Shuttle Countdown Clock Restarted

Engineers restarted the shuttle Endeavour's countdown Wednesday on the assumption the ship's damaged robot arm will be cleared for launch Friday night "as is."

While an analysis of the arm's structural integrity continues, engineers have wrapped protective tape around an area of torn outer insulation and plan to close Endeavour's cargo bay doors later in the day, reports CBS News Space Consultant William Harwood.

The countdown to a Friday night liftoff could stop if NASA determines the robot arm needs to be repaired or removed. A decision on whether the 50-foot crane is seriously damaged was expected Wednesday.

Endeavour's arm was bruised last week when workers accidentally knocked a platform into it near the shoulder joint. They were inside the payload bay trying to find and fix an oxygen leak that forced NASA to call off a Nov. 11 launch for the space station construction mission.

The impact tore through the thermal blanket covering the arm and an outer honeycomb layer, leaving a 2-inch-square bruise on the actual carbon composite structure. NASA conducted ultrasound tests on the bruised area and asked the Canadian Space Agency, which supplied the arm, to recreate the damage on an arm replica in Toronto and gauge its strength. Those findings were to be presented to top shuttle managers later Wednesday.

NASA expressed confidence that the replacement of a pair of flex hoses had fixed the oxygen leak.

Endeavour is loaded with a 14-ton girder that is supposed to be installed on the international space station. A crane is needed for the attachment.

If NASA decides that the shuttle arm cannot be used because of the bruise, then the station arm would have to be called into service unless another shuttle arm is installed aboard Endeavour. Such a lengthy repair job would bump the mission into January.

If the shuttle arm has to be repaired or removed from Endeavour's payload bay, the mission would be pushed back until the beginning of December.

Besides construction work, a main objective of the mission is to exchange space station crews. One American and two Russians moved into the orbiting complex in early June; Wednesday was their 168th day in orbit.

The latest countdown began late Tuesday night, but NASA would not confirm that until Wednesday morning under its post-Sept. 11 security guidelines. A liftoff Friday would occur sometime between 7 p.m. and 11 p.m., and would not be announced until about 24 hours in advance. The forecast calls for an 80 percent chance of good weather, with more of the same on tap Saturday should launch be delayed another day. But the weather at two emergency landing sites in Spain is currently forecast "no go" and one of them must be available for Endeavour to be cleared for launch, said Harwood.