CAPE CANAVERAL, Florida - NASA will try to launch space shuttle Discovery to the international space station late Friday night, after back-to-back delays caused by bad weather and fuel valve trouble.
It will be the third try for NASA, which is still struggling to understand why a critical shuttle fuel valve appeared to malfunction Tuesday midway through the fueling process.
The valve was tested Wednesday night, and all indications were that it was a problem with a sensor rather than the valve itself, said NASA spokesman Allard Beutel. The hydrogen fuel valve, a big 8-inch device, is located in Discovery's engine compartment.
After meeting Thursday, mission managers decided they needed more time to settle on a plan if the problem reappears, and aimed for a liftoff late Friday night.
In an unusual lineup of events, NASA had two launch opportunities for Friday, in the early wee hours and just before midnight (0400 GMT).
Thunderstorms ruined the first launch attempt early Tuesday morning; the valve problem cancelled an early Wednesday attempt.
NASA has until Sunday to launch Discovery, otherwise the shuttle will have to get in line behind a Japanese cargo ship and a Russian spacecraft set to go to the space station in September. That would push the shuttle mission into mid-October.
Seven astronauts are assigned to the 13-day flight. They will deliver a full load of space station supplies, including a treadmill named for Comedy Central's Stephen Colbert.
Colbert won the online vote earlier this year for naming rights to a yet-to-be-launched space station room. NASA went with the name Tranquility, however, in honour of this summer's 40th anniversary of the first manned moon landing.
"Yeah, that will scare the aliens," Colbert said of the name Tranquility.
