Concern Grows Over Dangers Posed by Orbiting Space Junk
Faster than a rifle bullet, able to cream a satellite with a single blow, space junk is finally getting the serious attention its destructive potential deserves.
Last month, a committee of the National Research Council (NRC) of the National Academy of Sciences raised the risk to astronauts to the same level as the risks of launch and reentry. This reverses a dangerous complacency.
American, European, and Russian space-flight managers have considered space junk a relatively low-level risk in mission planning. But, in releasing the report, NRC committee chairman Frederick Hauck said that "although NASA is taking steps to protect the shuttle from orbital debris, ... there still is a real risk that a collision could cripple the shuttle or threaten the safety of the crew."
Mr. Hauck, who is president and chief executive officer of AXA Space in Bethesda, Md., also warned that "NASA needs to obtain a more precise picture of the potential dangers [from debris] and assess additional methods for reducing these threats." A report from the General Accounting Office (GAO) of the US Congress, also released last month, made a similar point. It urged the Department of Defense and the National Aeronautics and Space Administration to improve surveillance. The agencies now have a joint task force looking into this.
No one knows how much debris is up there. According to estimates from the second European conference on space debris at Darmstadt, Germany, last March, radar and optical telescopes now track more than 10,000 objects. There are also between 70,000 and 150,000 untrackable fragments 1 to 10 centimeters across. The number of dust-size particles probably runs to several tens of millions.
The US Space Command's Space Surveillance Center in Cheyenne Mountain near Colorado Springs, Colo., tracks about 8,500 objects. Only about 500 are working spacecraft. The tracking network includes 31 radar and optical units at 16 sites worldwide. This is the network that the GAO report says can't meet either NASA or defense needs.
Debris of all sizes can be dangerous. A paint fleck can gouge a shuttle window. NASA has had to replace more than a dozen shuttle windows in the past few years.
Controllers sometimes have to put spacecraft through an orbital two-step. If the collision of the robot freighter with Russia's space station Mir last June 25 had not diverted attention, the near-miss of Europe's ERS-1 environmental satellite with Russia's abandoned Cosmos 614 military satellite would have grabbed headlines.
Space shuttle crews also have had to duck. During the Hubble telescope repair mission last February, Discovery fired thrusters to avoid an upper-stage rocket fragment from a commercial Pegasus launcher. Shuttles dodge the big ones and generally fly backwards so the tail and underbelly take the smaller hits. The soon-to-be-built space station will also rely on dodging and shielding.
THE NRC's recent report and a report a year ago on space-station safety each say these strategies aren't good enough. The earlier report calls for more shielding, especially in the poorly protected Russian module. Both reports urge a stronger international effort to minimize creating new debris.
The European Space Agency likewise notes that "clean-up in space is neither technically nor financially feasible and all efforts must be directed towards minimizing the risks of creation of [new] space debris."
The main ways of doing this are to remove old satellites from orbit or park them in safe graveyard orbits and drain residual fuel from spent rocket casings. The main creators of debris fragments are rocket explosions and collisions of large objects.
There has been little legal or financial incentive to do these things. That's changing.
Last year, LLC of Washington, D.C., Teledesic of Kirkland, Wash., and Globalstar L.P. of San Jose, Calif., said they plan eventually to de-orbit or safely park the hundreds of satellites they, collectively, will be putting in low-orbit communications networks over the next few years.
Also, the Federal Aviation Administration is writing trash-control provisions into launch licenses of commercial launch providers.
Much remains to be done to understand the space-junk problem well enough to develop universal standards for orbital safety. The need for enforceable standards, however, is now clear.