By Justin Mullins
A laser "broom" that will sweep space junk out of the path of the International Space Station will be tested on a space shuttle misssion in 2003. The high-tech broom, known as Project Orion, is designed to sweep up objects the size of tennis balls. NASA scientists say that unless some of the debris is removed there is a 1 in 10 chance that the International Space Station will be holed during the next ten years.
Orbiting space junk has long been recognised as a problem for the ISS. The vehicle is designed with a shield that protects it from impacts with objects smaller than 1 centimetre across. The shield will explode objects on impact, creating a harmless shower of tiny particles.
Pieces of space debris that are larger than 10 centimetres aren't a problem, because they can seen from the ground and the space station can be warned about them so the crew can take avoiding action. But NASA engineers believe that impacts with intermediate objects will generate a shower of particles, several of which could penetrate the hull.
"The result could be much worse, like the difference between a single bullet and a shotgun blast," says Jonathan Campbell, a scientist at the Marshall Space Flight Center in Huntsville, Alabama, who leads Project Orion. "With a laser system we could clear from orbit all the debris between 1 and 10 centimetres in size within two years," says Campbell. The cost of such a clear-up would be $200 million.
Campbell's team has been measuring the forces that megawatt laser pulses can exert on debris of different types. He has shown that a laser broom could sweep away a piece of debris by locking onto it and slowing it down, deflecting it from the path of the space station. "The results are even more promising than we thought. We now know we can decelerate and de-orbit the debris with the types of laser that are available to us." The next stage of the project is to test whether debris of this size can be spotted and tracked from the ground.
NASA and the US Air Force, which are jointly funding the test, are keen not to breach international treaties preventing the use of laser weapons in space. So Project Orion is only designed to test the ability of the laser to lock onto space junk. The shuttle will release simulated space debris equipped with GPS so that its position can be monitored. Then a
ground-based laser will "light up" the target.
But this strategy may not be enough to prevent the technology being linked with missile defence projects. "There's certainly a track record of space debris being used as a cover story for missile defence projects," says John Pike, a policy analyst at the Federation of American Scientists in Washington DC. "I have no doubt that the NASA project is innocent but other countries have plenty of reasons to be suspicious."
New Scientist issue: 19 August 2000
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