NASA checking if repairs may have caused foam piece to break off

SPACE CENTER, Houston -- NASA is investigating whether repairs to a small crack in the foam on Discovery's fuel tank may have caused a 1-pound section of the insulation to break off during liftoff, officials said late Friday.

The shallow crack -- just six-tenths of an inch long and two-tenths of an inch wide -- was sanded away at the Louisiana manufacturing plant before the tank was shipped to Cape Canaveral, Fla. No new foam was applied to the spot.

It's a common repair procedure, NASA officials said.

What's intriguing, officials said, is that the repair was made to the approximate area where the big chunk of foam came loose during Discovery's launch on July 26. They cautioned, however, that there is no evidence yet that the repair contributed to the foam loss.

The external fuel tank was redesigned following the 2003 Columbia tragedy, but no improvements were made to the area where the foam came loose.

Among the many theories being investigated, besides the crack: whether a mistake was made in the manual spraying of the foam, whether the new environmentally friendlier foam that was used in that area was defective, whether too many people handled the foam and tank, and whether the foam was damaged during the tank's shipment to Florida.

The tank lost four or so pieces of foam that were bigger than NASA wanted to come off.

"The amazing thing is, well, not amazing, but the good thing is almost all of the tank changes worked. Some didn't," NASA Administrator Michael Griffin said earlier Friday. "So what's the difference between the ones that did and the ones that didn't?"

The earliest that the next shuttle could launch is Sept. 22, but that's only "if next week, the guys have a eureka moment on the foam and spot why this big chunk came off," Griffin said.

Many speculate it could be next year before another shuttle flies, if the cause proves elusive.

Late Friday, the astronauts awoke and began preparations to undock from the international space station. The crew is scheduled to return Monday in a pre-dawn landing at the cape.

Earlier in the day, the space shuttle made a long-overdue trash pickup at the international space station on Friday -- the first in 2 1/2 years.

The Discovery astronauts hoisted a giant garbage can holding 5,000 pounds of broken machines, discarded equipment, empty food cartons and other junk into the shuttle's cargo hold.

It was one of the last chores before the shuttle pulled away from the station early today after more than a week of linked flight.

The two space station occupants were glad to get rid of the stuff since it left them with a much tidier home. One of them, cosmonaut Sergei Krikalev, said before Discovery arrived that the place looked as messy as Russia's old Mir station.

The Columbia disaster in early 2003 had prevented shuttles from returning to the space station until now, forcing the resident crews to rely on the much smaller and less frequent Russian supply ships for garbage disposal.

The shuttle's latest grounding could mean another trash pileup.

Discovery took up some 3,000 pounds of badly needed station supplies like prepackaged meals and spare parts in the massive canister. Once it was attached to the space station and emptied, it was filled to capacity with all the discarded station objects and placed back aboard the shuttle, with the help of a robot arm.

Everything had to be bagged or tied down just so for the shaky ride down through the atmosphere on Monday.

A call from Mission Control went unanswered for a few minutes as the astronauts stepped through the tedious job. "Sorry to ignore you," astronaut Stephen Robinson radioed as the crew secured items in large white bags. "We all have our heads down in bags."

The shuttle astronauts also put away the inspection boom that they used during their 13-day mission to survey Discovery's thermal skin, in a hunt for any launch damage.

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