NASA conducts tests to assess shuttle damage

Nasa conducted a swift series of tests on the ground to determine whether spacewalking astronauts need to fix a deep gouge in Endeavour’s belly for re-entry, and assembled a special team to weigh the repair options.

The gouge is relatively small, but part of it penetrates through the protective thermal tiles, leaving just a thin layer of coated felt over the space shuttle’s aluminium frame to keep out the more than 2,000-degree heat of re-entry. The exposed area is one inch long and less than a quarter-inch wide.

Mission managers expect to decide by tomorrow 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 post-flight repairs to any possible structural damage, said John Shannon, chairman of the mission management team.

“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 following 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 at lift-off, 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.

Depending on how Nasa addresses the latest problem, space shuttle flights could possibly come to a temporary halt, stalling construction at the international space station once more. Foam problems have caused two lengthy hold-ups.

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 manoeuvred under the spacecraft, and apply black paint and possibly squirt in goo, as well.

The black coating, intended to help dissipate heat, was tested on a previous shuttle flight. The caulk-like goo has been tested in vacuum chambers on Earth, but never in space. A third option, a screw-on panel that’s intended for bigger damage, was ruled out late yesterday.

Shannon said the fact that the space shuttles are due to retire in 2010, and the space station needs to be completed by then, did not enter the discussions.

The damage occurred a minute after lift-off last week when a baseball-sized piece of debris broke off a bracket on the external fuel tank, bounced off a strut further down on the tank, then slammed into Endeavour’s belly. It’s also possible part of the strut broke off when the debris hit it and that’s what may have shot into Endeavour, Shannon said.

By comparison, the chunk of foam that carved a 6-10-inch hole in Columbia’s left wing back in 2003 was the size of a small carry-on suitcase.