NASA is reconsidering whether tank foam debris caused the Columbia disaster. That’s quite a shift from days earlier when the foam was the "leading candidate" -- an explanation that quickly became embarrassing.

We may never know precisely what happened to Columbia, but one thing should be clear -- NASA should not be in charge of investigating itself.

A chunk of foam insulation broke off the external fuel tank during launch, perhaps damaging Columbia’s heat-protecting tiles. “We’re making the assumption that the external tank was the root cause of the accident,” said shuttle program manager Ron Dittemore in the immediate aftermath.

It seemed a very reasonable assumption based on Columbia’s history.

Until 1997, Columbia’s external fuel tanks were insulated with a Freon-based foam. Freon is a chlorofluorocarbon (CFC) supposedly linked with ozone depletion and phased out of widespread use under the international treaty known as the Montreal Protocol.

Despite that the Freon-based foam worked well and that an exemption from the CFC phase-out could have been obtained, NASA succumbed to political correctness. The agency substituted an allegedly more eco-friendly foam for the Freon-based foam.

PC-foam was an immediate problem.

The first mission with PC-foam resulted in 11 times more damaged thermal tiles on Columbia than the previous mission with the Freon-based foam.

A Dec. 23, 1997, diary entry on the NASA Web site reported: “308 hits were counted during the inspection, 132 were greater than 1-inch. Some of the hits measured 15 inches long, with depths measuring up to 1.5 inches. Considering that the depth of a tile is 2 inches, a 75 percent penetration depth had been reached.”

More than 100 tiles were damaged beyond repair, well over the normal count of 40. Flaking PC-foam was the chief suspect.

In 2001, the Environmental Protection Agency exempted NASA from the CFC phase-out. Even assuming for the sake of argument that widespread use of CFCs might significantly damage the ozone layer, the relatively small amount used by NASA would have no measurable impact. The bulk of CFC use, after all, was in consumer products such as air conditioners, refrigerators and aerosol cans.

But contrary to the exercise of common sense, NASA didn’t return to the safer Freon-based foam. Instead, NASA knowingly continued to risk tile damage -- and disaster -- with reformulated PC-foam.

This is obviously a potentially embarrassing situation for NASA.

In what smacks of an effort to avoid blame, NASA is now claiming the disintegration of Columbia has turned into a scientific mystery.

NASA says computer modeling fails to show how foam insulation striking the thermal tiles could do enough damage to cause catastrophe -- apparently ignoring that flaking foam substantially penetrated thermal tiles on an earlier flight.

NASA has even offered up the ultimate exculpatory theory -- that space junk or even a meteor could have hit the wing and damage the thermal tiles.

It’s certainly possible that a force majeure could have caused the disaster. But I’d like to see qualified independent experts come to that improbable conclusion.

Instead, NASA administrator Sean O’Keefe has activated the Space Shuttle Mishap Interagency Investigation Board. The board is a standing panel created by NASA in the mid-1990s. Its members are generals and other senior bureaucrats from the Department of Transportation -- except that no one from the National Transportation Safety Board is on the panel.

The appearance of independence is lacking. The board is a NASA creation. Its senior government bureaucrats may be reluctant to blame fellow senior bureaucrats. I also wonder whether the panel members personally possess the requisite technical expertise to investigate the accident.

The combination of NASA’s “lone meteor theory” and self-anointed commission strikes me as eerily similar to the Warren Commission and its controversial, if not dubious “lone gunman theory” for the assassination of President Kennedy.

Further, NASA previously dismantled its supposedly “independent” Aerospace Safety Advisory Panel after it questioned the agency’s long-term plans for safety.

NASA is not above pulling the wool over the public’s eyes for its own benefit.

Facing significant budget cuts in 1997, NASA produced the “Mars rock” -- a softball-sized meteorite found in Antarctica in 1984 containing complex organic molecules. Hoping to boost interest in the agency’s mission -- and its budget --  NASA boasted the rock was “evidence of  primitive life on early Mars.”

Mars rock soon turned out to be Mars crock. Independent scientists arrived at a much more plausible Earth-bound explanation for the presence of the organic molecules.

NASA is an agency under pressure -- its mission is unclear and its budget demands are high. The last thing NASA needs is for its political correctness or other avoidable errors on the part of the agency to be the cause of the Columbia disaster.

The investigation into what happened to Columbia needs to be turned over to a truly independent and qualified commission -- and before the evidentiary trail starts to disappear.

Steven Milloy is the publisher of JunkScience.com, an adjunct scholar at the Cato Institute and the author of Junk Science Judo: Self-defense Against Health Scares and Scams (Cato Institute, 2001).

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