Our junkyard in space

October 17, 1997|By Jim Lovell

THE RECENT near-collision between the Russian space station Mir and an inoperative U.S. research satellite -- the closest Mir has come to an unrelated spacecraft in its 11-year history -- reminds us of the importance of taking responsibility for spent spacecraft and finding ways to reduce the number of man-made objects circling Earth.

This month marks the 40th anniversary of the Soviet Union's launch of the world's first satellite, Sputnik 1.

Since then, approximately 4,800 satellites and space probes have been launched on missions to explore the universe and develop technology for use on Earth.

Today, satellites provide telecommunications, navigation aids, weather data, television and data-transfer services worldwide. We have begun to take such benefits for granted.

Without responsible action, however, the orbital home of these satellites could become crowded with space junk -- nonfunctioning spacecraft, fragments from in-orbit disintegration, and even tools dropped by astronauts -- making the environment unsafe and the use of space more difficult and costly.

Nearly half of the satellites launched since Sputnik 1 are still in orbit. The U.S. Vanguard 1, launched in 1958, has been inactive for 33 years and may continue to circle the globe for another 500 years.

Until recently, obsolete satellites such as Vanguard 1 and other orbiting man-made objects were simply left to ''decay'' -- falling back into the earth's atmosphere to disintegrate and burn during re-entry -- or continue in their paths indefinitely.

The U.S. Space Command currently tracks more than 8,600 objets, ranging from baseball-size pieces to the house-size Russian space station Mir. Only 6 percent of these are operational vehicles, the rest being inactive satellites, fragments and debris cast off during normal operations.

The Space Command staff keeps vigilant watch and advises NASA up to 36 hours in advance when one of these objects appears in the path of an operating spacecraft, allowing time to adjust its orbit when necessary.

An ozone-measuring satellite released from the Space Shuttle Discovery in mid-August was monitored carefully as it came within 1.5 miles of a discarded rocket motor, with controllers on the ground ready to fire small thrusters to slowly maneuver it out of a collision course.

Earlier this summer, a European ERS-1 radar satellite barely avoided a head-on collision with a spent Russian satellite when ground controllers moved the ERS-1 to a higher orbit just an hour before impact.

While the Russians don't maneuver Mir away from orbiting objects, NASA alerted Russian space officials to the approaching satellite last month, allowing the Mir crew to board the escape capsule as a precaution.

NASA, the Department of Defense, commercial satellite operators and foreign launch agencies are already considering steps to minimize future space debris.

These include requiring that spent rocket stages and dying spacecraft be moved into short-duration orbits or be directed back into the atmosphere to be destroyed on re-entry and burning or venting unused propellants to reduce the risk of debris-producing explosions.

Space cemetery

Space hardware can be designed so they will disintegrate completely on re-entry. A safe ''space cemetery'' should be set aside for out-of-service satellites.

The United States is assisting in the effort as it designs the new evolved expendable launch vehicle (EELV).

EELV, which will launch future satellites, is being designed with venting valves to eliminate all fuel from its upper stages to reduce the risk of explosions and will not be painted to keep from adding more paint chips to those already in orbit.

To date, no major catastrophes have occurred as a result of a collision in space, although a French satellite was lost in 1996 after hitting a piece of space junk.

Over the next decade, however, hundreds of telecommunications satellites designed to provide such conveniences as global mobile telephone service will be launched into Earth orbit.

Members of the space industry worldwide are considering ways to minimize the amount of space debris created by these future missions. At the same time, collision-avoidance models and techniques are being improved.

Is space still safe for our orbiting investments?

Yes, but space-faring nations share a common stewardship responsibility. They must plan and work together to ensure that space assets continue to deliver vital services safely and economically for generations to come.

Jim Lovell commanded the Apollo 13 lunar mission. He chairs Mission HOME (Harvesting Opportunity for Mother Earth), a national initiative to rekindle enthusiasm for U.S. space endeavors.

Pub Date: 10/17/97

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