Humans have spent four decades dumping nuts, bolts and entire unused satellites into a growing orbital junkyard, and experts say if the littering doesn't stop now, human spaceflight and all satellite-based technology -- from DirectTV to weather forecasts -- will be imperiled within two decades.
More than 4 million pounds (2 million kilograms) of dangerous debris float above the Earth.
Billion dollar spacecraft play dodge ball with all this trash. Just last Wednesday the International Space Station was maneuvered to avoid an 8-year-old Russian rocket body that could have caused a dangerous collision. Three similar maneuvers were executed last year.
"There is nowhere else to go once certain regions of space are polluted," said Richard Crowther, a space debris expert at European science consultancy, QinetiQ.
In an article in Friday's issue of the journal Science, Crowther calls for an international effort to clean up the mess, or at least keep it from getting worse. He said simple measures will help solve the problem.
Equipment normally tossed into orbit, like lens covers and exploding bolts, begs for the addition of hinges and tethers, Crowther says. More complex solutions, like intentionally burning expired craft in the Earths atmosphere, would eliminate the largest sources of debris. Releasing leftover fuels from rocket stages and other crafts would eliminate explosions that frequently release countless, deadly particles into space.
The space station is wrapped in the bulletproof material Kevlar for protection from particles smaller than 1 centimeter. In space, these bits pack the wallop of a bullet from a .22 caliber rifle.
Even more menacing is debris larger than 1 centimeter but under 10 cm in length. These objects are too small to be spotted by radar and too large to be stopped by Kevlar.
"If the ISS gets hit at a critical spot with one of those, it's going to be a bad day," said Nicholas Johnson, chief scientist and program manager for orbital debris studies at NASA Johnson Space Center. "A 5-centimeter object coming toward the space stationis going to put a hole in it."
Looming crisis
The time is right for action, said both Crowther and Johnson, because the latest terrestrial technologies depend more and more on satellite communications and therefore a safe near-Earth environment. Future space-exploring craft and telescopes, as well as satellite navigation and communication systems, will not be economically feasible in 20 years if the current rate of littering continues, Johnson said.
Removing most existing space junk is prohibitively expensive, so all the new Earth-orbiting spacecraft will require designs that retain expelled equipment and make sure unused fuel is released.
An international group of scientists from 11 major spacefaring organizations will present a set of guidelines next February to the United Nations Committee for the Peaceful Uses of Outer Space. The guidelines will work on a voluntary basis because there's a conservation interest, Johnson said. "If anyones going to fly in twenty years from now without the risk of interference, there will have to be [cooperation]."
NASA, the European Space Agency, and other major space organizations already follow many of the schemes that will be outlined, but the plans call for worldwide government and industry cooperation.
All players will cooperate, because economics will force them to, said Crowther.
"As the scale of space projects grow and the investment required increases, it will take longer to recoup investment," Crowther said. "Therefore, venture capitalists will seek to insure projects that are sustainable. Also, insurance underwriters will consider penalizing those projects [that expose] them to a greater risk of higher premiums, and licensing by governments of space projects is becoming more prevalent, so governments may impose these guidelines at a national level."
Still, "these are not trivial expenses," said Johnson, who compared these spacecraft advances to adding catalytic converters or air bags to automobiles. "Theres a cost to being responsible and any cost increase that is incurred must be justified."
Damage done
A centimeter-long piece of metal off an old Delta launch vehicle orbits the Earth at 6.2 miles per second, and packs the same punch as a small bus traveling 62 mph on Earth. Pieces even smaller can inflict damage.
A tethered rocket was lost in 1994 when a miniscule bit of space debris effectively sliced through the tether. The Hubble Space Telescope had a three-quarter-inch hole
its high-gain antenna by a small object about a decade ago.Potentially more dangerous are the leftover satellites and rocket boosters that make up 99 percent of the mass of debris. Orbiting telescopes and the International Space Station can be steered clear of this big rubbish because objects 10 centimeters and larger are spotted by radar and tracked at the U.S. Space Command in Colorado Springs.
Crowther said such craft should come down when their missions are over. If steered into the atmosphere properly, they burn up harmlessly. Otherwise, they can break into countless smaller objects that are harder to track and harder to avoid.
Also, propellants left inside craft and jettisoned rockets often explode and create huge amounts of space debris. One recent explosion of an Indian-built upper stage rocket produced 300 trackable objects and countless pieces too small to be detected by radar but too large to be deterred by Kevlar, says Johnson.
Crowther classifies objects between 1 and 10 centimeters as the "lethal population," because satellites and human lives are at their mercy.
Far-out plans
To minimize the lethal population, new satellites and rockets from the United States, Asia, Europe, and Russia are already fitted with release valves that let out leftover combustibles. Johnson said there is international acceptance of the need for this measure.
"As for preventing explosions, everyone's on board, but the biggest issue we have now is removing the large objects from Earth orbit," Johnson said.
The only feasible way to remove objects from orbit is by incinerating them in the upper layers of the atmosphere. NASA and the ESA already dispose of spent machines this way. The UN guidelines will recommend that all new spacecraft be fitted with propulsion valves that will propel objects toward Earth's atmosphere within 25 years after they expire.
A handful of far-out and costly ideas have been put forth to collect or destroy existing smaller debris, such as mile-wide "Nerf" objects that slow the orbits of debris to send them into the atmosphere, or ground based lasers that evaporate materials.
For now, it's best to just stop littering the skies, the experts say.
"That's the most we can do for the next century," Johnson said.
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