Discovery To Lift Off At 11:38 A.M. Tomorrow With Acceptable Risk
Space Shuttle Discovery will launch at 11:38 a.m. ET tomorrow from Pad 39A at Kennedy Space Center (KSC) in a flight that may not be completely safe, but will have what NASA terms acceptable risk.
Some engineers recommended removal and replacement of three heat-shielding tiles on the leading edges of an orbiter vehicle wing, a repair job that would set back the two-week Discovery STS-120 Mission to the International Space Station (ISS) by about 60 days.
The tiles show problems with a coating that has degraded.
But senior NASA policymakers decided the ship could fly as is with acceptable risk. (Please see Space & Missile Defense Report, Monday, Oct. 15, 2007, and Wednesday, Oct. 17, 2007.)
Heat shielding on orbiter vehicle wing leading edges became a major concern for NASA following the 2003 Space Shuttle Columbia disaster.
During launch and ascent, a large chunk of foam insulation broke free from the external fuel tank and punched a hole in the leading edge of an orbiter wing. Later, when Columbia attempted to return to Earth, searing hot gases of reentry rushed into the wing and heated it to the point of structural failure, and the ship and crew were destroyed, making a fiery streak across the sky.
Potential weather problems make it uncertain whether Discovery will lift off on schedule tomorrow. Weather officer Kathy Winters said there is a 60 percent chance weather will prevent liftoff.
She explained that meteorologists continue tracking a frontal boundary that may arrive Wednesday, earlier than previously predicted. The front should be out in the Gulf of Mexico tomorrow, launch day, but depending on when the front arrives, it could cause problems for a Wednesday launch attempt should launch not occur tomorrow.
Weather should improve once the front passes through the area. There still is only a 10 percent chance that weather could prohibit tanking for liftoff tomorrow.
Mike Leinbach, space shuttle launch director, sees no mechanical or electronic problems in sight that would prevent a launch, adding that the ship has been well prepared for the mission.
The Discovery crew of seven astronauts arrived in Florida Friday and have been going through final checklists and preparations for the liftoff.
Retired Air Force Col. Pamela A. Melroy will command the STS-120 mission to take the Node 2 connecting module to the station. Melroy, a veteran shuttle pilot, is the second woman to command a shuttle. Marine Corps Col. George D. Zamka will be pilot. Mission specialists will be Scott E. Parazynski, Army Col. Douglas H. Wheelock, Stephanie D. Wilson and Paolo A. Nespoli, a European Space Agency astronaut from Italy. Zamka, Wheelock and Nespoli will be making their first spaceflight.
Expedition 15/16 Flight Engineer Clayton Anderson will return to Earth from the space station aboard Discovery. That flight will carry his replacement, Daniel Tani, to the station. Tani will return on shuttle mission STS-122 set to launch Dec. 6.
STS-120 is the 23rd shuttle mission to the space station, where the Italian-built U.S. multi-port module will be attached to the station.
That module in turn will provide attachment points for further additions to the space station in the form of laboratories built by several nations.
Discovery is scheduled to return to KSC at 4:47 a.m. ET Nov. 6.