NASA to Decide Endeavour Repair

JOHN YDSTIE, host:

NASA says it will decide today if astronauts need to take a spacewalk to repair damaged tiles on the belly of the space shuttle Endeavour. For days, engineers have been trying to determine if a small gash in the tiles would endanger the shuttle during the extreme heat of reentry.

NPR's David Malakoff has more.

DAVID MALAKOFF: Yesterday, even shuttle Commander Scott Kelly was asking mission control what were NASA officials likely to decide.

Commander SCOTT KELLY (U.S. Navy): And no indication of which way they're leaning?

Unidentified Woman (NASA employee): Unfortunately, we have no idea which way the wind is blowing at the moment.

MALAKOFF: But NASA did tell Kelly that two astronauts should start preparing for a repair mission on Saturday.

Just in case, the agency's Joel Montalbano told the press.

Ms. JOEL MONTALBANO (ISS Flight Director for STS-118, NASA Johnson Space Center): Basically, we have to plan worst case. We need to get ahead of this, get some procedures up to the crew, get the ground team and everybody moving in that direction.

MALAKOFF: Meanwhile, NASA engineers continued to study computer models and experiments designed to reveal if the gashed tiles really post a danger. About 20,000 tiles protect the shuttle from the extreme heat of reentry, and when the shuttle lifted off, a small chunk of foam broke off its fuel tank and hit two tiles on the bottom of the shuttle. It created a gash about three inches long and two inches wide. The gash has exposed a tiny slice of felt covering the shuttle's aluminum frame.

John Shannon, a leader of the shuttle mission, says that so far the evidence suggests the gash poses no grave danger to the astronauts.

Mr. JOHN SHANNON (Chairman, Endeavor Mission Management Team, NASA): The analysis that we have shows that there would be no damage at all to the underlying structure, which was very good news to us, and we would not even reduce our 1.4 factor of safety.

MALAKOFF: Even so, NASA could still decide to do a repair because it could prevent minor damage to the shuttle, damage that could delay Endeavour's next launch. And officials say a repair space walk would go something like this. First, a robotic arm would carry astronauts Clay Anderson and Dave Williams under the belly of the shuttle, then, Shannon says, they would brush some special paint into the gash and then use a squirt gun to squeeze in some pink goo.

Mr. SHANNON: This is kind of like when you epoxy something or caulk something. You put a certain amount in there and you try to get it in all the right areas. If it's mixed right, it will start to cure. But it's not like a mechanical fix. It's something that takes a little bit of practice to get it in exactly the right spot.

MALAKOFF: Shannon says NASA needs to decide if the benefits of a repair outweigh the risks. One potential problem is that spacewalkers have never ventured beneath this part of the shuttle before. A false move could damage the craft. The spacewalkers may also be unable to use some of the cameras that would normally help engineers on the ground guide the repairs. Steve Doering is one of NASA's experts on spacewalking.

Mr. STEVE DOERING (Spacewalk Office Manager, NASA): One of the risks that we're weighing is whether or not we can successfully perform this without any video.

MALAKOFF: NASA officials also want to be sure that the spacewalker's gloves are in good shape. Yesterday, a torn glove forced the agency to shorten a spacewalk. But NASA officials say that none of these issues would prevent them from moving ahead with the repair if they decide it's needed. A decision is expected later today.

David Malakoff, NPR News. Transcript provided by NPR, Copyright NPR.