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Shuttles fly before wing change Original Source Link: (May no longer be active)
http://www.usatoday.com/news/nation/2003-07-08-shuttle-usat_x.htmhttp://www.usatoday.com/news/nation/2003-07-08-shuttle-usat_x.htm
Fleet could fly before wing change
By Traci Watson and Alan Levin, USA TODAY
While NASA may not strengthen the space shuttle's wings before it resumes flight, Monday's dramatic test results raises new questions about how soon the program should start again.
Engineers shot a slab of foam at a mock-up of a shuttle wing Monday and revealed the extent of the wing's vulnerability. The impact opened a 16-inch square hole. NASA staffers inspecting the damage could poke their heads through the hole.
Investigators are convinced that foam falling from the shuttle's external fuel tank caused the loss of Columbia on Feb. 1. The seven crewmembers died.
The test results have prompted some observers to say NASA should make the front edge of the wing stronger before sending any more shuttles into orbit.
"That's an inescapable conclusion" of the tests, said Sherwood Boehlert, R-N.Y., chairman of the House Science Committee, on Tuesday.
Senior NASA officials said months ago that they will fix the external tank to ensure that it never again sheds large pieces of foam. Pieces of foam close to the size of the one that hit Columbia have come off the tank at least five other times.
But NASA officials so far have said nothing about making the panels more resistant to damage before flights resume. Instead, the agency will follow the recommendation of the Columbia Accident Investigation Board to develop better methods to test the carbon panels on the front of the wings for signs of aging.
Strengthening the wing may be less important than improving other parts of the shuttle, engineers say. And the need to keep the spacecraft as light as possible also must be considered.
"It's a balancing process," says Graham Candler, a University of Minnesota professor of aerospace engineering. "There are other things that can go wrong with the shuttle, and you're trying to minimize the overall system risk."
NASA is now searching for ways to repair the panels in orbit. Last month, the accident board recommended that the agency develop ways of repairing shuttles during missions. Repairs would be easier at the International Space Station, but crews should be able to make fixes anywhere in space, the board said.
Columbia was the only shuttle not equipped to dock with the space station, making a repair of its wing more difficult. And investigators say the damage from Monday's test shows it would have been extremely difficult for the Columbia astronauts to have patched the hole if they had known about it.
NASA has said it wants to restart flights as soon as early next year. And one official familiar with the board's investigation said Tuesday that the test results are not likely to delay the shuttle's return to space.
But there could be significant delays if the agency decides that it must be able to repair major damage to the front of the wings. Even small repairs on the carbon panels are difficult. Fixing a large hole like the one in the test would be far more problematic.
NASA should try to strengthen the panels, says Glynn Lunney, a retired NASA engineer and manager. But it may not be possible to make the panels harder, or it might be possible only if "you do a great big fix that only improved the wings by 10%," he says.
Then there's the matter of weight. The shuttle is a fine balance between strength and lightness. Most of its engine power is designed to boost cargo into space. Upset that balance, and you don't have a useful vehicle, experts say.
"You have all sorts of compromises you always have to make," says former astronaut Norm Thagard, an associate dean at Florida State University's College of Engineering.
Engineers are now exploring how to strengthen the carbon panels. Hal Gehman, chairman of the investigation board, said last month that making the panels thicker would be straightforward.
But engineers familiar with the panels and NASA's certification process say it would take years. And some think that the carbon material is always going to add a risk to flying the shuttle. The carbon material "is inherently subject to catastrophic oxidation," or burning, says Robert Rapp of Ohio State University, who has studied the carbon panels for NASA.
Super-hot air has seeped into the shuttle's interior at least once before. As first reported by the Associated Press on Tuesday, NASA documents show that heat melted components inside the wing of Atlantis during a flight in May of 2000. The hole in that incident was only a quarter of an inch wide, NASA documents said.
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