NASA on Tuesday delayed next week's launch of space shuttle Discovery while it runs tests to determine whether newly installed valves would cause serious damage if they broke during liftoff.
The launch will take place no sooner than Feb. 19, seven days after the shuttle was originally scheduled to take off on a space station construction mission. The delay is needed to make certain that Discovery can fly safely with the valves that control the flow of gaseous hydrogen into the external fuel tank, said NASA's space operations chief, Bill Gerstenmaier.
The small steel valves are critical parts.
"We want to make sure we've got this right. This has important consequences to us," Gerstenmaier said. "So we think standing down for a little bit of time and letting the folks do a little more work is a good thing."
Three new gas pressure valves were installed in Discovery's engine compartment after a small part of one broke off during shuttle Endeavour's launch in November. Endeavour's fuel tank maintained good pressure and, in the end, no harm was done.
Engineers believe fatigue caused by acoustic vibrations caused the valve in Endeavour to break. Over the next week, experts will use lab tests to try to ascertain whether a broken chunk of a valve could damage any of the downstream plumbing.
Engineers are confident that the three valves in Discovery are good — inspections show them to be strong and free of cracks — but want to take extra steps to make sure no serious damage could result if one of them broke during the 8 1/2-minute climb to orbit. The fuel tank needs to maintain a certain pressure during launch; shuttle program manager John Shannon said it's unclear how serious it would be if that did not happen.
"We're going to make sure. We're going to take that extra step," Shannon said.
Top NASA managers decided on the delay Tuesday evening after an entire day of closed-door meetings at the Kennedy Space Center to discuss launch preparations.
Discovery and its seven-man crew are set to deliver the last set of solar wings to the international space station.
Up at the space station, meanwhile, a two-minute engine firing last month caused the outpost to shake like never before. It was supposed to be a routine procedure to raise the altitude of the station; this time, though, there were errors in the firing commands sent up by Russian flight controllers outside Moscow.
NASA's space station program manager, Mike Suffredini, said even though the vibration exceeded acceptable limits on Jan. 14, no structural damage occurred to any of the pieces. Engineers also have determined that the 15-year design lifetime of the station is not in jeopardy because of the incident, he said.
Suffredini said the space station's commander, Mike Fincke, told flight controllers he'd never felt the complex shake so much. But Fincke never heard any creaking or groaning noises. Video from a shaking indoor camera showed equipment and notepads flowing back and forth.
"It really raises your eyebrow," Suffredini said. When you put that kind of vibration into the space station, "which is what you spend your whole time trying to avoid, that really piques your interest."
A similar engine firing that had been planned for Wednesday, to boost the space station, has been canceled pending further analysis.