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Shuttle astronauts set for second spacewalk

Posted on: Monday, 1 August 2005, 02:02 CDT

By Jeff Franks

HOUSTON (Reuters) - Two shuttle astronauts were set to replace a failed gyroscope on the International Space Station on Monday in the second of three planned spacewalks as NASA pondered whether to add a fourth to repair loose material on Discovery's heat shield.

Steve Robinson and Japan's Soichi Noguchi were to work outside Discovery and the space station, linked together 220 miles above Earth, for 6 1/2 hours to remove the bad gyroscope and replace it with a new one brought by the shuttle.

Gyroscopes keep the 200-ton space station correctly positioned. It has four of them but only two were working before Discovery's arrival.

Robinson and Noguchi repaired the other malfunctioning gyroscope in their first spacewalk on Saturday.

The $95 billion station can maintain position with just two working gyroscopes but if only one is functioning, the station crew would have to fire rocket thrusters, which burn precious fuel, to keep it steady.

Discovery is making the first shuttle flight since the Columbia disaster on Feb. 1, 2003, and is the first shuttle to link up with the space station since November 2002.

The spacewalking astronauts were scheduled to venture out once more on Wednesday to install a storage platform outside the station.

NASA said on Sunday they might be asked to perform an unprecedented repair to the shuttle's heat shield during that spacewalk or it may add a fourth spacewalk on Friday for the task.

Video inspections of Discovery after it launched last week found that two strips of material known as "gap fillers" between heat-resistant tiles on the shuttle's belly are protruding about an inch.

NASA managers fear the protrusions could change aerodynamics and increase heat on the shuttle by as much as 25 percent when it re-enters Earth's atmosphere for landing scheduled on Aug. 8.

Heat shield damage was responsible for the loss of shuttle Columbia and its seven astronauts on Feb. 1, 2003.

The gap filler problem has cropped up on previous missions and the shuttles landed without problems but deputy shuttle program manager Wayne Hale said NASA engineers were assessing the risk of trying it again versus performing a repair that would involve trimming or removing the loose material.

"I think the jury is out at this point on whether we'll do anything," Hale said.

But, he said, "The Columbia accident made us realize that we had been playing Russian roulette with the shuttle crews."

The Columbia disaster was caused by a piece of foam insulation that broke off the ship's fuel tank during launch and smashed into the ship's wing.

After the accident, NASA adopted new procedures, spent $1 billion on safety upgrades and built equipment to inspect the shuttle while it is in orbit.

Videos showed pieces of tank foam flying off during Discovery's launch, which prompted NASA to ground the shuttle fleet until the problem is solved.

The shuttle suffered minor damage to its heat shield, but the protruding material is not believed to have been caused by foam impacts.

Source: REUTERS

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