The Orbiting Junkyard : Shuttle Endeavour’s Near Miss With Abandoned Satellite Underscores Dangers of Space Debris

It was well past 1 a.m. on Jan. 12 when, alerted by flight controllers in Houston, astronauts aboard the space shuttle Endeavour fired the control jets to avoid slamming into an abandoned U.S. Air Force satellite hurtling toward them.

The 350-pound disabled satellite, designed to detect ballistic missile launches, had been orbiting out of contact with Earth since being launched 18 months earlier from Vandenburg Air Force Base. Even after taking evasive action, the shuttle missed it by less than five miles.

It was the sixth time in recent years that shuttle astronauts have had to maneuver the spacecraft to avoid catastrophic collisions with orbiting man-made debris.

At orbital velocities, even a fleck of paint is powerful enough to damage a space shuttle. In its first 75 shuttle flights, NASA has replaced 60 cockpit windshields--at $40,000 per window--because of pitting from debris. And when Endeavour landed a week after the satellite incident, technicians discovered that a second undetected piece of orbiting flotsam had pierced the shuttle’s speed brakes. They still worked, but it was the largest impact that anyone in the shuttle program had seen.

More than ever, spacecraft circling Earth must brave an orbital hailstorm of spent satellites, jagged booster fragments, lens caps, circuit boards, clamps, cables and other space junk--all enveloped in an abrasive fog of rocket exhaust dust and oxide particles.

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Even though the United States and other countries have adopted an array of preventive measures in recent years, the problem of orbital debris is getting worse, a White House panel of space experts recently warned.

“Of particular concern is the sustained rate of fragmentation events since 1989, despite the active efforts of the spacefaring nations to reduce the probability of such occurrences,” the National Science and Technology Council said.

Experts worry that there may be so much junk in orbit that it could trigger a chain reaction of collisions of orbiting debris. That could cause cascades of new, smaller fragments, which in turn could cause more collisions yielding more fragments--so many that space operations eventually could become simply too risky and expensive.

NASA officials said the danger is growing at every important orbital altitude--from the relatively low flyways where the shuttle maneuvers and the space station will orbit, to the high geostationary orbits crowded with communications and national security satellites.

Several communications consortiums are poised to launch hundreds of satellites to form global cellular networks in low orbits. Those satellites, the White House panel said, “present a significant new concern” because they will be vulnerable to debris damage unless special protective measures are taken.

“The United States and other countries depend on access to space to advance our national security, environmental and economic objectives,” said presidential science advisor John H. Gibbons. “Unless we seriously begin to address the problem of man-made space debris, that access could be jeopardized.”

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More than 10,000 objects bigger than a softball--and tens of millions of smaller objects--orbit the Earth. The U.S. Space Command maintains a catalog of more than 7,000 objects large enough to be detected and followed by ground-based radar in California, Massachusetts and Hawaii.

More than half of the debris tracked by the Air Force is the result of accidental explosions of booster rockets and spacecraft batteries. In the past four years alone, 19 spacecraft have broken up in orbit. Three of these involved satellites and the other 16 were rocket bodies, many of them booster units from the Russian Proton rockets.

Among the oldest known items is a spacesuit glove dropped by Neil Armstrong as he exited his Gemini space capsule for a spacewalk a generation ago. Among the newest are the few remaining fragments of a Chinese satellite that fell out of orbit in early March and an Italian tethered satellite that broke away from the space shuttle and fell into the atmosphere a few weeks later.

Because of the speed at which objects travel in space, even the smallest particles from such mishaps can pose a threat to satellites and manned spacecraft, experts said.

A piece of orbital debris no bigger than a BB, for example, carries the destructive punch of a bowling ball traveling at 60 mph, while a fragment only slightly larger--the size of a garden pea--carries the force of a hurtling 400-pound safe.

There is no conclusive evidence that any spacecraft has been destroyed by man-made debris. Space experts, however, suspect that at least one Russian Kosmos satellite exploded and perhaps several others, including a Strategic Defense Initiative satellite, were seriously damaged after collisions with space junk.

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The Hubble Space Telescope has sustained many small impacts and has been hit seriously at least once. A satellite designed to test the effects of long exposure to space conditions was hit by more than 32,000 pinpoint-sized bits of man-made debris during its 69 months in orbit.

As a result, satellite designers are taking greater protective measures. The space station has been redesigned to incorporate extra shielding to protect it from collisions. And NASA has adopted a variety of procedures to safeguard the space shuttle and its crew.

The shuttle has avoided any life-threatening collisions so far, but NASA technicians have noticed that its broad payload bay radiators, which present a large target to oncoming debris, are showing at least three times more impacts from man-made debris particles than they had predicted.

“The increased use of space has caused this orbital debris problem to grow,” said George Levin, NASA’s orbital debris program coordinator. “It is just like on Earth. There is no progress without some form of pollution.

“If we had not adopted mitigation measures, the problem would be enormously worse, far more serious,” he said. “Now, the problem is getting worse because space is being utilized more.”

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Tossed in Space

The United States and Russia are equally responsible for the amount of space debris. Here is what a Russian Proton rocket leaves in orbit.

Two Mission- Related Objects, Eliptical Orbit: Lifetime: 6- 36 Months

Two Fairings, Suborbital: Lifetime: 20 Minutes

Payload, Geosynchronous: Lifetime: 1 Million Years

Fourth Stage, Nearly Geosynchronous: Lifetime: 1 Million Years

Adapter, 200- km Orbit: Lifetime: 4 Days

Third Stage: 200- km Orbit: Lifetime: 4 Days

Second Stage, Suborbital: Lifetime: 20 Minutes

First Stage, Suborbital: Lifetime: 20 Minutes

Source: National Research Council