Satellite uses giant net to practice capturing space junk

A British satellite, designed to test out ways to clean up debris in space, just successfully ensnared a simulated piece of junk in orbit using a big net. On Sunday, September 16th, the vehicle, known as the RemoveDEBRIS satellite, deployed its onboard net, which then captured a nearby target probe that the vehicle had released a few seconds earlier. The demonstration shows that a simple idea like a net may be an effective way to clean up all the material orbiting Earth.

The RemoveDEBRIS satellite is meant to try out numerous different methods for cleaning up space junk, which has become a growing problem ever since we started launching rockets into orbit. Thousands of dead, uncontrollable objects linger in orbit, including defunct satellites, spent launch vehicles, and other pieces of debris that have come off other spacecraft. And all of this junk is moving fast, at upwards of 17,000 miles per hour. The more debris we have in orbit, the higher the chance that these pieces might collide at break-neck speeds, creating even more debris that could pose a threat to other spacecraft.

The US Department of Defense’s Space Surveillance Network is currently tracking around 8,000 objects in orbit with Earth-based antennas, in order to calculate the chances of two large pieces running into one another. However, many engineers are trying to come up with ways to clean up the junk that’s up there in order to make collisions even less likely. It’s tough, though, since these objects are moving fast, and removing them without creating more debris is tricky. Some engineers have come up with super innovative concepts, like space lasers that can heat up spacecraft or electrified wires that could drag objects out of orbit.

However, the RemoveDEBRIS satellite, built by the Surrey Space Centre at the University of Surrey, is meant to test out much more low-key means of space debris removal. Along with experimenting with a deployable net, the satellite is also equipped with a harpoon that can spear objects, as well as a drag sail that can help slow down debris and make them fall to Earth faster. The plan is to see if these technologies can even work, before trying them out on future spacecraft that are tasked with cleaning up debris.

“We thought technologies like the harpoon or net are relatively low-cost,” Guglielmo Aglietti, director of the Surrey Space Centre and principal investigator of the RemoveDEBRIS project, told The Verge in April after the satellite launched. “If we can demonstrate technologies that are affordable, there’s a much higher probability this will happen.”

RemoveDEBRIS launched to the International Space Station in April, on board a SpaceX Falcon 9 rocket. Then in June, the satellite was loaded into the Nanoracks Kaber Microsatellite Deployer and deployed into space. It’s remained in orbit since then, and this weekend it started the first phase of its experiments.

The idea behind the net is relatively simple: capture a piece of material and then drag it down to Earth’s atmosphere, where it will burn up. To see if this idea could work, RemoveDEBRIS was equipped with a small standardized satellite known as a CubeSat, which it deployed on Sunday. The tiny satellite drifted outward and then inflated a balloon to increase its overall size (in order to represent a larger, more realistic piece of debris). Once the CubeSat was more than 20 feet away, the RemoveDEBRIS vehicle then shot out its net. Masses at the edges of the net wrapped around the target to make sure it didn’t break free from the snare.

The netted CubeSat should fall to Earth within a month or two, but if this concept is used in the future, ideally the net will also contain some kind of technology that could tow the debris downward. “After you grab something with a net, you want to tow your piece of debris down to bury it in the atmosphere,” said Aglietti. “In our experiment, we just test the net. We’re not testing the towing part.”

However, RemoveDEBRIS will be testing out a way to tug debris down to Earth. It will be experimenting with something known as a drag sail, designed to slow down spacecraft in orbit. In low Earth orbit, where much of this debris resides, there are still small particles from our planet’s atmosphere that are constantly bombarding objects. These particles slightly push on spacecraft, bumping them out of orbit and dragging them down to Earth. And the more surface area a spacecraft has, the more it gets bombarded by these particles. So increasing the area of a vehicle with a sail, for instance, helps to knock it down to Earth more quickly.

In the months ahead, RemoveDEBRIS will deploy a thin sail that will do exactly this and ultimately take the satellite out of orbit. But before that happens, the vehicle will first try out its onboard harpoon. Soon, RemoveDEBRIS will deploy a flat target that will extend outward from the spacecraft. Quickly afterward, it will fire its harpoon and attempt to strike the target. The test is meant to demonstrate another way of capturing spacecraft.

Additionally, RemoveDEBRIS is equipped with special cameras and LIDAR technology that could also be used to image space debris and help with navigation. It’s all meant to show that these tools could be used to clean up real defunct satellites someday.

“If the demonstration is successful, we will learn a lot of useful stuff,” Aglietti said. “Then the idea is there will be real missions to capture a real piece of debris.” Such space junk-capturing satellites will need to have thrusters on board so that they can catch up with the fast-moving debris. But Aglietti hopes RemoveDEBRIS will inspire confidence that these methods are practical. “We think it will be a good stepping stone to prove that the building blocks of space debris removal are viable,” he said.