Lassos, grabbers, and sails would all tackle pieces of space junk one at a time. Going after the relatively few big pieces makes sense, Kessler notes, since they are potential sources of secondary debris. But doing a broader cleanup will require reaching deep into the bag of tricks, starting with the laser cannon.
A space laser turns out to be a highly effective way to knock debris out of orbit, especially smaller pieces that are impractical to snatch directly. One laser could effectively take out an unlimited number of targets, so long as you can find them and aim at them accurately. You don't even have to disintegrate the junk to get rid of it, notes Dr. Claude Phipps of Photonic Associates LLC in New Mexico. All you have to is vaporize a little bit, which will puff off and then propel the object out of orbit.
Engineers led by Toshikazu Ebisuzaki of Japan's RIKEN lab worked out a plan for a 10-watt laser mini-cannon that would be mounted on the ISS to test the concept. If the targeting and firing work as intended, they envision ramping up to a 500,000-watt free-range laser satellite that would patrol low-Earth orbit.
This system "could remove most of the centimeter-sized debris within five years," Ebisuzaki claims. Phipps questions the practicality of such a huge laser satellite but thinks the same basic plan could work just fine if carried out by a pulsed laser from the ground. He estimates that he could take out satellite-size objects for about $1 million a pop. Researchers at the Institute of Technical Physics in Stuttgart, Germany, are studying a similar system.
Once you have the technology to blast bits of space junk out of the low-Earth orbit, some glorious goals come within reach. Philip Lubin of the University of California, Santa Barbara, has drawn up plans for a system of ground-based lasers he calls DE-STAR. His lab has conducted promising experiments on laser-based space debris mitigation, but his ultimate goal is to scale up the system so it could protect Earth from larger external threats.
"It could be used for deflection of asteroids as well as evaporation of asteroids, among other uses," Lubin says. The amount of energy needed to avert an asteroid strike is far beyond what any existing laser system can achieve, so a space debris zapping system would be a crucial stepping stone technology.
But even warding off killer asteroids is not Lubin's ultimate goal. What he really wants to do is use the same laser array technology, bulked up even further, to accelerate miniature spacecraft to ultra-high velocities — up to 20 percent the speed of light. Those spacecraft would have sails to catch the laser beam. Once launched, the mini-probes could then explore planets and search for signs of life in the universe.
Yuri Milner, the Russian billionaire who founded the Breakthrough Institute, has committed a $100 million investment to this approach. "We know it will take a long time to launch a spacecraft that can travel interstellar, but we also know that the time to start is now," he said in an interview. To that end, Lubin is working with Milner on a proposal called Breakthrough Starshot, intended to visit an Earth-size planet around the star Proxima Centauri, 4.2 light years away.
But first, we have to get clear of the thickening garbage patch over our heads.
"The biggest hold up to doing that is that there's been no testing for any of the concepts you've mentioned," Kessler says. If we move through that research and development stage, he is optimistic future technology will be able to solve the problem that past technology created. Better yet, it may do much more. The mundane solutions to our space mess may be the ones that ultimately lead humanity beyond the stars.