Spacewalk repairs concern astronauts

A photo from the International Space Station shows the location of two protruding gap fillers on Discovery's underbelly, with closeups inset. Picture / Nasa

HOUSTON - The shuttle Discovery's crew had misgivings about performing a spacewalk to remove two fabric fillers dangling from the ship's delicate heat shield, astronauts said.

Nasa ordered the repair because it fears another heat shield failure, such as the one that claimed Columbia and its seven-member crew in February 2003.

"I think a number of us, we did have some misgivings," said astronaut Andy Thomas of Australia. "We were concerned about the implications of it and what was motivating it."

However, the more the astronauts learned about the plan, the more comfortable they became with the unexpected - and unprecedented - repair.

Spacewalker Stephen Robinson planned to go beneath the shuttle tonight to pluck out two pieces of ceramic-coated cloth sticking out from the ship's smooth, tiled belly.

"Like most kinds of repairs, it's conceptually very simple, but it has to be done very, very carefully," Robinson said during a news conference from space.

Robinson said his biggest concern will be to avoid butting the shuttle tiles with his helmet.

"The tiles, as we all know, are fragile and a crewmember out there is pretty large mass," Robinson said. "The thing I'll be watching most closely is the top of my helmet because I'll be leaning in toward the orbiter. So that's what I'll be most careful with."

The protruding strips are only an inch long but Nasa fears they could affect how air flows over the orbiter and dangerously add to the intense heat as the ship re-enters Earth's atmosphere at 27,200 kph.

The primary risk of removing or cutting the strips is that Robinson could inadvertently damage the surrounding tiles that are made to resist that heat, but not an accidental knock from a space helmet.

The crew took a break from spacewalk preparations to take a call from President Bush.

"I just wanted to tell you how proud the American people are of our astronauts," Bush said. "I want to thank you for being risk-takers for the sake of exploration."

Robinson, who along with Soichi Noguchi has already made two spacewalks on the mission, will become the first astronaut in the 24-year shuttle program to venture beneath one of the ships in space. He will be strapped to the station's robot arm and watched by television cameras, so the spacewalk "sounds scarier than it is," flight director Paul Hill said.

MISGIVINGS

Mission specialist Charles Camarda said if pulling out the protruding material, called gap filler, lessens the risk of overheating during re-entry, the mission was worth the risk.

"It's a very close call," he said during the news conference.

Discovery is docked to the International Space Station and orbiting 220 miles above Earth. Robinson's repair mission was tacked on to an already scheduled spacewalk to attach a storage platform to the station.

Robinson will be maneuvered to the shuttle's belly on the space station's robot arm, then will try to pluck the thin, ceramic-covered strips out with his gloved fingers.

If that fails, he will tug at them with forceps and if that does not work he will try to saw them off with a modified hacksaw.

"There won't be yanking going on. It will be a gentle pull with my hand. The main tools I plan to use are right here," he said, holding out his hand and pinching his fingers together.

Columbia's demise was caused by a hole in the ship's wing panels that was hit by a piece of foam insulation that fell off the fuel tank during launch.

Superheated gases entered the breach during re-entry and the shuttle broke apart over Texas.

Videos showed loose tank foam at Discovery's launch last week, which prompted Nasa to ground the shuttle fleet.

- REUTERS