NASA was warned wings were vulnerable

Wednesday, February 5, 2003

SPACE CENTER, Houston -- NASA was warned nine years ago that the space shuttle could fail catastrophically if debris hit the vulnerable underside of its wings during liftoff -- the very scenario that may have brought down Columbia.

After receiving the warning, NASA made changes in materials and flight rules to lessen the risk of debris breaking loose, Paul Fischbeck, an engineering professor at Carnegie Mellon University who conducted the 1994 analysis, said Tuesday.

"There are very important tiles under there. If you lose the tiles on those stretches ... it can cause the shuttle to be lost," he said.

The underside of the left wing is where NASA is focusing its investigation into Saturday's disaster.

A spokesman at NASA's Johnson Space Center, David Drachlis, said Tuesday night that no one was available to comment on the report.

Fischbeck and a colleague at Stanford University studied the damage caused by debris during the first 50 shuttle launches and concluded that on average, 25 thermal tiles per flight sustained damage of at least once inch.

He said his risk analysis showed that the most vulnerable spots on the shuttle were the undersides of both wings close to the fuselage, and right under the crew compartment.

It is not clear exactly where under the wing Columbia was hit, but just before the shuttle break up, temperature spikes were detected around the left wheel well, which is close to the fuselage, and on the left side of the fuselage itself.

Fischbeck said NASA "took a lot of our advice to heart" and made improvements such as changing the foam insulation on the top of the booster rockets.

The investigation into the Columbia disaster is focusing on the possibility that a 2 1/2-pound chunk of foam insulation from the shuttle's external fuel tank fell off during liftoff and hit the left underside of the wing, causing damage to the thermal tiles.

From the start

The foam and the tiles have been a source of concern at NASA practically from the start.

Over the years, foam insulation often damaged the tiles. In fact, soon after NASA stopped using Freon in the foam, for environmental reasons, Columbia sustained significant tile damage during a 1997 liftoff because of flyaway foam, according to a report by NASA engineer Gregory Katnik.

While the foam is a lightweight spray-on material that goes on like shaving cream, it hardens like Styrofoam. And given the speed at which shuttles hurtle into space during takeoff, it can have a devastating effect. Moreover, the black, silica glass fiber tiles that cover the belly of the shuttle are famously fragile, so much so that even a bump or nudge can cause cracks or dings.

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