Nasa hold urgent talks on shuttle gash

Nasa is urgently calculating whether risky spacewalk repairs are needed today, after a close-up inspection revealed that a three and a half inch-long gouge penetrated the thermal shielding on the shuttle’s belly.

A chunk of insulating foam hit the Endeavour at lift-off last week in an unlucky ricochet off the fuel tank.

The unevenly shaped gouge – which straddles two side-by-side thermal tiles and the corner of a third – is and just over 2ins wide.

Yesterday’s inspection showed that the damage went all the way through the 1in-thick tiles, exposing the felt material sandwiched between the tiles and the shuttle’s aluminium frame.

Mission managers expect to decide today or tomorrow at the latest whether to send astronauts out to patch the gouge. Engineers are trying to determine whether the marred area can withstand the searing heat of atmospheric re-entry at flight’s end. Actual heating tests will be conducted on similarly damaged samples.

“We have really prepared for exactly this case, since Columbia,” said John Shannon, chairman of the mission management team.

This area is subjected to as much as 2,300 degrees Fahrenheit (1,260 Celsius) during re-entry. A hole, if large and deep enough, could lead to another Columbia-type disaster.

Columbia was destroyed in 2003 when hot atmospheric gases seeped into a hole in its wing and melted the wing from the inside out. A foam strike at lift-off caused the gash.

Endeavour’s damaged thermal tiles are near the right main landing gear door. In a stroke of luck, they are right beneath the aluminium framework for the right wing, which would offer extra protection during the ride back to Earth.

Teacher-astronaut Barbara Morgan – who was the back-up for Challenger’s Christa McAuliffe in 1986 – conducted the slow and painstaking survey, along with crewmate Tracy Caldwell. They used the 100ft robotic arm and extension boom that flew up on Endeavour.

Laser sensors and cameras zoomed in on the damage, white and easily visible against the black tiles.

Engineers believe the piece of foam struck the shuttle’s underside, creating the big gouge, then skimmed along the bottom and nicked it in at least three spots. Those smaller gouges posed no threat, Shannon said.

The foam came off a bracket on the external fuel tank 58 seconds after Wednesday’s launch. Ice apparently formed before liftoff near the bracket and caused the foam to pop off when subjected to the vibrations of launch.

It is possible some ice was attached to the foam, which would have made the impact even harder. The debris that came off is believed to have been grapefruit-sized.

The brackets have lost foam in previous launches, a concern for Nasa, Shannon said. A switch to titanium brackets, eliminating foam, will not occur before next year.

Shannon said he did not know whether the recurring foam problem would delay the next shuttle flight, currently scheduled for October.

“We have a lot of discussion to have before we decide to fly the next tank,” he said.

The inspection consumed much of the astronauts’ day. Today, two of them will go back out for the second spacewalk of the mission to replace a broken gyroscope at the international space station.

Endeavour has been docked at the space station since Friday. It will remain there until August 20 for a record 10-day stay. Mission managers yesterday approved the prolonged visit based on the successful testing of a new power transfer system flying on Endeavour. The system is drawing power from the station and converting it for use aboard the shuttle.

On the space station, meanwhile, two cosmonauts continued repairs to a Russian computer system that failed during the shuttle Atlantis’ visit in June. Condensation from an air conditioning unit apparently is collecting behind the panels where the computer equipment is located.

And a US command-and-control computer that shut down during Saturday’s spacewalk was working again yesterday.