Nineteen thousand pieces of space debris are orbiting the earth’s low orbit. This junk consists of things like spent rockets, solid fuel, nuts, bolts, tools, cameras, and lens caps—all hurtling around the world at about 17,000 mph.
An encounter with one of these high-velocity pieces of debris could spell disaster for a communications satellite or a manned space station. So, how can these potential collisions be eliminated?
Laser brooms, Terminator Tethers, collection vehicles, and aerogram balls are all been considered in the war against space junk.
In Project Orion, the USAF devised a promising solution to space junk: blast it into lower orbit with a laser. These so-called laser brooms could eliminate much of the smaller-sized debris within two years. A pulsating laser beam—either on earth or in space—could zap the surface of the debris, expanding the gasses and particles on its surface. This would create friction and slow the debris down, sending it into the earth’s atmosphere.
There are problems with laser brooms, however. In space, low-powered lasers are mainly used as measuring devices. International space treaties forbid the use of more powerful lasers—in fear that they could be used for hostile action and not just cleanup. The technology is also expensive (about $200 million) and it may only work for small pieces of debris.
Electrodynamics tethers, such as Terminator Tethers, are also being considered. A long wire or plasma tape, up to 10km in length, would be lowered from a defunct satellite or spent rocket booster.
The charged wire would create an ionic drag, slowing the satellite down and dropping it into a decaying orbit. This would accelerate the time for a decommissioned satellite to re-enter the atmosphere. Tethers are pro-active solution, however. They would have to be attached prior to launch. And while these tethers work in theory, there has never been a successful demonstration in space.
But the tethers are not the only self-removal devices on the table. Booster rockets could be used to re-direct old satellites. This procedure was demonstrated by the France’s Spot-1 satellite. At the end of the Spot-1’s service, the remainder of its fuel pushed the satellite into a graveyard orbit, accelerating its re-entry into the earth’s atmosphere by nearly 200 years. This is important because the more time an unused satellite lingers in orbit, the more likely it will collide with another object and create even more debris.
Another solution to the space junk problem is to update the old-fashioned garbage truck. Debris collection vehicles could be sent into orbit to rendezvous with orbiting space junk. The debris could be gathered in large collection bags and sent back to earth or shot out to deep space. The collection vehicles could also be used to attach propulsion systems to large pieces of debris and send them out of orbit. The glitch with this solution is that it may be too expensive.
A more creative idea is to intercept space debris with a giant ball of aerogel—an orbital debris collector, or ODC. These giant Nerf balls—over a mile wide—could be put into collision courses with space debris. The friction generated from the collision would send the debris back to earth. The problem is that unlike lasers, an ODC couldn’t pick its target. Working satellites might also collide with the ODC and be plunged back to earth.
These ideas all share one thing in common: they are expensive and complicated. But as space junk accumulates and makes space travel more risky, private companies and governments will need a solution. They will have to ask themselves: what is more expensive—cleaning up the waste, or not venturing into space at all?