NASA just gave a quick, inadvertent illustration of why it’s not a slam-dunk decision to send astronauts on a spacewalk to go fix the gouge in the shuttle’s underside. Astronauts Rick Mastracchio and Clay Anderson were outside, configuring components of the space station, when Mastracchio noticed he had cut through one of the outer layers of his left glove. The cut was in the left thumb. Mastracchio was told, as a precaution, to go back to the station’s airlock, so that they could repressurize quickly if his suit began to leak oxygen. Anderson was told to come back in as well. The men were about five hours into a six-hour EVA, and were running ahead of schedule, so they had finished most of the work planned for them. "The gloves were good. I don’t know where this hole came from," Mastracchio told controllers in Houston. Since the end of the EVA, Mastracchio has reported "a couple of little pinholes" in the Vectran layer of his right glove as well. The gloves have five layers. The outermost is a laminated cover over some parts for thermal protection, and the second, made of a synthetic polymer called Vectran, protects against cuts and scuffs. That’s what was damaged. Beneath that is a layer of nylon, and then a layer of rubber that actually keeps air inside the suit. Finally, there’s a fabric liner so that the astronaut’s skin doesn’t rub against the rubber bladder layer. Vectran, used for all sorts of things from parachute cords to helicopter rescue cables, makes for a protective glove, but also a clumsy one. NASA’s been trying to come up with a more comfortable design for years, and recently held a contest to invite ideas from the public. Another astronaut, Robert Curbeam, found a cut in the Vectran layer of his glove after he came in from a spacewalk last December. Since then, astronauts have been told to check their gloves every half hour during a spacewalk. How does this figure into whether to fill in the gouge in that heat-shield tile? It’s a reminder that spacewalks carry their own risks. The greater one is that an astronaut, in that big, clumsy suit, might bang against other tiles on the way to fixing the one in which they were interested. See our interview with astronaut Piers Sellers, posted earlier today. NASA’s John Shannon made it sound like they felt pretty satisfied that a tile repair would not be necessary–one test suggested that the air swirling into the gouge would not reach a temperature of 350 degrees F. Aluminum, a little of which is exposed, melts at 1,200 degrees at sea level. But they wanted to see one more test result, and at last word, we were told not to expect a decision today.
(NASA Photo: Astronaut Robert Curbeam in December, during a space walk on the STS-116 mission.)