Lots in space
Orbiting junk, from old satellites to space gloves, has scientists worried for spacecraft - and engineers working on ways to clean it up.
If you want to get rid of an old fridge or an obsolete TV, you could call for curbside pickup. But an obsolete satellite? Or a spent rocket?Skip to next paragraph
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Increasingly, the space about Earth is getting cluttered with such junk. And it's not just messy, it's dangerous. Full-size rocket bodies can destroy. Even smaller pieces - such as a 1965 space glove that zipped around for a month at 17,000 miles per hour - amount to more than a smack in the face. They can puncture space suits and cripple satellites.
Fortunately, the aerospace community is giving the problem increasing attention. Engineers are considering everything from techniques for rendering derelict satellites and boosters less harmful, to an international "space traffic control" system, to Earth-based lasers that can zap the stuff.
But the problem is expected to get worse as governments and companies prepare to triple the satellite population over the next two decades and send more people into space.
"If we don't change our ways, this could become a serious problem," says William Ailor, who heads the Center for Orbital Reentry Debris Studies at the Aerospace Corporation in El Segundo, Calif.
As if to underscore the concern over space-junk hazards, over the past year the United States government has adopted spacecraft and mission-design rules to minimize the contribution its spacecraft make to the space-debris problem. Now, the International Bureau of the US Federal Communications Commission (FCC) is putting the finishing touches on proposed debris-reduction rules that would govern commercial satellites as well. The drafts could hit the commissioners' in-boxes as early as December, notes Karl Kensinger, associate chief of the bureau's satellite division.
Ever since Sputnik, humans have lobbed more than 20,000 metric tons of hardware into orbit. In addition, Dr. Ailor notes that the number of operating satellites is expected to grow from 700 today to as many as 3,000 in 2020.
This hardware can yield space junk in several ways: When satellites separate from their boosters, they shed shrouds and other bits and pieces. They can collide. Boosters can malfunction and explode. Or spent booster segments with still-pressurized fuel tanks can explode when hit by debris or after joints weaken from the constant freezing and thawing. Solid-fuel motors can give off "slag" as part of their exhaust plumes.
Even satellites parked in "graveyard" orbits can shed material over time. Defunct nuclear-powered spy satellites launched by the former Soviet Union are slowly leaking their sodium-based coolant. The lumps have been tracked to lower and lower altitudes.
All of this junk can travel at sizzling speeds and packs a wallop, according to Richard Crowther, a space consultant with the British research and development firm QinetiQ. He notes that for an object to remain in orbit at altitudes below 620 miles (1,000 km), it must travel at speeds of nearly 18,000 miles per hour. It's within this region of space that critical satellites and craft, including the International Space Station and the shuttle, operate. A small coin hurtling along at 22,000 miles an hour hits with the impact of a small bus traveling at 62 miles an hour on Earth.
So far, spacecraft operators have experienced only one confirmed hit from space junk and several near misses. The hit came in July 1996, when a small French military satellite was struck by debris from an Ariane rocket that had been launched in 1986. The debris hit the satellite's altitude-control arm at more than 33,500 m.p.h. and knocked the craft into a different orbit. Space shuttles have been guided out of the way of potentially threatening debris at least eight times. The International Space Station has performed orbital duck-and-weave maneuvers at least three times.