Scientists working with the European Space Agency (ESA) are investigating a novel technology that might one day rid the planet of all its orbiting space junk. The idea is to use powerful magnetic beams from a chaser satellite to nudge redundant satellites out of orbit.
We've only begun to send things into space in the last 60 years or so but we've already amassed a huge 'pile' of garbage around our planet. By the most recent estimates, humanity's careless deployment of various spacecraft and satellites into the planet's orbit has led to the formation of 170 million pieces of debris which range from 1cm to a few meters in diameter.
Despite their small size, all that junk whizzes at 17,500 mph which means the transferred kinetic energy can be huge when they impact a spacecraft or satellite. Yes, the horrific scenes from Gravity are extremely plausible and astronauts stationed at the International Space Station are well aware of this when they're sometimes ordered to man the escape pods. The waiting is not very pleasant at all, to say the least.
Magnets to the rescue
So what are our solutions? For now, there really isn't one. In 2012, Swiss scientists launched a pilot program called the CleanSpace One which is basically a ‘space janitor’. The function of the satellite is to track and offset debris so that their trajectory puts them on a collision course with Earth’s atmosphere. Japan has a mission called Kounotori 6 which can tether space junk with electromagnetic forces. Astroscale, a Japanese startup, plans is to launch a satellite called ELSA-1 that will track debris and stick to it with glue. Other ideas are even wilder, like using lasers to vaporize the surfaces of small pieces and force them down. The bottom line though is that all of these have either failed or are in the making.
Emilien Fabacher from the University of Toulouse in France is working on what looks like the most promising 'space janitor' so far.
"So the idea I'm investigating is to apply magnetic forces either to attract or repel the target satellite, to shift its orbit or deorbit it entirely," Fabacher said in a statement.
"With a satellite you want to deorbit, it's much better if you can stay at a safe distance, without needing to come into direct contact and risking damage to both chaser and target satellite."
The power to attract or repel
To grip derelict satellites, the chaser would generate a strong magnetic field from superconducting wires cooled to cryogenic temperatures. The magnetic field would then target the satellites' ‘magnetorquers’, which are reliable electromagnets already fitted to adjust orientation using Earth’s magnetic field without needing any special equipment.
Not only would a magnetic gripper safely remove junk from space, it would also serve a more constructive purpose. The same space tug could be used to root several satellites in place by keeping them in formation above Earth. Such satellite swarms are being considered for future astronomy or Earth-observing missions because they can act as a single giant telescope as long as they're stable. Many ground-based radio telescopes around the world have joined hands, for instance, to essentially form a telescope the size of planet Earth with the intended purpose of peering into a black hole's event horizon.
“This kind of contactless magnetic influence would work from about 10–15 m out, offering positioning precision within10 cm with attitude precision 1–2º," commented Finn Ankersen, an ESA expert in rendezvous and docking, formation flight.
For now, Fabacher and colleagues are still crunching the numbers to see how all of this might work in a practical setting. Fabacher has already combined a rendezvous simulator with magnetic interaction models for his PhD thesis. "The first surprise was that it was indeed possible, theoretically – initially we couldn’t be sure, but it turns out that the physics works fine," he said.