Discovery Astronauts Confident in Planned Spacewalk Repair to Heat Shield

HOUSTON - The Discovery astronaut tapped to pluck out two strips of filler material jutting from the orbiter's heat shield said Tuesday that the first-time repair appears simple, but that great care must be taken to avoid damaging the shuttle.

Shuttle astronaut Stephen Robinson, a mission specialist and spacewalker for Discovery's STS-114 flight, said he is confident in NASA's plan to send him under the orbiter Wednesday to remove two strips wedged between the heat-resistant tiles as part of third extravehicular activity (EVA) of the mission. That spacewalk will begin at 3:14 a.m. EDT (0714 GMT) on Aug. 3.

"Like most repairs, its conceptually simple but it has to be done very, very carefully," said Robinson, speaking via video downlink from the International Space Station (ISS) where he and other Discovery and ISS astronauts spoke to reporters. "The tiles, as we know, are fragile and an EVA crewmember has a lot of mass, so we'll have to be very careful."

Robinson will be the first astronaut to be sent beneath a NASA space shuttle, let alone to repair its ceramic tile heat shield in orbit, when he rides the ISS robotic arm under the forward section of Discovery Wednesday. Taking care not to bump his helmet or any other part of his spacesuit against the fragile black tiles along Discovery's belly, he will pluck his targets - two pieces of stiff ceramic fiber cloth used to fill excess space and prevent tiles from shaking against one another during launch.

"The main tools I plan to use are right here," Robinson said, pinching the thumb and forefinger of his right hand together. "It'll be a gentle pull with my hand and if that doesn't work I have some forceps and will give it a stronger pull. If that doesn't work, I saw it off with a hacksaw."

Known to NASA as gap-fillers, the small strips have been seen jutting from between tiles on orbiters in the past and are not caused by impact or foam debris damage, shuttle officials said, adding that they likely became unglued from their bases during launch.

Shuttle officials are concerned that the two gap-fillers, which jut out 1.1 inches (2.7 centimeters) and up to nine-tenths (2.3 centimeters) respectively, could cause higher than normal heating to downstream tiles and the wing leading edges during reentry. They decided Monday to press ahead with the repair.

Some members of Discovery's seven-astronaut crew were concerned about the added risk of the gap-filler repair, but conceded that the straightforwardness of the task and from flight controllers on the ground justified the action.

"When we first heard about it I think a number of us did have misgivings, we were concerned about it," said STS-114 mission specialist Andrew Thomas, who will choreograph the spacewalk repair from inside Discovery. "However, it's a lot better for a number of performance reasons to remove the material, and that justifies doing it since the removal should be pretty straightforward and pretty easy."

Discovery's STS-114 commander, veteran astronaut Eileen Collins, said she is confident that the repair plan drawn up by flight controllers will be effective and safe for her crew and spacecraft.

"This situation, I believe, will certainly be safe for us for reentry," Collins said, adding that NASA engineers have made progress in orbiter progress and repair methods. "We are able to repair small types of damage...we have come to a point where we know what is safe to come home with."

Collins said that while the gap-filler repair is a departure from the training Robinson and his spacewalking partner Soichi Noguchi, of the Japanese Aerospace Exploration Agency (JAXA), received before launch, can be folded in line with the astronaut's experience.

"It's important to do the gap-filler task...I think we have the flexibility to do that," Collins said, adding that she and her crew have been reviewing the new EVA operations today. "We're starting to get comfortable with it."

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