Foam still under consideration as cause of disaster, NASA says

SPACE CENTER, Houston -- A day after all but ruling it out as a leading cause, NASA said Thursday that investigators are still considering whether a piece of insulating foam that struck Columbia's wing during liftoff was enough to bring down the shuttle.

Shuttle program manager Ron Dittemore said that even though the possibility appeared remote, investigators must remain open to every option as they put together a so-called fault tree into what caused Columbia's fiery breakup just minutes from its landing Saturday.

"The foam that shed off the tank and impacted the left wing is just one branch, and we are pursuing that," he said. "Even though we scratch our heads, we're going to pursue it and we're going to pound it flat."

Eighty-one seconds into launch, a 2 1/2-pound, 20-inch chunk of foam from Columbia's external fuel tank broke off and slammed into the underside of the shuttle's left wing.

The accident investigation board, led by retired Navy Adm. Harold Gehman Jr., arrived at Johnson Space Center on Thursday and met with Dittemore and other shuttle officials. NASA Administrator Sean O'Keefe pledged from Washington that "every single piece of evidence, every fact, every issue" will be checked, and the board's conclusions will be final and absolute.

Extensive testing

Before ruling the foam out as a culprit, NASA will be testing its impact on the thousands of fragile thermal tiles that cover each space shuttle. In addition, the entire analysis that was conducted during Columbia's flight is being redone "to see if there was anything that we missed," he said.

On Monday, NASA officials had said the foam may well be "the leading candidate" for the cause of the accident. Two days later, Dittemore all but discounted the theory that it was the main cause, saying NASA computer simulations had shown the debris hit was not severe and could not have been the sole cause of the disaster.

Dittemore said the camera views of the flyaway foam during liftoff Jan. 16 could have been better. "It's a disappointment that the camera with the very best view turned out to be out of focus," he said. "We're just going to have to live with what we have."

NASA also has not yet written off the possibility that other debris during launch might have damaged Columbia. Nothing else unusual was photographed, however.

Engineers taking part in NASA's so-called reverse analysis struggled Thursday to make sense of the eight minutes recorded between the time the first sign of trouble appeared aboard Columbia over California -- a surge in temperature in the left landing gear compartment -- and the shuttle's final, dying moment over Texas.

Most of the debris field has been in East Texas and Louisiana, but Dittemore said none of the shuttle parts considered crucial to the investigation had yet been found. He said reports of debris west of Texas, including in California, had not been confirmed as shuttle parts.

NASA has been swamped with reports of sightings, some of them caught on camera, of pieces coming off Columbia as it streaked across California. Dittemore said the reports have yet to be verified, and he stressed that all indications in Mission Control suggested no such breakup so far west.

Gehman, appointed by NASA to head the investigation board shortly following Saturday's accident, helped probe the 2000 terrorist attack on the USS Cole.

Meanwhile, in the nation's capital, Vice President Dick Cheney addressed a memorial service for the seven astronauts Thursday at the National Cathedral, where a stained glass window holds a piece of moon rock.

"They were soldiers and scientists and doctors and pilots, but above all they were explorers," Cheney said. "They advanced human understanding by showing human courage."

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