Columbia board blasts use of analysis tool

The Columbia Accident Investigation Board harshly criticized NASA for using specialized software to assess damage to the space shuttle, even though it may have been the only tool available to engineers attempting the analysis.

Because there was not an in-flight program designed to assess damage to Columbia's Reinforced Carbon-Carbon panels on its wing, the debris assessment team used the Crater software developed by Boeing Co. engineers.

Crater is normally intended for prelaunch predictions about how small debris, usually ice, could damage the shuttle's external tank. The software is also used postlaunch to analyze divots in the shuttle's exterior tiles.

Crater was neither designed to analyze the panels nor intended for use as an in-flight tool, Boeing officials said. Making the Columbia analysis even more difficult was the fact that engineers were attempting to analyze a piece of debris that was 400 times larger than the standard in the Boeing database, the company's spokesman said.

Regardless, Crater's analysis predicted significant damage to Columbia's wing.

However, the review board's final report cites several problems with the engineers' use of the software. "The use of Crater in this new and very different situation compromised NASA's ability to accurately predict debris damage in ways that Debris Assessment Team engineers did not fully comprehend," the report states.

Harold Gehman Jr., chairman of the Columbia review board, called Crater a "rudimentary kind of model," saying the board was not satisfied with the application.

But according to Boeing officials, Crater was the most logical instrument available in the absence of a proper risk-assessment tool.

"Crater was not designed for that, but it was the only tool [the Debris Assessment Team] had," said Ed Memi, spokesman for Boeing's NASA Systems. "They didn't have time to design anything, and the team decided it was the only tool for tile impact. It had been compared with foam impact in the past, and Crater had been right, but had been conservative" over-predicting damage.

Because of Crater's tendency to overestimate damage and the suggestion that the denser layer at the base of each tile would blunt the foam's effect, the team determined that the tile would survive.

In its investigation, the review board determined that the foam actually had hit the wing's leading-edge panels, making the tile assessment useless. There had been no previous data collected on foam damage to the panels.

"They need to develop something more specialized in the future," Memi said. "But there was not a problem per se with the use of Crater; it was just not designed for that use and not for a piece of foam of that size in the analysis."

"At the time, what else would you use?" he asked.

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