Valve tests delay space-shuttle launch

Nasa said today it had delayed the launch of space shuttle Discovery while it runs tests to determine whether newly-installed valves would cause serious damage if they broke during lift-off.

The launch will now take place no sooner than February 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 small steel valves that control the flow of gaseous hydrogen into the external fuel tank, said Nasa’s space operations chief Bill Gerstenmaier.

“We want to make sure we’ve got this right. This has important consequences to us,” Mr 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 see 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 eight and a half-minute climb to orbit. The fuel tank needs to maintain a certain pressure during launch; shuttle programme manager John Shannon said it was 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,” he said.

Top Nasa managers decided on the delay after a day of closed-door meetings at Florida’s Kennedy Space Centre to discuss launch preparations.

Discovery and its seven-man crew will deliver the last set of solar wings to the international space station.

At the space station, meanwhile, a two-minute engine firing last month caused the outpost to shake like never before, it emerged today.

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 January 14, no structural damage occurred to any of the pieces.

Mr Suffredini said the space station’s commander, Mike Fincke, told flight controllers he had never felt the complex shake so much. Video from a shaking indoor camera showed equipment and notepads flowing back and forth.

A similar engine firing that had been planned today to boost the space station has been cancelled.