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NASA worries object falling from Discovery
(chinadaily.com.cn)
Updated: 2005-07-27 11:54
It was a large hole in the left wing's leading edge, caused by impact with a
1.67-pound piece of insulating foam during the launching, that led to the
Columbia disaster.
But if a crack is detected, said Iain Christie, director of research and
development for Neptec, "how is NASA supposed to explain that this is not a
problem?"
Nor is it clear how it could be fixed. NASA's efforts to create a repair kit
for tile and leading-edge panels, a recommendation of the board that
investigated the Columbia accident, have not been successful. Techniques will be
tested during a spacewalk in coming days, but they are not ready for an actual
repair, and the Discovery astronauts have said they would not want to trust any
patchwork on a return to Earth.
Another option, the "safe haven" plan, would involve abandoning the $2
billion shuttle and having the astronauts wait in the space station for a rescue
mission. For that to work, another shuttle would have to be launched within a
few weeks.
That is theoretically possible but carries risks of its own: the chance, for
example, that the orbiting astronauts would run out of food, water or oxygen
before the mission could be mounted.
"There is risk in anything you do," Kyle Herring, a NASA spokesman, said.
"Staying at the station is risky."
The intense scrutiny of the Discovery's mission is an effort to make up for
decades of ignorance. Until the Columbia accident, NASA officials generally
believed that something as light as insulating foam could not harm the shuttle.
The disaster sent the space agency into a two-year struggle to learn just how
fragile the craft's thermal protection system is and how to detect damage to it.
Much of the effort has been devoted to determining what kind of damage needs
immediate action and what can be left until the shuttle is safely home. The
search for a range of allowable debris hits has involved millions of computer
simulations and testing with wind tunnels, arc jets and more, Mr. Herring said.
History, too, is a guide. "We have this database of 15,000 tile damages," Mr.
Herring said, "and we know what those sizes are."
But Edward Tenner, an author and expert on technology issues, warned that
using technology to analyze complex systems cut both ways. While such analysis
can "give you a true power and a true view" of a problem, he said, it can "make
it look better than it really is." He called this "the illusion of
control."
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