Shuttle Discovery and seven astronauts will attempt to launch from Kennedy Space Center at 7:43 p.m. Sunday, NASA officials announced this morning. The decision delays Saturday's planned launch of a United Launch Alliance Atlas V rocket with a military communications satellite payload until next week.
The Atlas V launch now is tentatively targeted for 9:24 p.m. Tuesday from Cape Canaveral Air Force Station.
Engineers have not yet determined what caused a valve to leak hydrogen gas on Wednesday during fueling of Discovery's orange external tank, an issue that forced managers to scrub the mission's first launch attempt that day.
"We don't have any smoking guns yet," said Mike Leinbach, NASA's shuttle launch director, during a briefing this morning at KSC.
He said it wouldn't be clear if a repair that technicians are working on today is successful until reaching the same point during fueling on Sunday, which is set to begin at 10:18 a.m.
Technicians are working to replace a quick-disconnect device that includes a seven-inch diameter valve. The device is part of a line that vents hydrogen gas from the external tank to a stack of flares on the ground.That helps maintain proper pressure in the tank during fueling of super-cold liquid hydrogen.
Tests of the valve using helium at room temperature show no problems, Leinbach said, so it appears that the transition to extreme cold is causing the problem.
With a successful launch on Sunday, Discovery would embark on a slightly shortened mission to the International Space Station. The mission would last 13 days instead of 14, and the last of four planned spacewalks would be dropped.
That's because NASA needs to leave the station before the planned March 26 launch of a Russian Soyuz spacecraft carrying three new station crew members.
If Discovery can't launch by Tuesday, it would have to wait until April 7.
The crew will attempt to complete the space station's power supply by adding a final set of power-generating solar array wings. The wings are packed on the 11th and final piece of the station's truss, or backbone, which will measure 335 feet when complete.
The weather forecast for Sunday is good, with an 80 percent chance of conditions allowing a launch.
Conditions worsen after Sunday, with a 70 percent chance of good weather Monday but only a 40 percent chance on Tuesday.
You can read today's official forecast released by the Air Force here.
NASA plans to hold a pre-launch press conference no earlier than 3 p.m. Saturday at KSC.
You can watch it live here on The Flame Trench. Just click on the NASA TV still image on the right side of the page to launch a NASA TV viewer.
ABOUT THE IMAGES: Click to enlarge and save the cell phone photo that shows a Kennedy Space Center closed-circuit television view of NASA contractor technicians working on Thursday around the area where a leaky gaseous hydrogen valve is located on the shuttle Discovery stack. Photo credit: James Dean, Florida Today. Below: A closeup of the seven-inch quick disconnect that was to be replaced on the hydrogen vent line to the Ground Umbilical Carrier Plate of space shuttle Discovery's external fuel tank. Photo credit: United Space Alliance.
3 comments:
Question -- granted it is dangerous and probably expensive, but why can the tank not be test loaded today or tomorrow to see if this is fixed one way or the other?
Given the tightness of the launch window it seems like that would be a good thing to do.
Mr. Boyer: thanks for the note, and good question. I checked on this for you, and NASA's answer is that it would simply take too long to fill the tank again, empty it and wait for all the liquid hydrogen to boil off. After the tank is emptied, another 20 hours must still pass before it's safe for crews to go to work. So essentially, Sunday's launch attempt is the test load. If there's another serious leak, the launch will be scrubbed. If not, they're 'go' for launch.
Space shuttle should always be launched in proper conditions however time may it take.
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