NASA backs away from foam as 'root cause' of disaster

SPACE CENTER, Houston -- After days of analysis, NASA backed away Wednesday from the theory that a piece of foam that struck Columbia during liftoff was the root cause of the space shuttle's disintegration over Texas.

Shuttle program manager Ron Dittemore said investigators now are focusing more closely on the desperate effort of Columbia's automatic control system to hold the speed of the spacecraft stable despite an increasing level of wind resistance, or drag, on the left wing.

Dittemore said that after a careful study of the damage possible from the fall of a chunk of foam insulation that was believed to be 20 inches and 2 1/2 pounds, investigators are "looking somewhere else."

"Right now, it just does not make sense to us that a piece of debris would be the root cause for the loss of Columbia and its crew," he said. "There's got to be another reason."

Dittemore said investigators are now asking if there was "another event that escaped our attention" that might have caused Columbia to break up just minutes before the end of its 16-day mission, killing all seven astronauts.

Foam theory

Practically from the start, investigators have been looking at the possibility that the piece of foam that fell off the shuttle's big external fuel tank 81 seconds after liftoff Jan. 16 caused damage to the thermal tiles under the left wing that doomed the flight. The thermal tiles keep the ship from burning up during re-entry into Earth's atmosphere.

While Columbia was still aloft, NASA engineers analyzed the potential damage to the thermal tiles and concluded that based on such factors as the estimated size, weight and trajectory of the chunk of foam, any damage to the tiles was minor and the crew was in no danger.

Dittemore said the engineers in their study doubled the relative velocity of the foam and shuttle, from the actual 513 mph to 1,026 mph, and were conservative in estimating the weight of the debris.

"We're looking somewhere else," he said. "Was there another event that escaped detection?"

In recent days, some space experts have speculated that the chunk of foam was coated or infused with ice, which could have increased the weight -- and destructive potential -- of the piece that hit the shuttle.

"I don't think it's ice. I don't think there's an embedded ice question here," Dittemore said, adding that the foam is water-resistant and that an inspection team found no ice conditions that day. "So it is something else."

Dittemore said that during Columbia's final minutes, the autopilot was causing the craft to rapidly move the control surfaces and to eventually even fire small rockets in a losing effort to gain control of the yawing motion of Columbia.

Final bits of data from the spacecraft showed that "we were beginning to lose the battle," he said.

For this reason, Dittemore said his team is intensifying efforts to recover a final 32 seconds of data from the spacecraft.

This data, the very last signals from the dying Columbia, was not processed at Mission Control because the quality of the electronic signals was too poor to be considered reliable.

But Dittemore said the signals are being extracted from computers and will be examined to find clues to why Columbia's left wing was encountering so much drag.

"Perhaps the 32 seconds will help us understand," he said.

No 'red-tag items'

So far, no significant pieces of shuttle wreckage -- "red-tag items" -- have been found, Dittemore said. Searchers have discovered, however, a large portion of the nose cone as well as at least two possible wing sections.

Any pieces of Columbia found in California would be "very, very significant," Dittemore said, because it would indicate that the shuttle was falling apart long before its final breakup over Texas.