The space thriller “Gravity” may have just ruined the popular image of space as a breathtaking abyss. Between us and the stars, we all now know, there’s a hazardous cloud of “space junk”—the growing quantity of man-made debris orbiting Earth (and the closest thing the film has to a villain).
Space junk is making orbit an increasingly risky place. A fragment of debris less than a millimeter in size, traveling at the typical low-earth orbit speed of 17,500 miles per hour, has enough force to pierce an astronaut’s spacesuit. A centimeter-wide piece could disable a satellite the size of a bus. A big one, measuring 4 inches or more, could destroy it.
Today, after more than 50 years of human activity in space, there are more than 22,000 of these big pieces known to be orbiting Earth, along with hundreds of thousands of fragments larger than a centimeter, and millions larger than a millimeter. The problem is getting worse. Every time a company or a country sends up a satellite or a spacecraft, the new object ejects bits and pieces of launch equipment on its way. And an overtly destructive act, like the test of an antisatellite weapon, creates thousands of new pieces.
“Even if we don’t put anything else in orbit, in the long term, everything is going to collide with one another,” says Donald Kessler, the retired NASA physicist who first warned about space debris in the 1970s. Create enough debris and eventually, his calculations showed, humanity will have trashed orbital space so thoroughly that we won’t be able to send anything else up.
Why is this happening? What might it do to the satellite industry without an intervention? Those are the questions that attracted a trio of economists who recently took a systematic look at the incentives that shape our treatment of orbital space. They took a simple model, often used to show connections between the environment and the economy, and applied it to the exotic environment above our heads. In the resulting paper, posted in May 2013 and now under review in a journal of environmental economics, they propose “the first theoretical economic model...of satellite launches and space debris.”
What they found is that individual companies or government agencies have a strong financial incentive to launch new satellites, but much less incentive to clean up the debris around them, even if it poses a threat. “They don’t internalize the impact on themselves, and they definitely don’t internalize the impact of the debris on other launchers,” says coauthor Brendan Cunningham, an economics professor at the US Naval Academy. As a result, satellites are being sent into space at a rate too high to be sustainable.
Space, in other words, is a classic “tragedy of the commons” problem, in which many individuals benefit from a collective resource but no one has an incentive to bear the cost of maintaining it. Eventually, everyone suffers. But in space, there’s also a twist. Unlike most pollution, space junk is self-perpetuating. More debris increases the likelihood that a satellite will be disabled, prompting the launch of a new satellite to replace it—creating more debris, and spiraling from there.
On the practical front, space agencies are looking at strategies for debris removal—sending up new spacecraft to harpoon large pieces, or shooting at them from earth with lasers. It may soon be possible to start addressing a handful of the largest pieces every year, but it will be colossally expensive. As a preventive measure, certain rules are already in place: Some national governments, including the United States, require operators to move their satellites away from the most trafficked space within 25 years of the end of their mission. The United Nations also encourages satellite owners to harden satellites against smaller impacts, and refrain from intentionally destroying objects in space.
But these rules alone aren’t enough. “If everybody followed the 25-year rule, it would still be insufficient to keep debris from increasing,” says Kessler. “We started it too late.” Someday, someone’s going to have to go clean this mess up. Based on their study, the economists suggest a cleanup tax on space launches could be useful: It would both limit the growth of debris, by decreasing the number of launches, and provide some funds for debris removal. (However tough it would be to convince international negotiators to agree on these policies, the other options— command-and-control regulation of debris creation, or waiting for private companies to clean up—seem even less realistic.)Continued...