President George W. Bush smiles while speaking to members of the Discovery crew from the White House. (AFP)

Houston, Aug. 2 (Reuters): Discovery’s astronauts had misgivings about the risky spacewalk mission to the shuttle’s fragile belly but agreed to try the repair because it seemed relatively easy to do, crew members said today.

Tomorrow, Steve Robinson will make space history when he ventures out to Discovery’s smooth underside to try to remove two loose fibre strips sticking out from between the crucial heat-resistant tiles.

“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 on Nasa’s first shuttle flight since the 2003 Columbia disaster.

The protruding strips are small ? only 2.5 cm long ? but Nasa fears they could affect aerodynamics and dangerously add to the intense heat on the shuttle as it re-enters Earth’s atmosphere on August 8. The primary danger is that the tiles, which can withstand hellish heat, are easily broken if touched.

Robinson, who, along with Soichi Noguchi, has already made two spacewalks on the mission, will become the first astronaut in the 24-year shuttle programme to venture out to the belly of an orbiting spacecraft.

Nasa is undertaking the risky repair because it does not want to lose another shuttle and crew because of heat damage, as it did with Columbia.

The astronauts admitted they initially had reservations when told about the repair mission, but said they agreed with it now because it seemed like an easy thing to do.

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

“It’s a very close call,” added mission specialist Charles Camarda. “We think it is a pretty simple (spacewalk) if all goes well.”

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 crew member 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.”

Discovery is docked to the International Space Station and orbiting 352 km above the Earth. Robinson’s repair mission was tacked on to an already scheduled spacewalk to attach a storage platform to the station.

Robinson will be manoeuvred to the shuttle’s belly on the space station’s 15-metre robot arm, then 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 makeshift handsaw put together by the shuttle crew.

“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.