ExtremeTech

Next month, Japan’s space agency (JAXA) will launch a space trawler — a spacecraft that will drag a giant aluminium and steel net while orbiting Earth, hoping to bag itself some space junk. NASA tracks around 20,000 pieces of larger (5cm+) orbital debris, but there’s an estimated 500,000 pieces of marble-sized, untrackable debris in orbit as well. If a single piece of space junk hits an orbiting, functional spacecraft, the collision is likely to be catastrophic — just like in the movie Gravity — and create more debris in the process. If we don’t get on top of orbital debris now, it’s feared that one day the junk will be so dense that we won’t be able to leave the surface of Earth without being smashed to pieces.

Dealing with orbital debris is a relatively new area of research, brought into focus by China’s 2007 anti-satellite missile test, and the 2009 collision of two satellites (one of which had been inactive since 1995; it was space debris). In both cases, huge amounts of orbital debris were created — debris that might then go on to strike other satellites. The International Space Station, because of its size and the fact that it has human occupants, is of particular concern. As you can see in the images throughout this story, there’s a lot of junk out there, and the problem will only get worse unless we do something about it.

A polar view of orbital debris. You can see how the debris is generally either in LEO (near the Earth) or GEO (farther away).

An oblique view of the Earth showing space debris in both LEO and GEO, and Russia’s infatuation with north polar orbits.

Fortunately, most of our space agencies are currently working on some kind of plan to clean up both low Earth orbit (LEO, where most of the junk is) and geostationary Earth orbit (GEO). NASA has toyed with the idea of a “laser broom” — an Earth-based laser that fires up into space, shifting debris that’s on a collision course, or possibly de-orbiting it. Another option is sending up another spacecraft that attaches a small rocket onto the debris, allowing it to guide itself into a safer orbit, or de-orbit in the atmosphere. DARPA’s Phoenix project wants to take small satellites up into space and attach them to old, inactive satellites — the small satellites would use the old satellite’s antennae array, reducing the amount of waste (but not the amount of junk floating around in space).

JAXA’s electrodynamic tether

And then there’s JAXA’s method, which is almost sci-fi in its approach. Basically, the Japanese space agency wants to launch a specialized spacecraft that carries an electrodynamic tether. JAXA teamed up with Nitto Seimo, a fishing equipment company, to create this mesh of steel and aluminium wires. The tether generates an electromagnetic force that pulls space debris towards it. Once the net is full of junk, it de-orbits and burns up in the atmosphere. The first version, which is being launched in February, will be 700 meters long — if it goes well, the next version will be 10 kilometers (6.2 miles) long. JAXA’s net is by no means a sure thing — there researchers who think that the net will get torn up by debris and become space junk itself, or it might inadvertently snag an operational satellite.

Proactive measures are being taken, too: satellite makers are increasingly required to include functionality that allows the craft to maneuver into a graveyard orbit (an orbit specifically for debris, so it can’t interfere with operational satellites), or to de-orbit and burn up in the Earth’s atmosphere. (Read: The hunt for alien, star-encompassing Dyson Spheres begins.)

If we simply sit back and do nothing, then the scenario predicted by NASA’s Donald Kessler may indeed come to pass. Back in 1978, Kessler proposed that, one day, there would be so many objects in low Earth orbit (LEO) that a few collisions could cause a runaway cascade, with each collision creating yet more debris that would go on to cause more collisions, creating more debris… and so on, eventually rendering space travel and exploration impossible. This scenario is now called the Kessler effect or syndrome. Hopefully our space agencies can club together and sort out our space junk problem before such a scenario occurs, because getting stuck here on Earth would be rather annoying.