Cleaning Up Our Cosmic Backyard

Space junk refers to the vast amount of human-made objects that are left abandoned and orbiting the Earth. These objects include old satellites, spent rocket stages, fragments from collisions, and even tiny flecks of paint. As space exploration and satellite deployments have increased over the decades, so has the accumulation of this debris. Currently, there are estimated to be millions of pieces of space junk, ranging from larger debris to smaller fragments that are too small to be tracked. Of these objects, NASA estimates that about 23,000 of them are the size of a softball or larger.

The presence of space junk poses a significant problem for various reasons. Firstly, the sheer quantity of debris increases the likelihood of collisions occurring in space. These collisions can lead to the creation of even more debris, exacerbating the problem and creating a cascade effect known as the Kessler syndrome. With each collision, the risk of further collisions and subsequent destruction of functional satellites or spacecraft increases, posing a serious threat to both manned and unmanned missions. The presence of space junk also limits the number of remaining orbital parking spots for new satellites, which are rapidly dwindling.

Cleaning up this debris is a big challenge, however. With much of it traveling at thousands of miles per hour, coming into contact with it, even the very small particles, in any way can be very dangerous. Researchers at the University of Colorado Boulder have taken a page out of a science fiction novel with their recent proposal that seeks to solve this tricky problem. They have described a type of tractor beam that can push or pull on an object without physically touching it. It may not be nearly as powerful or fast as the tractor beam of the Starship Enterprise, but hey, you have to start somewhere.

The technology behind this innovation is not so sophisticated as the gravitational beams of science fiction, but rather relies on an ion gun that can generate fast-moving currents of argon ions. Blasting a piece of space junk with this ion stream will endow it with a negative charge, while simultaneously making the vehicle with the ion gun more positively charged. These differing charges will cause the objects to move towards each other over time by leveraging essentially the same electrostatic effect that takes place when you rub a balloon on your head.

Conditions in space are obviously much different than here on Earth, so the team had to construct a vacuum chamber that they call the Electrostatic Charging Laboratory for Interactions between Plasma and Spacecraft (ECLIPS) to test their methods out. Inside ECLIPS they can simulate the thin gas of free electrons and plasma that surround our planet at orbital altitudes. Using this realistic environment, they were able to introduce pieces of debris, and confirm that their ion gun could attract them with the expectation that the same effect would be seen in space.

This would be a slow process, however. Based on the results of the experiments conducted in ECLIPS, and a series of computer simulations, it was estimated that the tractor beam could pull a satellite weighing a few tons about 200 miles in a span of two or three months. That may not sound especially impressive, but it is sufficient to safely free up some very valuable real estate for new satellites. It is also important to note that one such garbage collector could be reused many times, eventually cleaning up large swaths of the sky.

But simulations and testbeds are not quite reality, so the team still has a lot of work to do before their tractor beam can be deployed in the real world. For one thing, debris often tumbles around wildly in its orbit, which would make it difficult to latch onto. The researchers believe that the tractor beam could be used to stabilize these objects before pulling them in, which could solve this problem, but that has yet to be tested. There are also many questions yet to be answered around the deployments of these tractor beams, and what to do with the captured junk. But with a bit more work, the space around Earth may become a friendlier place for satellites and other spacecraft in the future.