Realtime coverage of STS-133 launch countdown

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Shuttle Launch Director Michael Leinbach has told NASA and contractor engineers that launch of the shuttle Discovery will be delayed to Nov. 30, the opening of the year's final launch window, because of work to repair a leaking hydrogen vent line.

Engineers also are assessing a large crack in the foam insulation in the intertank region of Discovery's external tank that was spotted after engineers began draining the tank earlier Friday.

NASA managers had held out hope initially that engineers could possibly repair the vent line in time for a launch attempt Monday, the final day of the current window. But after additional engineering assessments, Leinbach decided to push launch back to Nov. 30 to give the team more time to assess the problem and take corrective action.

Additional details will be posted as they become available.

12:25 p.m. EDT Update: Engineers assess an apparent crack in the shuttle Discovery's external tank

Engineers have found an 8-inch crack in the intertank section of the shuttle Discovery's external tank, sources said, indicating another major problem that threatens tentative plans to ready the ship for launch Monday. The crack in two rib stringers was spotted after NASA managers ordered a launch scrub because of a hydrogen leak in a 7-inch vent line attached to the left side of the intertank area. Whether the crack is related to the leak or not is not known. It also is not known whether the crack penetrates the metal structure of the stringers in question or foam insulation on the outer surface.

Two shuttle missions were delayed in 2009 by hydrogen leaks at the ground umbilical carrier plate quick-disconnect fitting and it's not yet known what the problem might be with Discovery's vent line. Even without the additional burden or a crack repair, the timeline is extremely tight for a Monday launch attempt.

Additional details will be posted here as they become available.

10:15 a.m. EDT Update: Discovery grounded until at least Monday

Shuttle Launch Director Michael Leinbach at a news briefing Wednesday. (Photo: NASA)
A "significant" hydrogen leak in a vent arm attached to the shuttle Discovery's external tank will delay another launch attempt until at least Monday, the final day of the current launch window, NASA officials said Friday. If Discovery is not off the ground by then, launch will be delayed to Nov. 30, the opening of the year's final shuttle launch opportunity.

Engineers are draining the shuttle's external tank in preparation for gaining access to the hydrogen vent line over the weekend. Launch Director Michael Leinbach said the magnitude of the leak was so high engineers suspect they will find an obvious defect when the mechanism is disassembled for an inspection.

"The signature of the leak is similar to what we've seen in the past when we've had leaks there, although the magnitude was higher this time and it occurred earlier in our tanking process," said Leinbach. "It actually occurred during fast-fill where in the past we'd gotten into a topping regime before the leak occurred."

Engineers cycled the vent valve in the mechanism in hopes of clearing whatever might be preventing a tight seal, but the leak persisted and Leinbach ordered a launch scrub at 8:11 a.m. EDT (EDT=GMT-4).

"The leak followed the vent valve cycling very closely, every time we cycled the vent we saw the leak, so that's indicative of something going wrong down inside of that quick-disconnect," Leinbach said.

It will take almost a full 24 hours to drain and "inert" the huge external tank, preventing inspections and troubleshooting until Saturday.

"It's my hope that given the magnitude of the leak that once we get the GUCP (ground umbilical carrier plate) taken apart, we'll see something wrong that's obvious to us, go fix it, put it back together and get a launch attempt before the end of this window," Leinbach said. "That's my hope. I'm not sure that's how it's going to turn out, but that's the challenge that we've put out to the team."

In the meantime, he said, launch was off until at least Monday.

"We've gone officially into a 72-hour scrub turnaround, knowing that's our last launch attempt in this window," Leinbach said. "There's certain tricks that we might be able to do when we pull the GUCP apart that says you get to the work quicker. A lot of the engineering contingent are going to want to take very, very detailed measurements as we're taking this thing apart, and that may end up being what we do. If we do all that detailed work, that probably extends the timeline because that's what we did in the past to get to that 72 hours.

"So we're not going to push the team, but we have asked them if 'is there anything you can do in a 72 to get to that launch attempt on Monday' because a lot of us believe that given the magnitude of the leak we're going to see something obvious when we get it apart. If that's the case, then we'll change out whatever has gone wrong and put it back together and hopefully that supports Monday."

NASA's Mission Management Team will meet Saturday to discuss repair options and whether to press ahead for a Monday launch attempt.

"We're going to get together later this morning with the OPS and engineering teams, review that kind of top-level assessment, top-level plan that we've asked (the team to carry out)," Leinbach said. "Then the detailed engineering reviews and troubleshooting plans will kick in later this afternoon. We'll present that to the program tomorrow sometime, what the actual options are. We won't know what's gone wrong with the GUCP until we get our hands on it, which will be tomorrow afternoon.

"So right now it's a lot of speculation, but obviously the hardware was talking to us, it leaked significantly and it was a case where we were violating not only launch commit criteria but also some of our ground safety requirements -- limits on hydrogen in free air. So we elected to scrub, obviously, and that was the best course of action."

8:30 a.m. EDT Update: SCRUB! Leak in hydrogen vent line forces launch delay

A leak in the gaseous hydrogen umbilical that connects a vent line, called the ground umbilical carrier plate, or GUCP, to the side of the shuttle Discovery's external tank has forced NASA to call off the countdown for today's planned launch. It is not yet known what might be needed to repair the problem or whether another launch attempt can be made before the current launch window closes Sunday or, possibly, Monday.
A closeup of the ground umbilical carrier plate attached to the shuttle Discovery's external tank. (Photo: NASA TV)

Another view of the leaking hydrogen vent line. (Photo: NASA TV)
"We have officially scrubbed today's launch attempt," said NASA commentator Allard Beutel. "The launch team here in Firing Room No. 4 is currently in the process of draining the external tank."

Problems with the ground umbilical carrier plate caused lengthy delays for two shuttle missions in 2009. There have not been any problems with the system since then.

The vent line is used to carry excess hydrogen gas away from the shuttle when the tank is filled with super-cold propellant. A valve used to route hydrogen to the vent line is closed a few minutes before launch when the tank is pressurized for flight.

In the most recent previous GUP leak, the shuttle Endeavour was grounded June 13 and 17, 2009, when sensors near the umbilical attachment plate detected hydrogen concentrations of more than 60,000 parts per million, or 6 percent. The allowable concentration near the shuttle is 4 percent.

After the second launch scrub, engineers collected detailed measurements and concluded the problem was caused by an alignment issue between the hydrogen vent port on the tank and the vent line interface. To ensure a tight fit, engineers replaced a rigid Teflon seal with a more flexible design, modified the umbilical plate mounting pins and installed washer-like shims to counteract the alignment issue.

The shims provided additional pressure on one side of the attachment fitting that was believed to be pulling away slightly as the hardware contracted under cryogenic conditions.

The fix worked, Endeavour was safely launched an no other GUP problems occurred before Discovery's fueling Friday.

Discovery's current launch window closes Sunday. The next launch window opens Dec. 1.

6:20 a.m. EDT Update: Shuttle fueling operations begin

Engineers began pumping a half-million gallons of supercold liquid oxygen and hydrogen rocket fuel into the shuttle Discovery's external tank early Friday, setting the stage for launch on an 11-day space station resupply mission, the orbiter's 39th and final flight. Liftoff is targeted for 3:04:01 p.m. EDT.

The shuttle Discovery at pad 39A early Friday, ready for fueling. (Photo: NASA TV)
Forecasters are predicting a 70 percent chance of acceptable weather, with the only concern being possible 24-knot headwinds at the shuttle runway in the wake of a cold front that moved through the area Thursday. The forecast calls for a 60 percent chance of good weather Saturday, dropping to 40 percent "go" on Sunday, the final opportunity in the current launch window.

"The launch teams are not working any issues right now that would prevent us from launching on time this afternoon," said NASA commentator Allard Beutel. "The mission management team gave unanimous approval to go ahead with fueling operations."

Working by remote control, engineers began the three-hour fueling procedure at 5:58 a.m., pumping liquid hydrogen and oxygen through transfer lines leading to the shuttle's aft engine compartment and from there, into the huge external tank. The procedure began 20 minutes behind schedule, but that will have no impact on the remainder of the countdown.

If all goes well, commander Steven Lindsey, pilot Eric Boe, Nicole Stott, Michael Barratt and spacewalkers Timothy Kopra and Alvin Drew will begin strapping in around 11:43 a.m. to await liftoff on the 133rd shuttle mission.

The primary goals of Discovery's mission are to deliver a new cargo module, loaded with supplies and equipment, to the International Space Station along with an external storage platform and a spare set of cooling system radiators.

Launch originally was scheduled for Monday, but the flight was delayed to Tuesday and then Wednesday by work to replace suspect quick-disconnect fittings in the pressurization system of Discovery's right-side orbital maneuvering system rocket pod. Then, during checkout of the avionics used to control Discovery's three main engines, an electrical glitch was encountered that prompted a 24-hour delay to Thursday.

Fueling began a few minutes late because of overnight work to replace loose weather covers over three forward rocket nozzles in Discovery's nose.. (Photo: NASA TV)
After a detailed engineering review, NASA managers decided the unexpected electrical "signature" was not a threat and Discovery was cleared for launch. But the weather refused to cooperate, and NASA's mission management team decided early Thursday to order another 24-hour delay to Friday.

Overnight, yet another problem cropped up. Engineers spotted loose covers over three maneuvering rocket thruster nozzles in the shuttle's nose section. Concerned about water intrusion and the possibility of ice in orbit, engineers moved a rotating gantry back into place around Discovery and engineers attached new covers. The rotating service structure was moved away again around 2:20 a.m.

Discovery's launch window closes Sunday or, possibly, Monday if engineers can resolve concerns about high heating once docked with the space station. If the shuttle isn't off the ground by Sunday, the flight will be delayed to Nov. 30 or Dec. 1, the opening of the year's final shuttle launch window.

Here is a timeline of the remaining countdown milestones. All times before the final hold at T-minus nine minutes are one minute earlier than (in EDT and launch-minus time; best viewed with fixed-width font):

08:38 AM......Begin 2-hour 30-minute built-in hold (T-minus 3 hours)
08:38 AM......Closeout crew to white room
08:38 AM......External tank in stable replenish mode
08:41 AM......Ascent flight control team on console
08:53 AM......Astronaut support personnel comm checks
09:23 AM......Pre-ingress switch reconfig
09:30 AM......NASA TV launch coverage begins
10:33 AM......Final crew weather briefing
10:43 AM......Crew suit up begins
11:08 AM......Resume countdown (T-minus 3 hours)

11:13 AM......Crew departs O&C building
11:43 AM......Crew ingress
12:33 PM......Astronaut comm checks
12:58 PM......Hatch closure
01:28 PM......White room closeout

01:48 PM......Begin 10-minute built-in hold (T-minus 20m)
01:58 PM......NASA test director countdown briefing
01:58 PM......Resume countdown (T-minus 20m)

01:59 PM......Backup flight computer to OPS 1
02:03 PM......KSC area clear to launch

02:09 PM......Begin final built-in hold (T-minus 9m)
02:34 PM......NTD launch status verification
02:55:01 PM...Resume countdown (T-minus 9m)

02:59:01 PM...Orbiter access arm retraction
02:59:01 PM...Launch window opens
02:59:01 PM...Hydraulic power system (APU) start
02:59:06 PM...Terminate LO2 replenish
03:00:01 PM...Purge sequence 4 hydraulic test
03:00:01 PM...Inertial measurement units to inertial
03:00:06 PM...Aerosurface profile
03:00:31 PM...Main engine steering test
03:01:06 PM...LO2 tank pressurization
03:01:26 PM...Fuel cells to internal reactants
03:01:31 PM...Clear caution-and-warning memory
03:02:01 PM...Crew closes visors
03:02:04 PM...LH2 tank pressurization
03:03:11 PM...SRB joint heater deactivation
03:03:30 PM...Shuttle flight computers take control of countdown
03:03:40 PM...SRB steering test
03:03:54 PM...Main engine start (T-6.6 seconds)
03:04:01 PM...SRB ignition (LAUNCH)