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Astronauts test repairs; mission extended
(AP)
Updated: 2005-07-31 09:34
Two spacewalking astronauts armed with caulking guns, putty knives and foam
brushes practiced fixing deliberately damaged shuttle heat shields Saturday, as
NASA extended what could be its last trip to the space station for a long while,
the Associated Press reported.
With future shuttle flights grounded because of
Discovery's fuel-tank foam loss during liftoff, mission managers decided to keep
the crew at the international space station an extra day to haul over surplus
supplies and help with station maintenance.
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Astronaut Steve
Robinson is seen outside the shuttle docking port hatch in Discovery's
payload bay in this view from the helmet camera of Soichi Noguchi of Japan
at the end of their spacewalk July 30, 2005.
[Reuters]
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It could well be next year before the foam problem is fixed and a shuttle
returns to the space station.
The two spacewalkers, meanwhile, practiced repair maneuvers they hope they'll
never have to do for real.
The tests were designed in the wake of the 2003 Columbia tragedy and aren't
related to the damage Discovery suffered during lift off. NASA officials say
Discovery received some scrapes and chips but nothing that appears to warrant
orbital repairs.
Astronauts Soichi Noguchi and Stephen Robinson worked on samples of thermal
tile and panels that were cracked and gouged before flight. They squeezed dark
goo into the crevices as the sticky material got on their gloves and clumped at
the ends of their putty knives. Spacewalk managers had feared a much bigger
mess, though, and were pleased with the relative neatness of it all.
"It's about like pizza dough, like licorice-flavored pizza dough," Robinson
said as the near-black filler material oozed from his high-tech caulking gun. He
used a putty knife to smooth down the substance, again and again.
"The cleaner it is, the better work you do, just like anything," he added,
holding out his knife for Noguchi to wipe.
The astronauts reported some bubbling in the two repair materials — a
paintlike substance for the thermal tiles that cover most of a shuttle, and a
thick paste for the reinforced carbon panels that line the wings and nose cap.
The paste swelled up in the cracks like rising dough and, as the experiment wore
on, was harder to get to stick because of colder-than-desired temperatures
outside.
It was all valuable feedback; engineers wanted to see how their creations
fared in the weightlessness of space for possible future use in an emergency.
Neither the bubbling nor swelling was surprising, said Cindy Begley, the lead
spacewalk officer.
Columbia's astronauts had no such tools or techniques at their disposal. Of
course, neither they nor flight controllers knew Columbia had a gaping hole in
the left wing, left there by a 1.67-pound chunk of fuel-tank foam insulation
that broke loose at launch.
A piece of foam just over half that size came off Discovery's external fuel
tank during last week's liftoff. It missed Discovery, but was enough to ground
all future shuttle flights. A smaller foam fragment may have struck the right
wing, but lasers and other sensors found no evidence of damage.
None of the repair kits flying on Discovery could mend a hole the size of the
one responsible for Columbia's catastrophic re-entry, estimated between 6 and 10
inches across. It could be years before engineers come up with such a big patch.
For now, the largest hole that any of the repair methods aboard Discovery could
tackle would be 4 inches.
The astronauts will test a third repair technique, essentially a plug, inside
Discovery later this week.
Once the repaired samples are back on Earth, engineers will analyze them to
see how deep and how well the filler material penetrated. None will be torched,
however, to simulate the searing heat of re-entry. The spacewalkers had to skip
the one sample intended for laboratory test-firing because they ran out of time.
In the first of three spacewalks planned for what now is a 13-day mission,
Noguchi and Robinson also made some long-overdue space station repairs. They
restored power to a gyroscope that stopped working four months ago and replaced
a broken Global Positioning System antenna.
"Great job. Everything was just perfect. Extra stuff got done," Mission
Control radioed as the seven-hour spacewalk came to a close. "You guys get some
rest."
As soon as Robinson and Noguchi were back inside, their shuttle crewmates
pulled out their 100-foot, laser-tipped inspection crane to survey Discovery's
left wing one more time. Engineers wanted to make sure they didn't miss any
signs of damage.
On Monday, NASA expects to wrap up all its analysis of Discovery's thermal
shielding and give the final safety clearance for the shuttle's descent on Aug.
8, a day later now than originally planned. A final decision was expected
Sunday, but was put off to give engineers a little more time to analyze a couple
of protruding gap fillers between thermal tiles.
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