Shuttle Doomed By a Quarter-Inch?

By Mike Gudgell

March 13 — Put your thumb and index finger together and allow for about a quarter-inch of space. That may have been the difference
between a successful shuttle landing and the disaster of Feb. 1, according to a NASA analysis detailed to ABCNEWS. After foam debris
from the external fuel tank hit Columbia on liftoff, engineers at Boeing, a major shuttle contractor, used a sophisticated software
program to predict damage for NASA.

The program, named Crater, predicted the foam debris strike would make its own crater in the shuttle's wing, leaving about a
quarter-inch of protective tile. The tiles, some of them more than 2 inches thick, protect the spacecraft from heat buildup as it returns to
the Earth's atmosphere at speeds of more than 12,000 mph.

The prediction was the shuttle would land but would suffer significant damage.

Obviously, that's not what happened, so NASA has just completed an analysis based on the assumption that the damage extended all
the way to the orbiter's aluminum skin — just that quarter-inch more.

Hot gases would have burned through the shuttle's unprotected skin in 500 seconds, or eight minutes 20 seconds.

The first indication of a burn-through on Columbia showed up on sensors on board the shuttle at eight minutes 17 seconds after the
start of re-entry — almost the exact amount of time predicted. A quarter-inch of protection could have made a big difference.

Despite the analysis, and the suggestive timing, investigators are far from declaring an ultimate cause, or even concluding that the
analysis is at all relevant to the investigation.

Investigators still don't know if the foam debris falling from the fuel tank during liftoff caused the hole or burn-through in the wing that
ultimately caused the shuttle to break apart, killing all seven astronauts on board. One of the problems with the theory is that evidence
may show a breach in the wing opened up on re-entry ahead of where the debris struck the shuttle during liftoff.

Read complete shuttle coverage.
— Lisa Stark and Dennis Powell contributed to this report.

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