Manmade debris crowds the not-so-friendly skies
As dump-sites go, there’s nothing quite like Earth orbit: Totally gone or near-dead spacecraft, spent motor casings and rocket stages, all the way down to pieces of solid propellant, insulation, and paint flakes. Toss in for good measure thousands of frozen bits of still-radioactive nuclear reactor coolant dribbling from a number of aged Russian radar satellites.
Here’s the heavenly clutter count as of December 29, 2004.
There were 9,233 objects large enough to be tracked and catalogued by the USSTRATCOM Space Surveillance Network. Of this total there were 2,927 payloads, along with 6,306 object classed as rocket bodies and debris.
That’s the stats as listed in the January issue of The Orbital Debris Quarterly News, issued by the NASA Johnson Space Center Orbital Debris Program Office in Houston, Texas.
Hardware survivors
A major contributor to orbital debris is an object suddenly breaking up. This can be caused when propellant and oxidizer inadvertently mix; leftover fuel becomes overpressurized due to heating; or when onboard batteries blow their tops. Some spacecraft have been purposely detonated. Explosions can also be indirectly triggered by collisions with fast-moving debris.
An example of fragmentation took place last October. A Russian Proton Block DM auxiliary motor busted up, adding more than 60 pieces of junk to the overall orbital debris scene.
At times some of this high-tech scrap survives its fiery plunge through Earth’s atmosphere. A growing list of these hardware survivors is maintained by The Center for Orbital and Reentry Debris Studies at The Aerospace Corporation in El Segundo, California.
Last year, for instance, a titanium rocket-motor casing weighing roughly 155 pounds (70 kilograms) was found near San Roque in Argentina. It was identified as debris from a third stage of an American Delta 2 booster that had been orbiting since October 1993.
Similarly, in July a metal pressure sphere and metal fragment fell into Brazil, the likely debris from a second stage of a Delta 2 booster that hurled the Mars Exploration Rover, Opportunity, toward the red planet a year earlier.
Leonard David
