- The Washington Times - Saturday, April 19, 2003

CAPE CANAVERAL, Fla., April 19 (UPI) — A series of tests to determine if falling debris during shuttle Columbia's launch could have triggered its catastrophic break-up 16 days later is about to begin.

The board investigating the Feb. 1 accident, which claimed the lives of seven astronauts, has hired an independent lab to expand upon tests first conducted in 1999 to determine how chunks of foam insulation falling off the shuttle's fuel tank at launch might affect the ship's critical thermal protection system.

"Currently, the data (we have about the accident) are not all pointing in the same direction," said Scott Hubbard, a member of the Columbia Accident Investigation board. "So part of what we're having to do is to be as flexible as we can in structuring the test … Out of this will come results which ultimately will contribute to establishing the most probable cause" of the accident.

Those first tests, by the Southwest Research Institute in San Antonio, Texas, only used samples that were a couple of inches long and weighed a few ounces, whereas the piece of debris seen in launch video hitting Columbia's wing is estimated to weigh about 2 pounds and measure 25 inches by 15 inches by 5 inches.

The new round of testing, which is scheduled to last through May, will not only fire much larger chunks of foam at heat-resistant tiles — the only materials tested in 1999 — but also at other thermal protection components and support hardware found on the shuttle's wings. The tests also include firing foam chunks at actual flight panels borrowed from the Discovery space shuttle, which closely match the age and flight history of Columbia's components, as well as from the prototype shuttle Enterprise.

The samples will be shot out of a nitrogen gas gun to replicate the roughly 500 mph force of impact that Columbia's left wing sustained when it was struck by a chunk of foam insulation during its final launch.

Investigators initially were interested in the U-shaped reinforced carbon-carbon heat panels that make up the leading edges of the shuttles' wings, with the foam strike believed to have hit somewhere between panels seven, eight and nine. However, attention has now shifted to the T-seals that are bolted to the frameworks that hold the RCC panels in place. The T-seals are attached to the frame with two bolts at each end.

"The space between panels eight and nine happens to line up with where the T-seal is so that has become a suspicious region," said Hubbard. "In the preliminary planning for the impact tests, we're putting strong consideration on hitting … that intersection where the T-seal is and seeing what happens, what kind of damage would be caused."

Investigators believe the loss of a T-seal would leave an inch-wide or larger slit between the heat panels. The board has determined a breach somewhere in the left wing of Columbia allowed hot plasma to penetrate inside the structure shortly after the shuttle began dipping into Earth's atmosphere for re-entry and landing.

"The jury is still out on how much of a breach you would have to have in order to create the effects you see," Hubbard said. He added that thermal dynamic analysis is under way to determine how a long, narrow slit, as opposed to a hole, fits with data already known about the shuttle's demise.

A key source of data has been a flight recorder salvaged from the wreckage. ABC News on Saturday reported that engineers have found a temperature spike from a sensor embedded in the left wing recorded less than 40 seconds after the launch debris impact, adding to the evidence that the foam strike was the trigger for the accident.

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