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Shuttle Recorder Casts Doubt On Tile-Damage Crash Theory

By Matthew L. Wald

THE NEW YORK TIMES -- WASHINGTON

Newly recovered data from a recorder on the shuttle Columbia raise doubts that the much-discussed tile was the site of the flaw that led to the shuttle’s destruction, the chairman of the panel investigating the accident said Monday.

Instead, the data focus attention on the reinforced panels at the leading edge of the shuttle’s left wing, said the chairman, Harold W. Gehman Jr., a retired admiral.

The new information, gleaned by 100 NASA engineers who spent the weekend laboring over data recovered from an old-fashioned magnetic tape, does not undermine a leading theory of the accident -- that damage to the left wing, perhaps from debris that fell off the shuttle’s external fuel tank during liftoff, doomed the orbiter.

But if the problem is eventually demonstrated to have been in the panels, made of reinforced carbon-carbon, then a hurried analysis of possible tile damage by Boeing, a NASA subcontractor, during Columbia’s 16-day mission, would appear to have literally missed the point. During the mission, engineers on the ground worked frantically to determine whether the tiles could have been damaged enough to endanger the orbiter, but spent little time discussing the panels on the wings.

Still, if officials had asked for a photographic examination of the tile by ground-based telescopes or spy satellites during the mission, that might have located the damage to the leading edge. What could have been done to repair the part, or reduce the load during re-entry, is not clear. But pinpointing the location of the breech would also help NASA engineers determine what improvements can be made to the surviving fleet.

Gehman also said on Monday that the new data hinted that the shuttle already had severe damage when it began its re-entry into the atmosphere, and not a minor flaw that was made worse by the heat of re-entry. Engineers had theorized that minor damage to the thin layer of protective silicon carbide on the panels could have allowed hot oxygen to begin eating away at the leading edge, but Gehman’s comments suggest that this is unlikely. Damage before re-entry is likely, he said, because the data show extreme heating early, while the force of air passing over the wing was still quite weak. Gehman spoke in a conference call with reporters Monday afternoon.

The recorder, which contains data from hundreds of sensors that measure heat, vibration and strain, was recovered two weeks ago near Hemphill, Texas.