• E-mail
• Print
• Comment
• Font Size
• Digg
• del.icio.us
• Discuss article

NASA Weighs Fix-It Space Walk

Posted on: Monday, 1 August 2005, 15:00 CDT

HOUSTON -- Astronauts on the shuttle Discovery may conduct the first space walk on the underside of a shuttle to prevent a possible re-entry heating problem caused by errant strips of heavy insulating cloth.

Analysts at the National Aeronautics and Space Administration are still studying whether two strips of cloth poking out from the Discovery's underbelly could cause the shuttle's most severe heating during re-entry to start earlier and become as much as 25 percent hotter.

The evaluation of the problem has provoked "strong disagreement" among NASA analysts about whether or not it poses a safety hazard, said Paul Hill, the mission's lead flight director, in a morning briefing. Some engineers are very concerned about the situation, he said, while others believe "this is not a big deal."

Mission managers expect to have enough data and aerodynamic analysis to reach a conclusion by today, he said.

If a space walk is decided on, astronauts will try to pluck the tough material the rest of the way out, push it back into place or cut it off with a hacksaw.

Removing the protruding material, called gap filler, could be as simple as grabbing it between the thumb and forefinger and pulling it free, said Wayne Hale, the shuttle program's deputy manager, in an afternoon press briefing.

If the job can be done with such relative ease, Hale said, the astronauts will probably go ahead.

"Why should I lose sleep over these gap fillers if we can take care of them that easy?" he said.

But any activity close to the shuttle can cause damage, and the orbital repairman would have to stand on a robot arm to reach the spot -- an untried maneuver.

Gap fillers, as their name implies, fill the gaps that NASA leaves between some shuttle tiles to allow for expansion and contraction of the shuttle's body from the extremes of heat and cold that it is exposed to. The fillers are made of alumina-borosilicate fiber and are tough and heat-resistant.

If a filler pokes out too much, especially if it is far forward on the shuttle so that its downstream heating affects a larger part of the shuttle's belly, it could bring on the period of high heating, known as boundary layer transition, earlier than usual, Hill said.

The space agency, through a long examination of all previous landings with protruding bits of gap filler, is comfortable with protrusions of a quarter of an inch in these areas, he said. But the two pieces on this flight protrude by 1 inch and six-tenths of an inch.

Located near craft's nose

And both pieces are near the nose of the craft, which is a reason for the concern, he said.

"I can tell you that if we have thin tiles, or we already had damage right there, it would be something we would be very worried about with a protrusion as far as an inch at a forward location like that," Hill said.

In the afternoon news briefing, Hale said that a gap filler had protruded by an estimated 1.4 inches on a previous mission, a Columbia flight that launched in October 1995, and that the shuttle returned safely to Earth with some heat damage to the tiles. But that gap filler's position was some 10 feet behind the two on Columbia, in an area that does not experience the same amount of heating.

The Discovery's flight is the first shuttle mission since February 2003, when the Columbia broke up on re-entry because of a debris strike during its launching. Since then, NASA has focused intensely on ways to limit debris and look for damage on orbit.

In response, the Discovery and the International Space Station have been outfitted with more cameras and sensors than ever before. And so, mission managers say, they might be detecting a gap filler phenomenon that has occurred unseen many times in the past; it is possible that the feltlike material burns down like a wick during re- entry.

If mission managers do order a space walk, it is most likely to take place on Wednesday, during an already-scheduled space walk that was originally planned to focus on installing an external equipment cabinet on the space station's air lock.

It is also possible, but less likely, that the task would take place on a new space walk that could occur on the extra day NASA has added to the mission to raid the shuttle for additional supplies for the station.

NASA has completed the analysis of the shuttle's delicate tiles and the heat-resistant blankets that coat the top of Discovery, and no risks to the shuttle or the crew have been discovered there, Hill said. Analysis of the panels that line the leading edge of the wing and the nose cap should be completed by today, he said, but the general impression of the shuttle team on the ground is that the panels, too, pose no safety concerns.

Commander has 'confidence'

NASA officials made the rounds of the Sunday talk shows as well - - even from space. In interviews from aboard Discovery, the shuttle's commander, Eileen Collins, said that she was "surprised" to find the external tank lost such a large piece of foam after all the work NASA had done to correct the problem. "There are 2 1/2 million other parts on the space shuttle that are working perfectly right now," she added, "and we have confidence in that and we know the shuttle is going to get us home."

Speaking on "Meet the Press," NASA administrator Michael Griffin said, "We think Discovery is safe to bring home," though the team on the ground is still "working a couple of issues."

Source: Daily Breeze

More News in this Category