Spacewalking astronauts test repair techniques

HOUSTON - Two astronauts stepped outside shuttle Discovery in the first US spacewalk since 2002 as they tested damage-repair techniques that Nasa hopes will prevent another Columbia disaster.

"What a view," Japan's Soichi Noguchi said as he drifted out into space while Discovery, docked to the International Space Station, sailed 358km above southeast Asia.

"Yeah, it's been a long road," said spacewalking partner Steve Robinson.

They looked a little like do-it-yourself homeowners as they used a specially-designed caulking gun and putty knives to apply black paste to damaged insulating tiles and wing materials that shield the shuttle from the heat of re-entry.

They worked only on test tiles stowed in the shuttle's cargo bay, not on the orbiter itself, which sustained minor damage at launch on Tuesday from flying debris.

Nasa engineers are to review the test upon Discovery's return, but Robinson generally he liked what he saw.

"No bubbling at all. It's behaving very nicely," he told Mission Control. "It's a little bit like pizza dough." Developing ways to repair an orbiting shuttle was one of the recommendations of investigators into the crash of Columbia, which broke apart while returning to Earth on Feb. 1, 2003, after debris struck its wing heat shield at launch 16 days before. The seven astronauts on board died.

Nasa said it does not think the nicks to Discovery pose a similar danger, but has kept open the possibility of using the still-unproven repair techniques for real if they decide there is a safety risk.

Videos showed that insulating foam from Discovery's external fuel tank came loose and possibly struck the shuttle as it rose from Florida.

Discovery was the first shuttle flight since Columbia fell. Nasa thought it would be free of the flying-foam problem after 2 1/2 years and $1 ($1.48) billion spent making it safer.

Nasa said on Wednesday it would ground its shuttle fleet until the problem is fixed. Nasa administrator Michael Griffin told reporters he does not expect it to be "a long, drawn-out affair" to get shuttle back to space.

In their 6 1/2 hour spacewalk, Noguchi and Robinson were to replace the space station's a failed global-positioning satellite antenna and fix the power supply to one of the gyroscopes that keep the 200-tonne station correctly positioned.

The $95 billion space station has four gyroscopes, but two are not working, and recently a third began acting up but is still functioning. If it had only one working gyroscope, rocket thrusters, which burn precious fuel, would have to be used to maintain position.

On Monday, Robinson and Noguchi will use their second spacewalk to replace the other broken gyroscope with a new one brought from Earth.

On their third spacewalk, scheduled for Wednesday, they will install a stowage platform outside the space station.

Discovery is scheduled to return from space on Aug. 7, but Nasa managers said they may extend the mission a day to transfer more supplies to the space station, just in case the shuttle fleet remains grounded for a long time.

- REUTERS