NASA has given the heave-ho to some of the foam insulation surrounding the space shuttle鈥檚 external fuel tank and has cleared the shuttle Discovery鈥檚 tank for a launch in July.
During Discovery鈥檚 last launch in July 2005, a 450-gram chunk of foam fell off the external tank鈥檚 鈥減rotuberance air load鈥� (PAL) ramp, which is a manually applied foam structure. It did not hit the orbiter, but it concerned NASA engineers enough to remove the two PAL ramps for the next flight. It was a chunk of falling foam that was responsible for the Columbia disaster in 2003.
Some concerns remained, though, as the PAL ramps normally deflect some of the forces experienced during launch away from sections of the fuel tank. Using wind tunnel tests and computer simulations, NASA has shown that the tank is safe without the ramps. The agency found that each bolt, bracket and cable its engineers analysed on the outside of the tank had at least 140 per cent of the strength needed to withstand the strongest forces expected during launch.
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鈥淚n all areas, we can show we meet the required factor of safety and we are structurally safe to fly without those two large pieces of foam,鈥� says Wayne Hale, the shuttle programme manager.
Discovery will deliver supplies and a third crew member 鈥� European Space Agency astronaut Thomas Reiter 鈥� to the International Space Station. The seven-person crew will undergo a countdown dress rehearsal at the Kennedy Space Center in Florida this week.
