Tuesday, November 02, 2010
NASA Will Decide Wednesday On Possible Launch Thursday
NASA will decide Wednesday afternoon whether to try to launch shuttle Discovery the following day or perhaps delay its mission until early December so repairs can be made to one of its three liquid-fueled main engines.
Discovery and six astronauts now are tentatively slated for a 3:29 p.m. Thursday blast-off, but engineers still have to explain trouble with a circuit breaker that plays a key role in routing commands from the shuttle's primary flight computers to a computer that controls Discovery's Engine No. 3.
The engine controller failed to immediately power up during prelaunch checkouts Tuesday, an indication that the circuit breaker was not operating properly. The controller subsequently powered itself on and was in the midst of a self-test when engineers detected an small-but-unusual drop in voltage -- another sign the breaker might be faulty.
Mike Moses, chairman of NASA's prelaunch Mission Management Team, said dust or some type of contaminant might be keeping the circuit breaker from fully connecting with metal contacts. Similar problems have been resolved in the past by repeatedly turning power on and off, clearing any transient contaminant.
NASA engineers still are trying to pinpoint the exact cause of the two glitches, and they must develop a full understanding of the problem before the agency commits to proceeding with a countdown. The countdown will remain in the T-Minus 11-hour hold for the time being.
The Mission Management Team will meet at 2 p.m. Thursday. Engineers will brief them and then managers will decide whether to press ahead with external tank propellant-loading operations Thursday morning.
The weather forecast for launch on Thursday is not good. Air Force meteorologists say there is a 70 percent chance n approaching cold front will bring low-level clouds and rain into the Kennedy Space Center area at launch time -- conditions that would force NASA to scrub a launch attempt.
NASA must launch Discovery by Sunday or delay its International Space Station outfitting mission to early December. The sun angle on the station between Monday and Nov. 23 will be such that the outpost could not generate enough power and the shuttle could not dispel enough heat to complete the 11-day mission.
Then a three-person crew is departing the station Nov. 29, and a shuttle mission in that timeframe would interrupt that operation.
Posted by Todd Halvorson at 7:34 PM