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Breach was farther out { April 16 2003 } Original Source Link: (May no longer be active)
http://www.washingtonpost.com/wp-dyn/articles/A33350-2003Apr15.htmlhttp://www.washingtonpost.com/wp-dyn/articles/A33350-2003Apr15.html
Shuttle Wing Breach Was Farther Out
By Kathy Sawyer
Washington Post Staff Writer
Wednesday, April 16, 2003; Page A09
A fatal breach opened in the shuttle Columbia farther out on the left wing than early evidence suggested, accident investigators said yesterday.
It has been clear for some time that an opening in the wing allowed the intrusion of deadly superheated air as the orbiter descended toward its landing Feb. 1, triggering its destruction. But investigators continue to refine the accident scenario based on evidence from three sources: the wreckage, onboard sensors and enhancements of imagery obtained during the mission.
Pinpointing where the heat entered the wing as precisely as possible over the next month is important to determining what caused the breach, Scott Hubbard, a member of the Columbia Accident Investigation Board, said at a briefing in Houston. "We're closing in on it."
The three lines of evidence, however, point in slightly different directions on the wing. "The challenge that we've discovered is to try to integrate and reconcile differences between these different data streams," he said.
A leading candidate for the cause of the breach is foam insulation from the shuttle's external propellant tank that came loose and struck the orbiter about 80 seconds after its Jan. 16 liftoff.
The investigators have scheduled tests at an independent laboratory, beginning next month, in which a special gun will fire chunks of foam at a facsimile of the wing fitted with spare shuttle parts from the suspect leading-edge area, including heat-shield panels made of a composite called Reinforced Carbon Carbon, the associated bolts, fillers and other materials.
"In order to understand what happened when the foam hit the left wing, we need to come up with the best possible impact tests," Hubbard said. "So we're looking at this data [on the breach] to help inform and structure that test."
Based on painstaking enhancements of the film and video record of the foam impact during launch, with participation by government and private organizations, the latest analysis has moved the possible strike zone outboard to heat-shield panels seven and eight out of 22 such panels on the wing. A previous analysis had focused on panel six.
A second line of evidence, from onboard sensor measurements of temperature and other variables taken during Columbia's flight, indicates that substantial heating occurred at heat-shield panel nine and at the interface between numbers nine and 10, or slightly farther out than the visual record seems to show, Hubbard said.
He noted that the sensor record should grow considerably in coming weeks, as engineers analyze information from a flight data recorder, which has so far yielded readouts from 622 channels.
The final body of evidence is the recovered wreckage, which has grown to represent about 36 percent of the orbiter's dry weight and more than 70,000 pieces, said retired Adm. Harold W. Gehman Jr., who is chairman of the investigating board. Searchers have been finding crucial left-wing pieces in areas outside the primary search grid, he said.
The recovered wing components show "very significant and unusual damage" from heat at the interface between panels eight and nine, Hubbard said. "For example, splattered metal on panel eight is much heavier than elsewhere, and there is erosion of the reinforced carbon elements.
"What we see is something that's not seen thus far anywhere else on the wing leading edge or indeed in the orbiter debris, which is the pieces of a very tough material, this Reinforced Carbon Carbon, eroded to knife edges."
Where a normal piece is a half-inch thick, he said, "it's been eroded to about the thickness of a dime." This indicates extreme heating of long duration.
He said the board is considering that the breach may not have been so much a round hole as a long slit.
Air Force analysts are still working to identify an object captured in radar images as it separated from Columbia on its second day in orbit. It could have been a crucial piece of the wing front.
© 2003 The Washington Post Company
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