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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.

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In low-earth orbit, gravity and atmospheric drag help sweep a good portion of humanity's leavings - from abandoned space stations and rocket stages to astronauts' gloves and lens caps - back into the atmosphere to burn up or break up. Many more of these objects at higher orbits could remain in space for thousands of years or more.

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In all, more than 9,000 objects larger than about 4 inches have been cataloged. Within 1,200 miles of Earth, some 2,200 tons of debris orbits. If smaller but still-lethal objects were included, the catalog could number more than 100,000. Ailor adds that the figure is likely to grow as the number of satellites mushrooms.

Confronted with growing space debris, the FCC is proposing that applicants for new commercial satellites show that the craft is robust enough to prevent fragmenting in the face of any remaining fuel, pressurization, or sudden discharge of the crafts batteries. Ideally, leftover fuel would be vented, as would any pressurized system. And batteries would be discharged. The proposed rules also set guidelines for moving an over-the-hill spacecraft into a disposal orbit.

But additional shielding or fuel add weight and thus cost. European Space Agency engineers, for example, calculate a $2 million price tag for the additional fuel needed to steer a 1-ton satellite from geosynchronous orbit toward reentry into Earth's atmosphere.

Others suggest more high-tech approaches, such as using ground-based lasers to zap orbital debris - a plan that also could have space-weapon implications. The idea, which NASA reportedly pronounced workable after studying the approach in the late 1990s, relies on high-powered lasers to vaporize small bits of material from the surface of a hunk of space junk. The vapor emitted acts like a tiny rocket motor, propelling the junk either into a less threatening orbit or on a path toward a fiery reentry.

Others have proposed using space tethers, which a satellite could lower at the close of its career. Taking advantage of electrical properties induced at each end by its motion through Earth's magnetic field, the tether would slow the satellite, dropping it into ever-lower orbits toward reentry.

Even if these approaches prove practical, Ailor maintains that space debris and growing traffic raise the need for an international space-traffic control system. Currently, the US Air Force maintains the 9,000-entry catalog of large objects. But it warns the relevant agency only if a manned vehicle is threatened.

Unfortunately, Ailor concludes, it may take a high-profile collision to jump-start the kind of system he envisions.

Space Junk Highlights

• Oldest debris still in orbit

The US Vanguard 1 satellite, which was launched on March 17, 1958, and worked for six years.

• Most dangerous garment

US astronaut Edward White's glove, lost during a Gemini-4 spacewalk in 1965, orbited Earth for a month at 17,398 miles per hour.

• Heftiest garbage disposal

The Mir space station, where cosmonauts jettisoned more than 200 objects, most of them bags full of garbage, during the station's first 10 years of operation.

• Most debris from the destruction of a single spacecraft

The explosion in 1996 of a Pegasus rocket used in a 1994 launch. The blast generated 300,000 fragments bigger than 4 millimeters (0.15 inches). Some 700 of these objects were big enough to earn entries in catalogs of large space debris. The explosion doubled the Hubble Space Telescope's risk of colliding with a large piece of space junk.

• Most heavily shielded spacecraft in history

The International Space Station.

Source: European Space Agency