Despite the vastness of space, the region around the earth used by satellites, spacecraft and other orbital devices is becoming dangerously cluttered with aerospace junk. The danger is not to earthbound inhabitants, but to satellites, astronauts and future space projects.
A congressional study released a few days ago shows that some 6,645 artificial objects - each at least the size of a softball and some, of course, enormously larger - are being tracked in earth orbit. In addition, as many as 70,000 smaller items, some as tiny as chips of paint, also are in orbit.The problem arises from the velocity of these objects. Their average speed in low-earth orbit is about 6.2 miles per second. At that velocity, a tiny object that could be blown away with a breath on earth would have in space the impact of a rifle bullet.
The junk comes from a variety of sources. About half is the result of rockets drifting in orbit after they have lifted a spacecraft above the atmosphere. Other debris is from satellites, particles from solid fuel motors, paint chips that have flaked off, and explosions in orbit or near orbit. For example, the Soviets used to blow up their spy satellites in orbit after their usefulness had ended - so they wouldn't fall into U.S. hands.
There are three possible responses to the problem. None would solve the junk danger entirely.
One would be to suspend all space launches for a lengthy period - years. Some junk eventually slows and falls back into the atmosphere where it burns up. But this approach would mean abandoning the launch of any more satellites, an unacceptable answer.
A second possibility is sending astronauts into orbit to retrieve the larger pieces. But the expense would not be worth the minimal result.
A third idea - and the only one really feasible - is an international effort to keep junk out of space by redesigning space devices so they do not break up or shed paint so easily. Upper stages of rockets could use lower altitudes so they would fall into the atmosphere more quickly.
Near-earth orbits used by aerospace projects are still mostly a vast emptiness. But let's not keep littering in such a way that future space missions are jeopardized by the junk left behind from previous ones.