- The Washington Times - Wednesday, March 19, 2003

Investigators are continuing to focus on damage to the Space Shuttle Columbia's tiles while struggling to determine the path and the extent of damage caused by superheated gases that penetrated the shuttle's left wing.

Even though the Columbia Accident Investigation Board still can't explain the cause of the Feb. 1 destruction of the shuttle, it expressed a measure of optimism following its third public hearing yesterday.

"My confidence is still pretty high that we will ascertain with some certainty the root cause," said retired Adm. Harold W. Gehman, chairman of the independent board investigating the disaster.

Investigators are looking into potential damage to a carrier panel on the shuttle's left wing. The carrier panel is a removeable piece covered with a protective tile. The rectangular panel sits behind the panels on the wing's leading edge and connects them to thermal tiles on the wing.

If foam insulation that shed from Columbia's external fuel tank during liftoff knocked the carrier panel off, the 22 tiles on the wing's leading edge could be vulnerable, said James Hallock, a member of the accident investigation board.

"If the carrier panel came off, it would be very easy to have damage to the leading edge," he said.

The carrier panel could have been the piece seen coming off Columbia during the second day of its mission, said Mr. Hallock, who heads the Transportation Department's aviation safety division.

The National Aeronautics and Space Administration is having radar signature tests conducted at Wright-Patterson Air Force Base in Dayton, Ohio, to determine if the debris was a carrier panel.

Separate tests are being conducted at NASA's Langley Research Center in Hampton, Va. Researchers told the accident investigation board that wind-tunnel tests there on a scale model of Columbia indicate two panels on the leading edge of the left wing could have been damaged by the foam insulation that peeled from the shuttle's external fuel tank.

Initial wind-tunnel tests to study potential damage have not duplicated the catastrophic damage experienced by Columbia, said Stephen Labbe, chief of the Applied Aeroscience and Computational Fluid Dynamics Branch at the Johnson Space Center in Houston.

"We're going to be looking at multiple panels missing … We'll do a survey of the wing leading edge and look at other scenarios," he said. "These are very preliminary results. It's premature to draw too many conclusions from these results."

Mr. Hallock confirmed that it is possible Columbia may have had multiple holes.

"We haven't dismissed that. Whether that's happened here, I don't know," he said.

Some theories about the cause of the disaster have been dismissed. It is unlikely that solar flares or meteors played a role in the shuttle's destruction, Mr. Hallock said.

Perhaps the most difficult work for investigators is trying to determine how superheated gases reacted once they penetrated the Columbia's left wing. Investigators believe gases flowed into the wheel well before the shuttle broke up, burning electrical wires and raising temperatures, a phenomenon measured by some sensors.

But investigators are trying to understand whether a plume of gas streamed out of the wing or out a landing-gear door. If investigators and NASA engineers can determine the path gas took as it ravaged the orbiter, it may help them figure out why it began.

Steven Wallace, another member of the investigation board and the director of accident investigations for the Federal Aviation Administration, said NASA officials at the agency's headquarters in the District will be questioned this week as part of the inquiry.

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