Posted on behalf of Alexandra Witze
KENNEDY SPACE CENTER, Florida — The second-to-last space shuttle flight will have to wait a bit longer. Mission managers scrubbed the scheduled 29 April launch of Endeavour, its 25th and last planned journey into space.
After the shuttle’s massive fuel tanks were filled and engineers were running through last-minute checks, NASA discovered a problem with a heater in an auxiliary power unit, or APU, which keeps the hydrazine fuel flowing through the orbiter. Endeavour has three APUs, with two heaters on each fuel line. “Had we not caught this pre-launch it would not have been a bad day in orbit,” says mission manager Mike Moses of the Kennedy Space Center. The shuttle would have continued to fly, relying on its backup heater.
But caught on the ground, the problem became a showstopper. “You don’t like lifting off without redundancy,” says launch director Mike Leinbach . NASA declared a scrub at 12:16 p.m., three and a half hours before Endeavour’s scheduled liftoff.
Engineers are now troubleshooting how to fix the heater. One solution would be relatively simple: if the thermostat controlling the heater is blown, engineers can simply replace it and launch as early as Monday, May 2. If the thermostat is fine, NASA will have to go in and replace a more complicated box of electrical switches, says Leinbach. That process could take a number of days. And after Wednesday, May 4, Endeavour won’t be able to lift off for three more days because a military Atlas V launch is planned.
Endeavour’s problems were tempered somewhat by President Barack Obama visiting the space center on Friday afternoon. Obama had been scheduled to attend the launch with his wife and children, and went ahead with the visit after the launch was scrubbed, triggering a frenzy of Secret Service agents across the space center campus. The president toured the Atlantis shuttle (right), being prepped for the program’s final launch in June. “He came in and met with the crew families and talked to some folks along the way,” said center director Bob Cabana.
Crew families, of course, include Arizona Congresswoman Gabrielle Giffords, injured during a fatal January shooting. Contents of the conversation between Obama and Giffords, wife of Endeavour commander Mark Kelly, were not made public.