Endeavour Cleared For Launch

With a final check complete, NASA cleared space shuttle Endeavour for a Friday liftoff and said its damaged robot arm would be safe to use for space station construction.

The decision came Wednesday night, less than 24 hours after the countdown clocks began ticking.

Mission Control quickly relayed the good news to the three residents of the international space station. They have been on board since June, and Endeavour is their ride home.

"All right!" astronaut Peggy Whitson said.

Shuttle program manager Ron Dittemore said extensive testing found Endeavour's 50-foot robot arm to be sturdy despite damage inflicted last week by workers. He also expressed confidence that a leaking oxygen line aboard Endeavour is fixed.

"It has been a tremendous effort over the past week to get to this point," Dittemore said.

There was an 80 percent chance of acceptable weather at the cape for a Friday night launch, but rainy weather at NASA's two overseas emergency landing sites, both in Spain, could still force a postponement.

Endeavour's robot arm was bruised Nov. 12 when workers accidentally knocked a platform into it. They were inside the payload bay trying to find and fix an oxygen leak that forced NASA to call off a launch attempt the day before.

The platform tore through the thermal blanket covering the arm and an outer honeycomb layer, and left a 2-inch-square bruise on the actual carbon composite structure. NASA conducted ultrasound tests on the bruised area and asked the Canadian company that built the arm to recreate the damage on an arm replica and gauge its strength.

The replica was subjected to overloads and, to NASA's relief, the bruise did not grow, Dittemore said.

"The structural integrity of the boom remained intact and, in fact, showed to us we had large margins of safety, which is very good news," he said.

No repairs or patches were needed for Endeavour's robot arm.

Endeavour is loaded with a 14-ton girder that is supposed to be installed on the space station. A robot arm — essentially a high-tech crane — is needed for the job.

As for the leak in the oxygen supply for the astronauts, a pair of flex hoses were replaced and the system passed all tests.

Thursday was the 169th day in orbit for Whitson and her two Russian crewmates, who should have been back on Earth long before now. Their mission was extended more than a month because of this summer's grounding of NASA's entire space shuttle fleet.

Endeavour will carry up their replacements.

Friday's liftoff will occur sometime between 7 p.m. and 11 p.m. Because of post-Sept. 11 security measures, NASA is keeping the exact launch time secret until 24 hours in advance.

By Marcia Dunn