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article imageShuttle Danger a Result of Environmental Concerns?

By Eric S. Wyatt     Aug 14, 2007 in Science
Some information calls into question NASA's change of foam coating material which contributed to the Columbia disaster and is the cause of the current concern for the crew of the Shuttle Endeavour.
As NASA weighs the option of sending Space Shuttle astronauts out to attempt to repair a three inch gash in the heat-shield tiles that will protect Endeavour during its return to Earth next week, questions about the safety of the shuttle's external fuel tank have taken an interesting turn.
The gash was caused by chunks of insulating foam which pealed off the large external fuel tank and struck the space craft during lift off. The size of the foam piece - and the damage done to the shuttle's heat shields - appears to be less significant than the foam which struck the shuttle Columbia in 2003. The damage done during that flight was so severe that it led to the loss of heat protection during reentry which led to the loss of the craft and all crew members on board.
At the time of the Columbia accident, many casual observers - who were inundated with reports that "foam coming off the external fuel tank is common" - were left wondering why this foam issue had never been addressed. Was there no way to secure the foam?
NASA, in the years since Columbia, has developed ways to better monitor the rain of foam that comes off the tank and has devised several - as yet untested - methods for repairing tile damage. They also spent hundreds of millions of dollars to change the way they cover the tank with foam, which was shown to be less than successful from the first flight back to space. Despite early enthusiasm for the new procedures, the dislocation of foam continues, as is evidenced by the current mission.
Yet, in 2003, questions about exactly WHY the foam had become such an issue were raised, and to all appearances have not been addressed.
In 1997, NASA bowed to environmental pressure from the EPA to change the chemical makeup of the foam used to coat the tank to exclude freon, a gas some have suggested led to ozone damage which was a major environmental point of contention in the 90's. The new foam did not stick to the tank and was quicker to fail under the extreme conditions of a rocket launch. In the first launch with the new foam formula, the shuttle orbiter sustained eleven times more damage from failing foam than in launches using the freon-laced coating.
Doubts were raised by workers at the space agency, almost immediately, but went unheeded. Between 1997 and 2003, NASA was eligible for an exemption from the freon ban, but they did not take advantage of it, seemingly due to either public relations pressure or a lack of proper care. In either case, it seems reasonable to conclude that the change in coating procedures directly contributed to the loss of Columbia.
The foam incidents are reminiscent of the circumstances surrounding the first Space Shuttle disaster. It is widely known that the 1986 explosion of the Challenger shortly after lift off was the result of a faulty O-ring which allowed hot gases to escape from the solid rocket booster and pierce the skin of the external fuel tank. What is less well-known - according to the report cited above - is that the faulty O-ring was also a "replacement part".
For the Challenger's mission, NASA had been forced to stop using a putty used to insulate the O-rings from hot gases (which had worked during the first nine flights) because the manufacturer stopped using asbestos in the paste. The manufacturer had bowed to public pressure to stop using the flame-retarding material it had produced since the Second World War.
A researcher with 41 years of experience in the field noted that the U.S. military had similar back-to-back launch failures of the Titan rocket after replacing the asbestos putty. The asbestos putty was not only a better heat reducer, it remained consistent under the cold conditions that were the primary trigger for the failure of the Challenger's O-rings.
Unlike the O-ring paste, NASA has had an alternative for the insulating foam: use freon. In 2001, an "essential use exemption" was issued which would have allowed NASA to resume using freon in the foam. NASA chose to not return to the original formula. As the crew of Endeavour readies the shuttle for return to earth, let us hope their lives are not endangered by faulty foam and that NASA finds a way to better protect the shuttle in the remaining scheduled flights.
More about Space shuttle, Freon, Environmental concerns