Space shuttle final launch delayed

CAPE CANAVERAL, Fla. —Space shuttle Discovery's final mission is off until February, three months late because of fuel tank cracks that are stumping engineers.

NASA's top spaceflight managers announced the latest delay on Friday. They said they need more time to understand the cracking, which cropped up following a failed launch attempt in early November.

Discovery remains on the launch pad, holding a load of equipment for the International Space Station. The launch team plans to conduct a fueling test by month's end — rigging the external tank with gauges and sensors, then loading it up — in hopes of solving the elusive crack problem.

"Analysis can only get you so far," said shuttle program manager John Shannon. "It's time to go test."

Bill Gerstenmaier, head of NASA's space operations, said liftoff tentatively is set for around Feb. 3, the opening of the next practical launch window. That will push the final mission of shuttle Endeavour back a full month, into April.

Six astronauts are assigned to the Discovery mission, as well as the first humanoid robot bound for space, Robonaut, which will stay packed aboard the shuttle.

Gerstenmaier said the postponements should not hinder space station activities.

The cracking occurred in two of the many aluminum alloy ribs, or brackets, that surround the central portion of the fuel tank. Equipment, but no fuel, is in this area.

Back on Nov. 5, after a hydrogen gas leak foiled a launch attempt, inspectors discovered a large crack in the insulating foam that covers this area. It wasn't until the foam was removed that four cracks were found in the exterior of the 15-story tank itself, in two adjacent 21-foot-long brackets.

Technicians repaired the cracks and installed fresh foam. But engineers still aren't sure why the problem arose in the first place.