NASA scrambling to determine whether drooping material on Discovery’s belly poses danger | VailDaily.com
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NASA scrambling to determine whether drooping material on Discovery’s belly poses danger

SPACE CENTER, Houston – A couple of short strips of material dangling from Discovery’s belly had NASA scrambling Sunday to determine whether the protrusions might endanger the shuttle during next week’s descent and whether the astronauts might need to attempt a repair.The potential trouble has nothing to do with foam or other launch debris – for a change – but rather the accidental slippage of material used to fill the thin gaps between thermal tiles.Flight director Paul Hill said two engineering teams are working “aggressively” on the problem, with heated discussions raging on what to do, if anything.It will be Monday before the analysis is complete and mission managers decide whether to have the crew’s two space walkers cut, pull out or shove back in the hanging material, Hill said.Discovery and its crew of seven may be perfectly safe to fly back with the two drooping pieces, Hill stressed, as space shuttles have done many times before, although not necessarily with dangling pieces as large.One piece is sticking out an inch between thermal tiles, the other six-tenths of an inch. For those areas, far forward near the nose, the general wisdom and flight history indicate that the limit should be a quarter-inch, Hill said.He noted, however, that the quarter-inch measurement was taken following previous re-entries and the intense heat could have burned some of it off. Discovery’s flaws were spotted in orbit because of all the photography and laser imaging being aimed at normally hard-to-see spots.The extremely thin gap fillers are made of a feltlike material and ceramic, and are held in place with glue and by the tight fit of the thermal tiles.”If the protrusions were lower, clearly if they were at a quarter inch or lower, then we wouldn’t be having this discussion,” Hill said.Any repair, if deemed necessary, would most likely be performed during the third and final spacewalk of the mission on Wednesday, although a fourth unplanned spacewalk might be required, he said. The second spacewalk, for space station repairs, is set for Monday.The astronaut would have to stand on either the shuttle or station’s 50-foot robotic arm in order to reach the two hanging strips of filler. There are drawbacks to using either arm, namely clearance and time constraints.One extreme option under consideration would be to put an astronaut on the end of the brand new 100-foot inspection crane, but it would likely be a bouncy ride and that makes lots of spacewalk and robotic specialists “understandably nervous,” Hill said. The boom could bang into the shuttle and cause severe damage.”The options get complicated,” Hill explained at a news conference. “There are pretty strong arguments for and against most of the options.”Anything dangling from the normally smooth bottom of the shuttle will overheat the area and downstream locations during re-entry; temperatures there typically hit 2,000 degrees.A hole in Columbia’s left wing, carved out by a large chunk of flyaway fuel-tank foam, led to the spacecraft’s destruction during re-entry on Feb. 1, 2003. All seven astronauts were killed.NASA has cleared Discovery’s thermal tiles for landing on Aug. 8; they constitute the vast majority of the shuttle’s exterior. The only remaining issues, before the final go-ahead can be given for descent, are the reinforced carbon panels that line the wings and nose cap, and the two dragging gap fillers.In a series of TV interviews from space, commander Eileen Collins and her crew said they believe Discovery is safe to come home. She expressed surprise and disappointment that a big piece of foam came off Discovery’s tank during last Tuesday’s liftoff, after everyone – including herself – signed off on analysis that showed the area did not need to be improved in the wake of the Columbia tragedy.”Was there a sound technical reason why they made that decision or was it subject to cost pressures or schedule pressures?” said astronaut Andrew Thomas. “I think we do need to address the question of why that area was not examined.”Vail – Colorado


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