NASA weighs repairs in space

The shuttle could fly back without fixing a gouge, but a patch may limit damage.

By ASSOCIATED PRESS
Published August 14, 2007

CAPE CANAVERAL - NASA conducted tests on the ground Monday to determine whether spacewalking astronauts need to fix a deep gouge in Endeavour's belly for re-entry, and it assembled a team to weigh the three repair options.

The gouge is relatively small - 3 1/2 inches by 2 inches - and does not pose the potential of catastrophe, John Shannon, the NASA official overseeing the mission, said Monday.

But part of the slash penetrates through the protective thermal tiles, leaving just a thin layer of coated felt over the space shuttle's aluminum frame to keep out the more than 2,000 degree heat of re-entry. The exposed area is 1 inch long and less than a quarter-inch wide.

Mission managers expect to decide by Wednesday whether astronauts should go out and patch the gouge. The damage is benign enough for Endeavour to fly safely home - it's more a matter of avoiding extensive postflight repairs to any possible structural damage, Shannon said.

"This is not a catastrophic loss of orbiter case at all. This is a case where you want to do the prudent thing for the vehicle," Shannon said.

NASA has never attempted this type of repair on an orbiting shuttle, and two of the three remedies - all developed after Columbia's catastrophic re-entry - are untested in space.

Engineers are uncertain whether it was foam insulation that came off Endeavour's external fuel tank and struck the shuttle, as was the case for Columbia four years ago, or whether the debris was ice or a combination of materials, Shannon said.

Despite extensive redesigning of the shuttle fuel tank that has already cost NASA a few hundred million dollars, foam has repeatedly fallen off the tank during launch, although nothing nearly as big as the piece that crippled Columbia. That chunk of foam, which carved a 6-inch to 10-inch hole in Columbia's left wing in 2003, was the size of a small carry-on suitcase and weighed 1.67 pounds.

A fix is being made to future tanks. Brackets on the 17-inch fuel line will be titanium, which will not be covered in foam and will be more resistant to icing. The tanks scheduled for the next three shuttle missions, however, will not have the modification.

Depending on how NASA addresses the latest problem, shuttle flights could be halted temporarily, stalling construction at the space station once more.

To patch the gouge, spacewalking astronauts would have to perch on the end of the shuttle's 100-foot robotic arm and extension boom, be maneuvered under the spacecraft, and either apply black paint, screw on a protective plate or squirt in goo.

The black coating, intended to help dissipate heat, was tested on a previous shuttle flight. The two other repair methods have been tested in vacuum chambers on Earth, but never in space.

Monday's space walk

A 6 1/2-hour space walk by two of Endeavour's astronauts Monday, on the other hand, was comparatively routine.

Astronauts Rick Mastracchio and Dave Williams ventured outside for the second time in three days, removing a failed gyroscope weighing more than 600 pounds from the space station's exterior. They installed a new one in its place that was carried up aboard Endeavour. The space station has four gyroscopes to keep it steady and pointed in the right direction.

Teacher-astronaut Barbara Morgan - Christa McAuliffe's backup for Challenger's doomed mission in 1986 - helped monitor the space walk from inside the joined shuttle-station complex.

Even before Endeavour's liftoff, NASA was planning a third space walk for Wednesday and a fourth for Friday to carry out more space station work. Any shuttle repairs, if ordered, would take place on one of those two outings. The shuttle isn't due to leave the station until Monday; landing is set for Aug. 22.

The current space shuttle fleet will be retired in 2010, after the space station has been completed, in part because the United States has made commitments to other nations about the station.

Until then, every time the space shuttle takes off there's a risk that foam will break off and cause damage, said John Logsdon, director of the Space Policy Institute at George Washington University.

"The folks in charge of the program have made a decision that finishing the space station is worth accepting the risk, and they kind of hold their breath every time the shuttle mission is under way that their decision turns out to be a good one," Logsdon said.

In a worst-case - and unlikely - scenario, NASA could evacuate the astronauts into the space station and send another shuttle, he said.

But Logsdon and another expert, former NASA administrator Hans Mark, said that so far reports concur with NASA's assessment that the gouge is not too threatening.

"I think they could land it the way it is," Mark said.

Times staff writer Jennifer Liberto contributed to this report.

Fast Facts:

What happened?

Engineers are uncertain whether the material that hit Endeavour was:

Foam insulation from the external fuel tank that struck the shuttle at liftoff. The speed at which the debris broke off the tank - 300 feet per second - is puzzling if it was solely foam, NASA said.

Ice buildup behind a bracket on the external fuel tank.

A combination of materials. It's possible part of a strut broke off and shot into Endeavour.

[Last modified August 14, 2007, 01:00:59]