Board blasts shuttle analysis

Columbia Accident Investigation Board

A computer program that predicted possible damage prior to the space shuttle Columbia's accident seven months ago was disregarded and used inappropriately, according to the final report issued today by the Columbia Accident Investigation Board.

The Crater software developed by Boeing Co. engineers predicted tile damage to Columbia's wing because of an impact from a loose piece of foam. But members of the debris assessment team, formed on the second day of Columbia's mission to assess the impact of a piece of foam that struck the shuttle during liftoff, discounted the findings. Members of the team listed two reasons: the results of calibration tests with small projectiles showed that Crater predicted a deeper penetration than would actually occur and the Crater equation did not take into account the increased density of a tile's lower densified layer.

The accident review board, however, listed several problems with the way NASA used the Crater system. "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 full comprehend."

This incident was the first time Crater had been used to assess a shuttle in orbit. It is intended for prelaunch predictions on whether or not small debris, usually ice, could damage the shuttle's External Tank. Making the procedure more difficult, the engineers attempted to use Crater to analyze a piece of debris that was 400 times larger than the standard in the Boeing database.

In what the report labeled a crucial failure, the analysts in Boeing's Houston office that performed the assessment were inexperienced, and did not defer to the company's Huntington Beach, Calif., office, which had previously been responsible for Crater. In fact, the engineer responsible for the testing had only used Crater twice before he attempted to assess damage to Columbia.

The review board criticized engineers for damage conclusions that "were based primarily on judgment and experience rather than analysis." Also, the report criticized mission managers for not being concerned with the large number of uncertainties that arose in the assessment and instead labeled the procedure as not being a "safety-to-flight" issue.

Overall, the report criticized NASA for a lack of communication throughout the assessment process and for a lack of action in regard to all available opportunities to assess shuttle damage before attempting re-entry.