Early in the (now-Oscar-winning) movie Gravity, a satellite explodes in orbit and creates a massive shower of debris that travels around the Earth wiping out (nearly) everything in its path. A great many words have been traded over the scientific accuracy of this movie, but this plot point is actually rooted in reality. And JAXA, the Japanese space agency, is testing a new system intended to forestall a catastrophe like the one the movie imagines.
Right now, there are as many as 500,000 pieces of debris floating in space. In February 2009, for instance, a Russian satellite smashed into a U.S. one, creating thousands of chunks of orbital shrapnel. This collision isn't the only source of space debris—lost parts, shed rocket boosters and dead satellites all pose a risk—and other satellites, including the International Space Station, have been dancing and dodging for years to stay out of harm's way.
The danger here is that all the bits and pieces of matter that we've sent into space will start colliding with each other at high speeds, creating more debris, heightening the risk for even more collisions and, eventually, creating a chain reaction of collisions that would keep humans from ever going to space again.
This idea is called Kessler syndrome. As Stuart Clark explains in the Guardian, in 1978, NASA's Donald Kessler and Burton Cour-Palais suggested that "as the number of satellites rose, so would the risk of accidental collisions. The resulting debris would take out further satellites, sparking a chain reaction that would swiftly encircle the planet with a vast cloud of debris. Orbits would then become unusable because anything placed up there would be sandblasted into smithereens, exacerbating the problem. Eventually our access to space would be lost.”
It's a pretty bleak scenario, and governments and research teams all over the world are trying to figure out what to do about it; JAXA has gotten as far as actually testing one method.
This particular clean-up plan, says Fast Company, will involve “a giant cable of wires that can sweep through space while generating an electric current. In theory, this will cause the debris to slow down, start to fall towards Earth, and then burn up as it reaches Earth’s atmosphere.”
Unlike a net you would use in the ocean, this one is a 700-metre-long mesh of aluminium and steel wires that hangs from an uncrewed spacecraft. The net is fitted with sensors that look for light reflecting from small pieces of debris and automatically aligns itself so that it can attract the material. The tether changes its orbit thanks to an electrical current flowing through the wires, which creates an electromagnetic field that attracts the debris and pushes the net away from Earth's geomagnetic field. Once the net has grabbed enough debris it is ordered to slow down and de-orbit, allowing the debris, spacecraft and net to burn up as they enter Earth's atmosphere.
The plan certainly seems a bit better than the one proferred by the U.S. Navy, which wants to release even more debris with the aim of turning everything to dust. Both of these plans, though, are probably better than letting space become increasingly clogged, building up to Kessler-style chaos.