Can magnets and a giant claw save us from space junk?

IN SEPTEMBER 2020, A TINY PIECE OF SHRAPNEL from the body of a Japanese H-2A rocket hurtled towards the International Space Station (ISS) and its crew at 28 200 km/h. An hour before the projected collision, flight controllers back on Earth powered up the spacecraft’s thrusters and moved it out of the way. That scrap of junk could have punched a hole in the hull of the space station, and it was the station’s third close call in two weeks. Since the Soviet Union launched Sputnik in 1957, we’ve sent more than 10 000 objects into orbit. As these spacecraft increasingly collide, break apart, or explode,

they generate massive clouds of debris that sweep across low-Earth orbit and pose a threat to the roughly 3 300 functioning satellites we rely on for navigation, communication and reconnaissance.

NASA, the European Space Agency (ESA), and other agencies around the world are developing plans with commercial partners and research institutions to declutter Earth’s orbit. One in particular, Tokyo-based Astroscale, has proposed a way to remove debris using a magnetic docking plate designed to connect with ailing spacecraft and drag them out of orbit. If successful, the method could become universal.

Early last year, the company launched the ELSA-d mission, to test the new method for capturing and de-orbiting disabled spacecraft with a 180 kg servicing satellite and a 20 kg target satellite. The servicing satellite is designed to usher dilapidated vehicles (in this case, that target satellite) either to a safer orbit or towards re-entry in Earth’s atmosphere. The first step was a success.

Both the servicing satellite and the target satellite are equipped with ferromagnetic docking plates that, when aligned, snap together like extremely strong refrigerator magnets. In the next step of the mission, operators will spin the target satellite to simulate docking with a piece of debris that is tumbling out of control. For the third and final test, the servicing satellite will ‘lose’ the target and use both ground-based and on-board sensors to locate it again.

Astroscale isn’t alone in its space-sanitation efforts. The Surrey Space Centre at the University of Surrey’s RemoveDEBRIS project successfully deployed a debrisgobbling net in 2018 and a space junk harpoon in 2019. And the ESA is partnering with a Swiss company, ClearSpace SA, to launch the ClearSpace-1 mission in 2025; the spacecraft will capture a decommissioned satellite using a giant claw mechanism similar to the opening scene of the 1967 James Bond flick You Only Live Twice.

Still, not all space junk is created equal, so a single removal method won’t work for all shapes and sizes. ‘If we have to build a bespoke capture capability or satellite for each [piece of debris], obviously, it’s going to be more expensive,’ says Astroscale COO Chris Blackerby.

Of the debris, rocket stages pose the greatest threat, due to their immense size. They’re also often filled with unspent fuel and unstable batteries, and they generate more debris when they decay, collide, or, in the case of that Japanese rocket stage, explode.

‘That would be the first thing to clean up,’ explains Moriba Jah, PhD, an aerodynamicist at the University of Texas, Austin. ‘Get rid of the ticking time bombs.’

Eventually, Astroscale hopes to install a magnetic docking plate on every vehicle that makes it into orbit. This coordination could make it easier and cheaper to remove future scraps of space junk.

Still, it’ll be several years before these programmes can reliably capture and remove massive amounts of space junk. Jah insists that these flashy missions will be pointless if the world’s space agencies and commercial satellite operators do not better coordinate efforts to track debris and mitigate collisions .

‘There are multiple participants making decisions in the absence of knowledge of the decisions that other people are making,’ Jah says. ‘That’s a recipe for the tragedy of the commons if I’ve ever heard one.’