Shuttle debris may not reveal much

Debris from an air disaster can supply important clues to what went wrong. But pieces of Columbia may have been so damaged by the searing heat during their fall through the atmosphere that they may not have much of a story to tell.

The shuttle broke up at 200,000 feet and 12,000 mph, and "things burn up very quickly at that speed" from heat generated by contact with the air, said one expert, Jerry Grey. In contrast, airliners typically fly at around 560 mph and a maximum altitude of about 40,000 feet.

Grey also suggested that fuel cells on board the shuttle might have exploded after the initial breakup, shattering surrounding material and obscuring potential evidence.

NASA's shuttle program manager, Ron Dittemore, said investigators are particularly interested in pieces of the shuttle that came loose early in Columbia's breakup, including pieces of protective tile. The agency was looking into a California observer's claim that he saw something resembling tiles come off the shuttle's outer shell, earlier than suspected. The space shuttle disintegrated over Texas.

He said NASA would try to reassemble parts of the shuttle thought to have contributed most directly to Columbia's failure.

"That missing link is out there and we just need to be persistent and go find it," Dittemore said Monday.

But Grey, director of science and technology policy for the American Institute of Aeronautics and Astronautics, said in all, "it's going to be very hard to find a piece that still preserves the initial condition at the failure."

He added that investigators "have to hunt for it. Most of the stuff they find will be of no value, but they may find one or two pieces that give them an indication."

Columbia's pieces are strewn over thousands of square miles of piney woods, lakes, creeks, pastures and neighborhoods in Texas and Louisiana. A typical high-altitude airplane accident typically scatters debris over 10 square miles, said Bill Waldock of the Embry-Riddle Aeronautical University western campus in Prescott, Ariz.

Still, he emphasized that the debris might still yield clues.

Patterns of burning or scorching in debris could shed light on the theory that protection against the extreme heat of re-entry failed, he said. In fact, if investigators can find enough debris, they may be able to trace the temperatures reached in different areas of the shuttle, indicating where heat protection may have failed, he said.

Beyond that, patterns of cracks might reveal the slow structural weakening called metal fatigue.

And the spots where the Columbia debris is found could alone give clues to the sequence in which various pieces fell off, which in turn could help investigators determine the cause of the disaster, he said.

Grey advised being wary of early ideas about what happened to Columbia. Even in airplane crash investigations, he said, "your first guess as to what caused it is almost always wrong."