Cape Canaveral: 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 cracking 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. A series of unmanned cargo ships from other countries are due to fly to the orbiting lab in the next few months, complicating matters. Also on tap is the arrival of a new station crew in mid-December, via a Russian Soyuz spacecraft.
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.
"One of the great things about robots is that we`re patient! I can wait like nobody`s business! And wait ... and wait ... " Robonaut said in a Twitter update. (The tweet actually came from a NASA spokeswoman.)
Gerstenmaier said the postponements should not affect NASA`s effort to secure funding for an extra shuttle mission next summer. Nor should they hinder space station activities.
NASA is retiring its shuttle fleet next year under the direction of the White House, after 30 years of flight.
"Our commitment has been ... to stay focused on these flights and fly them safely," Gerstenmaier said.
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 located 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.
The concern is that any more cracking in the brackets could cause chunks of foam to pop off and slam into Discovery at liftoff. A slab of foam pierced Columbia`s wing in 2003; the shuttle was destroyed upon re-entry.
Until now, any cracks in the ribs cropped up during assembly of the tank and promptly were fixed. This time, it looks to be a "unique event," Shannon said.
"It`s unfortunate that we`re not making the December launch window," he told reporters. "We want to make sure, though, that we do this exactly right."
An unintended consequence of the delay is that NASA`s identical twin astronauts, Scott and Mark Kelly, will not unite in orbit.
Scott is currently the commander of the space station; Mark is the skipper for Endeavour`s flight. Had the shuttle missions remained on track, the brothers would have become the first blood relatives to fly in space at the same time. Now, Scott will be gone from the station by the time his brother arrives.