CAPE CANAVERAL, Fla. – NASA plans to remove a suspect foam insulation ramp from the space shuttle’s external fuel tank before the next mission launches in 2006.
The ramp has been under scrutiny since July 26, when a one-pound piece broke free during Discovery’s liftoff and narrowly missed hitting the orbiter. It was the first shuttle mission after a foam strike doomed Columbia in 2003 by smashing a hole through heat shielding on the ship’s left wing.
Engineers are close to concluding that eliminating the so-called Protuberance Air Load, or PAL, ramp won’t have any adverse effect on future tanks. The ramp is designed to shield fuel pressurization lines and a tray of electrical cables on the tank’s exterior from potentially damaging winds during liftoff.
“We think that the best thing to do is just to take it off,” said Bill Gerstenmaier, NASA’s associate administrator for space operations. “There is still a lot of engineering to be done.”
Shuttle managers have yet to pinpoint what caused part of the ramp to break off. Initially, there were concerns that workers might accidentally have crushed the foam while building the tank.
In November, however, technicians discovered small cracks in a ramp on another tank that was fueled for tests before Discovery’s flight and later removed for unrelated reasons. Shuttle managers think the cracks were caused by flexing of the tank after it was filled with super-frigid liquid oxygen and liquid hydrogen propellants.
NASA is studying a variety of relatively minor modifications that could be made to the tank’s foam exterior after the PAL ramp is removed. A fix likely will be chosen within the next few weeks. Preliminary tests will be done in January to evaluate whether the design changes are safe.
Despite the amount of work ahead, shuttle managers have yet to publicly give up on the current target launch window of May 3-23.
“Depending on what engineering solution gets picked, May is still very viable,” Gerstenmaier said Thursday. “Some of the other engineering solutions … may move us somewhere else.”
If NASA is unable to make the May launch window, the next two opportunities would be July 1-20 and Aug. 28-Sept. 14.
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