From: Aviation Week
Posted: Friday, February 21, 2003
NASA documents as far back as 1988 show that wing roughness, similar to that associated with the shuttle Columbia's left wing, could result in catastrophic burn-through when combined with wing impact damage like that being investigated in the reentry accident, Aviation Week & Space Technology reports in its February 24 issue.
Shuttle project office documents obtained by AW&ST spell out how wing gouge damage near the landing gear wheel well or wing leading edge, could combine with Columbia-type wing roughness in a "fatal combination" that would spike reentry temperatures to nearly 1,000 deg. higher than allowable at the site of the debris strike.
The AW&ST report displays a 1988 NASA document illustrating what could happen to a wing gouge at the identical location where similar damage is believed to have occurred during Columbia's launch January 16.
A gouge at that location, in connection with aerodynamic wing roughness characteristics, could results in "massive shrinkage" or "melting" of wing thermal protection tiles and "exposure of the aluminum wing structure" to temperatures in excess of its melting point, the document says.
The former chief of the NASA Astronaut Office, Robert L. (Hoot) Gibson who has piloted five space shuttle missions, told Aviation Week that he was "ignored and disregarded" by the shuttle engineering community when a year after the initial thermal assessment, he coupled serious reentry tile damage that had occurred on an earlier mission to the Columbia wing roughness issue. "I was never quite satisfied that we had exhausted everything that maybe we should have looked at," Gibson said.
AW&ST also reveals a new set of e-mails exchanged between engineers at the NASA Langley Research Center in Hampton, Va., while Columbia was still in orbit. The new e-mails express elevated flight safety concerns in spite of a Boeing analysis that showed there should be no danger from debris that may have fallen from the Lockheed Martin external tank.
"One of the bigger concerns is that the 'gouge' may cross the main landing gear door thermal barrier and permit a breach there. No way to know of course," Langley engineer Robert Daugherty wrote to fellow engineer Mark Shuart on January 29, AW&ST said.
The magazine quotes the engineer's message as saying, "We can't imagine why getting information is being 'treated like the plague'. Apparently the thermal folks have used words like they think things are 'survivable' but 'marginal'", Daugherty wrote, adding, "I imagine this is the last we will hear of this." Two days later Columbia and her crew were lost.
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EDITORS NOTE: Full text of the Aviation Week & Space Technology article and related charts, as well as interviews providing analysis, are available.
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