This article arises from Future Tense,a collaboration among Arizona State University, the New America Foundation, and Slate.
A few years ago, I was riding shotgun with my cousin, traveling down a Greek highway lined by olive trees. The view was marred when I watched him casually finish a Coke, roll down the window, and throw the can out. While I've spit my gum out on the street plenty of times, such casual littering startled me. But my cousin saw no harm in tossing a little soda can into the vast world.
For nearly 40 years—from the launch of Sputnik in 1957 to 1995, when NASA issued the world's first space pollution guidelines—space-faring nations acted just like my cousin: Whenever they were in space, they would casually throw trash out the window.
And now those cans are coming home to roost. On Feb. 10, 2009, for the first time, two big satellites accidentally collided. A derelict Russian communications satellite, Cosmos 2251, ran into a working American one owned by the company Iridium, adding more than 2,000 trackable pieces of debris to the 19,000 already in orbit. It's tough to predict where the more than 22,000 pieces of debris currently in orbit (each bigger than about 10 centimeters, the smallest trackable size) will go. The U.S. Air Force had informed Iridium that the Cosmos satellite would pass within a couple of thousand feet, but it disregarded the warning. The collision was the first step in what Donald Kessler, a NASA scientist, had predicted in 1978: a chain reaction in which collisions created more debris, which in turn begot more collisions.
According to modeling by NASA and others, there is already so much debris up there that even if everybody stops creating more ("debris mitigation"), this runaway reaction will make low Earth orbit (roughly speaking, 100 to 1,000 miles above the planet's surface) a very tough, and expensive, place to operate. What is needed is "debris remediation"—taking out the trash. Doing so will be expensive and require a huge leap in space technology. But this investment of money and brainpower will not just solve our space-junk conundrum. It may help us in the next phase of space exploration.
In response to the 2009 collision, DARPA, a military research agency, and NASA jointly organized a conference to debate the space-junk problem. The conference triggered a DARPA study, evocatively titled "Catcher's Mitt," that was released earlier this year. The study concluded that efforts to remove debris from orbit should begin soon. But a new National Research Council report, released today, says that efforts need to be redoubled. The NRC report, by a group chaired by Kessler, says NASA has not paid sufficient attention to orbital debris. "The increasing scope of work, and the complexity and severity of the debris and meteoroid environment are outpacing in real dollars the decreasing funding levels of NASA's MMOD [orbital debris] programs." The report continues: "NASA's management structure has not kept pace with the expanding responsibilities of its MMOD programs." This is about as close to a slam as government science research bodies get.
On June 28, 1961, there were just 54 tracked objects in space. The next day, a U.S. Ablestar rocket exploded into 300 large pieces. Since then, space has hosted a carnival of explosions. At one point in the 1970s, nine Delta II upper rocket stages exploded in a row. Another Delta II explosion in 1981, says Kessler, finally got NASA's attention and brought about the requirement that upper stages burn off extra fuel, so the fumes wouldn't explode. The Europeans didn't follow suit until 1986; it took the Russians until 1989 and the Chinese until 1990. In the 1960s, the United States deliberately put 480 million pieces of copper wire in orbit in an attempt to create an artificial meteor trail for radio signals to bounce off. It took until January 2008 for the United Nations to adopt comprehensive guidelines for debris mitigation. But by then, as the 2009 collision showed, it was too late.
In April, the International Space Station maneuvered to avoid a piece of debris that had been thrown off in the 2009 Iridium-Cosmos collision—the fifth time in the last two and a half years it was forced to do so. In June, the crew of the space station took to "lifeboats" when another piece of debris came hurtling by, too small to have been detected in time for an evasive maneuver. Other satellites maneuver to avoid debris on an almost daily basis. This is a problem for two reasons. Fuel is precious in space and can't yet be replenished; wasting fuel on maneuvering shortens a satellite's lifetime. And when collisions do occur, they typically render inoperable the fragile, enormously expensive satellites used for communications, scientific research, or Earth observation. Part of the high cost for satellites is related to the fact that the technology for launching them hasn't improved much since the days of Sputnik. The good news is that better technology to launch satellites and to allow for refueling of satellites might help us deal with the debris problem.
According to Joseph Carroll of the startup Tether Applications, which hopes to get into the space-junk-removal game, debris comes in three sizes: cars, hubcaps, and bullets. The bullets and hubcaps are the real threat—because there are many more of them, and because they are harder to track. But since there are just too many of the bullet- and hubcap-size objects, our best bet is to focus on removing cars (though some argue that the larger hubcaps should be tackled as well). NASA's J.C. Liou, who has been at the forefront of modeling the debris problem, says that in order to reduce the destructive potential of space debris, "you need to remove five objects per year." But a paper published on Aug. 10 in the Journal of Geophysical Research suggests the problem might require more drastic action than Liou proposes: Global warming, the authors of the paper say, might cause the outer atmosphere to contract, reducing atmospheric drag on objects in low Earth orbit and, they speculate, doubling the number of objects that would have to be removed, from five to 10.
To stop the debris-generating game of bumper cars before it starts, we need to overcome two major obstacles. The first is that it's a legal nightmare. The second is that we don't even have the technology to do it.
One problem: "The U.N. committee on Peaceful Uses of Outer Space are still arguing about where space begins—the same argument they've been having for 40 years," says Victoria Samson of the Secure World Foundation, a lobbying group. Ram Jakhu, a professor of space law at McGill, notes that there's no legal distinction between an out-of-control derelict satellite or rocket stage (which is what Carroll's "cars" are) and a working satellite. "There is nothing but space objects," he says.
Joanne Gabrynowicz, who teaches space law at the University of Mississippi, suggests that a logical way to start remediation would be to ask everyone to retrieve their own junk. The problem is that, according to Carroll, more than two-thirds of the space garbage is Russian, and Russia just doesn't have the money. Another proposal is to institute a fee on new launches to cover debris cleanup efforts. But the fee would have to be pretty substantial: Fernand Alby of the European Space Agency says that 5 percent of launch costs might be reasonable, a sum that would total in the millions of dollars per launch.
"We might have to lose two or three more major satellites [to collisions] before the international community can agree on a legal framework and on payment," says Frans von der Dunk of the University of Nebraska. The destruction of two or three satellites could be a direct cost of several hundred million dollars, and might double the amount of debris in low Earth orbit.
What about the mechanics of getting rid of large objects? There are a few different proposals floating around. The first is lasers, which have the advantage that they could, in theory, be used from the ground without requiring expensive rocket launches. But, says Kessler, lasers are "dead on arrival because of the security implications." If the laser misses its target, it could hit something else. "On top of that," Kessler says, "you don't know if you are going to ablate it or cause it to explode." It would be simpler to just go up and connect large pieces of debris, like a dead satellite or rocket body, to a rocket that would slow it down, knocking it down toward Earth's atmosphere, where it would burn up. But attaching something to a piece of debris that's tumbling out of control is not simple; it would also require large amounts of fuel. Some more forward-looking proposals would use ion thrusters (which are much more efficient) instead of conventional rockets to slow down debris.
So now we turn to propellant-less solutions. Perhaps the most promising are electrodynamic tethers. These would work by attaching the debris to a long strand—anything from tens of meters to kilometers—that would conduct electricity. That electricity, combined with the Earth's magnetic field, would cause drag and slow the object down. Tethers are not an easy fix. Attaching them is also tricky, for instance. Maddeningly, because they are much bigger than satellites, they raise the risk of still more collisions. But a single working tether could de-orbit many satellites. Carroll's firm is in the final stages of a negotiation with NASA for $2 million of tether funding for the next two years.
As sci-fi writer Neal Stephenson pointed out in Slate, even as electronics have undergone many revolutions in the half-century since Sputnik, there has been very little change in how we get to orbit and what we can do there. Rockets have been good enough at doing what needed to be done: getting to space. But they won't be good enough to clean it up. We'll need tethers and other propellant-less technologies to clean up low Earth orbit and prevent it from becoming unusable. Once developed, these technologies will find other uses as we move into a new phase of space exploration and commercialization.
Right now, once you get to an orbit, you are more or less stuck there. Maneuvering is possible, but it's expensive, because it requires precious fuel. The more efficient on-orbit maneuvering that's required for debris removal opens the door to repairing satellites on orbit. (Other proposals for repairing satellites, like a recent project announced by Intelsat, might beat debris removal systems to the punch.) Then there are ideas like a hybrid hypersonic jet, which would get you to the outer reaches of the atmosphere, and a tether that would reach down and fling you the rest of the way into orbit. Currently, these proposals are so ambitious as to be in the realm of science fiction. But if we develop expertise at using tethers, they are a bit less remote, and stand to make launching cheaper. And, need it be said, once you get good at maneuvering in space, you start to be able to think about maneuvering a bit farther afield than low Earth orbit.
Having to clean up after ourselves may prove ultimately beneficial.