging those cells. So if I'm benign there, I'll let the engineering guys assess that for weeks, let them get comfortable and figure out whether it's a good idea to compress that final 40 inches and latch down.
"My goal for 116, to allow me to execute the rest of the flight, is to get to one bay. If everything's great, we'll go ahead and do the final retraction. (If not) I don't want anybody to think that that means something's bad, it just means we're being conservative."
If the array doesn't retract for any reason, gets jammed or suffers some sort of mechanical failure, Curbeam and Fuglesang can attempt repairs during a subsequent spacewalk - the array can be retracted manually if the drive motor fails or the spacewalkers could attempt to re-spool a tensioning cable if it popped off its rollers.
But there is little else the spacewalkers can do. If a problem crops up that can't be fixed, they are prepared to dump the costly array overboard.
"If you have your three-sigma bad day, those are your two big things," Curbeam said in an interview with CBS News. "Hopefully it's just a motor problem or a gear problem where you can just retract it manually, which is fine. It's going to take a long time to get that done, but we can do it.
"But if that's not working for you, and the right answer comes out we've got to get rid of this thing so we can have fairly normal ops, well, we get rid of it. In the big scheme of things, if you have to fabricate and fly another array, that's a lot better than some of the bad things that can happen when you have a piece of structure that's been compromised on the station, i.e., it can come off, it can hit something. Not a good idea."
The P6 arrays cannot be moved to their eventual P5 attachment point with either wing extended. Aside from extremely tight clearance issues, a structural analysis indicates the fragile support mast likely would fail if subjected to the sort of loads it would experience being moved about on the end of the station's robot arm.
"That would be reassessed in realtime," Curry said. "But when we previously looked at it, it had two issues. Kinematically, it was really hard to figure out how to move the wing using the arm and move it out forward and just not hit anything. And then secondarily, and this is the one that killed it, they determined that because these wings are so flimsy you would end up permanently damaging them on the way to moving them outboard. Otherwise... the preference would be not to retract."
In any case, jettisoning the arrays is a strictly worst-case scenario.
"Let's say we start retracting and one of the battens breaks or the mast starts to ball up on itself or the array just gets all crumpled up on itself to the point where it can't be fixed," Curry said. "That's the only way we would ever consider that.
"I haven't spent a lot of time worrying about this because I can't imagine the program telling us to dump those arrays on this mission. If the array got stuck, I think we would spend a lot of time, two EVAs worth, trying to figure out what's wrong with the arrays and if there's any way to fix it. That means another flight has to be added to the manifest anyway."
Assuming P6-4B successfully retracts, flight controllers will configure its fully charged batteries to operate in "parachute mode." While the three nickel-hydrogen batteries cannot easily be recharged with the port array retracted, they can provide up to eight hours of emergency power to channel 1/4 if any problems crop up with the P4 arrays.
Then, within an hour of solar array retraction, computer commands will be executed to power up the left-side solar-alpha rotary joint, or SARJ, to begin rotating the P4 solar arrays as needed to track the sun. Because of the angle between the sun and the plane of the station's orbit, the array must start active tracking right away to generate enough power in the absence of the P6-4B wing.
"Once we get retracted down to one bay, I have a 'go' for loads and attitude controls so I can start rotating P4," Curry said. "This is going to be cool because we're going to be retracting P6 and rotating the SARJ ... basically at the same time. That will put the SARJ in the configuration where it starts tracking the sun like it's supposed to do. First time we will have done that. There are a lot of people really worried about the loads of this and trying to determine how much momentum we put into the system because of the fact that the wings are out."
When the SARJ is activated, control computers will carry out calculations to determine where the sun is relative to the arrays. The massive joint then will be driven at a higher-than-normal rate to get in the proper position. When the SARJ drive motor engages the teeth of a large gear and begins turning, the arrays will be deflected as momentum is transferred to the fragile mast.
"It will put momentum into the system," Curry said. "Because the way it works, as soon as you do that SARJ activation it's calculating an algorithm and figuring out where the sun is and it moves itself to wherever the sun is. So it could go forward or backward depending on where the sun is and when we start it up. ... It will dump momentum into the system, that's for sure."
With P6 successfully retracted and the port-side SARJ slowly rotating the new P4 arrays, the stage will be set for a second and third spacewalk to carry out the main power switch over that is the primary goal of Discovery's mission.
10:15 p.m., 12/12/06, Update: Spacewalk ends
Astronauts Robert Curbeam and Christer Fuglesang re-entered the space station's Quest airlock module, sealed the hatch and began repressurizing at 10:07 p.m. to successfully close out the first of three spacewalks planned for the shuttle Discovery's mission.
The six-hour 36-minute excursion, the 74th devoted to station assembly and maintenance, pushes total space station EVA time to 450 hours and 50 minutes since construction began in 1998.
Including three spacewalks during a 2001 station visit, Curbeam has now logged 26 hours and 25 minutes of EVA time over four spacewalks, moving him to 21st on the list of most experienced spacewalkers. Tonight's outing was the first for Fuglesang, Sweden's first astronaut.
The primary goal of the spacewalk was to bolt a new solar array truss segment to the left end of the station's main power beam. The astronauts also repositioned a grapple fixture and replaced a faulty television camera on the opposite end of the truss. Finally, they performed a few minor "get ahead" tasks to save time for future assembly crews.
Before ending the spacewalk, Curbeam radioed congratulations to John Mather, a NASA astrophysicist at the Goddard Space Flight Center in Greenbelt, Md., who shared this year's Nobel Prize in physics for his work studying the remnant heat left over from the big bang birth of the universe.
"I just want to say congratulations to all the Nobel Prize winners this year and especially to John Mather of the Goddard space center," Curbeam said. "We're proud of you."
"Thanks to both of you for those very gracious words," astronaut Stephen Robinson radioed from mission control. "And from here on the ground, we'd like to extend our congrtatulations for a 100 percent successful first EVA. It was a real pleasure for us to watch it."
08:30 p.m., 12/12/06, Update: Grapple fixture moved; get-ahead tasks complete; camera replacement in work
Spacewalkers Robert Curbeam and Christer Fuglesang are moving to the right end of the space station's solar array truss to replace a camera needed for the next shuttle assembly mission. Four hours and 50 minutes into a planned six-hour spacewalk, the astronauts have completed all of their other objectives: attachment of the P5 spacer truss segment; relocation of a radiator grapple fixture; and several "get-ahead" tasks, including electrical connections between P5 and the P4 solar array segment and tests of a cable lock assembly. The camera replacement work is the final item on today's spacewalk agenda.
06:50 p.m., 12/12/06, Update: P5 segment attached; grapple fixture relocation in work
Spacewalkers Robert Curbeam and Christer Fuglesang successfully bolted a short spacer segment to the space station's main solar power truss today to accomplish the primary objective of their planned six-hour excursion. After moving a cooling system radiator panel grapple fixture, the astronauts will float to the far end of the truss - on the right side of the station - and replace a camera needed for future assembly work.
05:50 p.m., 12/12/06, Update: Shuttle heat shield in good shape; no focused inspection required
NASA's Mission Management Team met today and decided against ordering any additional heat shield inspections by the shuttle Discovery's crew.
Earlier today, image analysts and engineers completed an assessment of post-launch heat shield inspection video and other data, along with an impromptu inspection late Monday to check the health of Discovery's left wing leading edge panels. Data from a sensor indicated a possible low-energy micrometeoroid hit on the outboard section of the leading edge earlier Monday.
In addition, photography by the station crew during Discovery's final approach to the outpost earlier Monday revealed some tile dings near an umbilical door in the shuttle's belly. But the MMT decided the damage was minimal and not a threat to the shuttle during re-entry.
As such, no additional "focused" inspections will be required Wednesday. The astronauts will, however, carry out a final heat shield inspection after leaving the station next week, as originally planned, to check for any signs of damage since the initial inspection was completed.
"Based on all the imagery gathered so far, no focused inspection is required," astronaut Kevin Ford radioed Discovery today during the first of three planned space station assembly spacewalks. "And the TPS (thermal protection system) is not suspect."
"Well that's outstanding news!" said shuttle skipper Mark Polansky. "I read the MMT summary and saw some of the pictures, so it sounds like you guys have obviously done your usual, thorough analysis and we're happy to hear we can go on with the normal timeline tomorrow."
"Good news for us, too," Ford said. "Hated to bother you during the EVA but thought you might be interested in that."
"I'd be really interested in that," Polansky said. "And then my understanding from that is that with regards to the wing leading edge system, everything else, we'll just kind of use late inspection as a confirmation or just a chance to go ahead and see if there were any problems we might have missed."
"That's absolutely right, that's the plan," Ford said.
"OK, well that's great," Polansky replied. "That'll give us a great start tomorrow for the solar array retract and we do have some tremendous views out the window to enhance that. So hopefully, that'll work according to the plan."
He was referring to the planned retraction of one side of the P6 solar arrays that have been providing power to the U.S. segment during the initial assembly of the space station. During two spacewalks Thursday and Saturday, the astronauts will switch the station over to its permanent power system. But first, the crew must successfull retract the P6-4B array. That's the crew's major objective Wednesday.
05:15 p.m., 12/12/06, Update: P5 truss positioned for attachment
An hour and 45 minutes into a planned six-hour spacewalk, astronauts Bob Curbeam and Christer Fuglesang are on schedule and gearing up to bolt a new spacer segment to the space station's P4 solar array truss.
Four protective launch locks have been removed and Sunita Williams and Joan Higginbotham, operating the station's robot arm from inside the Destiny laboratory module, have successfully moved the P5 spacer segment a final eight inches, permitting Curbeam and Fuglesang to begin the process of bolting the structure to P4.
One concern going into today's spacewalk was tight clearance between the P5 spacer and a device called a sequential shunt unit, or SSU, on the P4 segment. The P4 arrays are not yet providing power to the station and most of the electricity being generated is being routed back into the solar cells by the SSU to be dissipated as heat.
Williams and Higginbotham, relying on verbal guidance from the spacewalkers, guided P5 into position with just two inches or so of clearance.
"Ah, that's beautiful," Fuglesang said as P5 inched into position.
"Yes, it is," Curbeam agreed.
A few moments later, two guidance pins on Curbeam's side of the structure were in position while Fuglesang's were still slightly out of alignment. The arm operators then ran a procedure to use a bit more force to get all four guidance pins properly seated.
"We don't want to scream on the loops, but we're realy happy," Higginbotham radioed when the last pin was in place.
"You're not the only one," Curbeam said.
It will take about an hour and a half to tighten the four bolts, attach electrical grounding straps and a wireless communications system connector to complete P5's attachment.
03:40 p.m., 12/12/06, Update: Spacewalk begins
Floating in the Quest airlock module, astronauts Bob Curbeam and Swedish flier Christer Fuglesang switched their spacesuits to internal battery power at 3:31 p.m. to begin a planned six-hour spacewalk.
It will take about a half hour for the spacewalkers to set up the tools and safety tethers needed for today's work to attach a short spacer segment to the space station's solar array truss. Another hour will be required to remove launch locks before the attachment work begins around 5 p.m.
This is the first of three spacewalks planned for Discovery's mission and the 74th devoted to station assembly or maintenance since construction began in 1998. Going into today's excursion, 45 Americans, 13 Rusians, two Canadians and one astronaut each from Japan, France and Germany had logged 444 hours and 14 minutes building and maintaining the lab complex.
This is Curbeam's fourth spacewalk. He completed three earlier station assembly spacewalks in 2001, logging 19 hours and 49 minutes. Fuglesang, Sweden's first man in space, is making his first EVA.
Curbeam's call sign is EV1; his spacesuit has red stripes on the legs; Fuglesang is EV2; his spacesuit has no stripes. Based on the presumed start time for today's excursion, here is an updated timeline (in EST and event elapsed time; NOTE: for guidance only; actual times likely to change).
EST........HH...MM...EVENT 03:31 PM...00...00...Spacesuits to battery power (actual) 03:36 PM...00...05...Airlock egress; tool setup 04:01 PM...00...30...P5 launch lock removal (1 hour) EV1: Corners 1 & 3 setup; EV2: Corner 2 setup Verbal guidance for station arm (SSRMS) P5 move in to 8 inches EV1: Launch lock removal (corner 3); EV2: launch lock removal (corner 2) EV1: Launch lock removal (1); EV2: launch lock removal (4) 05:01 PM...01...30...P5 to P4 attachment (1.5 hours) Verbal guidance for SSRMS P5 move in to soft capture EV1: Bolt 1 (forward top) torque; EV2: bolt 2 (forward bottom) EV1: Bolt 3 (aft top); EV2: bolt 4 (aft bottom) EV1: Ground strap 3 installation; EV2: ground strap 4 EV1: P4 soft capture pin 3 removal; EV2: P5 wireless connector EV1: Bolt 1 final torque; EV2: Bolt 2 final torque EV1: P4 soft capture pin 1 removal; EV2: ground strap 2 06:31 PM...03...00...Radiator grapple fixture (PVRGF) move to P5 keel (1 hour) 07:31 PM...04...00...S1 truss CP3 camera R & R (1.5 hours) EV1: CP3 worksite setup; EV2: Camera retrieval from airlock EV1: Failed camera removal; EV2: same EV1: Spare camera installation; EV2: same 09:01 PM...05...30...Payload bay cleanup 09:21 PM...05...50...Airlock ingress 09:41 PM...06...10...Repressurization begins; spacewalk ends
11:15 a.m., 12/12/06, Update: Astronauts gear up for spacewalk to install truss segment
The Discovery astronauts are gearing up for their first spacewalk today, a planned six-hour excursion to bolt a new 4,110-pound spacer segment to the left side of the international space station's main solar array truss. Astronaut Robert Curbeam, call sign EV-1, and Swedish flier Christer Fuglesang, call sign EV-2, are scheduled to exit the station's Quest airlock module around 3:42 p.m.
The astronauts were awakened around 10:50 a.m. by a recording of "Waterloo" by the Swedish group ABBA beamed up from mission control in Houston.
"Good morning, Discovery," astronaut Shannon Lucid radioed from mission control. "And a special good morning to you this morning, Christer, and we wish you well as you step outside of the airlock for the first time today."
"Morning Houston, thanks a lot," Fuglesang replied. "Nice music this morning."
Curbeam and Fuglesang, Sweden's first man in space, spent the night in the station's NASA airlock with the pressure lowered to 10.2 pounds per square inch. The so-called "campout" procedure is designed to help the spacewalkers avoid the bends after working in their 5 psi spacesuits. After a hygiene break today, they will re-enter the airlock and lower the pressure again before donning their spacesuits.
This is the first of three spacewalks planned for Discovery's mission and the 74th devoted to station assembly or maintenance since construction began in 1998. Going into today's excursion, 45 Americans, 13 Rusians, two Canadians and one astronaut each from Japan, France and Germany had logged 444 hours and 14 minutes building and maintaining the lab complex.
For identification purposes, Curbeam's spacesuit features red stripes on the legs while Fuglesang's is unmarked.
Here is a timeline of today's activities (in EST and mission elapsed time):
12/12/06 10:47 AM...02...14...00...Shuttle crew wakeup 11:17 AM...02...14...30...Station crew wakeup 11:22 AM...02...14...35...EVA-1: Crew airlock 14.7 psi repress 11:22 AM...02...14...35...EVA-1: Hygiene break 12:07 PM...02...15...20...EVA-1: Crew airlock depress to 10.2 psi 12:52 PM...02...16...05...Station arm (SSRMS) to preinstall setup 02:02 PM...02...17...15...EVA-1: Spacesuit purge 02:17 PM...02...17...30...EVA-1: Spacesuit oxygen prebreathe 03:07 PM...02...18...20...EVA-1: Crew lock depressurization 03:42 PM...02...18...55...EVA-1: Airlock egress 04:07 PM...02...19...20...EVA-1: P5 launch lock removal 05:07 PM...02...20...20...EVA-1: P5/P4 attachment 06:37 PM...02...21...50...SSRMS (at worksite 7) ungrapples P5 06:37 PM...02...21...50...EVA-1: Keel pin relocate 07:37 PM...02...22...50...EVA-1: S1 camera R & R 09:07 PM...03...00...20...EVA-1: Payload bay cleanup 09:17 PM...03...00...30...SSRMS mobile transporter moves to worksite 3 09:27 PM...03...00...40...EVA-1: Airlock ingress 09:52 PM...03...01...05...EVA-1: Airlock repressurization 10:17 PM...03...01...30...Shuttle arm (RMS) powerdown 10:17 PM...03...01...30...Logistics transfer tagup 11:30 PM...03...02...43...Post MMT/mission status briefing on NTV 12/13/06 12:02 AM...03...03...15...Cameras positioned for P6 retraction 02:17 AM...03...05...30...Shuttle/station crew sleep begins 03:00 AM...03...06...13...Daily video highlights reel on NTV 04:00 AM...03...07...13...MMT briefing replay on NTV 07:30 AM...03...10...43...Station flight director update on NTV 09:00 AM...03...12...13...NASA video file on NTV 10:17 AM...03...13...30...Discovery crew wakeupTo put today's spacewalk in context, it is helpful to review the current configuration of the international space station.
The lab complex currently consists of six pressurized modules. At the back end of the outpost is the Russian Zvezda command module featuring two solar arrays and an aft docking port that can accommodate Progress supply ships or Soyuz crew capsules. An airlock/docking module called Pirs is attached to a downward-facing port on Zvezda's front end. Zvezda's forward port is attached to the Russian Zarya module, a supply and propulsion segment equipped with its own pair of solar arrays.
Zarya's front end is bolted to a pressurized mating adapter that, in turn, is attached to NASA's Unity module, a multi-hatch node with six ports. Its starboard port is occupied by the Quest airlock module while its upper, or zenith, port accommodates the Z1 truss and the P6 solar arrays that for the past six years have provided power to the U.S. segment. Unity's downward facing port is used by cargo modules brought up by the shuttle and its port hatch is home to another pressurized mating adapter that will be relocated later in the assembly sequence.
Unity's forward port is attached to the Destiny laboratory module. On the forward end of Destiny is another pressurized mating adapter used as a docking port by visiting space shuttles. On top of the lab module is the station's multi-segment solar array truss, which is mounted at right angles to the long axis formed by the pressurized modules.
The S0 truss segment sits in the middle atop the lab, flanked by the S1 and P1 truss elements. S0 houses the major electrical components of the permanent electrical system: four main bus switching units, or MBSUs, and transformers called DC-to-DC converter units - DDCUs - that serve to step down and regulate solar array power to levels needed by station equipment.
S1 and P1 house the station's two independent cooling systems, each of which include large ammonia tanks, a nitrogen gas pressurization system and a massive pump module to pushes ammonia coolant through cold plates and heat exchangers and out into deployable radiators, three on S1 and three on P1. To maximize heat rejection, the radiators are mounted on a rotating beam that can point them toward deep space and away from the sun.
In September, the crew of mission STS-115 attached two new truss segments to the left side of the solar array beam. The first, P3 (there is no P2) features a powerful solar alpha rotary joint, or SARJ, while the second, P4, includes a new set of solar arrays that stretch 240 feet from tip to tip.
The solar array truss eventually will feature two SARJ joints, one on each side, to rotate the station's solar arrays like giant paddle wheels as the lab complex circles the Earth. That rotation, 360 degrees every 90-minute orbit, will keep the arrays generally face on to the sun. The orientation of the blankets can be fine tuned by so-called beta gimbal assemblies, or BGAs, that automatically adjust the pitch of each solar array wing like the orientation of an airplane propeller can be adjusted in flight (solar array orientation diagram).
Up to this point, the MBSUs, their associated electronics and the two cooling loops have never been fully activated. The goal of Discovery's mission is to activate the electrical and cooling equipment in the solar array truss and to rewire the station so all of its solar array power is routed through the MBSUs.
The Discovery astronauts docked with the station Monday and used the shuttle's robot arm to pull a short spacer segment - P5 - from the orbiter's cargo bay. The 4,110-pound tress segment then was handed off to the station's robot arm and positioned near the left end of the main solar array truss.
Today, Curbeam and Fuglesang will carry out a spacewalk to connect P5 to the outboard side of the P4 solar array segment. The spacer measures 11 feet long, 14 feet 11 inches wide and 13 feet 11 inches tall. Next year, the P6 arrays now providing interim power atop the Z1 truss will be moved to the left end of the power truss and bolted to P5.
NASA planners initially planned for Curbeam and Fuglesang to manually move P5 into position and then bolt it into place. But due to an oversight, planners did not realize the current position of P4 would leave the spacewalkers with just two inches of clearance while moving the spacer into place.
As a result, Sunita Williams and Joan Higginbotham, operating the station's robot arm from inside the Destiny laboratory module, will position P5 while Curbeam and Fuselgang, positioned near P4, provide visual guidance and verbal cues.
"They move it in for the mating and then Christer and I actually bolt it manually," Curbeam said in an interview. "It doesn't have the automatic (attachment) system. They'll bring it in really, really close, we'll take the launch locks off, which actually just protect the mating bolts, and once we take the launch locks off ... we drive the bolts to permanently connect them."
Spacer truss P5 attachment to P4 solar array segment
During the final stages of P5 installation today, the truss segment will pass within two or three inches of the sequential shunt unit on the P4 solar array segment, "which all the juice from the solar array goes through," Curbeam said. "Not a good thing to hit."
"As a matter of fact, that's why we ended up doing it robotically. The first idea was to grab it and put it in by hand. But the problem was, when they did the evaluation, they had the SARJ angle wrong. The sequential shunt unit was in the wrong orientation for mating. So they thought they had plenty of clearance, they said you can do this by hand. Then I went like, wait a minute, no, I'm looking at it and I see two inches of clearance, maybe and inch and a half. And they went like, no. Then we did our homework and like yes!
"I said there's no way - and it's a blind mate if you do it EVA - there's no way I can sit here with a straight face and tell (lead station flight director) John Curry that I wasn't going to hit that thing. So I told him, I said John, I'm sorry but we've got to look at a different way of doing this because I can't tell you we're not going to hit it. It was a blind stick.
"I think everyone is comfortable with the arm install now," Curbeam said. "But in the beginning, they said hey, this is not what we had planned. I said I know it's not, but I don't feel comfortable doing this EVA because if we do it ourselves we are going to hit something. ... if we hit that SSU, that could turn into a really, really bad scene quickly."
Along with attaching P5, Curbeam and Fuslegang will re-position a radiator grapple fixture and replace a faulty camera on the S1 truss segment that will be needed next year when astronauts build out the right side of the solar array beam.
Once today's first spacewalk is out of the way, the astronauts and ground controllers will turn their attention to the heart of mission STS-116: electrical bypass surgery to wire in the new solar arrays.
Overnight, flight controllers will slightly retract the left wing of the P6 solar array to make sure the retraction mechanism is working normally. Because the P6 arrays extend at right angles to the new P4 arrays on the main truss, the P6-4B wing must be retracted to provide clearance for the SARJ to begin rotating the new arrays.
Because of the delay caused by the Columbia disaster, the P6 arrays have been extended for six years and engineers don't know for sure how smoothly the P6-4B wing will retract. But if all goes well, the astronauts will complete the retraction Wednesday, setting the stage for two critical re-wiring spacewalks Thursday and Saturday.
10:45 p.m., 12/11/06, Update: Engineers assess tile dings, possible low-energy wing impact; Shannon downplays threat
The Discovery astronauts used the space station's robot arm for a quick, unplanned inspection of the shuttle's left wing outboard leading edge panels based on sensor data indicating a possible micrometeoroid hit earlier today. John Shannon, chairman of NASA's Mission Management Team, said if the data reflected a real impact - and that remains to be seen - it was about 100 times below the threshold expected to cause any real damage.
Television views from the station arm did not show any obvious signs of damage to the reinforced carbon carbon panels in question. The astronauts promptly moved on to using the shuttle's robot arm to pull a new solar array truss segment from Discovery's cargo bay for handoff to the station arm. The spacer segment will be attached to the end of the station's main truss during a spacewalk Tuesday.
Shannon said data from a wing leading edge sensor, a post-Columbia system designed to detect possible impacts during launch or in orbit, recorded a 0.12-G "hit" around 5:30 a.m. Impacts registering 1 G "root mean square" are NASA's threshold for concern and that's 10 times less than the force required to cause serious damage.
By that standard, the force recorded by the sensor on the left wing was some 100 times less than required to cause entry-critical damage. But Shannon said time was available in the crew's schedule to take a quick look and while "I don't think anybody saw anything there," it was the right call to check it out.
Of more interest, perhaps, is a photograph taken by the station astronauts earlier today during Discovery's final approach to the outpost. The picture shows an area of the shuttle's belly around one of the two propellant-line umbilical doors that close after the ship's external tank separates in space.
The imagery shows a reddish, cellophane-like material extending from the door hinge line area and chipped heat-shield tiles just outboard of the door.
As for the former, "what the team thinks this is is some purge barrier material," said Shannon. "It's a cellophane-type material that is put inside the external tank umbilical area and it keeps the (pre-launch) nitrogen purge in that area, it's basically like you're sealing it up, like a baggy, so when you get the N2 purge in there, it doesn't just go out in the atmosphere, it stays where you want it to stay.
"This stuff is ... like orange Saran wrap, orange cellophane. It'll burn off very quickly (during re-entry). The team is looking at it just to make sure the compression seal we get around (the door), that this wouldn't interfere with that at all. I think that's going to prove to be very true and it's not going to be an issue. But, of course, the team is still working it."
As for the chipped tile just outboard of the door, "it looks like we had some recirculating flow back in there (during ascent) and something was hitting those tiles and taking small chips out of them," Shannon said. "Is this an issue? I don't know at this point. The team is working on it. I don't expect it to be a big deal. The thing we're always concerned about is if you had tile damage that goes across a seal. It doesn't look like it goes across a seal in any of these, it looks really shallow."
But to be on the safe side, the imagery assessment team "is going to meet at midnight tonight and determine if that's an area we'd like to look at some more, to go do a focussed inspection, or if they have sufficient data ... to clear that as no issue at all."
As part of NASA's post-Columbia safety improvements, shuttle crews are now launched with repair materials capable of fixing relatively minor heat shield damage. But they would be asked to do that only if engineers believed the shuttle was at risk. The damage in question does not appear nearly that serious.
"Am I concerned about this?" Shannon mused. "Not really, not right now. But I refuse to short-circuit the team. I'm going to let them go off and do their analysis and we'll just take it a step at a time."
Discovery docked with the international space station at 5:12 p.m. after a two-day orbital chase. After the impromptu wing inspection, astronaut Nicholas Patrick used Discovery's robot arm to pull the 4,110-pound P5 truss segment from the shuttle's cargo bay. He then handed the spacer segment off to astronaut Sunita Williams, operating the station's robot arm.
Williams, a Navy helicopter pilot and diver, hitched a ride aboard Discovery to join the station's full time crew as a flight engineer. She replaces German astronaut Thomas Reiter, who was launched to the station in July. He will return to Earth aboard Discovery in Williams' place.
The P5 truss segment will serve as a spacer between two huge sets of solar arrays on the left side of the station's main truss. One set of arrays, P4, was attached to the station in September along with a massive rotary joint known as P3 that will rotate the arrays like giant paddle wheels to track the sun.
The arrays that ultimately will be bolted to P5 are currently mounted atop the station's Unity connecting module. The P6 arrays were launched six years ago to serve as an interim source of power during the initial stages of station assembly.
One of the P6 solar wings will be retracted on this flight and the other on the next shuttle mission in March. If all goes well, P6 will be attached to P5 next fall to complete the left side of the station's main solar array truss.
During a spacewalk Tuesday, astronauts Robert Curbeam and Christer Fuglesang, Sweden's first astronaut, plan to bolt P5 to the P4 segment. Two more spacewalks Thursday and Saturday will be devoted to re-wiring the station to take advantage of the permanent power system.
08:10 p.m., 12/11/06, Update: Astronauts interrupt schedule to photograph 'area of interest' on shuttle's left wing
The Discovery astronauts and their station counterparts interrupted their timeline tonight to make a quick inspection of the shuttle's left wing leading edge panels. Astronaut Steve Robinson in space station mission control told the crew an accelerometer in the shuttle's wing leading edge sensor system, part of a post-Columbia safety upgrade, had recorded a possible hit overnight.
"We're going to take advantage of the timeline here and perform an inspection of opportunity," Robinson said. "We'd like to take a look at the port wing tip with the SSRMS (station's robot arm). Overnight, the WLES system, a single accelerometer gave us a signal on what we think is the locations of RCC panels on the port side, 19 through 22."
The astronauts had been in the process of gearing up to unberth a new space station truss segment using the shuttle's robot arm. The plan then was to hand it off to the station arm, which would hold it overnight. The segment, known as P5, is scheduled to be attached to the station's main solar array truss during a spacewalk Tuesday.
"Before we do the handoff, we'd like to take the SSRMS out and take a look at it," Robinson said, referring to the outboard panels making up the shuttle's left wing leading edge. "The idea is go ahead and do the shuttle grapple of P5 on time but not to unberth it."
The shuttle's reinforced carbon carbon nose cap and wing leading edge panels - 22 per wing - experience the most extreme heating during re-entry and one of NASA's post-Columbia requirements is to inspect the panels in orbit to assess their health. The astronauts did just that Sunday, using cameras and a laser sensor on the end of a 50-foot boom. At that time, there were no obvious signs of any ascent damage.
The WLES system was put in place in the wake of Columbia to detect the sort of forces one might expect from wing leading edge debris impacts during launch or from micrometeoroid impacts during orbital flight. Herring said the sensors can occasionally produce "false positives" and the area of interest on the left wing may turn out to be nothing of any concern. Herring said the relatively low-energy reading was recorded around 5:30 a.m. today while the crew slept.
Tonight's unplanned inspection, he said, "should be only about a half-hour impact on the schedule." The astronauts then will press ahead with unberthing P5 while analysts on the ground study the imagery.
07:30 p.m., 12/11/06, Update: Hatches opened; welcome aboard; 'areas of interest' on left wing
The crew of the international space station welcomed the Discovery astronauts aboard this evening, ushering them into the Destiny laboratory module a little less than two hours after the shuttle docked with the outpost.
"Space shuttle Discovery, arriving," station commander Michael Lopez-Alegria, a Navy captain, said at 6:54 p.m., ringing the ship's bell per naval tradition.
Video from the lab module showed the 10 shuttle and station astronauts embracing, shaking hands and sporting broad grins as they floated about in the roomy lab module. Someone waved a Swedish flag behind Christer Fuglesang, the first Swede to fly in space.
Posing for a group portrait, German astronaut Thomas Reiter, launched to the station in July, oculd be seen enthusiastically hugging his replacement, NASA astronaut Sunita "Suni" Williams, who will officially take his place later this evening as a member of the Expedition 14 crew. Reiter will return to Earth in Williams' place aboard Discovery.
It was a welcome, albeit brief moment of camaraderie in a tightly scripted, extraordinarily complicated mission to rewire the station's power system. After a quick safety briefing, the astronauts turned their attention to moving Williams' Soyuz custom seatliner into the station and gearing up to pull a 4,110-pound solar array truss spacer segment from Discovery's cargo bay.
The seatliner is required in case Williams' and her ISS-14 crewmates ever have to abandon ship in a Russian Soyuz capsule. Once her seatliner is in place, she will officially become a member of the ISS-14 crew.
NASA commentator Kyle Herring in mission control said flight controllers may alter the P5 spacer segment unberthing to give the crews time to aim a camera on the station's robot arm at Discovery's outboard left wing leading edge panels.
It's not yet clear what flight controllers may be looking for, but an unplanned inspection means some sort of "area of interest" has been identified, either during leading edge inspections Sunday or during another inspection earlier today, that warrants a closer look. By checking tonight, NASA planners may be able to avoid a so-called "focused inspection" later in the mission.
"There's been some joint discussions between the shuttle and station team on modifying the timeline a bit, proceeding on with the grapple of the P5 truss element by the shuttle's robotic arm and hold in that position while the station robotic arm is used to maneuver out to a viewing position of the shuttle's left hand wing, the outermost panels on the shuttle's left wing, the reinforced carbon carbon panels," Herring said.
"Some of the early looks showed some areas of interest that they wanted a little bit more detail on in terms of the imagery analysis folks. And the opportunity may present itself to use the station arm here early to get some closeup data. They'll look at panels 19 through 21 which are outboard on the left wing. That can be done with very little impact to the overall timeline tonight."
05:15 p.m., 12/11/06, Update: Shuttle Discovery docks with space station
With commander Mark Polansky at the controls, the shuttle Discovery docked with the international space station today as the two spacecraft sailed 220 miles above southeast Asia at 5 miles per second.
Approaching the station from directly ahead, with its payload bay docking module lined up with a port on the front of the lab complex, Polansky guided Discovery to a gentle linkup at 5:12 p.m. to close out a two-day orbital chase.
"Houston and (space station) Alpha from Discovery, capture confirmed," shuttle pilot William Oefelein called as the docking systems engaged.
After waiting for any residual motion to damp out, the docking system will firmly lock the two spacecraft together and leak checks will be carried out to make sure seals are tight. Hatches between the shuttle and station should be open within the hour and after a brief welcoming ceremony and safety briefing, the combined crews will press ahead with a busy schedule.
For station commander Michael Lopez-Alegria, flight engineer Mikhail Tyurin and European Space Agency astronaut Thomas Reiter, the highlight of the day will be transferring astronaut Sunita Williams' Soyuz seat liner from Discovery to the station. At that point, shortly after 8 p.m., Williams will become a member of the Expedition 14 crew. Reiter, launched to the station in July, will return to Earth aboard Discovery in Williams' place.
A few minutes after the seat liner transfer, Nicholas Patrick, operating the shuttle's 50-foot-long robot arm, will latch onto the P5 solar array truss segment making up Discovery's major cargo. After hoisting the segment out of the payload bay, Patrick will position it for handoff to the station's robot arm, operated by Williams, around 9 p.m. P5 will remain parked overnight on the end of the station arm until installation Tuesday during a spacewalk by Robert Curbeam and Swedish astronaut Christer Fuglesang.
04:15 p.m., 12/11/06, Update: Discovery closes in on space station
Passing 600 feet below the international space station, on course for a docking around 5:06 p.m., shuttle commander Mark Polansky guided Discovery through a graceful 360-degree back somersault this afternoon to let the station's crew photograph the critical heat-shield tiles on the ship's belly.
The seemingly slow-motion back flip, called a rendezvous pitch maneuver or RPM, is a critical element in NASA's post-Columbia imperative to inspect the shuttle's heat shield in orbit to assess its health before clearing the crew for re-entry.
As Discovery's belly rotated into view, station flight engineer Mikhail Tyurin used a digital camera with an 800mm lens to shoot high-resolution closeups while European Space Agency astronaut Thomas Reiter used a 400mm lens to provide wider-angle views. The imagery - up to 300 photos - will be downlinked later today for analysis by engineers at the Johnson Space Center in Houston.
Live television from the station provided a spectacular bird's eye view of the RPM, showing Discovery's back flip 220 miles above the cloud-draped South Pacific Ocean. No obvious signs of damage were visible in the TV views, but a final verdict must await detailed analysis on the ground.
With the pitch maneuver complete, Polansky will guide Discovery to a point about 310 feet directly in front of the station with the orbiter's tail pointing toward Earth and its open cargo bay toward pressurized mating adapter No. 2 on the forward end of the Destiny laboratory module.
From that point, it will take about 40 minutes to complete the rendezvous, with docking on tap around 5:06 p.m.
06:00 a.m., 12/10/06, Update: Shuttle docking timeline
The shuttle Discovery is closing in on the international space station for a linkup today around 5:06 p.m. The terminal phase of the rendezvous procedure will begin with a rocket firing at 2:28 p.m. Trailing the station by about eight nautical miles, commander Mark Polansky will guide Discovery through a carefully choreographed approach that will put the shuttle about 600 feet directly below the lab complex a few minutes past 4 p.m.
The space station crew will train telephoto lenses on the shuttle as Polansky guides the craft through a 360-degree pitch maneuver, exposing Discovery's belly to view for a detailed heat shield inspection. The shuttle's nose cap and wing leading edge panels were inspected by the Discovery astronauts Sunday and today's inspection is intended to characterize the health of the tiles that play such a crucial role during re-entry.
With the rotational pitch maneuver complete, Polansky will guide Discovery to a point about 310 feet directly in front of the station with the orbiter's tail pointing toward Earth and its open cargo bay toward pressurized mating adapter No. 2 on the forward end of the Destiny laboratory module.
From that point, it will take about 40 minutes to complete the rendezvous, with docking on tap around 5:05 p.m. If all goes well, hatches between the two spacecraft will be opened about an hour later and after a brief welcoming ceremony and safety briefing, the combined crews will press ahead with a busy schedule.
For station commander Michael Lopez-Alegria, flight engineer Mikhail Tyurin and European Space Agency astronaut Thomas Reiter, the highlight of the day will be transferring astronaut Sunita Williams' Soyuz seat liner from Discovery to the station. At that point, around 8 p.m., Williams will become a member of the Expedition 14 crew. Reiter, launched to the station in July, will return to Earth aboard Discovery in Williams' place.
A few minutes after the seat liner transfer, Nicholas Patrick, operating the shuttle's 50-foot-long robot arm, will latch onto the P5 solar array truss segment making up Discovery's major cargo. After hoisting the segment out of the payload bay, Patrick will position it for handoff to the station's robot arm, operated by Williams, around 9 p.m. P5 will remain parked overnight on the end of the station arm until installation Tuesday during a spacewalk by Robert Curbeam and Swedish astronaut Christer Fuglesang.
Revision D of the NASA TV schedule is posted on the CBS News STS-116 Quick-Look page. Here is an updated timeline of today's activities (in EST and mission elapsed time):
EST........DD...HH...MM...EVENT 10:17 AM...01...13...30...STS crew wakeup 11:17 AM...01...14...30...Group B computer powerup 11:32 AM...01...14...45...Rendezvous timeline begins 12:47 PM...01...16...00...Spacehab prepped for docking 12:55 PM...01...16...08...NC-4 rendezvous rocket firing 02:28 PM...01...17...41...TI burn 03:04 PM...01...18...17...Sunset 03:26 PM...01...18...39...Range: 10,000 feet 03:35 PM...01...18...48...Range: 5,000 feet 03:39 PM...01...18...52...Sunrise 03:40 PM...01...18...53...Range: 3,000 feet 03:45 PM...01...18...58...MC-4 rendezvous burn 03:49 PM...01...19...02...Range: 1,500 feet 03:51 PM...01...19...04...RPM start window open 03:54 PM...01...19...07...Range: 1,000 feet 03:57 PM...01...19...10...KU antenna to low power 03:58 PM...01...19...11...Shuttle directly below ISS 04:03 PM...01...19...16...Range: 600 feet 04:05 PM...01...19...18...Start rendezvous pitch maneuver 04:07 PM...01...19...20...Noon 04:13 PM...01...19...26...End pitch maneuver 04:15 PM...01...19...28...RPM full photo window close 04:15 PM...01...19...28...Initiate pitch up maneuver 04:23 PM...01...19...36...RPM start window close 04:27 PM...01...19...40...Shuttle in front of station; range: 310 feet 04:28 PM...01...19...41...Range: 300 feet 04:32 PM...01...19...45...Range: 250 feet 04:35 PM...01...19...48...Sunset 04:36 PM...01...19...49...Range: 200 feet 04:38 PM...01...19...51...Range: 170 feet 04:40 PM...01...19...53...Range: 150 feet 04:44 PM...01...19...57...Range: 100 feet 04:47 PM...01...20...00...Range: 75 feet 04:47 PM...01...20...00...PMA-2 prepped for docking 04:51 PM...01...20...04...Range: 50 feet 04:55 PM...01...20...08...Range: 30 feet; start stationkeeping 05:00 PM...01...20...13...End stationkeeping; push to dock 05:04 PM...01...20...18...Range: 10 feet 05:06 PM...01...20...18...DOCKING 05:10 PM...01...20...23...Sunrise 05:27 PM...01...20...40...Hard mate 05:27 PM...01...20...40...Leak checks; PGSC reconfig 05:47 PM...01...21...00...Group B computer powerdown 05:57 PM...01...21...10...Docking system prepped for entry 06:17 PM...01...21...30...Hatches open 07:07 PM...01...22...20...Safety briefing 07:32 PM...01...22...45...Spacesuit, EVA tools transfer 07:32 PM...01...22...45...Soyuz seatliner transfer 08:02 PM...01...23...15...Soyuz seatliner installation 08:17 PM...01...23...30...P5 grapple by shuttle arm (SRMS) 08:32 PM...01...23...45...P5 unberth by SRMS 09:00 PM...02...00...13...Post-MMT/mission status briefing on NTV 09:02 PM...02...00...15...P5 handoff from SRMS to station arm (SSRMS) 09:12 PM...02...00...25...Equipment lock preps 09:47 PM...02...01...00...SRMS ungrapples P5 10:02 PM...02...01...15...Docking video replay 11:02 PM...02...02...15...EVA-1: Procedures review 11:47 PM...02...03...00...P5 video playback 12:37 AM...02...03...50...EVA-1: EV1/EV2 mask prebreathe 12:37 AM...02...03...50...EVA-1: EV1/EV2 airlock campout begins 01:27 AM...02...04...40...EVA-1: Crew lock depress to 10.2 psi 02:47 AM...02...06...00...Crew sleep begins
09:30 p.m., 12/10/06, Update: No major debris events seen in ascent video; Shannon pleased with shuttle performance so far
Preliminary analysis of ascent video and radar indicate the shuttle Discovery's external tank performed well and that no major debris events occurred that might have damaged the orbiter's fragile heat shield. While it will take several more days to complete the assessment, incorporating crew inspections today and more planned for Monday, NASA managers said they were pleased with Discovery's performance so far.
"All in all it's going really well," said John Shannon, chairman of NASA's Mission Management Team at the Johnson Space Center in Houston. "All the reports that came in were that we had a very typical ascent, there were no surprises as of yet. We're just waiting for the inspection data to come down. We'll take a look at that and work it into the mission as appropriate."
Discovery's crew used a long sensor boom today to inspect the shuttle's reinforced carbon carbon nose cap and wing leading edge panels and the space station crew will photograph the heat shield tiles on the ship's belly during final approach before docking Monday afternoon. The linkup currently is targeted for 5:06 p.m.
Video of the heat shield shot by cameras mounted in the shuttle's twin solid-fuel boosters will be assessed after the big rockets are towed back to shore.
For Discovery's launching, one ship was stationed to the north along the shuttle's ground track while the other was positioned to the south, closer to shore. During recovery operations, a man on the southern ship was injured, interrupting booster recovery operations.
"We did not put the southernmost ship where we typically do, it was not out at the recovery zone," Shannon said. "We had the northern ship out there, the southern ship was closer to the coast so we could get a good Doppler comparison between the two radars of anything coming off the stack.
"The southern ship went out with radar technicians and the plan all along was after the launch for it to come back to port, let the radar technicians off, on load some guys for the retrieval of the boosters and then steam overnight to the recovery zone. They got out there and there was an accident, I'm not going to get into exactly what happened, it's not life threatening, but a guy got hurt out there during the frustrum recovery.
"They halted recovery operations and started coming back and we got a Coast Guard helicopter to go out and pick him up and take him to the hospital and they're back on station to do the recovery starting tomorrow morning. So it's probably going to put our, what we call the open assessment of the solid rocket boosters, down by a day."
One of the ship-borne radars suffered a malfunction and was unable to collect data. Other radars noted two possible debris events during launch, both occurring well after the first minute and 35 seconds or so of flight when atmospheric density is high enough to result in high impact velocities.
Two bits of debris, presumably ice, could be seen floating away as the shuttle separated from the external tank. But nothing significant was seen actually striking the spacecraft.
Accelerometers mounted behind the wing leading edge panels detected six "events" during launch, four on the left wing and two on the right. All were in the 1.2- to 1.3-G range, just slightly above the 1-G limit that requires additional analysis.
Shannon said engineers aren't sure what might have triggered the readings, which are very similar to what was observed during the first three post-Columbia missions. It may be the result of the wing leading edge panels and support hardware settling, or snapping into place under the stress of launch, or it could be the result of very small bits of debris.
In any case, the events were at least 10 times weaker than the force needed to cause actual damage to the panels.
"The team sees nothing of concern at this time," Shannon said. "Of course, it was a dark launch at night, so we did not have all of the capability that we have enjoyed on STS-114, 121 and 115. The long-range cameras, though, showed typical performance. We could see a few very small pieces of foam or ice come off, none impacted the orbiter. The pad cameras showed very good performance.
"The ET feedline camera was interesting. We were able to get enough reflected lighting from the solid rocket boosters and the main engines to be able to see a few small pieces of what looked like foam that were highlighted against that plume. They were all well after the time of concern and it was very typical of what we've seen in past flights."
Overall, Shannon said, the team was pleasantly surprised by how well the cameras performed during the first night launching since November 2002.
"The long-range tracking cameras showed us a lot of detail on the lower part of the stack," he said, referring to the shuttle, its tank and boosters. "We're also able to see better at night when any piece of foam comes off of the stack if it goes into the main engine plume, it really brightens that plume up, you see a little streak in there and you can see it a lot better at night.
"As well, at external tank separation when the attitude control thrusters fired, it was bright as it could be and the imagery team has already taken snapshots of that data and made a preliminary assessment of the underside of the vehicle and said they don't see anything that's unexpected. So I was very encouraged by what we saw."
Photographing the tank after separation with a camera mounted in the shuttle's belly was not considered an option for Discovery's flight because separation occurred in orbital darkness.
"We didn't do it because we thought it was going to be dark," Shannon said. "But based on the results we saw from the attitude control firings, I think we will go ahead and do that (in the future) and just use that lighting from those jet firings to light the tank up for us."
Asked if the initial results gave him confidence in launching shuttles at night, Shannon said "we were confident before we stepped into this flight with night launch."
"We're very confident the vehicle is going to be safe to fly and we're also confident we have sufficient data through the radars and the imagery we did get to show we didn't have anything unexpected happen on the stack," he said. "As I said, it was as we expected."
The only other issues under discussion are problems with a controller used by one of the shuttle's cooling systems and a glitch in an automated system used to unlatch the ship's robot arm from whatever it is locked onto. Additional troubleshooting is planned for the controller issue but it is not expected to impact the mission. As for the robot arm, the astronauts will use a manual system to unlatch the snare mechanism as required. Again, no mission impact is expected.
10:50 a.m., 12/10/06, Update: Heat shield inspection on tap; rendezvous burns, equipment prep
The Discovery astronauts were awakened for their first full day in space today by a recording of the Beatles' "Here Comes the Sun" beamed up from mission control around 11:50 a.m. The crew faces a busy day of heat shield inspections and equipment preparation as the shuttle continues its approach to the international space station for a docking Monday afternoon.
"Good morning, Discovery, and a special good morning to you, Mark," astronaut Shannon Lucid called from Houston. "We especially want to thank you for the burst of sunshine you brought into our lives last night. It was an awesome launch."
"Well good morning, Houston, good morning Shannon and everybody there," shuttle commander Mark Polansky replied. "It was pretty great for all of us, too, and we're really looking forward to getting started today."
The primary goal of today's activity is a lengthy inspection of Discovery's nose cap and wing leading edge panels using the 50-foot orbiter boom sensor system, an extension for the shuttle's robot arm equipped with a laser scanner and high-resolution camera. The reinforced carbon carbon wing leading edge panels and the ship's RCC nose cap experience the most extreme heating during re-entry and the flight day 2 inspection is needed to spot any damage that might have occurred during launch.
The task takes on added significance for Discovery's flight because takeoff Saturday marked NASA's first night launch since the Columbia disaster. While the brilliant light from the shuttle's twin boosters illuminated the belly of the orbiter during the most aerodynamically dangerous stages of the climb to space, lighting was not optimum for ground-based cameras.
The only incident noted by reporters watching replays from a camera mounted on the external tank occurred around 65 seconds after liftoff when something flew through the left side of the frame and out of view well outboard of the orbiter. To the untrained eye, it was not possible to tell if the object was debris of some sort, a rocket nozzle cover coming off late or some other phenomenon.
During checkout of the robot arm Saturday night, astronaut Nicholas Patrick ran into a problem with an arm system used to automatically unlatch the snares in the crane's so-called end effector from whatever the arm might be locked onto. After a bit of checkout, engineers determined the arm can be used in its current state but the operator will have to manually release the snares as required, a procedure requiring a few additional computer inputs. But the glitch is not expected to cause any problems.
John Shannon, chairman of NASA's Mission Management Team at the Johnson Space Center in Houston, will brief reporters this evening at 8 p.m. on preliminary results of the ascent imagery and other data. A detailed inspection of the shuttle's heat-shield tiles will be carried out by the space station's crew during Discovery's final approach to the outpost Monday afternoon.
Here is an updated timeline of today's activities (in EST/GMT and mission elapsed time; includes rev. C of the NASA TV sked):
DATE/EST.......DD...HH...MM...EVENT 10:47 AM...00...14...00...Crew wakeup 01:02 PM...00...16...15...Laptop computer setup (part 2) 01:43 PM...00...16...56...NC-2 rendezvous rocket firing 01:47 PM...00...17...00...OBSS unberth 01:47 PM...00...17...00...Logistics transfer preps 02:32 PM...00...17...45...NPC rendezvous rocket firing 03:07 PM...00...18...20...Spacesuit checkout preps 03:12 PM...00...18...25...OBSS surveys starboard wing 03:37 PM...00...18...50...Spacesuit checkout 04:42 PM...00...19...55...OBSS surveys nose cap 04:57 PM...00...20...10...ETVCG assembly 05:12 PM...00...20...25...Ergometer setup 06:12 PM...00...21...25...Crew meals begin 06:12 PM...00...21...25...Centerline camera installation 06:42 PM...00...21...55...Orbiter docking system ring extension 07:12 PM...00...22...25...OBSS surveys port wing 08:00 PM...00...23...13...Post-MMT/mission status briefing on NASA TV 08:12 PM...00...23...25...Spacesuit transfer preps 08:47 PM...01...00...00...OBSS berthing 09:17 PM...01...00...30...Upper surface survey 11:02 PM...01...02...15...Rendezvous tools checkout 11:02 PM...01...02...15...OMS pod survey 11:42 PM...01...02...55...Survey videotape playback 11:51 PM...01...03...04...NC-3 rendezvous rocket firing 02:17 AM...01...05...30...Crew sleep begins 03:00 AM...01...06...13...Daily video highlights reel on NTV 04:00 AM...01...07...13...Status briefing replay 09:00 AM...01...12...13...Video file on NTVThe thermal protection system - TPS - inspection on flight day two is a now-standard part of every shuttle mission, requiring the astronauts to unlimber the robot arm, latch onto the OBSS and then make slow, repeated passes up and down each wing's forward edge. As much video as possible from a camera on the OBSS will be downlinked in realtime and video of the entire process will be downlinked later.
Data from impact sensors mounted behind the wing leading edge panels, another post-Columbia safety upgrade, was scheduled for downlink overnight.
"We don't anticipate any large foam shedding or debris impacts, but it's important to get those data down so we can quickly look at it and we can correlate it with anything we may see on the ascent radar or any video that we get during the first few minutes or at least through the SRB lighted phase of that," lead shuttle flight director Tony Ceccacci said at a pre-flight briefing.
Along with inspecting the shuttle's heat shield today, the flight plan "consists of all the standard rendezvous burns and also rendezvous prep activities, which include getting the docking ring extended and also doing rendezvous checkout," Ceccacci said. "The crew will also be doing some EMU (spacesuit) checkouts and doing transfer prep to get them ready for the EVA the day right after we dock.
"Again we'll have a full day of TPS surveys, the same thing we've been doing since STS-114. First, we are going to unberth the OBSS and scan the starboard wing. Both the starboard wing, nose cap and port wing take about an hour and half each to complete the actual scanning activities. The actual data that we get from these, that we have the crew record, is about 37 (minutes) on starboard side, 20 minutes on the nose cap and about 29 minutes on the port side. So you see, the majority of it is getting the arm configured. The scan is about a third of the whole time."
Once that work is complete, the astronauts will berth the OBSS and use the arm and one of its own cameras to inspect tiles and blankets on the upper sections of the shuttle's crew cabin and aft orbital maneuvering system rocket pods.
"After we get done with the LDRI scans, the laser dynamic range imager, we go ahead and berth the OBSS and we do our next set of thermal protection surveys," Ceccacci said. "We call it the crew cabin survey using the RMS end effector. These are areas that don't require the resolution of the LDRI. Once the crew completes this survey, they have one more survey task they have to perform and that's taking video pictures of the OMS pods."
At least two rocket firings are planned today to fine-tune Discovery's approach to the space station amid work to check out a variety of tools that will be used during the final stages of the rendezvous to help keep the shuttle on course.
"We are essentially checking out hardware that we need to get ready for our rendezvous and docking," astronaut Joan Higginbotham said in a NASA interview. "I specifically will be checking out the handheld laser. We point it towards the station and shoot at it, if you will, and this will tell us how far we are from the station and the range rate, which is the rate at which we are closing in on the station.
"We use all that data to dock with our space station, to come in according to the different velocities at which weÕre supposed to be tracking at different distances, as weÕre closing in," she said. "The EVA crews (Robert Curbeam, Christer Fuglesang and Sunita Williams) are going to be checking out some of the hardware that theyÕre going to use on the first spacewalk."
As it now stands, Discovery will dock with the space station around 5:05 p.m. Monday.
09:00 p.m., 12/09/06, Update: Discovery rockets into orbit
Running two days late, the shuttle Discovery thundered into orbit tonight, lighting up the night sky for hundreds of miles around as NASA kicked off a critical flight to conduct electronic bypass surgery on the international space station.
In the space agency's first night launch since 2002, Discovery's huge solid-fuel booster flashed to life at 8:47:35 p.m., instantly pushing the fuel-laden 4.5-million-pound spacecraft skyward atop 500-foot tongues of sky-lighting fire.
Accelerating through 140 mph in just 10 seconds - straight up - Discovery wheeled about its long axis and arced away over the Atlantic Ocean, blazing through the dark sky on a trajectory up the East Coast of the United States.
The 5,000-degree flame from its twin-solid fuel boosters was visible for hundreds of miles around, putting on a spectacular show. Despite earlier concern about high winds and possible low clouds, conditions improved as launch time approached and it was clear sailing for Discovery.
Two minutes and five seconds after liftoff, the two boosters were jettisoned, their combined 2.6 million pounds of solid propellant exhausted, and Discovery continued its ascent on the power of three hydrogen-fueled main engines.
With the boosters gone, live television views from a camera mounted on Discovery's external fuel tank became too dim to spot any debris possibly falling from the tank. But the view was stunning as the exhaust from the main engines interacted with the surrounding atmosphere to create a eerie, never-before-seen plume around the back of the vehicle.
No obvious signs of foam shedding could be seen during the most dangerous phase of flight, the first minute and 40 seconds or so when air density is high enough to result in high impact velocities.
Eight-and-a-half minutes after liftoff, the shuttle slipped into its planned preliminary orbit, the dimming plume flaring as maneuvering jets pushed the orbiter away from the tank.
If all goes well, commander Mark Polansky will guide Discovery to a docking with the space station around 4:48 p.m. Monday. Spacewalks are scheduled Tuesday, Thursday and Saturday to re-wire the outpost to take advantage of new solar arrays installed in September.
"It probably is the most complex shuttle mission we've had yet," NASA Administrator Mike Griffin said in an interview with CBS News.
Joining Polansky aboard Discovery are pilot William Oefelein, flight engineer Bob Curbeam, Nicholas Patrick, Joan Higginbotham, Swedish astronaut Christer Fuglesang and Sunita "Suni" Williams. Williams will remain behind on the space station when Discovery departs and German astronaut Thomas Reiter, launched to the lab complex in July, will come home in her place.
"We have a message for the crew of Discovery," station skipper Mike Lopez-Alegria radioed Houston after the shuttle reached orbit. "Congratulations. ... It's a wonderful achievement. We're going to turn our porch light on so they can find us."
Space station-bound shuttles must take off at roughly the moment Earth's rotation carries the launch pad into the plane of the lab's orbit. That moment moves 23 minutes earlier per day, resulting in alternating periods of lighted and nighttime launch opportunities.
NASA suspended night launchings in the wake of the Feb. 1, 2003, Columbia disaster to ensure good lighting, on the ground and in orbit, for photo documentation of the shuttle's external tank. The goal was to monitor the performance of the tank's foam insulation and to spot any debris impacts on the shuttle's heat shield.
But ruling out night launchings severely restricted NASA's launch opportunities. After two successful daylight flights in July and September, NASA managers concluded the redesigned tank was performing well and that the risk of a night launch was justified by the need to meet the Bush administration's 2010 deadline for finishing the station and retiring the shuttle.
As it turned out, the light from Discovery 's booster plumes provided enough illumination for at least some of NASA's launch cameras. Radars were positioned along the shuttle's ground track to look for signs of debris and a WB-57 jet flying off shore to one side of the shuttle's flight path photographed the orbiter using a powerful telescope with infrared and optical cameras.
But launch photography is not really required to determine if the current mission is at risk. An exhaustive orbital inspection will spot any signs of damage in greater detail than is possible with ground-based instruments. The major downside to a night launch is possibly not spotting a near miss that might pose a threat to the next mission.
"We're not relying on those ascent-based observations for the safety of that particular flight," said shuttle Program Manager Wayne Hale. "We're relying on the inspection of the heat shield, which we do in excruciating detail on orbit now to make sure they're safe to come back."
With two successful flights going into Discovery's launch campaign, Hale said, "we are as confident as we are likely to get that it's safe to return to the kind of operations that we simply must adopt if we're going to complete the international space station by 2010."
No obvious problems were seen during this evening's climb to space, but flight controllers won't know for sure how the shuttle's heat shield fared until a detailed inspection by the astronauts on Sunday. Additional inspections will be carried out by the station's crew during final approach prior to docking Monday afternoon.
Discovery's mission is considered one of the most challenging flights in space history.
Station construction has now reached the point where an interim power system, designed to support the station during its initial assembly, needs to be phased out. With the installation of new solar arrays in September, NASA is finally ready to activate the lab's permanent power grid, a major step that sets the stage for attachment of European and Japanese research modules.
But in order to do that, the Discovery astronauts and station crew must first retract one wing of the older solar arrays providing interim electricity to the U.S. segment of the station. If that goes well - and no one knows whether the fragile array wing will, in fact, retract smoothly - commands will be sent to begin slowly rotating the new set of arrays installed in September.
Flight controllers then will power down the lab's major circuits, two at a time, while spacewalking astronauts unplug and re-plug electrical cables into different sockets.
Precisely timed computer scripts will set electro-mechanical switches to begin routing power from the new arrays and the remaining older array wing through four big circuit control boxes called main bus switching units, or MBSUs, mounted in the center of the station's main solar power truss. The MBSUs, in turn, will send array power to a host of transformers, circuit breakers and other components to provide precisely regulated 124-volt DC power to the station's myriad systems.
But the MBSUs will begin heating up as soon as the power begins flowing. In a high-stakes race against the clock, the astronauts and flight controllers must quickly activate powerful pumps to push ammonia coolant through cold plates and radiators to keep the MBSUs and other components from overheating.
"This is pretty much your classic chicken-or-egg scenario here," said Paul Hill, mission operations manager at the Johnson Space Center in Houston. "You have to have active cooling to the switch boxes (main bus switching units, or MBSUs) in order to route power through them.ÊYou have to have power flowing through the MBSUs in order to power the cooling equipment."
It will take two virtually identical spacewalks - and hundreds of commands and cable switches - to reconfigure the station's four major circuits. There is little margin or error and a fair amount of uncertainty. While the MBSUs have at least been tested in space to confirm electrical continuity, the ammonia coolant system has never been activated or tested in space.
"We have these big boxes in the middle of the space station, big switch boxes," Hill said of the MBSUs. "You've got four pairs of solar arrays (when the station is complete) and you've got all these finger-thick copper wires that run from the solar arrays to the middle of the truss. Those are the boxes that, for an assembly-complete station, you want all your power flowing from and then going down to our converters that then flow power to individual pieces of equipment.
"In order to reconfigure the electrical system and the cooling system so we have the permanent cooling system up and we're flowing all power through these main switching boxes, we've got to power off a hell of a lot of equipment so we can safe those individual copper lines, disconnect them and reconnect them to where we want them. That will be a case where we'll have to power off almost all the U.S. segment one way or the other throughout that whole process."
Should any significant problems develop - an ammonia leak, an electrical glitch, a computer commanding issue - that might prevent the activation of a cooling system, the astronauts could be forced to quickly switch back to the interim power system, cutting of the flow of electricity to the MBSUs while engineers in Houston consider alternatives.
"What makes this mission singularly unique is the choreography between what we're doing in orbit and what the ground is doing because of the amazing amount of ground commanding to go ahead and power down and re-power the ISS electrical system while we're out there doing spacewalks," Polansky said in an interview.
"So yeah, we hold our breath like everybody else while the ground sends the commands and then wait to find out how it's going to work."
Said Curbeam, the lead spacewalker on the mission: "It is very complicated. The thing I think is kind of cool about it is, we have these three spacewalks, the second two, the big player in them both is mission control. ... The pressure is on those guys.
"While they have to be very slow and deliberate about how they do it, they can't be too slow because the clock's ticking on us. There's got to be a point where they say OK, it's going to be fine, you guys press on or OK, we have to back out of it and go back to (interim) power and we have to undo everything we did and then talk about what we're going to do after that."
In that case, the pressure will quickly switch back to the astronauts.
"Our tasks are relatively straight forward as long as you don't run into any of the contingencies," he said. "And that's the big deal. We probably train for contingencies more than most crews because we know that's where the devil is."
06:50 p.m., 12/09/06, Update: Weather now 70 percent 'go'
Forecasters have amended the forecast for tonight's planned launch of the shuttle Discovery, saying they now expect a 70 percent chance of acceptable weather. As day turned into night, conditions improved dramatically and the forecast for Discovery's 8:47:34 p.m. launch time calls for scattered clouds at 4,000 feet, a broken deck at 20,000 and winds out of 50 degrees at 8 knots with gusts up to 14. That translates into a crosswind of about 14 knots. NASA's safety limit is 15 knots, which can be raised to 17 depending on actual conditions. There are no technical problems at pad 39B and while forecasters say there's a chance for development of a broken deck of clouds at 4,000 feet, engineers are cautiously optimistic about getting Discovery off the ground.
06:00 p.m., 12/09/06, Update: Astronauts strap in; crosswinds, possible low clouds remain a concern
The shuttle Discovery's external tank is loaded with a half-million gallons of liquid oxygen and hydrogen rocket fuel and commander Mark Polansky and his six crewmates are strapped in for a launch attempt at 8:47:34 p.m.
Forecasters continue to predict crosswinds up to 18 knots - 3 knots over NASA's safety limit - at the shuttle's emergency runway and while the limit can be extended to 17 knots based on a recommendation from NASA's chief astronaut, the winds need to die down a bit for a launch tonight.
In addition, there's a chance for a low deck of broken clouds to develop at 3,000 feet, but forecasters are optimistic the cloud cloud cover will be more scattered than overcast.
Conditions at two of NASA's three emergency runways in Spain and France are expected to be "go" as is an emergency landing strip in New Mexico. The only issue for tonight's launch try appears to be the weather in Florida.
01:00 p.m., 12/09/06, Update: MMT 'go' for launch; fueling underway
NASA engineers began the three-hour process to refuel the shuttle Discovery at 12:46 p.m. The countdown is behind schedule, but NASA's Mission Management Team has decided to press ahead with an attempt to launch Discovery tonight at 8:47:34 p.m. on a critical space station mission. The forecast remains 70 percent no-go due to expected high winds and low clouds. The outlook for Sunday and Monday is 60 percent no-go.
12:40 p.m., 12/09/06, Update: MMT 'go' for launch
NASA's Mission Management Team met this afternoon and decided to press ahead this evening with another attempt to launch the shuttle Discovery on a critical space station mission. Engineers are behind schedule and fueling has not yet started, but MMT Chairman LeRoy Cain decided the team had made up enough time to press ahead with the countdown. Launch remains targeted or 8:47:34 p.m. and forecasters continue to predict a 70 percent chance of high crosswinds and low clouds that could cause another delay. This status report will be updated when fueling begins.
10:35 a.m., 12/04/06, Update: Refueling operations behind schedule; MMT meeting at 12:30 p.m. to re-assess shuttle status
NASA's Mission Management Team gave the shuttle Discovery's launch team a provisional "go" to press ahead with refueling operations for a launch attempt this evening at 8:47:34 p.m. But engineers are several hours behind schedule and the start of fueling, originally planned for 10:50 a.m., is on hold. Fuel loading must begin by around 1 p.m. to permit a launch tonight and the MMT plans to meet again at 12:30 p.m. to re-assess Discovery's status and make a decision on how to proceed.
08:30 a.m., 12/09/06, Update: Weather remains unfavorable; refueling on tap
Shuttle engineers are gearing up to refuel the shuttle Discovery for launch tonight at 8:47:34 p.m. to kick off a critical space station mission. Retraction of a huge service gantry ran behind schedule this morning, but a NASA spokesman said the work was expected to be completed in time to support fueling operations, scheduled to begin at 10:52 a.m.
Weather remains the only major concern, with launch forecasters at the Air Force 45th Space Wing predicting a 70 percent chance of high crosswinds and low cloud decks that could force another delay. The odds are 60 percent "no-go" Sunday and Monday.
"High pressure is dominating the Eastern U.S., inducing a strong pressure gradient over Central Florida," according to the morning forecast. "Over the course of the next several days the winds will gradually decrease and veer clockwise as the high pressure area migrates east.
"Also, the easterly flow causes low clouds and isolated showers moving onshore across the launch complex and Shuttle Landing Facility (SLF). Our primary concerns for launch day are SLF crosswinds, a low cloud ceiling, and isolated showers."
The Spaceflight Meteorology Group at the Johnson Space Center, responsible for predicting landing conditions in case of an emergency return-to-launch-site abort, predicts scattered clouds at 4,000 feet, a broken deck at 20,000 feet and a chance for showers and an out-of-limits broken deck at 4,000 feet.
SMG also predicts winds out of 60 degrees at 12 knots gusting to 18, a direct crosswind on shuttle runway 15/33. NASA's launch limit is 15 knots.
An initial attempt to launch Discovery Thursday night was scrubbed at the last minute by low clouds over the launch pad. NASA managers decided to skip a Friday opportunity because of a 90 percent "no-go" forecast. As it turned out, SMG was observed and forecast "go" at one point Friday night and it appeared to the untrained eye that Discovery's crew would have had a shot at getting off had NASA opted for a 24-hour turnaround instead of 48.
But that's hindsight. Florida's coastal weaher is notoriously difficult to predict, reinforcing former Launch Director Bob Sieck's observation that on any given day, the odds of launch are 50-50.
Here is a timeline of today's countdown activities (in EST):
DATE/EST......EVENT _________________________________________________________________ Sat 12/09/06 08:52:00 AM...Begin 2-hour built-in hold (T-minus 6 hours) 09:02:00 AM...Safe-and-arm circuit test 09:42:00 AM...Mission management team tanking meeting 09:52:00 AM...External tank ready for fueling 10:52:00 AM...Resume countdown (T-minus 6 hours) 10:52:00 AM...LO2, LH2 transfer line chilldown 11:37:00 AM...Hydrogen ECO sensors go wet 11:42:00 AM...LO2 fast fill 11:52:00 AM...LH2 fast fill 01:52:00 PM...Fueling complete 01:52:00 PM...Begin 3-hour built-in hold (T-minus 3 hours) 01:52:00 PM...Closeout crew to white room 01:52:00 PM...External tank in stable replenish mode 02:30:00 PM...NASA TV coverage begins 03:08:00 PM...Astronaut photo opportunity (time approximate) 04:27:00 PM...Astronauts don pressure suits 04:52:00 PM...Resume countdown (T-minus 3 hours) 04:57:00 PM...Crew departs O&C building 05:27:00 PM...Astronauts strap in 06:32:00 PM...Hatch closure 07:32:00 PM...Begin 10-minute built-in hold (T-minus 20m) 07:42:00 PM...NASA test director countdown briefing 07:42:00 PM...Resume countdown (T-minus 20m) 07:43:00 PM...Backup flight computer to OPS 1 07:47:00 PM...KSC area clear to launch 07:53:00 PM...Begin final built-in hold (T-minus 9m) 08:03:34 PM...NTD launch status verification 08:38:34 PM...Resume countdown (T-minus 9m) 08:40:04 PM...Orbiter access arm retraction 08:42:00 PM...Launch window opens (actual: 8:42:34 p.m.) 08:42:34 PM...Hydraulic power system (APU) start 08:42:39 PM...Terminate liquid oxygen replenish 08:43:34 PM...Purge sequence 4 hydraulic test 08:43:34 PM...Inertial measurement units to inertial 08:43:39 PM...Aerosurface movement check 08:44:04 PM...Main engine steering test 08:44:39 PM...Oxygen tank pressurization 08:44:59 PM...Fuel cells to internal reactants 08:45:04 PM...Clear caution-and-warning memory 08:45:34 PM...Crew closes visors 08:45:37 PM...Hydrogen tank pressurization 08:46:44 PM...Solid rocket booster joint heater deactivation 08:47:03 PM...Shuttle computers take control of countdown 08:47:13 PM...Booster steering test 08:47:27 PM...Main engine start (T-6.6 seconds) 08:47:34 PM...Booster ignition (LAUNCH)
03:50 p.m., 12/08/06, Update: Weather outlook remains bleak; rendezvous timeline, docking time updated
Shuttle weather officers are continuing to predict a 70 percent chance of bad weather for Saturday's attempt to launch Discovery on a space station assembly mission. "High pressure is migrating into the Eastern US, increasing the pressure gradient over Central Florida; therefore, cool, windy conditions will affect Kennedy Space Center (KSC) Friday," according to the official forecast. "By Saturday, winds will gradually decrease as the high pressure area migrates east, but Shuttle Landing Facility (SLF) crosswinds worsen as the winds continue to turn northeast.
"Also, the easterly flow causes concern for low clouds and isolated showers. Our primary concerns for launch day are SLF crosswinds, a low cloud ceiling, and isolated showers."
The Spaceflight Meteorology Group at the Johnson Space Center in Houston predicts scattered clouds at 3,000 and 20,000 feet with a chance for broken clouds at 3,000 feet and showers within 20 nautical miles - both violations of NASA's flight safety rules. Winds will be out of 40 degrees at 12 knots gusting to 18, translating into a 16-knot crosswind - another violation - on the shuttle's emergency runway.
Conditions are only marginally better Sunday and Monday, when the forecast for both days is 60 percent no-go.
Hoping for the best, engineers plan to top off on-board supplies of liquid hydrogen for Discovery's fuel cells tonight. That will permit launch tries Saturday and Sunday before a standown Monday to top of liquid oxygen. Additional attempts will be possible Tuesday, Thursday and Saturday, Dec. 16.
Dec. 17 is the end of the currently approved launch window. If Discovery is launched on or before Dec. 17, it can complete its 12-day mission and land before the end of the year, even if up to two contingency days are needed because of bad weather or other problems.
Based on the space station's orbit, the window extends through Dec. 26 but any launch past Dec. 17 would require NASA managers to approve flying Discovery over the new year transition. The shuttle's flight software was not designed for use during year-end rollovers and some internal clocks would consider Jan. 1 to be day 366 instead of the first day of a new year.
While the astronauts can reset the computers in flight, managers likely would want the shuttle docked with the international space station on New Year's day just to be safe. That requirement would rule out launches between Dec. 18 and 22.
The preliminary flight plan update posted earlier today has been revised to include the latest rendezvous timeline adjustments resulting from a Saturday launch. A separate rendezvous timeline is now available as well.
09:00 a.m., 12/08/06, Update: Preliminary flight plan, countdown update to reflect 12/9 launch attempt; revised NASA TV sked
An updated countdown timeline, preliminary flight plan and rev. A of the NASA TV schedule are posted on the CBS News STS-116 Quick-Look page. All other relevant SpaceCalc charts and timelines also have been updated. NASA has not yet updated the rendezvous timeline or ascent abort boundaries. Both will be posted here as soon as the data becomes available.
Launch Saturday is targeted for 8:47:34 p.m. The forecast calls for a 70 percent chance of high crosswinds at the shuttle's emergency runway, low clouds and isolated showers. The forecast is 60 percent no-go Sunday and Monday.
Discovery's countdown has been recycled to the T-minus 11-hour mark. The countdown will resume at that point at 3:52 a.m. Saturday. Here is a timeline of countdown highlights (a detailed countdown is posted on the Quick-Look page; all times in EST):
DATE/EST......EVENT _________________________________________________________________ Sat 12/09/06 03:52:00 AM...Resume countdown (T-minus 11 hours) 05:02:00 AM...Fuel cell activation 06:52:00 AM...Final fueling preps; launch area clear 08:52:00 AM...Begin 2-hour built-in hold (T-minus 6 hours) 09:42:00 AM...Mission management team tanking meeting 10:52:00 AM...Resume countdown (T-minus 6 hours) 10:52:00 AM...LO2, LH2 transfer line chilldown (fueling begins) 01:52:00 PM...Fueling complete 01:52:00 PM...Begin 3-hour built-in hold (T-minus 3 hours) 01:52:00 PM...Closeout crew to white room 02:30:00 PM...NASA TV coverage begins 03:08:00 PM...Astronaut photo opportunity (time approximate) 04:27:00 PM...Astronauts don pressure suits 04:52:00 PM...Resume countdown (T-minus 3 hours) 04:57:00 PM...Crew departs O&C building 05:27:00 PM...Crew ingress 06:32:00 PM...Hatch closure 07:32:00 PM...Begin 10-minute built-in hold (T-minus 20m) 07:42:00 PM...NASA test director countdown briefing 07:42:00 PM...Resume countdown (T-minus 20m) 07:43:00 PM...Backup flight computer to OPS 1 07:47:00 PM...KSC area clear to launch 07:53:00 PM...Begin final built-in hold (T-minus 9m) 08:03:34 PM...NTD launch status verification 08:38:34 PM...Resume countdown (T-minus 9m) 08:40:04 PM...Orbiter access arm retraction 08:42:00 PM...Launch window opens 08:42:34 PM...Hydraulic power system (APU) start 08:42:39 PM...Terminate oxygen replenish 08:43:34 PM...Purge sequence 4 hydraulic test 08:43:34 PM...Inertial measurement units to inertial 08:43:39 PM...Aerosurface profile 08:44:04 PM...Main engine steering test 08:44:39 PM...Oxygen tank pressurization 08:44:59 PM...Fuel cells to internal reactants 08:45:04 PM...Clear caution-and-warning memory 08:45:34 PM...Crew closes visors 08:45:37 PM...Hydrogen tank pressurization 08:46:44 PM...Solid rocket booster joint heater deactivation 08:47:03 PM...Shuttle computers take control of countdown 08:47:13 PM...Booster steering test 08:47:27 PM...Main engine start (T-6.6 seconds) 08:47:34 PM...Booster ignition (LAUNCH)Here is an overview of the mission flight plan based on a Saturday launch (a detailed flight plan update is posted on the Quick-Look page; all times in EST; rendezvous timeline, docking and undocking times are subject to change):
DATE/EST........DD...HH...MM...EVENT 12/09/06 Sat 08:48 PM...00...00...00...STS-116 Launch (flight day 1) 12/10/06 Sun 02:48 AM...00...06...00...Crew sleep begins Sun 10:48 AM...00...14...00...Crew wakeup Sun 03:28 PM...00...18...40...Heat shield inspection begins Sun 08:58 PM...01...00...10...Heat shield inspection ends 12/11/06 Mon 02:48 AM...01...06...00...Crew sleep begins Mon 10:48 AM...01...14...00...STS crew wakeup Mon 12:03 PM...01...15...15...Rendezvous timeline begins Mon 05:08 PM...01...20...20...Space station docking (exact time TBD) Mon 08:23 PM...01...23...35...P5 grapple by shuttle arm Mon 09:38 PM...02...00...50...P5 handoff from shuttle to station arm 12/12/06 Tue 02:48 AM...02...06...00...Crew sleep begins Tue 10:48 AM...02...14...00...STS crew wakeup Tue 03:43 PM...02...18...55...EVA-1: Airlock egress Tue 05:08 PM...02...20...20...EVA-1: P5/P4 attachment Tue 09:53 PM...03...01...05...EVA-1: Airlock repressurization 12/13/06 Wed 02:18 AM...03...05...30...STS/ISS crew sleep begins Wed 06:38 AM...03...09...50...MCC: SARJ checkout Wed 10:18 AM...03...13...30...STS crew wakeup Wed 01:28 PM...03...16...40...P6 retracted 3 bays Wed 02:08 PM...03...17...20...P6 retracted to 1 bay Wed 02:53 PM...03...18...05...P3 begins tracking Wed 06:23 PM...03...21...35...P6 port wing final 1 bay retraction 12/14/06 Thu 02:18 AM...04...05...30...STS/ISS crew sleep begins Thu 10:18 AM...04...13...30...STS crew wakeup Thu 03:13 PM...04...18...25...EVA-2: Airlock egress Thu 09:08 PM...05...00...20...EVA-2: Airlock repressurization 12/15/06 Fri 01:48 AM...05...05...00...STS/ISS crew sleep begins Fri 09:48 AM...05...13...00...STS crew wakeup Fri 03:48 PM...05...19...00...Joint crew news conference 12/16/06 Sat 09:48 AM...06...13...00...STS crew wakeup Sat 02:43 PM...06...17...55...EVA-3: Airlock egress Sat 08:48 PM...07...00...00...EVA-3: Airlock repressurization 12/17/06 Sun 01:18 AM...07...04...30...STS/ISS crew sleep begins Sun 09:18 AM...07...12...30...STS crew wakeup 12/18/06 Mon 12:48 AM...08...04...00...STS/ISS crew sleep begins Mon 08:48 AM...08...12...00...STS crew wakeup Mon 02:55 PM...08...18...07...UNDOCKING (exact time TBD) 12/19/06 Tue 12:18 AM...09...03...30...ISS crew sleep begins Tue 07:48 AM...09...11...00...STS crew wakeup Tue 11:53 AM...09...15...05...Heat shield inspection begins Tue 05:23 PM...09...20...35...Heat shield inspection ends Tue 06:43 PM...09...21...55...MEPSI deploy Tue 08:34 PM...09...23...46...RAFT deploy Tue 11:18 PM...10...02...30...Crew sleep begins 12/20/06 Wed 07:18 AM...10...10...30...STS crew wakeup Wed 10:18 AM...10...13...30...Flight control system checkout Wed 10:18 AM...10...13...30...Cabin stow Wed 11:28 AM...10...14...40...Reaction control system hotfire Wed 02:36 PM...10...17...48...ANDE deploy Wed 11:18 PM...11...02...30...Crew sleep begins 12/21/06 Thu 07:18 AM...11...10...30...Crew wakeup Thu 02:35 PM...11...17...47...Deorbit ignition Thu 03:37 PM...11...18...49...Landing
11:30 p.m., 12/07/06, Update: NASA managers stick with Saturday launch option
After reassessing a variety of launch options, NASA managers late tonight decided to stick with an earlier plan to recycle the shuttle Discovery's countdown for a launch try Saturday at 8:47:34 p.m. A revised flight plan, countdown and other timelines will be posted as soon as possible.
11:00 p.m., 12/07/06, Update: NASA managers assess launch options
NASA managers are meeting at this hour to reassess a variety of options for making another attempt to launch the shuttle Discovery on a complex space station mission. Launch is now on hold until at least Saturday, but managers may opt to reschedule launch for Sunday depending on the forecast and required top offs of internal fuel cell supplies. An update will be posted when a final decision is made.
10:15 p.m., 12/07/06, Update: Shuttle launch delayed by cloud cover
After a nail-biting, down-to-the-wire countdown, launch director Mike Leinbach called off an attempt to launch the shuttle Discovery tonight on a critical space station mission because of low, thickening clouds over the Kennedy Space Center.
"We gave it our best shot and did not get clear and convincing evidence in the end that the cloud-ceiling rule would clear enough or us," Leinbach radioed the astronauts at 9:36 p.m. "So we're going to have declare a scrub at this time. Appreciate your support and we'll come up with a scrub-turnaround plan for you."
"We understand," commander Mark Polansky replied from Discovery's flight deck. "Thank the team for all their hard work, try not to be too disappointed. We will be ready to support the next time we get a chance."
With a 90 percent "no-go" forecast for Friday, NASA managers decided to recycle Discovery for a second launch attempt Saturday night at 8:47:34 p.m. The forecast Saturday is 70 percent "no-go," improving slightly Sunday and Monday. But the forecast does not turn positive until Tuesday, when meteorologists expect a 60 percent chance of acceptable weather.
Launch tonight was targeted for 9:35:48 p.m., but low clouds caused concern throughout the final hours of the countdown, primarily because of their potential impact on a return-to-launch-site abort. Launch managers also were concerned about the weather at emergency runways in Spain and France.
As it turned out, the rain in Spain appeared within limits and conditions in Florida were deemed acceptable for an RTLS, should an emergency be declared shortly after launch. But during a hold at the T-minus nine-minute mark, weather officers decided a low deck of clouds over the space center was too thick, violating launch commit criteria.
Leinbach decided to take the countdown to the T-minus five-minute mark and hold there, hoping conditions would improve during the final five minutes of the 10-minute launch window. But it was not to be and he reluctantly cut off the countdown.
The shuttle's overall launch periord extends through Dec. 26. But NASA managers want to launch Discovery before Dec. 17 if at all possible to avoid having the shuttle in orbit on New Year's day. The shuttle's navigation software was not designed to fly over a year-end rollover and some clocks would consider Jan. 1 to be day 366 instead of the first day of the new year.
The astronauts can reset those systems, but it's a complex procedure in an already complicated flight. In addition, flight controllers don't want the shuttle to make the "YERO" transition unless it's docked to the space station at the time. That requirement would prevent a launch between Dec. 18 and 22.
05:50 p.m., 12/07/06, Update: Astronauts head head to launch pad
The Discovery astronauts, decked out in bright-orange pressure suits, departed crew quarters and headed to launch pad 39B today to strap in for blastoff on a space station assembly mission.
Despite low clouds from an approaching cold front, commander Mark Polansky and his six crewmates left the suit-up room and headed to the pad amid cheers and applause from space center workers lining their path to NASA's "Astrovan."
It will take the astronauts until about 7 p.m. to get strapped in aboard Discovery and begin communications checks with Houston. The shuttle's side hatch should be closed for launch by around 7:20 p.m., setting the stage for blastoff at 9:35:48 p.m., weather permitting.
The sky at the Kennedy Space Center is overcase and winds have kicked up in advance of the approaching cold front but as of this writing, it's not at all clear how the weather might play out. There are no technical issues under discussion.
02:50 p.m., 12/07/06, Update: Shuttle fueling complete
The shuttle Discovery's external tank has been loaded with a half-million gallons of rocket fuel. Engine cutoff sensors in the huge tank are working normally and there are no technical problems of any significance.
Liftoff is planned for 9:35:48 p.m., but the weather continues to pose a concern. Clouds have moved into the Kennedy Space Center area and all three of NASA's emergency runways in Spain and France are predicted to be no-go throughout Discovery 's brief launch window.
At least one of the European sites must be acceptable for a launch to proceed, along with good conditions at the Kennedy Space Center's emergency runway in case of an engine failure that might force the crew to make a quick return to Earth.
NASA managers pressing ahead with the countdown, hoping for a break in the weather. Weather officers say launch will depend on the speed of an approaching cold front. The astronauts arew scheduled to begin strapping in shortly after 6 p.m.
12:00 p.m., 12/07/06, Update: Shuttle fueling underway; weather 60 percent no-go
NASA's Mission Management Team, facing a dismal weekend forecast, cleared the shuttle Discovery for fueling today, setting the stage for a launch attempt at 9:35:48 p.m.
Forecasters are predicting a 60 percent chance of low clouds and rain that could prevent a liftoff this evening and all three of NASA's emergency runways in Spain and Africa are predicted to be out of limits due to wind, rain and cloud cover. At least one overseas landing site is required for launch in case of an engine failure that might prevent the shuttle from reaching orbit or returning to Florida.
The forecast for Friday has worsened to 90 percent no-go, "improving" to a 70 percent chance of more bad weather Saturday. The outlook improves somewhat for Sunday and Monday, but not dramatically.
Hoping for the best, engineers began pumping rocket fuel through propellant lines leading to the shuttle's external tank starting a few minutes past 11:30 a.m. The three-hour fueling operation should be complete by around 2:40 p.m. NASA television coverage of launch will begin at 3:30 p.m. and the shuttle's seven-member crew will begin strapping in around 6:15 p.m.
There are no technical problems of any significance at pad 39B and weather remains the only concern. See the 9:30 a.m. update for a detailed countdown timeline.
09:30 a.m., 12/07/06, Update: Shuttle Discovery set for fueling
With engineers gearing up to load the shuttle Discovery's external tank with rocket fuel, forecasters with the Spaceflight Meteorology Group at the Johnson Space Center in Houston have added a chance for rain showers to an already cloudy forecast.
But as of 9:30 a.m., shuttle forecasters in Florida were sticking with a 60 percent chance of a launch delay due to weather, the same probability announced Wednesday when rain wasn't part of the SMG forecast. Forecasters may update the outlook following a final pre-fueling management review that begins within the hour. Updates will be posted as warranted.
The latest SMG forecast for a return-to-launch-site - RTLS - abort calls for a chance of showers within 30 nautical miles and broken cloud decks at 3,000, 6,000 and 20,000 feet in the wake of a cold front. Winds will be out of 340 degrees at 15 knots peaking to 22, resulting in a peak crosswind component of less than 5 knots.
The forecast for two emergency runways in Spain calls for low clouds, turbulence and showers within 20 nautical miles. At an emergency runway in France, high tailwinds are a concern. All three sites are predicted to be "no-go" and at least one is required for a launching to proceed.
Hoping for the best, engineers are gearing up to pump a half-million gallons of liquid oxygen and liquid hydrogen into Discovery's external tank starting at 11:40 a.m. The three-hour procedure should be complete by around 2:40 p.m. NASA television coverage begins at 3:30 p.m. and the astronauts will begin strapping in around 6:15 p.m.
Here are countdown highlights for the rest of the day (in EST):
EST...........EVENT 09:40:00 AM...Begin 2-hour built-in hold (T-minus 6 hours) 09:50:00 AM...Safe-and-arm PIC test 10:30:00 AM...Mission management team tanking meeting 10:40:00 AM...External tank ready for fueling 11:10:00 AM...Orbiter ready for fueling 11:40:00 AM...Resume countdown (T-minus 6 hours) 11:40:00 AM...Liquid oxygen, liquid hydrogen transfer line chilldown 11:50:00 AM...Main propulsion system chill down 11:50:00 AM...LH2 slow fill 12:20:00 PM...LO2 slow fill 12:25:00 PM...Hydrogen ECO sensors go wet 12:30:00 PM...LO2 fast fill 12:40:00 PM...LH2 fast fill 01:55:00 PM...LH2 topping 02:35:00 PM...LH2 replenish 02:40:00 PM...LO2 replenish 02:40:00 PM...Begin 3-hour built-in hold (T-minus 3 hours) 02:40:00 PM...Closeout crew to white room 02:40:00 PM...External tank in stable replenish mode 02:55:00 PM...Astronaut support personnel comm checks 03:25:00 PM...Pre-ingress switch reconfig 03:30:00 PM...NASA TV coverage begins 03:56:00 PM...Astronaut photo opportunity (time approximate) 05:05:00 PM...Final crew weather briefing 05:15:00 PM...Astronauts don pressure suits 05:40:00 PM...Resume countdown (T-minus 3 hours) 05:45:00 PM...Crew departs O&C building 06:15:00 PM...Crew ingress 07:05:00 PM...Astronaut comm checks 07:20:00 PM...Hatch closure 08:05:00 PM...White room closeout 08:20:00 PM...Begin 10-minute built-in hold (T-minus 20m) 08:30:00 PM...NASA Test Director countdown briefing 08:30:00 PM...Resume countdown (T-minus 20m) 08:31:00 PM...Backup flight computer to OPS 1 08:35:00 PM...KSC area clear to launch 08:41:00 PM...Begin final built-in hold (T-minus 9m) 08:51:45 PM...NASA Test Director launch status verification 09:26:47 PM...Resume countdown (T-minus 9m) 09:28:17 PM...Orbiter access arm retraction 09:30:00 PM...Launch window opens (actual: 9:30:47 p.m.) 09:30:47 PM...Hydraulic power system (APU) start 09:30:52 PM...Terminate LO2 replenish 09:31:47 PM...Purge sequence 4 hydraulic test 09:31:47 PM...Inertial measurement units to inertial 09:31:52 PM...Aerosurface profile 09:32:17 PM...Main engine steering test 09:32:52 PM...LO2 tank pressurization 09:33:12 PM...Fuel cells to internal reactants 09:33:17 PM...Clear caution-and-warning memory 09:33:47 PM...Crew closes visors 09:33:50 PM...LH2 tank pressurization 09:34:57 PM...Booster joint heater deactivation 09:35:16 PM...Shuttle computers take control of countdown 09:35:26 PM...Booster steering test 09:35:40 PM...Main engine start (T-6.6 seconds) 09:35:47 PM...SRB ignition (LAUNCH!)
04:15 p.m., 12/06/06, Update: Technical issues resolved; weather only concern for Thursday launch
NASA managers today resolved two open technical issues, formally clearing the shuttle Discovery for launch Thursday night, weather permitting, on a critical mission to switch on the international space station's permanent power and cooling systems.
After reviewing electrical data, NASA's Mission Management Team concluded a brief transient, or voltage spike, overnight Monday did not cause any problems for the shuttle's electrical system. The transient occurred when an unexpected surge caused a launch pad power supply to malfunction. The 800-pound power supply has been replaced.
The MMT also concluded a recent test raising questions about the strength of an adhesive used in the joints between solid-fuel booster segments was not a concern for Discovery's launch and that the joints would perform as needed to prevent any catastrophic leaks.
With the resolution of both open issues, the only question mark now is the weather, with forecasters continuing to predict a 60 percent chance of low clouds that would prevent a launching Thursday. The outlook is 70 percent no-go Friday and 60 percent no-go Saturday.
Liftoff is scheduled for 9:35:49 p.m. Thursday, roughly the moment when Earth's rotation carries the launch site into the plane of the space station's orbit.
NASA's scrub/turnaround options permit seven launch attempts between Dec. 7 and Dec. 17, the end of the currently approved launch window. A launch on Dec. 17 would result in a landing before the end of the year and still provide two contingency days for bad weather or other problems.
Launches after Dec. 17 are possible - the station's orbit permits launchings as late as Dec. 26 - but NASA managers would have to agree on flying Discovery over the new year transition if it came to that.
As it stands today, NASA can attempt four launch attempts in five days - Dec. 7, 8, 10 and 11. That includes one 48-hour stand down to top off on-board supplies of liquid hydrogen between the second and fourth attempts.
After that, alternating hydrogen and oxygen top-offs would result in launch opportunities Dec. 13, 15 and 17.
However, if Discovery fails to get off Thursday - and if the forecast for Friday remains negative (it currently is 70 percent no-go) - NASA managers could opt to stand down Friday to top off liquid hydrogen supplies and make back-to-back attempts Saturday and Sunday.
Under that scenario, if Discovery is still on the ground, the launch team would stand down Monday to top off liquid oxygen to permit additional attempts Tuesday, Thursday and next Saturday (Dec. 12, 14 and 16).
Forecasters expect the weather to improve Sunday through Tuesday and to deteriorate later in the week. But readers are reminded that Florida's weather is notoriously difficult to predict and conditions likely will change between now and then.
11:30 a.m., 12/06/06, Update: Countdown proceeding smoothly as final troubleshooting winds up
NASA and contractor engineers are wrapping up around-the-clock work to resolve two last-minute technical issues that cropped up Tuesday during shuttle Discovery's countdown. While engineers are optimistic Discovery will be cleared for launch as planned Thursday, NASA's Mission Management Team will meet this afternoon to assess the data reviews.
Of more pressing concern, perhaps, forecasters now expect a 60 percent chance of low clouds that would prevent a launch attempt Thursday. In addition, conditions at all three of NASA's emergency runways in Spain and France are predicted to be no-go due to high winds, showers or both. At least one emergency trans-Atlantic landing site is required for launch, regardless of the weather in Florida.
"We're having a nice day here today at Kennedy Space Center, but tomorrow we are expecting a frontal system to come into the area and that is going to bring in a lot of cloud cover for the launch window," said shuttle weather officer Kathy Winters.
"So the forecast is trending toward the worst because right now, it looks like all that moisture is now trending on the models to be in the area. So because of that, we did increase our probability of KSC weather prohibiting launch to 60 percent due to low cloud ceilings."
Winters said the outlook for Friday is 70 percent no-go because of high winds, clouds and isolated showers, improving slightly to 60 percent no-go Saturday. Conditions in Spain and France improve, however, and at least one landing site should be available both days if conditions in Florida permit a launch.
Conditions should improve early next week but additional fronts are expected to move through Central Florida by the middle of the week, bringing more clouds and high winds.
"It does look like we're going to persist with this easterly flow through mid next week," Winters said. "But it does get a little more southeasterly on Tuesday and the winds come down some. ... So we're thinking weather starts getting more promising as we go into Sunday evening, Monday evening, but particularly Tuesday evening.
"We still are going to be concerned about crosswinds (at the shuttle landing strip), but we think Tuesday out of those three days is probably the best day. After that, we start being concerned about the next front that's going to be moving into the area. On Wednesday, we expect the weather to start deteriorating due to that front."
Discovery's mission to re-wire the international space station is scheduled to run 12 days. The shuttle needs to get off the ground by Tuesday to avoid being in orbit or landing on Christmas day.
Otherwise, the countdown is proceeding smoothly as engineers wrap up troubleshooting on two technical issues.
In one case, a large 800-pound launch pad power supply malfunctioned overnight Monday, sending a brief surge through the shuttle's electrical system. The power supply was replaced and engineers are reviewing data to make sure the spike didn't damage any orbiter systems. That review is almost complete and no problems have been found.
The other issue involves test data that has raised questions about the strength of a specific lot of adhesive used to secure insulation in joints between solid-fuel booster segments. Engineers are trying to determine if the adhesive is, in fact, suspect, if it is in place in Discovery's boosters and if so, does it represent a concern.
The insulation in question cannot be inspected at the pad. At least some engineers believe the adhesive isn't even needed because of how the joint operates when the motor is ignited. But the Mission Management Team ordered a review to make sure Discovery's boosters are good to go.
08:05 a.m., 12/06/06, Update: Weather forecast worsens to 60 percent no-go
The weather forecast for Thursday's launch of the shuttle Discovery has worsened to 60 percent "no-go" due to predicted low clouds in the wake of a cold front. The forecast for Friday is now 70 percent no-go due to low clouds, showers and high winds while the outlook for Saturday improves somewhat to 60 percent no-go.
At launch pad 39B, meanwhile, engineers successfully loaded Discovery's internal fuel cell oxygen and hydrogen tanks Tuesday night, a major countdown milestone. No word yet on troubleshooting to resolve questions about a voltage transient at the pad Tuesday and recent test results involving an adhesive used in solid-fuel booster joints. No other technical problems are under discussion.
Additional details will be provided at a countdown status briefing later this morning.
10:00 p.m., 12/05/06, Update: Engineers troubleshoot last-minute technical issues; weather now 60 percent 'go'
After a lengthy launch-minus-two-day review, NASA managers tonight tentatively cleared the shuttle Discovery for liftoff Thursday, weather permitting, pending resolution of two last-minute technical issues. The issues do not appear to be show stoppers, but engineers are collecting additional data to make sure.
"We're on track and on target for Thursday," said LeRoy Cain, chairman of NASA's launch-site Mission Management Team. "All in all, we're in great shape."
Discovery's liftoff on NASA's third shuttle mission of 2006 - the agency's first night launch since 2002 - is targeted for 9:35:49 p.m. The forecast calls for a 60 percent chance of favorable weather.
The goal of the 117th shuttle flight is to re-wire the international space station to take advantage of newly installed solar arrays in a complex transition from an interim power system, used during the initial stages of construction, to the station's permanent system.
"Many of us consider this the most challenging flight that the international space station will have done since we began the effort of assembling the ISS," said space station Program Manager Mike Suffredini.
"Now I need to tell you guys, when you look at the space station when the shuttle leaves, it's not going to look hardly any different than when they got there. But it will be a dramatically different vehicle inside when we finish all the reconfigurations. So this is a big flight for us and we're looking forward to it."
The Discovery astronauts need to rendezvous and dock with the station on their first opportunity - flight day three - to accomplish all of the mission's objectives. For a launch Thursday, that means a docking Saturday evening.
Given a successful reboost of the space station Monday, Discovery's crew now has flight-day-three docking opportunities through Dec. 26, the end of the 2006 launch window, should launch be delayed.
In addition, engineers successfully uplinked and tested new software today designed to detect and automatically correct motor-gear tooth misalignments in a massive rotary joint designed to rotate the station's huge solar arrays to keep them face on to the sun.
Engineers ran into problems with the software last week and while the rotary joint motors can be readjusted using ground commands, the software works much faster, a potential factor in Discovery's already complicated mission.
Today, engineers successfully tested a software patch to correct the problem and Suffredini said the new tool will be available to resolve any misalignments that might otherwise interrupt critical activities.
But Discovery will not be formally cleared for launch until engineers resolve two last-minute issues that were left open at the end of the L-minus two-day review:
- A brief, half-second electrical transient was noted early today when engineers were configuring the shuttle's electrical power systems for launch. Cain said he asked engineers to work through the night to collect data showing whether the brief surge could have caused problems for any of the electrical systems in the orbiter, the external tank or the ship's twin solid-fuel boosters. Cain said a preliminary assessment indicates the shuttle's systems were not affected by the transient, but additional data is needed to make sure.
- A recent engineering test uncovered a potential issue with an adhesive used to bond insulation in the joints between solid-fuel booster segments. The adhesive is associated with so-called J-seals, a post Challenger safety improvement, but Cain said the test results were new and not yet fully understood. Engineers are studying the test data to determine if there are any concerns about the joints in Discovery's boosters.
"I wouldn't want to speculate, really, on either one of those problems as to where they might lead, but you can be certain we'll follow the data."
The only other issue of any significance is the weather. Forecasters now say a cold front expected to pass through Central Florida Thursday has a 40 percent chance of leaving low clouds in its wake that could cause a delay.
The forecast for Friday and Saturday is 60 percent no-go both days.
NASA's scrub/turnaround options permit seven launch attempts between Dec. 7 and Dec. 17, the end of the currently approved launch window. A launch on Dec. 17 would result in a landing before the end of the year and still provide two contingency days for bad weather or other problems.
Launches after Dec. 17 are possible - the station's orbit permits launchings as late as Dec. 26 - but NASA managers would have to agree on flying Discovery over the new year transition if it came to that.
In any case, the launch team's normal scrub-turnaround policy calls for four launch attempts in five days - Dec. 7, 8, 10 and 11. That includes one 48-hour stand down to top off on-board supplies of liquid hydrogen between the second and fourth attempts.
After that, alternating hydrogen and oxygen top-offs would result in launch opportunities Dec. 13, 15 and 17.
11:30 a.m., 12/05/06, Update: Shuttle countdown on track; weather now 70 percent 'go'
The shuttle Discovery's countdown is proceeding smoothly toward blastoff Thursday, engineers said today. Forecasters now predict a 70 percent chance of good weather for NASA's first night launching since the 2003 Columbia disaster.
The countdown began at 11 p.m. Monday and engineers are gearing up to fill the shuttle's internal tanks with liquid oxygen and hydrogen this evening to power the ship's three electricity producing fuel cells.
"Our systems currently are in great shape, the countdown is progressing and we have no issues of consequence," said NASA Test Director Steve Payne. "The teams are ready and we're looking forward to an incredible mission of space shuttle Discovery and a safe and successful landing."
Discovery is scheduled for liftoff at 9:35:47 p.m. Thursday on a complex three-spacewalk mission to re-wire the international space station. The only question mark as of this writing is the weather, with forecasters calling for a 30 percent chance of low clouds behind a front that might block an on-time liftoff.
The odds worsen to 60 percent no-go for launch attempts Friday and Saturday, primarily due to low clouds and high winds. Shuttle weather officer Kathy Winters said the long-range outlook beyond Saturday is generally favorable, although winds will remain a concern next week.
The weather at emergency runways in California and New Mexico is expected to be favorable Thursday, Friday and Saturday and at least one emergency runway will be available all three days in Spain and France.
"Overall, the first day is the best day weather wise and the TAL sites look good all three days," Winters said. "So our main concern will just be the ceilings on launch day and then the winds the following two days."
This will be NASA's third flight this year and its first night launch since 2002. Payne said the launch team is eager to resume more normal launch operations after three years of recovery.
"We're getting more comfortable with being able to do this on a more regular basis," he said. "We came here to launch, this is what we do for a living, this is what we like to do. So getting to do it more often is exciting for most of us. It's a lot more fun doing launches than doing the in-between parts. So we're very happy to be here and we're eager to be here on Thursday night and get this launch in the air."
NASA managers are reviewing the status of Discovery's launch processing and will brief reporters later today. An update will be posted here as soon as possible.
11:05 p.m., 12/04/06, Update: Countdown begins for Thursday shuttle launch
Countdown clocks began ticking Monday night for the launch Thursday of space shuttle Discovery on a complex mission to re-wire the international space station to take advantage of its permanent solar power system.
The countdown began at the T-minus 43-hour mark - 11 p.m. - setting up a launch attempt at 9:35:47 p.m. Thursday, roughly the moment Earth's rotation carries launch pad 39B into the plane of the space station's orbit.
Assuming an on-time liftoff, Discovery will dock with the station Saturday evening, kicking off a three-spacewalk visit that many flight controllers consider the most complicated mission in shuttle history.
Here are updated countdown highlights based on the latest launch time estimate from NASA (Editor's note: All countdown events prior to the end of the T-minus nine-minute hold are targeted to the opening of the shuttle's launch window, which is 9:30:47 p.m. Please note that NASA rounds down, not up, for countdown calculations. The release of the final hold at T-minus nine minutes is targeted to the actual in-plane launch time, or 9:35:47 p.m. All times in EST):
DATE/EST......EVEMT _________________________________________________________________ 10:30:00 PM...Call to stations 11:00:00 PM...Countdown begins Tue 12/05/06 09:00:00 AM...Fuel cell loading preparations 02:40:00 PM...SRB master events controller powerup 03:00:00 PM...Clear crew module 03:00:00 PM...Clear personnel from blast danger area 03:00:00 PM...Begin 4-hour built-in hold 03:45:00 PM...Orbiter pyro-initiator controller test 03:55:00 PM...SRB PIC test 04:55:00 PM...Master events controller pre-flight BITE test 07:00:00 PM...Resume countdown 08:30:00 PM...Fuel cell oxygen loading begins 11:00:00 PM...Fuel cell oxygen load complete 11:00:00 PM...Fuel cell hydrogen loading begins Wed 12/06/06 01:30:00 AM...Fuel cell hydrogen loading complete 02:30:00 AM...Pad open; ingress white room 03:00:00 AM...Begin 4-hour built-in hold 03:00:00 AM...Crew module clean and vacuum 03:30:00 AM...OMBUU demate 05:00:00 AM...APU, engine covers off; RCS paper covers 07:00:00 AM...Countdown resumes 07:00:00 AM...Main engine preps 07:30:00 AM...Master events controllers 1 and 2 on 08:30:00 AM...Remove OMS engine covers, throat plugs 09:00:00 AM...Deflate service structure dock seals; tile inspection 09:30:00 AM...Tile inspection 02:00:00 PM...Tail service masts prepped for fueling 03:00:00 PM...Begin 13-hour 40-minute hold 05:00:00 PM...OIS communications check 05:55:00 PM...JSC flight control team on station 05:55:00 PM...ASP crew module cable inspection 07:00:00 PM...Comm activation 07:30:00 PM...Crew module voice checks 08:50:00 PM...Flight crew equipment late stow Thu 12/07/06 12:30:00 AM...RSS to park position 01:30:00 AM...Final TPS, debris inspection 02:30:00 AM...Ascent switch list 04:40:00 AM...Resume countdown 04:40:00 AM...Terminate pad tours 05:00:00 AM...APU bite test 05:00:00 AM...Pad clear of non-essential personnel 05:50:00 AM...Fuel cell activation 06:40:00 AM...Booster joint heater activation 07:10:00 AM...MEC pre-flight bite test 07:40:00 AM...Final fueling preps; launch area clear 09:25:00 AM...Fuel cell integrity checks complete 09:40:00 AM...Begin 2-hour built-in hold (T-minus 6 hours) 09:50:00 AM...Safe-and-arm PIC test 10:30:00 AM...Mission management team tanking meeting 10:40:00 AM...External tank ready for fueling 11:10:00 AM...Orbiter ready for ET loading 11:40:00 AM...Resume countdown (T-minus 6 hours) 11:40:00 AM...LO2, LH2 transfer line chilldown 11:50:00 AM...Main propulsion system chill down 11:50:00 AM...LH2 slow fill 12:20:00 PM...LO2 slow fill 12:25:00 PM...Hydrogen ECO sensors go wet 12:30:00 PM...LO2 fast fill 12:40:00 PM...LH2 fast fill 01:55:00 PM...LH2 topping 02:35:00 PM...LH2 replenish 02:40:00 PM...LO2 replenish 02:40:00 PM...Begin 3-hour built-in hold (T-minus 3 hours) 02:40:00 PM...Closeout crew to white room 02:40:00 PM...External tank in stable replenish mode 02:55:00 PM...Astronaut support personnel comm checks 03:25:00 PM...Pre-ingress switch reconfig 03:30:00 PM...NASA TV coverage begins 03:56:00 PM...Astronaut photo opportunity (time approximate) 05:05:00 PM...Final crew weather briefing 05:15:00 PM...Astronauts don pressure suits 05:40:00 PM...Resume countdown (T-minus 3 hours) 05:45:00 PM...Crew departs O&C building 06:15:00 PM...Crew ingress 07:05:00 PM...Astronaut comm checks 07:20:00 PM...Hatch closure 08:05:00 PM...White room closeout 08:20:00 PM...Begin 10-minute built-in hold (T-minus 20m) 08:30:00 PM...NASA test director countdown briefing 08:30:00 PM...Resume countdown (T-minus 20m) 08:31:00 PM...Backup flight computer to OPS 1 08:35:00 PM...KSC area clear to launch 08:41:00 PM...Begin final built-in hold (T-minus 9m) 08:51:45 PM...NTD launch status verification 09:26:47 PM...Resume countdown (T-minus 9m) 09:28:17 PM...Orbiter access arm retraction 09:30:00 PM...Launch window opens (actual: 9:30:47 p.m.) 09:30:47 PM...Hydraulic power system (APU) start 09:30:52 PM...Terminate LO2 replenish 09:31:47 PM...Purge sequence 4 hydraulic test 09:31:47 PM...Inertial measurement units to inertial 09:31:52 PM...Aerosurface hydraulic check 09:32:17 PM...Main engine steering test 09:32:52 PM...LO2 tank pressurization 09:33:12 PM...Fuel cells to internal reactants 09:33:17 PM...Clear caution-and-warning memory 09:33:47 PM...Crew closes visors 09:33:50 PM...LH2 tank pressurization 09:34:57 PM...SRB joint heater deactivation 09:35:16 PM...Shuttle computers take control of countdown 09:35:26 PM...SRB steering test 09:35:40 PM...Main engine start (T-6.6 seconds) 09:35:47 PM...SRB ignition (LAUNCH)
05:10 p.m., 12/04/06, Update: Russians boost station orbit; increases shuttle launch options
Russian flight controllers successfully fired engines on a Progress supply ship for nearly 23 minutes today, boosting the international space station's orbit and giving the shuttle Discovery more chances to reach the outpost during its upcoming launch window.
The rocket firing began at 4:36 p.m. and ended on time, boosting the high point of the station's orbit by about nine miles and the low point by a bit more than one mile. The station's orbit now measures 219.5 by 205.9 statute miles.
With a successful reboost maneuver, the shuttle Discovery's crew, scheduled for launch to the station Thursday night, will have docking opportunities on the third day of the mission for any launch through Dec. 23. One additional FD-3 docking opportunity is available for a launch on Christmas day if it came to that.
A reboost maneuver was aborted last Wednesday when on-board software concluded pre-set limits on how far the station could "yaw" to one side would be exceeded. It was the first reboost maneuver since a huge set of solar arrays was mounted on the left end of the station's main power truss during a shuttle flight in September.
The unbalanced mass of the station was at the root of the reboost abort last week. Before today's burn, engineers relaxed the yaw limits based on an analysis that showed the station would not move far enough out of its normal orientation to warrant any concern.
Today's successful reboost changed Discovery's launch time by two seconds. Liftoff is now targeted for 9:35:47 p.m. Thursday. The launch window chart has been updated throughout.
09:30 a.m., 12/04/06, Update: Weather 80 percent 'go' for launch; countdown begins Monday night
Engineers at the Kennedy Space Center are making final preparations to kick off the shuttle Discovery's countdown tonight for launch Thursday on a critical mission to rewire the international space station. The countdown is scheduled to begin at 11 p.m., setting up a launch attempt at 9:36 p.m. Thursday.
There are no technical problems of any significance at pad 39B, but a cold front is bringing low clouds, fog and light rain to the Space Coast area today. Forecasters expect clearing behind the front, along with lower temperatures, resulting in an 80 percent chance of good weather Thursday. The primary concern is a chance for low clouds as the countdown enters its final stages.
But conditions are expected to deteriorate Friday and Saturday, with a 60 percent chance both days of low ceilings, isolated showers and high crosswinds at the shuttle's emergency runway that would force a delay. Forecasters have not yet provided an assessment of weather at NASA's emergency landing sites in Spain and France.
The shuttle's launch window extends through Dec. 17 and possibly through Dec. 26 if lengthy delays are encountered and NASA managers approve flying Discovery over the new year transition.
More important in the near term is a rocket firing later today by a Russian Progress supply ship docked to the international space station. The 21-minute burn is needed to raise the lab's altitude and permit Discovery's crew to dock with the station on the third day of the mission for any launch between Dec. 7 and 23.
A reboost maneuver was aborted last week when on-board software concluded pre-set limits on how far the station could "yaw" to one side would be exceeded. Russian engineers plan to relax those limits for the burn today in a bid to complete the maneuver.
Without it, Discovery's launch opportunities are limited to Dec. 7, 9, 11, 13, 15-22, 24 and 26.
04:30 p.m., 12/03/06, Update: Astronauts arrive at Kennedy
The shuttle Discovery's seven-member crew flew to the Kennedy Space Center Sunday afternoon to prepare for blastoff Thursday on a complex flight to re-wire the international space station.
The astronauts - commander Mark Polansky, pilot William Oefelein, Nicholas Patrick, Robert Curbeam, European Space Agency astronaut Christer Fuglesang, Joan Higginbotham and Sunita "Suni" Williams - flew in aboard five two-seat T-38 jets shortly before 4 p.m.
Discovery's countdown is scheduled to begin at 11 p.m. Monday, targeted for a launch attempt at 9:36 p.m. Thursday night. It will be NASA's first night shuttle launch since 2002.
"Thank you all for coming out to see us today," Polansky said at the shuttle runway. "The STS-116 crew is absolutely just thrilled to be down here for launch week. We're going to go ahead and hopefully have one heck of a night show to give everybody this Thursday night. We're looking forward to the mission."
Williams, who will stay behind aboard the space station for a six-month stay, thanked her crewmates in advance "for hopefully taking me up there before too long."
"I'm just really happy to be here, it's been a long time coming," said Williams, a former Navy diver and helicopter pilot. She said space station commander Mikhail Tyurin "called the other day and said 'Suni, we're waiting for you.' So, I just can't wait to get to my new home and I'm really happy for the opportunity."
Monday afternoon, Russian flight controllers plan to fire rocket engines aboard a Progress supply ship docked to the aft port of the Zvezda command module to boost the space station's orbit. The 21-minute burn will permit Discovery to dock on the third day of its mission for any launch between Dec. 7 and Dec. 23.
A reboost maneuver was aborted last week when on-board software concluded pre-set limits on how far the station could "yaw" to one side would be exceeded. Engineers plan to relax those limits for the burn Monday to complete the maneuver.
Without it, the shuttle can launch Dec. 7, 9, 11, 13, 15-22, 24 and 26, the end of Discovery's launch window.
See the CBS News STS-116 Quick-Look page for a detailed countdown, television schedule, flight plan and other useful information.
11:00 a.m., 12/01/06, Update: Reboost attempt expected Monday; SARJ circuit breaker back in operation
Russian rocket scientists believe they understand the cause of an aborted rocket firing Wednesday to raise the orbit of the international space station. An attempt to complete the reboost maneuver, designed to ensure the shuttle Discovery can reach the outpost throughout its upcoming launch window, is expected Monday after adjustments to control software.
At the Johnson Space Center in Houston, meanwhile, engineers have reset an open circuit breaker in a critical solar array control system after tracing a glitch earlier this week to a software problem. While the remote power controller, or RPC, is working normally, additional attempts to activate new array motor control software have been unsuccessful.
The software is intended to automatically detect and fix motor-gear tooth misalignments in the mechanism used to rotate the station's new solar arrays so they can stay face on to the sun as the station circles the globe.
As it now stands, the mechanism is sound, full redundancy is available and there will be no impact on Discovery's Dec. 7 launch. But barring a quick software fix, any motor-gear tooth misalignments that might occur during Discovery's mission, when the solar alpha rotary joint begins operating full time, will require time-consuming ground commanding to resolve.
The reboost maneuver is needed to raise the station's orbit enough to permit Discovery to dock on the third day of its mission, whenever it gets off the ground. A FD-3 rendezvous is required for this flight because of the complexity of the mission and the time available to complete all the planned tasks.
A planned 18-minute 22-second reboost attempt Wednesday was cut short three minutes and 16 seconds after ignition of thrusters on a Progress supply ship docked to the aft port of the Russian Zvezda command module.
Even with the aborted burn, FD-3 opportunities are available Dec. 7, 9, 11, 13, 15-22, 24 and 26, the end of Discovery's launch window.
Russian engineers now think the burn terminated early when control software detected unexpected sideways "yaw" motion in the station. The motion was caused, engineers believe, because of the station's current unbalanced configuration. With a new set of solar arrays on the far left-side of the station's main power truss, the lab's mass is not symmetric about the direction of motion.
Engineers now believe they can safely relax the yaw limits built into the rocket control software and that the station will remain in an acceptable orientation throughout the planned 21-minute rocket firing Monday.
If the burn goes well, FD-3 docking opportunities will be available every day between Dec. 7 and Dec. 23 and on Christmas day if required.
01:30 p.m., 11/30/06, Update: Station reboost abort assessed; SARJ troubleshooting continues
Space station engineers believe a Russian rocket firing to boost the lab's altitude, needed to permit the shuttle Discovery to dock on flight day three of its upcoming mission, was aborted Wednesday because of the station's unbalanced mass.
Even with the abort, and if no additional firings are attempted before Discovery's launch, an orbital analysis shows the shuttle will have flight day three docking opportunities Dec. 7, the current launch date, as well as Dec. 9, 11, 13, 15-22, 24 and 26. Any launch through Dec. 17 will result in a landing before the end of the year, even with two contingency days for bad weather or other problems. But Dec. 26 is the actual end of the launch window.
The aborted rocket firing Wednesday would have boosted the station's orbit enough to permit FD-3 dockings every day through the Dec. 17 end-of-year launch target. But the planned 18-minute 22-second firing Wednesday shut down after just three minutes and 16 seconds, apparently due to the unbalanced mass and because the station's orientation was not constant.
"That consistent orientation, or attitude, is required for the reboost to continue to avoid any tumbling or excess stresses on the mechanical systems of the international outpost," NASA spokesman Kelly Humphries said today from space station mission control at the Johnson Space Center.
The station is asymmetrical at present due to the addition of a new set of solar arrays on the left end of its main power truss during a shuttle flight in September. The reboost maneuver Wednesday, using engines in a Progress supply ship attached to the back end of the Zvezda command module, was the first since the new arrays were added.
"Attitude managers have been watching over the systems and looking for opportunities that they could find a good configuration of the thrusters that would allow for another reboost attempt tomorrow," Humphries said. "No decision yet."
The next opportunity for a rocket firing is Friday, but engineers say it's doubtful Russian flight controllers will resolve the issue by then.
The shuttle Discovery is scheduled for launch Dec. 7 to re-wire the space station, allowing it take advantage of the new port-side solar arrays. But Discovery must dock on the third day of its mission to complete all the planned work.
While the Russians investigate reboost options, NASA engineers are troubleshooting a glitch Tuesday in which a circuit breaker popped open during tests of new solar array control software.
The new port-side arrays are designed to rotate like a big paddlewheel once operational, allowing them to stay face-on to the sun as the station circles the globe. During Discovery's mission, the solar alpha rotary joint, or SARJ, that physically turns the huge solar wings will be turned on for the first time.
But one of two circuit breakers that routes power to the SARJ motors tripped open Tuesday during a test of new software designed to adjust the alignment of the motors and the drive gear.
Engineers are conducting tests to determine whether the trip was caused by the software or by some sort of hardware problem. Based on preliminary testing, they suspect it was software related. But troubleshooting is not yet complete.
The issue is critical because without a fix, the system would have no redundancy. A second remote power controller trip during the upcoming space station re-wiring work could trigger a blackout aboard the lab complex.
"The work ongoing now is to gather additional data what might have happened in the software associated with that solar array rotary joint," Humphries said. "Later today, they are going to pull down some data from the multiplexer-demultiplexer computer that transmits the data back and forth between that remote power controller and the truss structure."
A software-related data communications glitch involving the MDM could be responsible for the trip. But troubleshooting is not yet complete.
08:45 p.m., 11/29/06, Update: Discovery cleared for Dec. 7 launch pending resolution of space station issues; ice-frost ramp, ECO sensor updates
NASA managers today wrapped up a two-day flight readiness review and officially set Dec. 7 as the target launch date for the shuttle Discovery on an unprecedented mission to rewire the international space station.
If all goes well, Discovery's countdown will begin at 11 p.m. Monday, setting the stage for a launch attempt at 9:35:45 p.m. Thursday. This will be NASA's first night launch since 2002.
But space station engineers are working two issues that must be resolved for Discovery to get off the ground next week:
- Russian engineers must resolve a problem that cut short a space station rocket firing today three minutes into a planned 18-minute 22-second burn. The rocket firing, using engines in the Progress-23 supply ship docked to the aft of the Russian Zvezda command module, is required to adjust the station's orbit, permitting the shuttle to dock on the third day of its 12-day mission. The next opportunity to complete the interrupted reboost maneuver is Friday.
- NASA engineers must resolve a glitch that cropped up Tuesday during tests of new solar array drive control software on the international space station. The software did not work as expected and one of two critical circuit breakers that deliver power to motors that allow the newly installed solar arrays to rotate and track the sun popped open. Two healthy circuit breakers are needed for Discovery's re-wiring mission to provide redundancy in case of additional problems that might otherwise stall the arrays. In a worst case scenario, that could lead to a blackout aboard the outpost.
"There is pretty complex software and commanding that's associated with those Progress burns and typically we'll find something there that was out of configuration that cut that burn a little bit short," Gerstenmaier said.
But the timing in this case is critical and relatively quick action is needed. Because of the complexity of Discovery's mission, docking must occur on flight day three. The reboost maneuver is designed to ensure FD-3 docking opportunities through Dec. 17, the last day the shuttle can launch and complete its mission, with two contingency days, before the end of the year.
With today's premature engine shutdown on the station, the shuttle does not yet have a flight-day three docking opportunity for a Dec. 7 launch.
The actual close of the current launch window, based on thermal issues when the shuttle is docked to the station, is Dec. 26. Should Discovery be delayed significantly, flight controllers say a second reboost maneuver Dec. 14 would permit FD-3 dockings through the end of the window.
But any launch after Dec. 19 would require Discovery to be in orbit during the year-end rollover from Dec. 31 to Jan. 1.
The shuttle's on-board flight control software was not designed to operate during a year-end rollover. Engineers are concerned about possible unknown consequences if Discovery's launch is delayed to the point where a flight across the 2006/2007 transition becomes an issue. Gerstenmaier said managers will revisit the issue if Discovery encounters any major delays. But as of today, Dec. 17 is the effective close of the launch window (additional launch window details are avaiable below in the Nov. 27 status report).
The goal of Discovery's mission is to switch the space station's electrical system from from its current interim configuration, sufficient for the lab's initial assembly, to its permanent system, which is required before attachment of additional modules.
During two spacewalks, the astronauts and flight controllers will power down the station's two major circuits, one at a time, to make the switchover. Each time a channel is powered down, critical station systems will no longer have redundancy.
As part of the re-wiring work, the astronauts must retract one wing of a set of solar arrays that served the interim system to permit a new set of arrays, installed during a shuttle flight in September, to begin tracking the sun.
The arrays are designed to rotate like a giant paddle wheel using a solar alpha rotary joint, or SARJ mechanism. The SARJ also was installed in September and after troubleshooting a software problem, flight controllers successfully engaged the teeth of the main drive gear with the motors needed to turn the arrays.
To avoid similar problems in the future, controllers uplinked new software to detect SARJ gear tooth misalignments and make adjustments as required for smooth operation. During tests Tuesday, however, a circuit breaker known as a remote power controller, or RPC, tripped and engineers have been unable to reset it.
The RPC in question is one of two that route power to the SARJ motors. Both are needed to provide redundancy. In a worst-case scenario - the second RPC fails while one power channel is down for re-wiring - the solar arrays would stop tracking the sun and power output might drop below the threshold needed by critical systems on the one operational channel.
Gerstenmaier said complex testing is underway at the Johnson Space Center in Houston using the same software and electrical components that operate like the hardware in orbit. If the problem is software related, engineers should be able to devise a fix to put the breaker back in operation.
If the problem is hardware related, the issue will be harder to resolve. No spares are available on the space station and while parts could be taken from station components awaiting launch, it's not yet clear how that might affect Discovery's eventual launch date.
Hoping for the best, Discovery's crew - commander Mark Polansky, pilot William Oefelein, Nicholas Patrick, Robert Curbeam, European Space Agency astronaut Christer Fuglesang, Joan Higginbotham and Sunita Williams - plans to fly to the Kennedy Space Center Sunday to prepare for launch.
Here are countdown highlights (in EST):
EST...........EVENT Sun 12/03/06 04:30:00 PM...Crew arrives at KSC Mon 12/04/06 10:30:00 PM...Call to stations 11:00:00 PM...Countdown begins (T-minus 43 hours) Tue 12/05/06 03:00:00 PM...Begin 4-hour built-in hold 07:00:00 PM...Resume countdown (T-minus 27 hours) 08:30:00 PM...Fuel cell oxygen loading begins 11:00:00 PM...Fuel cell oxygen load complete 11:00:00 PM...Fuel cell hydrogen loading begins Wed 12/06/06 01:30:00 AM...Fuel cell hydrogen loading complete 02:30:00 AM...Pad open; ingress white room 03:00:00 AM...Begin 4-hour built-in hold 07:00:00 AM...Countdown resumes (T-minus 19 hours) 03:00:00 PM...Begin 13-hour 40-minute hold 07:00:00 PM...Communications system activation 07:30:00 PM...Crew module voice checks 08:50:00 PM...Flight crew equipment late stow Thu 12/07/06 12:27:00 AM...Rotating service structure moved to park position 03:40:00 AM...Countdown resumes (T-minus 11 hours) 09:40:00 AM...Begin 2-hour built-in hold (T-minus 6 hours) 10:30:00 AM...Mission management team tanking meeting 10:40:00 AM...External tank ready for fueling 11:40:00 AM...Resume countdown (T-minus 6 hours) 11:40:00 AM...Liquid oxygen/hydrogen transfer line chilldown 11:50:00 AM...Main propulsion system chill down 11:50:00 AM...LH2 slow fill 12:20:00 PM...LO2 slow fill 12:25:00 PM...Hydrogen ECO sensors go wet 12:30:00 PM...LO2 fast fill 12:40:00 PM...LH2 fast fill 02:40:00 PM...Begin 3-hour built-in hold (T-minus 3 hours) 02:40:00 PM...Closeout crew to white room 02:40:00 PM...External tank in stable replenish mode 03:30:00 PM...NASA TV coverage begins 03:56:00 PM...Astronaut photo opportunity (time approximate) 05:15:00 PM...Astronauts don pressure suits 05:40:00 PM...Resume countdown (T-minus 3 hours) 05:45:00 PM...Crew departs O&C building 06:15:00 PM...Crew ingress 07:05:00 PM...Astronaut comm checks 07:20:00 PM...Hatch closure 08:20:00 PM...Begin 10-minute built-in hold (T-minus 20m) 08:30:00 PM...Resume countdown (T-minus 20m) 08:41:00 PM...Begin final built-in hold (T-minus 9m) 08:51:44 PM...NTD launch status verification 09:26:44 PM...Resume countdown (T-minus 9m) 09:30:00 PM...Launch window opens (actual: 9:30:45 p.m.) 09:35:45 PM...Liftoff 09:40:45 PM...Launch window closesShuttle Program Manager Wayne Hale said senior managers today agreed to press ahead with a launch attempt even if one of four engine cutoff - ECO - sensors in the ship's external fuel tank fails during the final hours of the countdown.
The sensors are part of a backup system that ensures the shuttle's main engines don't run too long and pump the tank dry with potentially catastrophic results. In the past, all four sensors were required and launch of the shuttle Atlantis was delayed 24 hours in September when one of its ECO sensors at one point indicated it was submerged in supercold hydrogen rocket fuel when, in fact, it was dry.
Because of the logic built into the circuitry, one sensor can "fail wet" without compromising redundancy, engineers have concluded. If a single sensor fails wet during Discovery's countdown, NASA will proceed with launch. If multiple sensors fail, or if one "fails dry," the launch will be delayed.
Hale also said engineers have revised their estimate of the danger posed by so-called ice-frost ramps on the shuttle's external tank. The foam ramps are in place to prevent dangerous pre-launch ice buildups around external fittings that hold pressurization lines in place.
For the last two flights, the ramps were officially classified as "probable/catastrophic," meaning it was probable, over the 100-flight design life of a given shuttle, that foam debris could come off and cause catastrophic impact damage to the shuttle's heat shield. NASA Administrator Mike Griffin said he did not believe that classification was correct and approved flying anyway while a permanent fix was developed.
Hale said today the probability of a catastrophic failure due to the IFRs, once thought to be in the neighborhood of 1-in-100, had decreased by an "order of magnitude" based on the actual performance of the ramps over the past two flights. While he did not provide any numbers, he said the ramps are now classified as "infrequent/catastrophic."
"We now know that the hazard is less than we thought it was last summer," Hale said. "It's still a hazard, we're working on it, we are making improvements and doing real things to the tank to make ourselves safer, but it's not nearly as bad as we thought it was because we now know more. ... We're concerned, but we're not nearly as frightened as we were before."
NASA managers ultimately plan to replace the ice-frost ramps with titanium fittings that will virtually eliminate the threat of foam debris. They originally planned to implement an interim fix early next year, but Hale said the next flight, currently targeted for March, will fly with the same IFR design that is currently in place on Discovery's tank.
Engineers now are debating whether to call off the interim work and focus instead on implementing the permanent fix as soon as possible.
01:30 p.m., 11/27/06, Update: Flight readiness review on tap; updating launch windows
NASA managers are gathering at the Kennedy Space Center for a two-day flight readiness review Tuesday and Wednesday to assess the shuttle Discovery's launch processing and to set an official launch date for mission STS-116.
Liftoff currently is targeted for Dec. 7 and there do not appear to be any major issues that would force a delay. But the launch window is complex because it includes lighting, holiday and end-of-year issues that are not normally on the table.
As it now stands, the window opens Dec. 7 and closes Dec. 26 because of a so-called "beta angle cutout," that is, thermal issues associated with the international space station due to the angle between the plane of its orbit and the sun. Based on the beta angle, the shuttle cannot launch between Dec. 27 and Jan. 13.
To reach the international space station, Discovery must be launched when Earth's rotation carries the launch pad into the plane of the lab's orbit. For mission STS-116, on Dec. 7, that works out to 9:35:45 p.m., resulting in NASA's first night launch since 2002. Daylight launch opportunities do not become available until Dec. 18.
Major post-Columbia objectives through the first three return-to-flight missions included photographing the shuttle's external fuel tank after separation in orbit to document how its foam insulation performed during ascent. For STS-116, NASA managers are relaxing that requirement based on the performance of the tank over the past three flights.
For the record, sufficient lighting for a camera mounted in the shuttle's belly does not become available until Dec. 20. For crew hand-held photography, good lighting is not expected until Dec. 24.
This Wednesday, rocket engines in a Progress supply ship will fire for 20 minutes to boost the space station's orbit slightly, giving Discovery's crew opportunities to rendezvous and dock on flight day three for any launch between Dec. 7 and Dec. 21.
Launches on Dec. 22, 24 and 26 would result in a flight day four rendezvous, which is considered unacceptable. If it comes to that, an additional space station reboost maneuver would be carried out Dec. 14 to ensure FD-3 dockings through the end of the shuttle's launch window. A launch past Dec. 19 would result in the shuttle being in orbit during the year-end rollover from Dec. 31 to Jan. 1. The "YERO" issue has received quite a bit of attention in recent months because of concern about possible computer glitches. The shuttle's flight software was not designed to handle the transition from one year to the next and YERO will be a topic of discussion during the flight readiness review this week.
Launches between Dec. 7 and 12 result in a landing before Christmas for a standard 12-day mission. A launch on Dec. 17 would result in a landing on Dec. 29, preserving two days for bad landing weather or some other contingency. Launches past Dec. 17 could result in a YERO flight, depending on weather or other problems, while a launch past Dec. 19 would require the shuttle to be in orbit over the year-end rollover.
Flight controllers are expected to recommend against flying across the transition, sources say, but senior managers may approve the option anyway based on recent tests and analysis. If so, flight controllers would prefer to have the shuttle docked at the station for the actual rollover to make sure they have time to resolve any computer glitches that might arise.
If the shuttle launches between Dec. 18 and 22, however, the shuttle would be undocked and in free flight. Launches Dec. 23 through Dec. 26 would result in a docked rollover.
That said, here are the latest launch times for Discovery. Readers should note the actual launch window opens exactly five minutes before the "in-plane" times listed below and closes five minutes later (all times in EST and subject to minor changes; YERO: year-end rollover; UM: umbilical camera; HH: handheld camera; Partial: some lighting available, but marginal):
DATE.......LAUNCH........DOCK...........LIGHTING...YERO.......ET IMAGERY 12/07/06...09:35:45 PM...FD-3...........Night......N/A........None 12/08/06...09:13:13 PM...FD-3...........Night......N/A........None 12/09/06...08:47:31 PM...FD-3...........Night......N/A........None 12/10/06...08:24:59 PM...FD-3...........Night......N/A........None 12/11/06...07:59:17 PM...FD-3...........Night......N/A........None 12/12/06...07:36:45 PM...FD-3...........Night......N/A........None 12/13/06...07:11:03 PM...FD-3...........Night......N/A........None 12/14/06...06:48:31 PM...FD-3...........Night......N/A........None 12/15/06...06:22:49 PM...FD-3...........Night......N/A........None 12/16/06...06:00:17 PM...FD-3...........Night......N/A........None 12/17/06...05:34:35 PM...FD-3...........Night......N/A........None Note.......All 12+2 flights above land on or before 12/31 12/18/06...05:12:03 PM...FD-3...........Day........Undocked...None 12/19/06...04:46:21 PM...FD-3...........Day........Undocked...Partial UM Note.......All flights below result in landings on or after Jan. 1 12/20/06...04:23:49 PM...FD-3...........Day........Undocked...UM 12/21/06...03:58:07 PM...FD-3...........Day........Undocked...UM 12/22/06...03:35:36 PM...FD-3/reboost...Day........Undocked...UM/partial HH 12/23/06...03:09:53 PM...FD-3...........Day........Docked.....UM/partial HH 12/24/06...02:47:22 PM...FD-3/reboost...Day........Docked.....UM/HH 12/25/06...02:21:39 PM...FD-3...........Day........Docked.....UM/HH 12/26/06...01:59:08 PM...FD-3/reboost...Day........Docked.....UM/HH
04:30 p.m., 11/10/06, Update: Updated flight plan, trajectory timeline posted
An updated STS-116 flight plan has been posted on the CBS News STS-116 Quick-Look page, along with the latest rendezvous timeline. The revised flight plan reflects a recent decision to insert an additional day (flight day 11) into the mission and to baseline a post-undocking heat shield inspection.
Here are mission highlights at a glance (in EST and mission elapsed time):
12/07/06 Thu 09:36 PM...00...00...00...STS-116 Launch 12/08/06 Fri 03:36 AM...00...06...00...Crew sleep begins Fri 11:36 AM...00...14...00...Crew wakeup Fri 04:06 PM...00...18...30...Heat shield inspections begin Fri 09:36 PM...01...00...00...Heat shield inspections end 12/09/06 Sat 03:36 AM...01...06...00...Crew sleep begins Sat 11:36 AM...01...14...00...STS/ISS crew wakeup Sat 07:36 PM...01...22...00...Discovery docks with space station Sat 10:46 PM...02...01...10...P5 truss segment unberth Sat 11:16 PM...02...01...40...P5 handoff from shuttle to station arm 12/10/06 Sun 03:06 AM...02...05...30...Crew sleep begins Sun 11:36 AM...02...14...00...STS crew wakeup Sun 04:31 PM...02...18...55...EVA-1: Airlock egress Sun 05:56 PM...02...20...20...EVA-1: P5/P4 attachment Sun 10:16 PM...03...00...40...EVA-1: Airlock ingress 12/11/06 Mon 03:06 AM...03...05...30...STS/ISS crew sleep begins Mon 11:06 AM...03...13...30...STS crew wakeup Mon 03:01 PM...03...17...25...P6 retracted 3 bays Mon 03:11 PM...03...17...35...P6 survey Mon 03:41 PM...03...18...05...P6 port panel retracted to 1 bay Mon 04:31 PM...03...18...55...P4 arrays begin sun tracking 12/12/06 Tue 03:06 AM...04...05...30...STS/ISS crew sleep begins Tue 11:06 AM...04...13...30...STS crew wakeup Tue 04:01 PM...04...18...25...EVA-2: Airlock egress Tue 04:26 PM...04...18...50...EVA-2: Channel 2/3 power reconfig Tue 09:31 PM...04...23...55...EVA-2: Airlock ingress 12/13/06 Wed 02:36 AM...05...05...00...STS/ISS crew sleep begins Wed 10:36 AM...05...13...00...STS crew wakeup Wed 05:36 PM...05...20...00...Joint crew news conference 12/14/06 Thu 02:36 AM...06...05...00...STS/ISS crew sleep begins Thu 10:36 AM...06...13...00...STS crew wakeup Thu 03:31 PM...06...17...55...EVA-3: Airlock egress Thu 03:56 PM...06...18...20...EVA-3: Channel 1/4 power reconfig Thu 09:11 PM...06...23...35...EVA-3: Airlock ingress 12/15/06 Fri 02:06 AM...07...04...30...STS/ISS crew sleep begins Fri 10:06 AM...07...12...30...STS crew wakeup 12/16/06 Sat 01:36 AM...08...04...00...STS/ISS crew sleep begins Sat 09:36 AM...08...12...00...STS crew wakeup Sat 04:20 PM...08...18...44...Discovery undocks from space station Sat 07:14 PM...08...21...38...MEPSI deploy Sat 09:05 PM...08...23...29...RAFT deploy 12/17/06 Sun 01:06 AM...09...03...30...STS/ISS crew sleep begins Sun 09:06 AM...09...11...30...STS crew wakeup Sun 12:06 PM...09...14...30...Late heat shield inspections begin 12/18/06 Mon 12:06 AM...10...02...30...Crew sleep begins Mon 08:06 AM...10...10...30...STS crew wakeup Mon 11:36 AM...10...14...00...Flight control system checkout Mon 12:46 PM...10...15...10...Reaction control system hotfire Mon 03:31 PM...10...17...55...ANDE deploy 12/19/06 Tue 12:06 AM...11...02...30...Crew sleep begins Tue 08:06 AM...11...10...30...Crew wakeup Tue 03:32 PM...11...17...56...Deorbit ignition (orbit 186) Tue 04:34 PM...11...18...58...Landing
01:00 p.m., 11/09/06, Update: Discovery moved to launch pad; mission baseline now 12 days; NASA rules out moving launch up a day to 12/6
UPDATED at 3:45 p.m. to include details of solar array software development issue
The shuttle Discovery was hauled to launch pad 39B today for work to ready the ship for blastoff Dec. 7 on a critical space station assembly and re-wiring mission. NASA managers considered moving launch up an additional day, to Dec. 6, but ruled that out today based on time needed to complete crew training and to develop software intended to prevent damage to the station's new solar arrays.
The software in question is designed to constantly monitor the positions of the sun-tracking arrays and warn flight controllers of possible rocket plume contamination or excessive structural loads, Sources said the new monitoring software - and the training needed to use it - likely cannot be formally certified before Discovery's current December launch window closes.
Instead, engineers hope to have a workable system in place by Dec. 7, although details about what needs to be done are not yet clear.
Mounted atop a powerful crawler-transporter, Discovery and its mobile launch platform began the 4.2-mile trip from the Vehicle Assembly Building to the pad at 12:29 a.m. The MLP was "hard down" at the pad by 9:03 a.m.
Discovery's crew - commander Mark Polansky, pilot William Oefelein, Nicholas Patrick, Robert Curbeam, European Space Agency astronaut Christer Fuglesang, Joan Higginbotham and Sunita Williams - plans to fly to the Kennedy Space Center next week to review emergency procedures and participate in a dress rehearsal countdown Thursday.
A two-day flight readiness review to assess Discovery's processing is scheduled for Nov. 28-29. If no problems develop, launch will be targeted for no earlier than Dec. 7. The launch window that day opens at 9:30:42 p.m. and closes at 9:40:42 p.m. Liftoff will be targeted for the middle of the window, at 9:35:42 p.m.
The goal of the flight is to attach a short spacer segment to the station's solar array truss and to carry out a complex two-spacewalk re-wiring job to switch the station over from interim power to its permanent electrical system. That change over, which requires extensive realtime ground commanding and system power cycling during ongoing spacewalks, makes Discovery's flight the most complex station assembly mission yet attempted.
Mission STS-116 initially was baselined for 11 days with the possibility of extending the flight one day in orbit if on-board supplies permitted. NASA managers recently made that official, baselining a 12-day flight and adding a post-undocking (flight day 11) heat shield inspection to the crew's timeline. Here is a revised summary timeline:
- FD-1 (12/07): Launch at 9:36 p.m.
- FD-2 (12/08): Heat shield inspection
- FD-3 (12/09): Space station docking; P5 truss removal from bay
- FD-4 (12/10): Spacewalk 1: P5 attachment to P4 solar array segment
- FD-5 (12/11): P6 port solar wing retraction
- FD-6 (12/12): Spacewalk 2: Electrical channel 2/3 re-wiring
- FD-7 (12/13): Crew off duty time; crew news conference
- FD-8 (12/14): Spacewalk 3: Electrical channel 1/4 re-wiring
- FD-9 (12/15): Equipment transfers
- FD-10 (12/16): Discovery undocks from space station
- FD-11 (12/17): Heat shield inspection
- FD-12 (12/18): Cabin stow
- FD-13 (12/19): Landing at 4:37 p.m.
Completing development of the new solar array monitoring software is a bit of a wild card in mission planning.
Before the station can be switched from interim to permanent power, one of the two solar array wings providing interim power must be retracted. In addition, the new array panels attached to the left side of the station's main solar power truss in September must begin rotating like a giant paddle wheel to keep face on to the sun.
As the arrays rotate on the end of a massive solar alpha rotary joint, or SARJ, their masts are moved at right angles, by so-called beta-gimbal joints, to change their pitch as required.
Engineers always knew the start of that complex, automated sun tracking would require careful monitoring to make sure station or shuttle thrusters did not deposit contamination on the solar cells or impart excessive loads that might damage or even break the fragile hardware.
As it turned out, the requirements for the software were late and development is not yet complete. Engineers are racing the clock to get a workable, if not certified, version in place by the opening of Discovery's launch window.
With that issue percolating in the background, Program Manager Wayne Hale asked the shuttle team to consider moving launch up to Dec. 6 as a way to add a day to Discovery's launch window. An extra day would provide a bit of insurance getting the shuttle mission off before running up against the end of the year.
When the shuttle's flight control software was developed in the 1970s, NASA managers did not envision the possibility of flying missions during the transition from one year to the next. Internal clocks, instead of rolling over to Jan. 1, 2007, would simply keep counting up, putting them at odds with navigation systems on the ground.
"It's an interesting problem because if you remember a few years ago, we went through the Y2K change and there was a lot of concern about what computers would do," Hale told reporters earlier this week. "The interesting thing about the shuttle computers and the ground computers that support the shuttle is they were never envisioned to fly through a year-end change over. So the shuttle computers actually keep counting and they believe it's day 366 instead of day 1 of the year.
"That sounds rather trivial, but the fact of the matter is to keep the navigation in synch with the rest of the world, which has changed from day 365 to day 1, you've got to make that change appropriately and it was never designed in."
Space station software, on the other hand, was designed from the ground up to handle year-end rollovers and in the wake of the 2003 Columbia disaster, engineers re-evaluated the shuttle's software to make sure an emergency rescue mission, if needed, could safely fly across a new year.
"We had certified that for contingency use in the sense that if we ever had to fly a launch-on-need rescue mission and it happened to cross a year-end rollover, it would work," Hale said. "So we did quite a bit of testing on the software at that point. But there is a different level of testing that you need to do when you want to execute a procedure like that for a normal, planned, not contingency kind of operation.
"In April, we asked the team to go off and do that work. There had been a series of problems with that work and it turns out while we feel confident that it would work if we had to use it, we did not get the normal amount of testing and a normal amount of runtime on what are some very complicated procedures, both on the ground and with the crew to keep everything in synch across the end of the year.
"So right now, coming out of a review last week, it looks like we will not try to execute the flight over the year end," Hale said. "We're going to review that at the flight readiness review, so I would not call it a hard constraint at this time but rather a recommendation to take forward."
NASA managers today officially ruled out a Dec. 6 launch. A requirement to be back on the ground by Dec. 31 at the latest means Discovery must take off by Dec. 17, which would result in a landing Dec. 29 and still preserve two additional landing days in case of bad weather or other problems.
Florida's nighttime December weather is relatively mild and with 11 launch opportunities from Dec. 7 through Dec. 17, flight controllers are optimistic they'll get Discovery into space before the 2006 window closes.
"With the more benign weather that we have in Florida in December," Hale said, "we think that would probably be adequate to get us off."
A detailed flight plan update to reflect the addition of post-undocking heat shield inspections on flight day 11 will be posted here shortly.
10:30 a.m., 10/26/06, Update: Astronauts, flight controllers gear up for complex mission to re-wire space station
Editor's Note...
A shorter version of this shuttle mission preview was posted here last month. It has been expanded, based on interviews with lead station Flight Director John Curry, shuttle commander Mark Polansky and lead spacewalker Bob Curbeam, and now includes detailed background on the operation of the station's electrical power and cooling systems and how those systems will be reconfigured during STS-116.
By WILLIAM HARWOOD
CBS News
Shuttle astronauts, flight controllers and space station engineers are in the final stages of training for a complex multi-spacewalk mission in December to conduct electronic bypass surgery on the orbital lab complex and activate its main power and cooling systems.
Construction has now reached the point where an interim power system, designed to support the station during its initial assembly, needs to be phased out. With the installation of new solar arrays in September, NASA is finally ready to activate the lab's permanent power grid, a major step that sets the stage for attachment of European and Japanese research modules.
But in order to do that, the Discovery astronauts and station crew must first retract one wing of the older solar arrays providing interim electricity to the U.S. segment of the station. If that goes well - and no one knows whether the fragile array wing will, in fact, retract smoothly - commands will be sent to begin slowly rotating the new set of arrays installed in September.
Flight controllers then will power down the lab's major circuits, two at a time, while spacewalking astronauts unplug and re-plug electrical cables into different sockets.
Precisely timed computer scripts will set electro-mechanical switches to begin routing power from the new arrays and the remaining older array wing through four big circuit control boxes called main bus switching units, or MBSUs, mounted in the center of the station's main solar power truss. The MBSUs, in turn, will send array power to a host of transformers, circuit breakers and other components to provide precisely regulated 124-volt DC power to the station's myriad systems.
But the MBSUs will begin heating up as soon as the power begins flowing. In a high-stakes race against the clock, the astronauts and flight controllers must quickly activate powerful pumps to push ammonia coolant through cold plates and radiators to keep the MBSUs and other components from overheating.
"This is pretty much your classic chicken-or-egg scenario here," said Paul Hill, mission operations manager at the Johnson Space Center in Houston. "You have to have active cooling to the switch boxes (main bus switching units, or MBSUs) in order to route power through them.ÊYou have to have power flowing through the MBSUs in order to power the cooling equipment."
It will take two virtually identical spacewalks - and hundreds of commands and cable switches - to reconfigure the station's four major circuits. There is little margin for error and a fair amount of uncertainty. While the MBSUs have at least been tested in space to confirm electrical continuity, the ammonia coolant system has never been activated or tested in space.
"We have these big boxes in the middle of the space station, big switch boxes," Hill said of the MBSUs. "You've got four pairs of solar arrays (when the station is complete) and you've got all these finger-thick copper wires that run from the solar arrays to the middle of the truss. Those are the boxes that, for an assembly-complete station, you want all your power flowing from and then going down to our converters that then flow power to individual pieces of equipment.
"In order to reconfigure the electrical system and the cooling system so we have the permanent cooling system up and we're flowing all power through these main switching boxes, we've got to power off a hell of a lot of equipment so we can safe those individual copper lines, disconnect them and reconnect them to where we want them. That will be a case where we'll have to power off almost all the U.S. segment one way or the other throughout that whole process."
Should any significant problems develop - an ammonia leak, an electrical glitch, a computer commanding issue - that might prevent the activation of a cooling system, the astronauts could be forced to quickly switch back to the interim power system, cutting of the flow of electricity to the MBSUs while engineers in Houston consider alternatives.
"What makes this mission singularly unique is the choreography between what we're doing in orbit and what the ground is doing because of the amazing amount of ground commanding to go ahead and power down and re-power the ISS electrical system while we're out there doing spacewalks," said Discovery commander Mark Polansky.
"So yeah, we hold our breath like everybody else while the ground sends the commands and then wait to find out how it's going to work."
Said Bob Curbeam, the lead spacewalker on the mission: "It is very complicated. The thing I think is kind of cool about it is, we have these three spacewalks, the second two, the big player in them both is mission control. ... The pressure is on those guys.
"While they have to be very slow and deliberate about how they do it, they can't be too slow because the clock's ticking on us. There's got to be a point where they say OK, it's going to be fine, you guys press on or OK, we have to back out of it and go back to (interim) power and we have to undo everything we did and then talk about what we're going to do after that."
In that case, the pressure will quickly switch back to the astronauts.
"Our tasks are relatively straight forward as long as you don't run into any of the contingencies," he said. "And that's the big deal. We probably train for contingencies more than most crews because we know that's where the devil is."
Launch of the 117th shuttle mission, the fourth since the Columbia disaster, is targeted for Dec. 7, around 9:39 p.m. It will be NASA's first night launch since 2002, the result of a recent decision to waive a post-Columbia requirement to launch shuttles in daylight.
The daylight constraint was put in place to ensure good photo documentation of the shuttle's heat shield and external tank foam insulation during the first few post-Columbia missions. Problems seen during the first such flight in July 2005 were addressed and NASA's two most recent launches, in July and September, were relatively debris free.
Given the tank's recent performance, and experience demonstrating that on-orbit inspections can spot any damage that does occur, NASA managers cleared Discovery for launch at night.
But the Dec. 7 target date had already been booked by the Air Force for launch of a Lockheed Martin Atlas 5 rocket carrying a suite of military payloads. If the Atlas stays on track, the shuttle launch will slip a few days. NASA planners want to get Discovery off the ground by Dec. 17 at the latest to avoid any possible software issues that might arise with a shuttle in orbit during the rollover to 2007.
Another wild card for mission STS-116 is the health of the space station's Russian Elektron oxygen generator. The device broke down in September and the crew has been tapping into oxygen stored in the Quest airlock module. Spare parts were launched aboard a Russian Progress supply ship Oct. 23 for a planned overhaul.
The oxygen system is a factor for shuttle planners because of a post-Columbia requirement to provide safe haven aboard the station for shuttle crews in the event of major problems that might prevent a safe re-entry. Enough oxygen must be available to support the combined station-shuttle crews - 10 people in this case - until NASA could launch a shuttle rescue mission.
Oxygen in tanks mounted on the Quest airlock cannot be used after Nov. 1 to ensure enough is available for the three spacewalks planned during Discovery's mission. Without an operational Elektron, the crew eventually will have to burn so-called "candles" and tap into oxygen launched aboard Progress modules. But NASA planners believe enough supplies will be available for Discovery's mission to proceed.
Joining Polansky and Curbeam aboard Discovery will be pilot William Oefelein (OH'-fah-line), Nicholas Patrick, European Space Agency astronaut Christer Fuglesang (FEW'-gull-sang), Joan Higginbotham and Sunita "Suni (SUH'-nee)" Williams, who will replace ESA astronaut Thomas Reiter aboard the station as part of the Expedition 14 crew.
Along with re-wiring the space station and retracting one of its existing solar array wings, the astronauts also will launch three small satellites after undocking from the space station.
The Atmospheric Neutral Density Experiment, or ANDE, will measure the composition and density of the thin air in low-Earth orbit to help satellite operators improve their understanding of atmospheric drag. The Microelectromechanical System-Based PICOSAT Instpector, or MEPSI, will test techniques for assessing spacecraft damage due to natural or man-made environmental threats. Finally, a U.S. Naval Academy student satellite known as the Radar Fence Transponder, or RAFT, will test an experimental communications technology. MEPSI and RAFT will be launched on the same day Discovery undocks from the station while ANDE will be deployed the following day.
Oefelein, Curbeam and Fuglesang were part of a different crew that was in training for the same mission in the summer of 2003. The Columbia disaster put station assembly on hold and that crew eventually was broken up. But the two spacewalkers and their in-cabin director - Oefelein - stayed together. Polansky, Higginbotham and Patrick were added in 2005 along with Williams, who is hitching a ride to join the Expedition 14 crew aboard the station.
Polansky is a veteran of one previous spaceflight while Curbeam has two shuttle missions to his credit, including three spacewalks. The rest of the crew members are rookies.
"It's kind of an unfair name, it has some connotations," Polansky said. "The fact of the matter is Joannie, who has never flown before, has worked here for 10 years. She showed up at the same time I did. Nick and Billy O, those two guys, they've been here for over eight years and they've got a lot of experience. Christer was in the same class that Joannie and I were in and he was an astronaut for ESA before we ever got selected.
"So these guys, while not flown, have been working as astronauts for a minimum of eight years. So they've got a lot of knowledge. The only thing they don't have is knowing exactly what it's going to be like to do this job on orbit."
Discovery will be launched into the plane of the space station's orbit and if all goes well, Polansky will guide the shuttle to a docking with pressurized mating adapter No. 2 on the forward end of the Destiny laboratory module two days later.
The international space station currently consists of six pressurized modules. At the back end of the outpost is the Russian Zvezda command module featuring two solar arrays and an aft docking port that can accommodate Progress supply ships or Soyuz crew capsules. An airlock module called Pirs is attached to a downward-facing port on Zvezda's front end. Zvezda's forward port is attached to the Russian Zarya module, a supply and propulsion segment equipped with its own pair of solar arrays.
Zarya's front end is bolted to a pressurized mating adapter that, in turn, is attached to NASA's Unity module, a multi-hatch node with six ports. Its starboard port is occupied by the U.S. Quest airlock module while its upper zenith port accommodates the Z1 truss and the P6 solar arrays that provide interim power. Unity's downward facing port is used by cargo modules brought up by the shuttle and its port hatch is home to another pressurized mating adapter that will be relocated later in the assembly sequence.
Unity's forward port is attached to the Destiny laboratory module. On the forward end of Destiny is another pressurized mating adapter used as a docking port by visiting space shuttles. On top of the lab module is the station's multi-segment solar array truss, which is mounted at right angles to the long axis formed by the pressurized modules.
The S0 truss segment sits in the middle atop the lab, flanked by the S1 and P1 truss elements. S0, S1 and P1 house the major electrical components of the permanent electrical system: The MBSUs and transformers called DC-to-DC converter units - DDCUs - that serve to step down and regulate solar array power to levels needed by station equipment.
S1 and P1 also house the station's two independent cooling systems, each of which include large ammonia tanks, a nitrogen gas pressurization system and a massive pump module to pushes ammonia coolant through cold plates and heat exchangers and out into deployable radiators, three on S1 and three on P1. To maximize heat rejection, the radiators are mounted on a rotating beam that can point them toward deep space and away from the sun.
In September, the crew of mission STS-115 attached two new truss segments to the left side of the solar array beam. The first, P3 (there is no P2) features a powerful solar alpha rotary joint, or SARJ, while the second, P4, includes a new set of solar arrays that stretch 240 feet from tip to tip.
The solar array truss eventually will feature two SARJ joints, one on each side, to rotate the station's solar arrays like giant paddle wheels as the lab complex circles the Earth. That rotation, 360 degrees every 90-minute orbit, will keep the arrays generally face on to the sun. The orientation of the blankets can be fine tuned by so-called beta gimbal assemblies, or BGAs, that automatically adjust the pitch of each solar array wing like the orientation of an airplane propeller can be adjusted in flight (solar array orientation diagram).
The same day Discovery docks with the space station, the astronauts will use the shuttle's robot arm to pull a short spacer segment - P5 - from the orbiter's cargo bay. The 4,110-pound tress segment will be handed off to the station's robot arm and positioned near the left end of the main solar array truss (P5 cargo bay extraction graphic).
The next day, Curbeam and Fuglesang will carry out a spacewalk to connect P5 to the outboard side of the P4 solar array segment. The spacer measures 11 feet long, 14 feet 11 inches wide and 13 feet 11 inches tall. Next year, the P6 arrays now providing interim power atop the Z1 truss will be moved to the left end of the power truss and bolted to P5 (P5 installation graphic).
NASA planners initially planned for Curbeam and Fuglesang to manually move P5 into position and then bolt it into place. But due to an oversight, planners did not realize the current position of P4 would leave the spacewalkers with just two inches of clearance while moving the spacer into place.
As a result, Williams and Higginbotham, operating the station's robot arm from inside the Destiny module, will position P5 while Curbeam and Fuselgang, positioned near P4, provide visual guidance.
"They move it in for the mating and then Christer and I actually bolt it manually," Curbeam said. "It doesn't have the automatic (attachment) system. They'll bring it in really, really close, we'll take the launch locks off, which actually just protect the mating bolts, and once we take the launch locks off ... we drive the bolts to permanently connect them."
Spacer truss P5 attachment to P4 solar array segment
"As a matter of fact, that's why we ended up doing it robotically. The first idea was to grab it and put it in by hand. But the problem was, when they did the evaluation, they had the SARJ angle wrong. The sequential shunt unit was in the wrong orientation for mating. So they thought they had plenty of clearance, they said you can do this by hand. Then I went like, wait a minute, no, I'm looking at it and I see two inches of clearance, maybe and inch and a half. And they went like, no. Then we did our homework and like yes!
"I said there's no way - and it's a blind mate if you do it EVA - there's no way I can sit here with a straight face and tell (lead station flight director) John Curry that I wasn't going to hit that thing. So I told him, I said John, I'm sorry but we've got to look at a different way of doing this because I can't tell you we're not going to hit it. It was a blind stick.
"I think everyone is comfortable with the arm install now," Curbeam said. "But in the beginning, they said hey, this is not what we had planned. I said I know it's not, but I don't feel comfortable doing this EVA because if we do it ourselves we are going to hit something. ... if we hit that SSU, that could turn into a really, really bad scene quickly."
Once the first spacewalk is out of the way, the astronauts and ground controllers will turn their attention to the heart of mission STS-116: electrical bypass surgery to wire in the new solar arrays.
CLIPPING ONE OF THE STATION'S WINGS
The space station's electrical system was designed to operate in an interim mode during the initial stages of construction, providing power to critical systems from a set of solar arrays - P6 - mounted atop the Z1 truss extending upward from the Unity module.
P6 provides electrical power to six DDCU transformers inside the lab module and two others in the Z1 truss. An interim cooling system keeps the electrical components from overheating.
Before the station's power system can be reconfigured, the left wing of the P6 array - known as the 4B wing - must be retracted to permit the newly installed P4 panels to rotate as needed to track the sun. The right wing of P6 - the 2B wing - will be retracted during the next shuttle flight in March. If all goes well, P6 will be moved, bolted to the P5 spacer truss and its 2B/4B solar blankets re-extended during a shuttle flight next fall.
"Until now, P6 has been parked in an interim location in the middle of the truss on top of Unity," Hill said in an email. "Not only has it provided electricity, but it used a smaller, temporary cooling system for the U.S. segment until the MBSUs and the more robust permanent cooling system were installed and activated.
"This set up has worked very well, but it also means we have many electrical and cooling lines connected to the early or temporary systems, rather than the permanent or assembly-complete architecture.Ê In order to finally connect all of the powered equipment to the their permanent power and cooling sources, the vast majority of the U.S. equipment must be powered down, the connections physically switched by spacewalking astronauts, then powered back up.
"This is a long, choreographed activity in order to ensure at least one of every critical component remains powered throughout the reconfigurations," he said. "The important element in all of this is that the additional power provided by the new solar arrays and the additional cooling the permanent cooling system provide are necessary before we can install the Japanese and European research laboratories which are also coming in the next year."
The P6 port wing retraction is scheduled for the day between the first and second spacewalks. The night before, flight controllers will begin moving critical station operations from hardware powered by the 4B solar array (through channels 1 and 4) over to hardware powered by the 2B solar array (through channels 2 and 3). The goal is to get the total load on the 4B array to around 6.5 kilowatts. On retraction day, flight controllers will execute a procedure known as "seamless power channel handover," which will move the 6.5-kilowatt load remaining on the P6-4B wing to the newly installed P4-4A wing on the left end of the main solar array truss. Once the handover is complete, the P6-2B wing will be providing power to station channel 2 and 3 while P4-4A will be powering channel 1 and 4.
At that point, commands will be sent to retract the left side P6-4B solar array wing. The wing must be retracted at least 40 percent to provide the clearance needed for the new P4 array to rotate as needed to track the sun. But from a structural loads standpoint, the array must be retracted to the point where no more than one of the 31 bays making up the central mast remains extended.
"Flight directors always worry about the worst case," Curry said in an interview. "These wings have been out there for six years now, taking thermal cycles and those kinds of things. The mechanism is relatively complicated. There's a chance that we might have a problem with that."
Working in a step-by-step fashion, the astronauts first will send commands to retract the mast the length of three 40-inch bays. If that goes well, retraction will resume and continue to the point where only one bay remains extended. All of that will happen during a single 45-minute-long daylight pass.
"We're going to retract to three bays, stop, survey, make sure everything looks good then start back up again," Curry said. "Then we're going to go from three bays all the way down to one bay, which is about 40 inches. I think there's a good chance that we could end up staying at that location for a long time. I've gotten the loads people to tell me that from an attitude control perspective, from a shuttle undocking perspective, those kind of things, I could go ahead and do the rest of the mission and still keep the array not fully retracted, keep the array at one bay."
The reason that might be needed is because the solar blankets, which were packed up like venetian blinds for launch, might not fold up smoothly during retraction."
"What I'm telling you is there's a decent chance that won't happen during the 116 mission, or that day, and I don't particularly care because it doesn't stop me from doing the rest of the flight," Curry said. "Why would I think we might stop at one bay? The analogy I always give people, when we buy a map at the store it's nice and compressed. But when you start using your map for six years and you decide it's time to fold it back up again, it doesn't fold as tightly as when it was bought at the store. That's what's going to happen here. There's definitely going to be some waves on those folds even if it comes back perfectly.
"So I think there's going to be some concern with compressing that last 40 inches because you could potentially be breaking glass, damaging those cells. So if I'm benign there, I'll let the engineering guys assess that for weeks, let them get comfortable and figure out whether it's a good idea to compress that final 40 inches and latch down.
"My goal for 116, to allow me to execute the rest of the flight, is to get to one bay. If everything's great, we'll go ahead and do the final retraction. (If not) I don't want anybody to think that that means something's bad, it just means we're being conservative."
If the array doesn't retract for any reason, gets jammed or suffers some sort of mechanical failure, Curbeam and Fuglesang can attempt repairs - the array can be retracted manually if the drive motor fails or the spacewalkers could attempt to re-spool a tensioning cable if it popped off its rollers.
But there is little else the spacewalkers can do. If a problem crops up that can't be fixed, they are prepared to dump the costly array overboard.
"If you have your three-sigma bad day, those are youre two big things," Curbeam said in an interview with CBS News. "Hopefully it's just a motor problem or a gear problem where you can just retract it manually, which is fine. It's going to take a long time to get that done, but we can do it.
"But if that's not working for you, and the right answer comes out we've got to get rid of this thing so we can have fairly normal ops, well, we get rid of it. In the big scheme of things, if you have to fabricate and fly another array, that's a lot better than some of the bad things that can happen when you have a piece of structure that's been compromised on the station, i.e., it can come off, it can hit something. Not a good idea."
The P6 arrays cannot be moved to their eventual P5 attachment point with either wing extended. Aside from extremely tight clearance issues, a structural analysis indicates the fragile support mast likely would fail if subjected to the sort of loads it would experience being moved about on the end of the station's robot arm.
"That would be reassessed in realtime," Curry said. "But when we previously looked at it, it had two issues. Kinematically, it was really hard to figure out how to move the wing using the arm and move it out forward and just not hit anything. And then secondarily, and this is the one that killed it, they determined that because these wings are so flimsy you would end up permanently damaging them on the way to moving them outboard. Otherwise... the preference would be not to retract."
In any case, jettisoning the arrays is a strictly worst-case scenario.
"Let's say we start retracting and one of the battens breaks or the mast starts to ball up on itself or the array just gets all crumpled up on itself to the point where it can't be fixed," Curry said. "That's the only way we would ever consider that.
"I haven't spent a lot of time worrying about this because I can't imagine the program telling us to dump those arrays on this mission. If the array got stuck, I think we would spend a lot of time, two EVAs worth, trying to figure out what's wrong with the arrays and if there's any way to fix it. That means another flight has to be added to the manifest anyway."
Assuming P6-4B successfully retracts, flight controllers will configure its fully charged batteries to operate in "parachute mode." While the three nickel-hydrogen batteries cannot easily be recharged with the port array retracted, they can provide up to eight hours of emergency power to channel 1/4 if any problems crop up with the P4 arrays.
Then, within an hour of solar array retraction, computer commands will be executed to power up the left-side solar-alpha rotary joint, or SARJ, to begin rotating the P4 solar arrays as needed to track the sun. Because of the angle between the sun and the plane of the station's orbit, the array must start active tracking right away to generate enough power in the absence of the P6-4B wing.
"Once we get retracted down to one bay, I have a 'go' for loads and attitude controls so I can start rotating P4," Curry said. "This is going to be cool because we're going to be retracting P6 and rotating the SARJ ... basically at the same time. That will put the SARJ in the configuration where it starts tracking the sun like it's supposed to do. First time we will have done that. There are a lot of people really worried about the loads of this and trying to determine how much momentum we put into the system because of the fact that the wings are out."
When the SARJ is activated, control computers will carry out calculations to determine where the sun is relative to the arrays. The massive joint then will be driven at a higher-than-normal rate to get in the proper position. When the SARJ drive motor engages the teeth of a large gear and begins turning, the arrays will be deflected as momentum is transferred to the fragile mast.
"It will put momentum into the system," Curry said. "Because the way it works, as soon as you do that SARJ activation it's calculating an algorithm and figuring out where the sun is and it moves itself to wherever the sun is. So it could go forward or backward depending on where the sun is and when we start it up. ... It will dump momentum into the system, that's for sure."
RE-WIRING THE STATION'S POWER GRID
With P6 successfully retracted and the port-side SARJ slowly rotating the new P4 arrays, the stage will be set for a second and third spacewalk to carry out the main power switch over that is the primary goal of Discovery's mission.
During the second and third spacewalks, the station's main electrical circuits will be powered down, channels 2/3 first and then 1/4. The output from the still-extended P6-2B wing will be switched to the main bus switching units on the solar array truss and the lab will begin drawing power from the MBSUs, downstream DDCU transformers and remote power control modules.
Complicating the work, certain command-and-control computers must remain operational throughout the power switch over, requiring the station crew to install jumpers between components in avionics racks in the lab module to provide redundancy for critical systems when a given power channel is shut down.
After the second spacewalk, all channel 2/3 power, provided by P6-2B and P4-2A, will be routed through MBSUs 2 and 3 on the S0 truss. After the third spacewalk, all channel 1/4 power, provided by P4-4A, will be routed through MBSUs 1 and 4. The retracted P6-4B array also will be tied into channel 1/4 to provide "parachute mode" battery power if needed.
While the electrical system is being reconfigured, the main ammonia cooling system in the truss - the external active thermal control system, or EATCS - must be activated to dissipate the heat that will be generated by the electrical power system as components come on line. The large radiators on each side of the main solar array truss will begin rotating for the first time to maximize heat rejection.
The space station's solar array truss eventually will stretch the length of a football field, sporting two sets of dual-wing solar arrays on each end of the main truss. The solar array wings, or SAWs, are numbered based on their position on the station with even numbers assigned to panels on the left, or port, side of the main truss and odd numbers assigned to SAWs on the right, or starboard, side.
The recently installed P4 segment's two SAWs are numbered 2A and 4A while the P6 SAWs are numbered 2B and 4B. The S4 arrays will be designated 1A and 3A while the S6 SAWs will be known as 1B and 3B.
The four sets of solar arrays are essentially identical. In each set, solar power flows from two SAWs into a sequential shunt unit. Power coming into the SSU can vary from 130 to 180 volts DC depending on a variety of factors, including blanket degradation, shadowing, etc.
Electrical power system components
Because each solar array wing powers a separate station circuit, the IEAs in each array include two sets of electronics. A direct current switching unit (DCSU), containing six high power switches, routes SAW electricity from the SSU into battery charge/discharge units that regulate the flow of power to and from six batteries, three for each SAW.
When the array's SAWs are in sunlight, the DCSU sends solar power to the MBSUs, through the SARJ, and also into the batteries to charge them up. As the station moves into Earth's shadow, the DCSU begins adding battery power to the flow going to its MBSU to maintain the proper voltage. When the arrays are completely eclipsed, the DCSU sends battery power alone to the MBSU in a continuous, automatic procedure.
The DCSU, the battery chargers and other components in each array's integrated electronics unit are cooled by ammonia circulated through cold plates and then routed to a single deployable radiator. Each of the four sets of arrays that eventually will be attached to the station include its own ammonia cooling system, which is independent of the main cooling systems in the S1 and P1 truss segments.
Electricity from the solar arrays is known as "primary power." The MBSUs take that primary power and route it to transformers known as DDCUs, which lower the voltage to a precisely controlled 124 volts DC. This so-called "secondary power" is then directed to the station's myriad electrical systems using numerous electro-mechanical switches known as remote power controllers.
The eight solar array wings on the completed space station will feed power through separate lines to the MBSUs. For redundancy, power from four SAWs will flow to a pair of major circuits - 1 and 4 - while power from the other four SAWs will be directed to a second pair of circuits - 2 and 3.
During the second spacewalk planned for Discovery's mission, flight controllers will power down components on the 2/3 channel and Curbeam and Fuglesang will re-plug cables on the truss to route solar array power to the channel 2/3 MBSUs and associated equipment in S0. DDCUs in the lab module will be disconnected from the interim P6 power system. The output from P6 will be connected to the MBSU inputs and the DDCUs on the truss and in the lab module will be connected to MBSU output. It will take about two hours to reach this point.
Next, flight controllers will power up the MBSUs and DDCUs in the permanent electrical distribution system and verify they are working properly, a procedure that will take about a half hour. Ammonia coolant loop B then will be activated to cool the electronic gear. The same procedures will be carried out for power channels 1/4 during the third and final planned spacewalk when coolant loop A will be activated.
Once the MBSUs are powered up, cooling must be activated within a few hours to prevent potentially serious damage.
"On EVA 2 we're going to turn off the 2/3 channel," Curry said. "Some boxes, it's just a loss of redundancy and on other boxes, the stuff is actually physically off. So when you've got things that are physically off, you've got what we call passive thermal limits, meaning it's stuff getting too cold and how long can it go without breaking the hardware?
"Of course, most of the things like that, you have to go based on analysis because when you turn the thing off, you no longer have telemetry on it to tell you whether it's doing well or doing poorly. So we spent a lot of time trying to figure out what are the things that are the biggest risks. And if you look at the way the EVAs are planned out, we broke up the power downs into two sections, one where we do the first set of wiring, which is for things - the majority of the stuff that can make it without power for the rest of the EVA, meaning five or six hours.
"There were three other things that were not in that category, mostly related to the comm system and to the cameras on the outside of the vehicle. So those ones we (do) late. Comm is obviously very important and you don't want to go a long period of time without the comm stuff. So the S-band antennas and the KU-band system, we do those very late so the amount of time they went without power was less than an hour. That was all passive thermal. So I think we're fine on passive thermal.
"The bigger concern is the active thermal, and it's not just the MBSUs but it's all the truss equipment. There's a whole bunch of boxes that are in line for power, your MBSUs, your DDCUs and then your RPCMs. The DDCUs and the MBSUs are cooled by cold plates that have this ammonia running through them. Right now, on the permanent system the ammonia is still sitting in the tanks, we haven't started pushing it through the system yet because we're waiting until we need it."
While the MBSUs can be cross tied to route power to different circuits in case of failures, the ammonia systems are independent and not connected to protect against a micrometeoroid impact that might rupture a line and take out the entire system.
But that lack of connectivity means a problem with loop A or B will take out two of the station's four primary electrical circuits.
"This is the one that from a station design perspective I wish they had plumbed it, cross tied it, because the pump and all the ammonia that's on the port side of the vehicle, that cools the 2/3 side, and then the pump and the ammonia tank and all that that's on the starboard side on the S1 truss, cools the 1/4 channel. So if a pump goes down or doesn't ever come up, the way that the guys when they designed the vehicle felt they got away with it, they said hey, I've got four power channels and so it's OK to lose two power channels and still be OK from a redundancy perspective.
"The problem is, that's not exactly the way the station's built, there are certain things that are wired to the 2/3 side and certain things that are wired to the 1/4 side. So they didn't cross tie the plumbing. So what that means is, on EVA-2 when I go to activate loop B's pump, if loop B's pump doesn't come up, if I have any kind of glitch - and I want you to know this in case it happens - there's a clock that I will be running for the MBSUs and the DDCUs and just in general and then I have to compare that clock against the crew's (spacesuit) clock, how long they can actually stay out.
"If I can't get that pump running within a certain amount of time, I have to save time on the back end of the spacewalk to allow the crew to unwire what they did before and to back out again. If I left the wiring the way it was and the pump never got up to speed and I sent the crew back in, the MBSUs and the DDCUs will overheat. It's just a matter of time."
Engineers initially concluded the MBSUs would overheat within an hour or so, but a later assessment using a qualification unit showed the devices could operate without cooling for five to six hours.
"So we think we're OK," Curry said. "I have telemetry on the MBSUs and I have telemetry on the DDCUs. So I have numbers in the flight rules that tell me thou shalt not let the temperature of the MBSUs or the DDCUs get above this certain number."
The DDCU limit is 140 degrees Fahrenheit while the limit on the MBSUs is 115 degrees.
"In terms of EVA requirements, it takes about two hours for the crew to get to the point where they're ready for us to power stuff back up again," Curry said. "We power all that stuff down so they don't shock themselves, they make the connections and then they tell us they're clear and we're ready for activation."
Lead station electrical officer Dave Crook "then activates a script that powers on a whole bunch of stuff really fast because obviously, we're racing against the clock we talked about earlier. So in the first 20 minutes, I'll know if the copper path worked. If any of those things don't work, I've also got a number that we can check against the limits on the suits, if one of the MBSUs fail or one of the DDCUs fail, we can do an R&R. And that would be during that specific EVA because hopefully, I have enough time for that. We've choreographed how that would work. There's an MBSU spare as well and that could be done in real time."
It will take about 20 minutes for the computer commands to execute, rerouting power to the MBSUs and downstream DDCUs. It will take another 45 minutes to an hour to activate each ammonia cooling system.
"The problem is, we don't want to cavitate the pumps (run them without fluid)," Curry said. "You have to get the ammonia pushed through the system at the proper pressure and the operating pressure of the pump is like 376 psi so we've got to get that pump up to minimum number before we can start trying to activate it so we don't cavitate. So that takes a little bit of time."
Adding up the numbers, Curry's team will know if power and cooling are active within about and hour to an hour and a half. While a spare MBSU or DDCU could be installed during the same spacewalk, trouble with an ammonia pump unit would cause a significant impact on the mission.
"Let's say the pump doesn't come up, or say I got bit by some software feature like what happened (when a SARJ commanding problem cropped up during the September shuttle mission)," Curry said. "If I can't figure that out within a short period of time, then I have to back out because I couldn't get the cooling done and there's not enough time to do the R-&-R of the pump.
"The pump weighs a lot, it's 1,500 pounds, so that's a complex remove-and-replace scenario. That would take an entire dedicated EVA to do that. There's a plan I've got in place where if the pump didn't come up to speed on EVA-2, then we would give the MMT (Mission Management Team) folks a day to think about it and then the next day after that, we would then use EVA-3 to R-&-R the pump."
In that case, EVA-2 "would end up being a waste of time," Curry said. "That's the part that concerns me, infant mortality. Every time you start up a new system you always learn something. Something could come up to bite us. The problem is, I've only got about an hour to figure that out. The pressure's on the ground. That's the difference between this flight and most others. This is a simple task for the crew. All they have to do is hook up a cable."
Polansky agreed, saying flight controllers will be under pressure to make quick decisions if things go wrong.
"You can't just sit there and say, 'I did this and that happened therefore it must have been because of what I did.' It could be because of a lot of things, you've got to be careful not to jump to the wrong conclusion," Polansky said. "And oh by the way, you don't have a day to think about it because people are sucking on their oxygen and using up their (carbon dioxide-absorbing lithium hydroxide). There's a very short fuse here."
Because of safety requirements and the toxic nature of ammonia, electrical components inside the station's pressurized modules are cooled by water circulating through cold plates. That water is then routed to heat exchangers tied into external ammonia loops and radiators.
In the near term, the primary external ammonia system will only be used to cool electrical components mounted on the solar array truss.
NASA planners initially considered having Discovery's crew complete the electrical switch over as well as the plumbing changes necessary to switch the module heat exchangers from interim to permanent cooling. But given the complexity of the electrical work, the cooling system re-plumbing was deferred to early next year when Williams and station commander Michael Lopez-Alegria will tie the module heat exchangers into the primary cooling system during two spacewalks.
"The first spacewalk will be one of the external power loops," Williams said in a NASA interview. "We call it loop A. We will switch it from using a radiator and cooling loop system on the P6 to its more permanent cooling system out on the truss. And that involves changing some electrical connectors in the 'rat's nest,' which is the area between Z1, S0 and the Lab. It's a small area that has a lot of electrical connections and a lot of fluid connections; it's this very tight space.
"As it's planned, both me and Michael Lopez-Alegria will be inboard in this small little area. On the first loop reconfiguration, I'll do the electrical connectors then he will follow that with the big fluid jumpers to switch the fluid lines from P6 to the external. Following that, we will be up on the P6 truss; they will retract the starboard radiator, which we've been using for the early external thermal control system. The ground will be doing that but our role in that is to cinch it down, because it needs to stay down and compacted so the radiators aren't moving around as the space station is rotating.
"He'll be up on the zenith side; I'll be on the nadir side of the radiator. We will wait and watch the radiator retract - potentially it could need a little bit of a push from us at the very end - and then we cinch bolts around the edge of it that we need to, simultaneously, connect to make sure that the radiator is contained nicely. That's the main portion of EVA number one."
The second is virtually identical to the first, but focusing on making the required loop B fluid connections and retracting the aft radiator on P6.
Curry likens the power downs and power ups planned for Discovery's mission to switching a house under construction from temporary generator power to utility power. But in this case, the computer commands needed to make that happen must be carried out with extraordinary precision.
"On 115 (the most recent shuttle flight), the EVA tasks, the robotics tasks, were without question more difficult than the similar tasks we do on 116," Hill said. "But we're doing a hell of a lot more commanding to the hardware outside the vehicle on 116 than we (did on STS-115)."
No specific task in this process is overly complex or challenging. But the sheer number of commands that must be sent, the complexity of the power system hardware and the close coordination required between the astronauts and flight controllers will make shuttle mission STS-116 the most complex station assembly flight yet attempted.
"All this reconfiguration we have to do on 116, those are big steps," Hill said. "It doesn't sound like much. It sounds pretty mundane and nerdy. We're sending a bunch of commands, changing over electrical and thermal controls. That flight right there and that choreography is something that when we first came up with this sequence in 1994, we all sat back and said, 'how are we going to figure this one out?'
"Today, the folks who have been leading that effort feel pretty good they've got their arms around it but they're ... keeping their fingers crossed that everything goes well."
06:00 p.m., 10/16/06, Update: Shuttle manifest updated
NASA managers today proposed new launch dates for the first three shuttle missions of 2007. Planning dates for all remaining flights through the end of shuttle operations in 2010 also were updated based on preliminary launch processing assessments. While several near-term flights face delays due primarily to external tank deliveries and possible conflicts with Russian Soyuz launches, NASA still expects to meet its 2010 deadline for completing the space station and retiring the shuttle.
Shuttle mission STS-116 (Discovery) remains on track for launch Dec. 7, at 9:39 p.m. - NASA's first night launch since 2002. But an Air Force Atlas 5 rocket carrying a military payload currently is scheduled for launch on Dec. 7 from the Cape Canaveral Air Force Station and if that flight stays on track, the shuttle launch will have to slip a few days.
The goal of mission STS-116 is to attach a short spacer truss to the left side of the station's main solar array truss, to retract one of two solar wings providing interim power and to rewire the station to utilize electricity from arrays installed during a shuttle flight in September.
Shuttle mission STS-117 (Atlantis), the next flight in the sequence, slips from Feb. 22 to March 16, around 5:20 a.m., under the new manifest proposal. The goals of that mission are to retract the second interim power solar wing and to attach a new set of arrays to the starboard side of the solar power truss. The March 16 target launch date assumes the next Russian Soyuz flight moves to early April. If the Soyuz stay where it is currently scheduled - March 9 - STS-117 would slip to around March 23.
NASA managers are considering a design change for so-called ice-frost ramps on the shuttle's external tank. One flight test option under discussion is to modify the top three ice-frost ramps on the liquid hydrogen section of the tank slated for STS-117.
NASA is holding open the option of requiring a daylight launch for any external tank design changes to ensure good photo documentation. If that is required for STS-117, launch would slip to April 20. But a final decision on whether to implement an IFR redesign has not yet been made.
STS-118 (Endeavour), which had been targeted for a June 11 liftoff, moves to June 28 under the new manifest proposal. The goals of that flight are to attach an external equipment storage platform, another solar array spacer truss and a system that will permit docked space shuttles to draw power from the station. The crew for STS-118 includes astronaut Barbara Morgan, high school teacher Christa McAuliffe's backup in the original "teacher in space" program.
While not currently planned, STS-118 could be used to launch a refurbished control moment gyroscope to the station in place of the external stowage platform. One of the four stabilizing CMGs currently aboard the station has been taken off line because of excessive vibrations.
NASA plans to launch a multi-hatch connecting module known as Node 2 during the next flight in the sequence, STS-120 (Atlantis), which slips from Aug. 9 to Sept. 7. Again, there is a possible Soyuz conflict that could delay the flight a week or so.
Launch dates for flights after mission STS-120 are based on preliminary hardware processing assessments only and likely will experience subsequent adjustments.
Flight STS-122, featuring the European Space Agency's Columbus research module, remains targeted for launch on Oct. 17, 2007. But that date assumes the station astronauts can carry out three complex spacewalks to hook up Node 2 and a shuttle docking port between the end of STS-120 and the arrival of Columbus.
STS-123, launch of a Japanese pressurized experiment module, moves to Dec. 8 and flight STS-124, launch of Japan's Kibo research module, moves from Feb. 7 to Feb. 29, 2008.
Launch of a Hubble Space Telescope servicing mission - STS-125 - will be targeted for April 17, 2008, if NASA Administrator Michael Griffin ultimately gives his approval. A meeting to discuss the Hubble mission is planned for Oct. 27.
Here are the rest of the flights on the latest shuttle manifest:
- 06/19/08 - STS-119: Outboard starboard truss segment and arrays
- 08/21/08 - STS-126: Station resupply; last flight of Atlantis
- 10/09/08 - STS-127: Kibo exposed experiment facility; logistics
- 01/15/09 - STS-128: Crew accommodations; six-person crew capability
- 04/09/09 - STS-129: Logistics flight; last flight of Discovery
- 07/09/09 - STS-130: Logistics flight
- 10/01/09 - STS-131: Contingency flight
- 01/14/10 - STS-132: Node 3, cupola; last flight of Endeavour
- 07/09/10 - STS-133: Contingency flight
http://www.cbsnews.com/network/news/space/manifest.html
10:30 p.m., 10/10/06, Update: Station gyro taken off line; impact on upcoming shuttle flight assessed
One of the international space station's four control moment gyroscopes, used to keep the outpost properly oriented without jarring, fuel-consuming rocket firings, was taken off line late Monday because of concern about repeated instances of excessive vibration.
While CMG-3 has not been officially declared failed, flight planners are scrambling to assess the potential impact of a failure on the shuttle Discovery's upcoming mission in December to rewire the space station to take advantage of newly delivered solar arrays.
During the third of three planned spacewalks during Discovery's flight, CMGs 1 and 4 will have to be shut down while spacewalking astronauts unplug and replug electrical cables routing solar panel power to two of four main electrical circuits.
If CMG-3 is not available to help control the station's orientation, rocket thrusters might have to be used to augment CMG-2.
But the newly installed P4 solar array panels, which stretch 240 feet from tip to tip, are designed to rotate to track the sun as the station circles the globe. It's not yet clear whether the fragile masts that support the extended arrays can withstand jarring rocket firings while rotating. And they need to rotate to generate the necessary power.
Depending on the results of an engineering assessment, CMG-3 could be put back on line full time, brought up for specific events like the spacewalk in question or left off line but available for use as an emergency backup. Engineers also are assessing whether the arrays can simply be locked in a power-favorable position, if necessary, during the spacewalk.
The station's four control moment gyroscopes maintain the lab's orientation in space without having to tap into limited supplies of on-board rocket fuel. They are housed in the Z1 truss, which was attached to the Unity module's upward-facing, or zenith, hatch during shuttle mission STS-92 in October 2000.
Along with saving fuel, the 800-pound gyros, spinning at 6,600 rpm, allow station crews and flight controllers to reorient the outpost and keep it stable without using rocket firings that would jar sensitive microgravity experiments. Or the new P4 solar arrays, installed during the shuttle Atlantis's mission in September.
The station's orientation can be maintained with just two CMGs in a worst-case scenario.
On June 8, 2002, CMG-1 suffered a malfunction and shut down. Station astronaut Carl Walz reported hearing an unusual noise inside the Unity module. He said the noise appeared to be coming from the module's zenith area. Mission control then told Walz engineers were working an issue with a spin bearing in CMG No. 1. Walz said the noise was quite noticeable inside the module.
"We're hearing a pretty loud, audible noise, kind of a growling noise, from inside the node," Walz reported.
"It looks like we have a mechanical failure of the spin bearings on CMG-1," an astronaut in mission control replied. "It's currently spinning down right now. The growling noise is undoubtedly due to vibration."
That CMG was replaced with a spare during the first post-Columbia shuttle mission in 2005. No other backups are available, but the failed gyro currently is being refurbished. Depending on what happens with CMG-3, the refurbished gyro could be added to an upcoming mission.
11:30 p.m.,10/05/06, Update: Night launch restriction lifted for December flight; ice-frost ramp redesign discussed; Atlantis impact damage assessed
NASA managers met Thursday and agreed to relax a self-imposed post-Columbia daylight launch constraint, clearing the way for the shuttle Discovery's liftoff Dec. 7, around 9:38 p.m. EST, on a complex space station assembly mission. It will be the first night shuttle launch since 2002.
But agency managers reserved the option of requiring daylight launches for flights with external fuel tanks featuring significant design changes.
One such proposed change is a modification of the tank's so-called ice-frost ramps, aerodynamically shaped foam insulation used to prevent pre-launch ice buildups on fittings that support external pressurization lines and a cable tray.
NASA and contractor engineers have been working on a redesign to reduce the amount of foam used to make the ice-frost ramps and thus minimize the possibility of debris shedding during ascent. But the ramps performed well during the past two missions and some engineers now favor leaving the design alone.
Another meeting to discuss the topic is planned for early November.
The ice-frost ramps are made up of foam poured into molds and then shaped by hand. Because the ramps are built up on top of already existing foam, engineers believed they were susceptible to temperature-induced cracks that could lead to in-flight debris shedding.
The ramps were officially classified as "probable-catastrophic" prior to the last two shuttle missions. That means if no changes were made, one could expect a 50-50 chance of a catastrophic failure over the 100-flight design life of a space shuttle.
Before mission STS-121 last July, NASA Administrator Mike Griffin said he did not agree with the probable-catastrophic designation and Discovery was cleared for flight as is. Likewise, Atlantis was cleared for launch last month on mission STS-115 with the understanding that a new ice-frost ramp design would be implemented as soon as possible.
As it turned out, no significant ice-frost ramp damage or foam shedding was seen during the last two flights. An ongoing engineering analysis, based in part on in-flight video of the tank, indicates what foam does separate in flight comes off after the tank is out of the dangerous lower regions of the atmosphere.
Going into Discovery's flight last July, the odds of a catastrophic IFR failure were believed to be between 1-in-75 and 1-in-100. The odds currently are believed to be in the neighborhood of 1-in-575 or better, according to a senior manager familiar with the ongoing analysis. As such, the ramps likely will not be classified as probable-catastrophic for Discovery's upcoming flight in December.
At the Kennedy Space Center, meanwhile, engineers are assessing options for fixing a radiator panel mounted on the inside of the shuttle Atlantis' right-side payload bay door. The panel apparently was damaged when a piece of space debris or a micrometeoroid slammed into the radiator, presumably during the shuttle's flight last month, blasting .108-inch-wide hole in the upper surface and destroying the aluminum honeycomb material below before exiting the other side.
The impact did not threaten the crew and the damage can be repaired. But it illustrates the danger posed by micrometeoroid/orbital debris (MMOD) and the reason why NASA considers such strikes a high risk. The odds of a catastrophic impact-related failure range between 1-in-210 to 1-in-350, depending on whether the astronauts inspect the ship in orbit prior to re-entry.
At orbital velocities, even tiny pieces of debris pose a serious threat. An aluminum sphere just 0.4 inches across moving at 10 kilometers per second, or 22,370 mph, carries the same impact energy as a bowling ball moving at 300 mph.
A preliminary engineering analysis shows the impact in question was one of the most significant instances of MMOD damage in shuttle history, second only to a cargo bay door impact during shuttle mission STS-72 in 1996.
The shuttle's 60-foot-long payload bay doors each feature four radiator panels that are exposed to space once the doors are opened in orbit. The forward two radiator panels measure about one inch thick, feature Freon coolant tubes positioned about 1.9 inches apart and can pivot to radiate from both sides. The aft panels are fixed and only radiate from one side. They measure a half inch thick and feature coolant tubes separated by about 5 inches. The interior of the panels is made up of an aluminum honeycomb material.
The impact on Atlantis's right-side, or starboard, radiator was found roughly midway between two coolant lines on panel No. 4. The object blasted a 0.108-inch-wide hole and presumably broke apart on impact. The resulting spray of debris created a cone-shaped damage cavity immediately below the face plate, destroying the honeycomb interior to the full half-inch depth of the panel. The lower face sheet was pushed out in two places. A 0.26-inch crack and a 0.03-inch-wide exit hole were found.
As part of NASA's post-Columbia safety protocols, the shuttle and space station fly in an orientation that protects the shuttle's critical wing leading edge panels from direct, worst-case impacts in the line of flight. In addition, the astronauts now carry out detailed inspections of the shuttle's heat shield after reaching orbit and again before re-entry to make sure no MMOD impacts occurred during the course of the mission.
Areas of the shuttle that are not critical for re-entry are not inspected and the damage to Atlantis's radiator panel No. 4 was not discovered until post-flight servicing at the Kennedy Space Center.
A senior NASA manager said the impact damage was unlikely to prompt a change in the shuttle's orbital orientation. He said program managers understand the radiator panels and overhead cockpit windows face a higher risk of impact damage because of the shuttle's orientation. But he said the risks associated with wing leading edge impacts are more severe.
The shuttle has two Freon coolant loops and while the loss of one would force a crew to return to Earth at the next available U.S. landing site, computer software is in place to immediately isolate a leak even if the event occurred when the crew was asleep or otherwise occupied. Assuming a leak was quickly isolated, the astronauts could implement contingency procedures and press ahead with a near-normal mission despite the damage to one radiator panel. As for an impact on the shuttle's cockpit windows, engineers do not yet know if the debris in question would have penetrated the thick multi-pane glass. The three panes making up the six forward cockpit windows have a combined thickness of 2.55 inches. The three panes making up each overhead window have a combined thickness of 1.58 inches.
Some 11,000 objects 3.9 inches in diameter or greater are currently tracked by Air Force radars and optical systems. About 100,000 objects are believed to be present that are between 0.39 inches across and 3.9 inches in diameter. Most of those are not tracked and pose a threat to spacecraft in low-Earth orbit and to communications and weather satellites in higher orbits.
04:00 p.m., 09/28/06, Update: Shuttle crew, flight controllers face complex electrical work during December flight; Dec. 7 new target launch date
Editor's Note...
-
NASA managers today agreed to move up the target launch date for the shuttle Discovery and mission STS-116 from Dec. 14 to Dec. 7 at roughly 9:38 p.m. EST. Agency managers have not yet formally relaxed a post-Columbia daylight launch constraint, but that issue will be discussed at the next program requirements change board meeting Oct. 5 at the Johnson Space Center in Houston. Still unresolved is conflict with a Lockheed Martin Atlas 5 rocket carrying a military payload that currently is scheduled for launch Dec. 7 from the Cape Canaveral Air Force Station.
An overview of the STS-116 mission is posted below and a detailed flight plan and list of mission priorities are available on the CBS News STS-116 Quick-Look page:
http://www.cbsnews.com/network/news/space/currentglance.html
Construction has now reached the point where an interim power system, designed to support the station during its initial assembly, needs to be upgraded to support the eventual attachment of new research modules. And with the delivery of new solar arrays by shuttle astronauts earlier this month, NASA is finally ready to activate the lab's permanent power and cooling systems.
But in order to do that, the astronauts must first retract one wing of the older solar arrays providing interim electricity to the U.S. segment of the station. Flight controllers then will power down the lab's two major circuits, one at a time, while spacewalking astronauts plug electrical cables into different sockets.
With the solar arrays attached by the shuttle Atlantis' crew in September, "we'll now be generating enough power we can bring the permanent cooling system on line and start using it," said Paul Hill, mission operations manager at the Johnson Space Center. "Once we have that system active, we can also start flowing power through those switch boxes that are sitting in the middle of the truss.
"This is pretty much your classic chicken-or-egg scenario here," he said. "You have to have active cooling to the switch boxes (main bus switching units, or MBSUs) in order to route power through them.ÊYou have to have power flowing through the MBSUs in order to power their cooling equipment."
The trick, Hill said, is to power up the MBSUs, route power through them to the cooling system and get it that system activated before the MBSUs overheat.
Launch of the 117th shuttle mission, originally planned for Dec. 14, is now targeted for Dec. 7. Assuming NASA managers relax a post-Columbia daylight launch constraint, liftoff around 9:38 p.m. will be the agency's first night launch since 2002.
On board will be commander Mark Polansky, pilot William Oefelein, Nicholas Patrick, Robert Curbeam, European Space Agency astronaut Christer Fuglesang, Joan Higginbotham and Sunita Williams, who will replace ESA astronaut Thomas Reiter aboard the station.
Curbeam and Fuglesang will carry out two spacewalks to attach a short spacer segment to the station's main solar power truss and to re-wire one of the lab's two primary electrical circuits. Curbeam and Williams, who will remain aboard the outpost in Reiter's place when Discovery departs, will re-wire the other power channel during a third spacewalk.
The spacewalks are not inherently difficult as such things go. As each electrical circuit is powered down by flight controllers in Houston, the astronauts will unplug various cables and plug them back into different sockets. But no one knows how the station's myriad electrical components will respond to a shutdown and power up.
Likewise, no one really knows how the big coolant pumps will operate in the weightlessness of space to push ammonia through various lines and radiators to dissipate the heat generated by those same electrical components.
Once a power channel is shut down, components plugged into that circuit will quickly cool down. During power up, they will rapidly heat up. The thermal control system is needed to keep temperatures in a carefully controlled range and if problems develop on either side of those power downs and power ups, the spacewalkers will have to act fast to prevent potentially serious trouble.
Lead station flight director John Curry likens the power downs and power ups to switching a house under construction from temporary generator power to utility power. But in this case, the computer commands needed to make that happen must be carried out with extraordinary precision.
"On 115 (the most recent shuttle flight), the EVA tasks, the robotics tasks, were without question more difficult than the similar tasks we do on 116," Hill said. "But we're doing a hell of a lot more commanding to the hardware outside the vehicle on 116 than we (did on STS-115)."
The space station's electrical system was designed to operate in an interim mode during the initial stages of construction, providing power to critical systems from a set of solar arrays - P6 - mounted atop a short truss - Z1 - extending upward from the multi-hatch Unity module. An interim cooling system keeps the electrical components from overheating.
During Atlantis' flight in September, a new set of solar arrays - P4 - was mounted to the end of the station's main solar array truss, a beam that eventually will stretch the length of a football field sporting two huge sets of arrays on each end.
Two massive rotary joints, one on each side of the truss - the first was attached during Atlantis' mission - will rotate the arrays like giant paddlewheels as the station circles the globe to keep them face-on to the sun. Each side of the truss also features a set of three large radiator panels mounted on rotating platforms to dissipate the heat generated by the station's electrical systems.
The heart of the station's electrical system is made up of the MBSUs mounted inside the S0 truss, the central segment of the solar array beam. The arrays on each end of the beam will feel electrical power to the MBSUs, which in turn can distribute electricity to virtually any station system. If one set of arrays, batteries or chargers fail, the MBSUs can redistribute power from the other panels to keep critical systems safely powered.
"We have these big boxes in the middle of the space station, big switch boxes," Hill said of the MBSUs. "You've got four pairs of solar arrays (when the station is complete) and you've got all these finger-thick copper wires that run from the solar arrays to the middle of the truss. Those are the boxes that, for an assembly-complete station, you want all your power flowing from and then going down to our converters that then flow power to individual pieces of equipment.
"In order to reconfigure the electrical system and the cooling system so we have the permanent cooling system up and we're flowing all power through these main switching boxes, we've got to power off a hell of a lot of equipment so we can safe those individual copper lines, disconnect them and reconnect them to where we want them. That will be a case where we'll have to power off almost all the U.S. segment one way or the other throughout that whole process."
That process begins when the left wing of the P6 array - known as the 4B wing - is retracted during Discovery's mission to permit the newly installed P4 panels to rotate as needed to track the sun. The right wing of P6 - the 2B wing - will be retracted during the next shuttle flight early in 2007. If all goes well, P6 will be moved, bolted to the P5 spacer truss and its 2B/4B solar blankets re-extended during a shuttle flight next August.
"Until now, P6 has been parked in an interim location in the middle of the truss on top of Unity," Hill said in an email. "Not only has it provided electricity, but it used a smaller, temporary cooling system for the U.S. segment until the MBSUs and the more robust permanent cooling system were installed and activated.
"This set up has worked very well, but it also means we have many electrical and cooling lines connected to the early or temporary systems, rather than the permanent or assembly-complete architecture.Ê In order to finally connect all of the powered equipment to the their permanent power and cooling sources, the vast majority of the U.S. equipment must be powered down, the connections physically switched by spacewalking astronauts, then powered back up.
"This is a long, choreographed activity in order to ensure at least one of every critical component remains powered throughout the reconfigurations," he said. "The important element in all of this is that the additional power provided by the new solar arrays and the additional cooling the permanent cooling system provide are necessary before we can install the Japanese and European research laboratories which are also coming in the next year."
The P6 port wing retraction is scheduled for the day between the first and second spacewalks. The night before, flight controllers will begin moving critical station operations from hardware powered by the 4B solar array (through channel 1/4) over to hardware powered by the 2B solar array (through channel 2/3). The goal is to get the total load on the 4B array to around 6.5 kilowatts. On retraction day, flight controllers will execute a procedure known as "seamless power channel handover," which will move the 6.5-kilowatt load remaining on the P6-4B wing to the newly installed P4-4A wing on the left end of the main solar array truss. Once the handover is complete, the P6-2B wing will be providing power to station channel 2/3 while P4-4A will be powering channel 1/4.
At that point, commands will be sent to retract the left side P6-4B solar array wing.
"The guys who built it, they designed it to retract and they expect it to retract," Hill said. "But for a solar array that's been hanging out in the breeze, where if we took a micrometeoroid strike and dinged one of those structural elements, there's a real good chance that we're not going to be able to fully retract those arrays. We'll see what we get."
Assuming P6-4B successfully retracts, flight controllers will configure its fully charged batteries to operate in "parachute mode." While the three nickel-hydrogen batteries cannot be recharged with the port array retracted, they can provide up to eight hours of emergency power to channel 1/4 if any problems crop up with the P4 arrays.
The interim P6 power system routed direct current electricity to six DC-to-DC converter units (DDCUs) in the Destiny laboratory module and two on the Z1 truss. To switch the station to its permanent power system, the Discovery astronauts will carry out two spacewalks in concert with complex ground commanding. A third spacewalk - the first EVA of the mission - will be devoted to hooking up the P5 spacer truss that will serve as the attachment point for P6 when those arrays are moved next year.
During the second and third spacewalks, the station's main electrical circuits will be taken off line, channel 2/3 first and then 1/4. The output from the still-extended P6-2B wing will be switched to the main bus switching units on the solar array truss and the lab DDCUs will be connected to the MBSU output.
Complicating the work, certain command-and-control computers must remain operational throughout the power switch over, requiring the station crew to install jumpers between components in avionics racks in the lab module to keep critical systems active when other elements of a given power channel are shut down.
After the second spacewalk, all channel 2/3 power, provided by P6-2B and P4-2A, will be routed through MBSUs 2 and 3 on the S0 truss. After the third spacewalk, all channel 1/4 power, provided by P4-4A, will be routed through MBSUs 1 and 4. The retracted P6-4B array also will be tied into channel 1/4 to provide "parachute mode" battery power if needed.
While the electrical system is being reconfigured, the main ammonia cooling system in the truss - the external active thermal control system, or EATCS - must be activated to dissipate the heat that will be generated by the electrical power system as components come on line. The large radiators on each side of the main solar array truss will begin rotating for the first time to maximize heat rejection.
Getting the thermal control system activated as quickly as possible is critical to prevent components from getting too cold or, in the case of the MBSUs, too hot.
"The ISS control team has to balance that race against overheating the MBSUs with the power downs necessary to disconnect and reconnect the power cables and cooling lines and the subsequent equipment reactivation necessary before moving on to the next set of power cables and cooling lines," Hill said.
"That means the clock is ticking on the MBSUs as they begin heating up without cooling, and much of the equipment that is powered off require power to keep them from getting too cold and breaking circuit boards and other sensitive components."
No specific task in this process is overly complex or challenging. But the sheer number of commands that must be sent, the complexity of the power system hardware and the close coordination required between the astronauts and flight controllers will make shuttle mission STS-116 the most complex station assembly flight yet attempted.
"All this reconfiguration we have to do on 116, those are big steps," Hill said. "It doesn't sound like much. It sounds pretty mundane and nerdy. We're sending a bunch of commands, changing over electrical and thermal controls. That flight right there and that choreography is something that when we first came up with this sequence in 1994, we all sat back and said, how are we going to figure this one out?
"Today, the folks who have been leading that effort feel pretty good they've got their arms around it but they're ... keeping their fingers crossed that everything goes well."
Here is an overview of Discovery's mission as it now stands, based on a Dec. 7 liftoff. Readers are advised the flight plan remains a work in progress and changes are expected. A more detailed flight plan is available on the CBS News STS-116 Quick-Look page:
http://www.cbsnews.com/network/news/space/currentglance.html
All times in EST and elapsed time from launch:
DATE/EST DD HH MM EVENT _____________________________________________________________ 12/07/06 Thu 09:38 PM 00 00 00 STS-116 Launch (flight day 1) 12/08/06 Fri 01:53 AM 00 04 15 Shuttle robot arm (RMS) checkout Fri 01:58 AM 00 04 20 External tank video downlink Fri 03:38 AM 00 06 00 Crew sleep begins Fri 11:38 AM 00 14 00 Crew wakeup Fri 04:03 PM 00 18 25 Wing leading edge, nose cap survey 12/09/06 Sat 03:08 AM 01 05 30 Crew sleep begins Sat 11:08 AM 01 13 30 Crew wakeup Sat 06:41 PM 01 21 03 Discovery docks with space station Sat 09:43 PM 02 00 05 P5 truss segment grapple by shuttle arm Sat 10:28 PM 02 00 50 P5 handoff from shuttle arm to station arm 12/10/06 Sun 03:08 AM 02 05 30 Crew sleep begins Sun 11:08 AM 02 13 30 STS crew wakeup Sun 04:03 PM 02 18 25 EVA-1: Airlock egress Sun 04:28 PM 02 18 50 EVA-1: P5 launch lock removal Sun 05:28 PM 02 19 50 EVA-1: P5 attached to P4 Sun 10:08 PM 03 00 30 EVA-1: Airlock repressurization 12/11/06 Mon 02:38 AM 03 05 00 STS/ISS crew sleep begins Mon 10:38 AM 03 13 00 STS crew wakeup Mon 01:53 PM 03 16 15 P6 port panel retraction (1 bay) Mon 06:23 PM 03 20 45 P6 port wing full retraction begins Mon 06:38 PM 03 21 00 P6 port wing full retraction complete 12/12/06 Tue 02:38 AM 04 05 00 STS/ISS crew sleep begins Tue 10:38 AM 04 13 00 STS crew wakeup Tue 03:33 PM 04 17 55 EVA-2: Airlock egress Tue 03:58 PM 04 18 20 EVA-2: Channel 2/3 power reconfig Tue 05:33 PM 04 19 55 MCC: EPS final activation Tue 09:23 PM 04 23 45 EVA-2: Airlock repressurization 12/13/06 Wed 02:08 AM 05 04 30 STS/ISS crew sleep begins Wed 10:08 AM 05 12 30 STS crew wakeup Wed 05:33 PM 05 19 55 Joint crew news conference Wed 06:03 PM 05 20 25 Crew off duty time begins 12/14/06 Thu 02:08 AM 06 04 30 STS/ISS crew sleep begins Thu 10:08 AM 06 12 30 STS crew wakeup Thu 03:03 PM 06 17 25 EVA-3: Airlock egress Thu 03:28 PM 06 17 50 EVA-3: Channel 1/4 power reconfig Thu 06:08 PM 06 20 30 MCC: EPS final activation Thu 09:03 PM 06 23 25 EVA-3: Airlock repressurization 12/15/06 Fri 01:38 AM 07 04 00 STS/ISS crew sleep begins Fri 09:38 AM 07 12 00 STS crew wakeup Fri 12:38 PM 07 15 00 Transfers resume 12/16/06 Sat 01:38 AM 08 04 00 STS/ISS crew sleep begins Sat 09:38 AM 08 12 00 STS crew wakeup Sat 04:18 PM 08 18 40 Discovery undocks from space station 12/17/06 Sun 12:38 AM 09 03 00 STS/ISS crew sleep begins Sun 08:38 AM 09 11 00 STS crew wakeup Sun 07:08 PM 09 21 30 Crew off duty time begins 12/18/06 Mon 12:08 AM 10 02 30 Crew sleep begins Mon 08:08 AM 10 10 30 Crew wakeup Mon 03:57 PM 10 18 19 Deorbit ignition Mon 05:03 PM 10 19 25 Landing