Space is getting awfully messy. The amount of debris in Earth's orbit keeps multiplying each year, damaging satellites and putting astronauts in harm's way. If the problem gets severe enough, it could eventually make low-Earth orbit unusable.
Scientists have known about the space trash problem since the 1970s. Humans have placed thousands of objects into orbit since Sputnik, and some of those old satellites and ejected rockets are breaking apart. As pieces collide with each other at high speeds and shatter, they create more debris. Repeat until space is saturated with high-flying junk.
Yet despite ample warning, the world's nations have never quite been able to agree how to solve the problem. The technology to clean up debris exists, but no one can decide how to pay for it. So that's where economists come in.
In a recent paper, three economists argue that orbital debris is a standard "tragedy of the commons" problem. Space is a precious resource and people overuse it because no one pays the price for waste created by satellites. Similarly, no one person has incentive to clean up the mess themselves. Economists typically solve this problem with what's known as a Pigouvian tax. Why not place a user fee on all orbital launches to pay for clean-up?
"User fees are a solution straight out of the Reagan era to deal with these environmental issues," says Peter J. Alexander, an economist at the Federal Communications Commission and a co-author of the paper. (He helped write the paper in his spare time, not on behalf of the U.S. government.) "This is a classic commons problem."
The orbits around Earth are undeniably valuable. Satellites are used for everything from communications to television to Earth monitoring and military surveillance. Roughly 49 percent of satellites are in low-Earth orbit, which is also where astronauts work. Another 41 percent are higher up, in geosynchronous orbit.
Yet those orbits are getting clogged. A map from NASA's Orbital Debris Program Office shows all the stuff humans have placed into orbit since Sputnik, including bits of satellites that have cracked apart or old upper-launch vehicle stages.
The U.S. Strategic Command is aware of more than 21,000 man-made objects in orbit larger than 10 centimeters, but there are hundreds of thousands of even smaller pieces circling the Earth that can't be tracked. Many of them are moving at extremely high speeds, some as fast as 22,000 mph.
That trash is increasingly a hassle. Satellites periodically have to adjust their orbits to steer clear of passing debris. Astronauts working on the International Space Station occasionally have to scramble into their Soyuz escape capsule when metal shards fly near, just in case a piece hits the station. "A 10-centimeter sphere of aluminum would be like 7 kilograms of TNT," one NASA scientist explained. "It would blow everything to smithereens."
"There are already a lot of costs associated with the ongoing debris cloud," says Brendan Michael Cunningham, an economist at the U.S. Naval Academy and another co-author of the paper. "We have very expensive programs to track all that debris in orbit, using radar to send out early warnings to satellite operators. And satellites are being degraded on a regular basis."
The nightmare scenario is a cascade of collisions that becomes unstoppable. Metal shards would start destroying satellites, which would create even more debris, until low-Earth orbit became unusable. This is known as the "Kessler syndrome," named after NASA astrophysicist Donald Kessler who first predicted the possibility in 1978.
So far, a chain reaction hasn't occurred, and Mr. Kessler's initial prediction of an apocalypse by 2000 turned out to be premature. But there are warning signs. Back in 2009, we saw the first major collision between two intact satellites -- a U.S. Iridium and an aging Russian Cosmos. The end result: 2,000 additional chunks of metal flying around Earth.
A major report by the National Research Council in 2011 warned that we've reached a "tipping point" where NASA can no longer track all the major bits of orbital debris. The researchers warned that we might be 10 or 20 years away from severe problems.
"Kessler was describing an orbital Nagasaki, where everything was annihilated," says Mr. Alexander. "But even before we get to that point, there are many degrees in which the orbital environment is severely degraded."
Here's the good news: Scientists have come up with clever schemes to mop up the orbital debris. We may be able to shove the really troublesome chunks into "graveyard orbit" 22,000 miles away from the Earth. Recently, aerospace engineers at the University of Colorado outlined a plan to haul away space debris using static electricity.
The problem, however, is that the world's nations can't agree on how to pay for these clean-up efforts. Everyone has an incentive to keep launching satellites into space. No one has any incentive to invest in cleaning up the orbital debris left behind.
So, in their paper, economists Alexander and Cunningham, along with Nodir Adilov of Indiana University-Purdue University, propose a simple solution: Countries should impose a basic fee or tax on all orbital launches. The fee would have to be set high enough so that companies and nations don't overpopulate space with objects. And the revenues could fund clean-up missions.
Still, a user fee would create its own set of headaches. How does the tax get divvied up? Most of the debris currently in space, after all, was put there by the United States and Russia, with China a close third. (In 2007, China blew up one of its own satellites to show off its weapons capabilities, creating an additional 3,000 bits of debris.) Should a launch tax apply retroactively? Should the United States and Russia pay most of it?
"Those are good questions," says Mr. Alexander. "The bargaining environment here has become incredibly complex. So we looked at the simplest solution, which was to impose a launch fee on a forward-going basis."
But even if an international fee wouldn't be easy to negotiate, the authors say, it's also clear that the current system is failing. "If you look at what NASA's saying, even in the absence of new launches, the amount of debris will continue to grow over the next 200 years," says Mr. Alexander.
"Up until now, we've had voluntary guidelines around launches, and the physics community is saying this is not sustainable."
Brad Plumer writes for The Washington Post.