From Magnets to Harpoons: How to Catch Space Debris

The world’s first commercial test mission to locate and remove space debris has finally launched to space. On March 22, 2021, Astroscale’s End-of-Life Services demonstration (ELSA-d) mission took off from the Baikonur Cosmodrome in Kazakhstan on a Soyuz rocket into cloudy and rainy skies. The highly anticipated experiment marks the major first step towards expanding on-orbit servicing and innovative space junk removal platforms.

The Japanese-based company is not the only private organization planning to de-clutter space. In fact, there are close to a dozen initiatives worldwide that are aiming to send technology to space to address orbital debris and encourage a safer, more sustainable environment. Some are even considering turning defunct satellites, rocket parts, and other human-made orbiting junk into 3D printing material.

Electromagnetic compatibility testing for Astroscale’s ELSA-d on February 2020. Image courtesy of Astroscale

Since the launch of Sputnik in October 1957, the space junk problem has only worsened as more and more defunct objects continue to colonize low-Earth orbit (LEO) just within 1,200 miles off Earth’s surface. From collisions to explosions, the threat of debris is hazardous for the future of spaceflight. According to an annual report from the European Space Agency (ESA), it has only gotten worse despite steps taken in the past decades to mitigate space debris. Launch traffic into the LEO-protected region is changing significantly, fueled by the proliferation of thousands of smaller and larger constellation payloads soon to orbit Earth.

Space technology solution provider Thales Alenia has even described the communications satellite market as “fiercely competitive,” with manufacturers racing to produce more, faster and cheaper. Advanced manufacturing technologies like 3D printing have become critical to increasing the satellite production rate. Giant corporations like Boeing and Rusal are using additive to manufacture satellites, and smallsat industry startups have also turned to the technology for faster throughput.

By lowering costs and making access to space easier, AM is disrupting an entire industry, which is crucial to predicting the weather, monitoring changes in Earth’s environment, exploring space in new ways, and providing the infrastructure to enable communications worldwide. Nonetheless, with exponentially greater payloads of satellites traveling to outer space, the already densely populated orbit could turn catastrophic.

Parts of the Thales Alenia satellite were 3D printed. Image courtesy of Thales Alenia Space.

According to the World Economic Forum, nearly 6,000 satellites are circling our planet. About 60% of those are defunct, and roughly 40% are operational. SpaceX alone has become the world’s largest active satellite constellation operator, with 1,000 satellites orbiting the planet, part of the Starlink mission to provide internet capabilities worldwide. This will soon be followed by Amazon’s ambitious internet project, Kuiper, set to deploy 1,600 satellites by July 2026. Even worse so, NASA has tracked at least 23,000 pieces of large debris, taking the total space litter to an excess of 8,000 metric tonnes as of January 2020.

At this rate, projects like Astroscale’s ELSA-d are essential to help make LEO and geostationary orbit safe to operate. The ELSA-d program is a spacecraft retrieval service for satellite operators that will demonstrate the core technologies necessary for debris docking and removal. Consisting of two spacecraft, a servicer satellite, and a client satellite launched stacked together, the demonstration mission will simulate a rendezvous with a satellite or debris in space, including non-tumbling and tumbling docking.

The servicer satellite has been developed to safely remove debris from orbit, equipped with proximity rendezvous technologies and a magnetic docking mechanism. Simultaneously, the client satellite is a piece of replica debris fitted with a ferromagnetic plate to enable docking. The servicer will repeatedly release and dock with the client in a series of technical demonstrations, proving the capability to find and dock with defunct satellites and other debris.

Similarly, Swiss company ClearSpace is set to launch a space cleanup mission backed by ESA, following an €86 million ($102 million) deal. The mission called ClearSpace-1 will see the first debris removed by 2025 by a robot-like spacecraft with four articulated arms, which will ultimately enable space debris to be removed safely. It is even expected to bring down the Vega Secondary Payload Adapter (Vespa) left by the expendable Vega rocket placed in orbit in 2013 by Arianespace, moving it closer to the earth’s atmosphere, where it will burn up and disintegrate.

Innovative ideas for space cleanup are escalating. For example, whenever SpaceX’s next-generation Starship system is not taking people to the Moon and Mars (as soon as it becomes operative in 2023), it may help clean up Earth’s orbit. SpaceX’s Chief Operating Officer Gwynne Shotwell described during an interview with Time Magazine Starship as an extraordinary new vehicle that will not only decrease the cost of access to space, but also possibly “go to some of these dead rocket bodies –other people’s rockets, of course– and pick up some of this junk in outer space.” It is not easy, she emphasized, but Starship could offer that possibility.

Planned for launch in 2025, the ClearSpace-1 mission will remove debris in orbit. Image courtesy of ClearSpace.

Other options include turning to satellites armed with high-powered lasers from Tokyo-based communications firm Sky Perfect JSAT or a  debris-catching harpoon, as proposed in an experiment conducted by Airbus UK. Mining space debris as a resource for 3D printing material is another suggestion from researchers at the French University of Toulouse, who argue that debris can be recycled and converted into fuel for other space ventures, such as producing metal for on-orbit 3D printing. Other academic institutions are also developing original technology to tackle the problem, including the University of Surrey‘s RemoveDEBRIS platform to capture space trash.

The Finnish Centre of Excellence in Research of Sustainable Space, headed by University of Helsinki Professor Minna Palmroth, has plans to send a satellite the size of a milk carton into space to test a plasma brake technology designed in Finland that can remove satellites from orbit, amongst other things. In an interview, Palmroth compared the space debris problem to leaving worn-out cars on motorways to collide with each other: “Failures in satellite technology can cause crisis pile-ups.”

Photographic documentation of an orbital debris strike on one of the window’s within the International Space Station’s Cupola. Image courtesy of NASA.

In fact, the word “crisis” truly defines the future of orbit if no viable measures can counteract the negative effect of littering in space. Aside from posing a hazard to satellites and even the International Space Station, the smallest, untracked objects are difficult to quantify. Moreover, orbital debris can travel at breakneck speeds, typically tens of thousands of kilometers per hour, making it the main risk for NASA’s human spaceflight programs. Debris specialist at ESA’s Space Operations Centre (ESOC) in Germany, Heiner Klinkrad, determined that the average time between destructive collisions might be 10 years. Still, even a single 10 cm debris collision event could wipe out a multi-million-Euro spacecraft. The threat of potential damages to functional spacecraft drives the new evolution in space cleanup, which we could expect to see in full force, just in time for some of the major milestones in space colonization in the coming years.