In addition to artificial satellites and the Moon, the Earth is orbited by man-made space debris, a collection of objects including anything from spent rocket stages and defunct satellites to collision fragments and astronaut pee. Some 3,000 still useful communications satellites orbit the Earth while the US military tracks about 20,000 pieces of space junk. But there are also tens of millions of small particles of debris like paint flakes and solid rocket fuel slag.
Such debris comprises a hazard to space travel. The small particles cause erosive damage, their effect similar to that of sandblasting, while bigger objects pose a more serious risk of obliteration to space vehicles. And the danger of collision with these more substantial objects is getting greater as junk is added to orbit faster than it is removed by natural causes such as disintegration in the Earth’s atmosphere. A runaway accumulation of debris known as the Kessler syndrome is probably already under way at certain orbit elevations.
Now NASA scientists have come up with an idea to minimise the risk of catastrophic collisions between space shuttles and space rubbish using mid-powered lasers. Rather than shooting the objects out of the sky, the lasers would be used to nudge them off any collision course they might be on.
Says NASA engineer Creon Levit, “If one [small, dense piece of debris such as a bolt] collides with a satellite or another piece of debris at the not-unreasonable relative velocity of, say 5 miles per second, it will blow it to smithereens.”
But according to a new NASA study, shining lasers on bits of space litter for a few hours a day could remove many of them from harm’s way as each photon of laser light carries a tiny amount of momentum.
“If you stop that cascade, the beauty of that is that natural atmospheric drag can take its natural course and start taking things down,” says William Marshall, a coauthor of the new study. “It gives the environment an opportunity to clean itself up.”
Don Kessler, who gave his name to the runaway syndrome, agrees – although a longer-term solution to the accumulation of space junk is needed.
Via Wired Science
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