NASA willnot fly a protective foam ramp aboard the fuel tank for its next space shuttle mission,eliminating a potential launch debris hazard that croppedup during July's launch of the Discovery orbiter, a top agency officialsaid Thursday.
Flying NASA'sSTS-121 shuttle mission - the second flight since the 2003 Columbia accident - withoutthe ramp could push the spaceflight past a May2006 launch window depending on the extent of modifications required, said WilliamGerstenmaier, NASA's associate administrator for space operations, in ateleconference with reporters.
Engineershave been discussingwhether remove a protective protuberance air load (PAL) ramp from shuttle fueltanks since July, when a one-pound chunk of foam insulation popped free fromthe ramp during Discovery's STS-114launch. A similar foam shedding event doomed the space shuttle Columbia and itsseven-astronaut crew in 2003 when it damaged the orbiter's heat shield.
"We thinkthat's the best thing to do, just take it off," Gerstenmaier said, adding thatmeeting a May 2006 launch window comes second to solving the PAL ramp issues. "Ithink we ought not to think about May right now."
Last month,NASA shuttle officials said investigators had discovered a series of finecracks along the PAL ramp of External Tank 120 (ET-120), which has beenfilled twice with supercold liquid fuel during tests and is one of severalunder scrutiny.
"We know alot about the cracking phenomenon, but we still haven't pinpointed the cause," Gerstenmaiersaid, adding that solving the problem is critical not just for STS-121, butlong-term shuttle program through its 2010 retirement date. "We know it'srelated to the chill down process and to some pressurization of the tank, buthow those fit together...it's not an easy problem."
Once theproblem is better understood, engineers will then decide the best fix for theexternal tank.
"We'regoing to do the right thing and let the data drive us where we need to go,"Gerstenmaier said. "I think we've got a unique opportunity to get this right."
- NASA's PAL Ramp Foam Problem a Lesson in Failure, Shuttle Chief Says
- Special Report: NASA's STS-114 Return to Flight Shuttle Mission
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