Fleet grounded as NASA seeks solutions.
After an embarrassingly large chunk of foam fell off the external fuel tank of the space shuttle Discovery during its 26 July launch, NASA has suspended further shuttle flights until the problem is solved. But as the agency has already spent two years and well over $1 billion trying to make the shuttle safe, critics say there will be no quick solution.
A similar piece of foam fell off Columbia's fuel tank during take-off in January 2003. The hole it punched in the shuttle's wing caused the craft to burn up on re-entry, killing all seven astronauts inside. At the insistence of the Columbia Accident Investigation Board (CAIB), NASA has poured resources into ensuring the safety of future missions, in particular to secure the insulating foam that prevents ice from building up on the fuel tank.
Although the foam that came off Discovery's tank last week didn't hit the craft, the size of the chunk, which weighed about 400 grams, shows that despite all the effort the problem is as big as ever.
Agency administrator Michael Griffin says it will be fixed “in short order”, and has put together a ‘tiger team’ to look for answers. But many engineers question what NASA can do that it hasn't tried already. “Unless there is a significant redesign, there will always be a safety issue with this foam,” says Henry McDonald, former head of the NASA Ames Research Center in California, and now at the University of Tennessee at Chattanooga.
Developing new foam could take at least a year, he says, with redesigns to the tank taking even longer. As the ageing shuttle fleet is due to be decommissioned in 2010, McDonald argues that NASA should now cut its losses and stop shuttle flights for good.
Doug Osheroff, a physicist at Stanford University in California, and a member of the CAIB, agrees that small tweaks won't help much, but major changes could take years. “We clearly don't understand all the mechanisms for foam shedding,” he says.
The best way for NASA to quickly reduce the risk to the shuttle crew is to fly with fewer people, Osheroff says. “There's no reason to go up with seven astronauts.”
As Nature went to press, Discovery's crew was preparing to make emergency repairs, unrelated to the foam incident, to the craft's underside. For the latest news on the shuttle's progress, see http://www.nature.com/news/specials/returntoflight.
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Peplow, M. More falling foam puts shuttle programme in serious doubt. Nature 436, 608 (2005). https://doi.org/10.1038/436608b