An estimated 1.2 million pieces of junk larger than 1cm (0.4in) are floating in Earth’s orbit, each of which could cause serious damage if it hit functional space equipment.
This problem has inspired scientists to propose some pretty weird cleanup solutions.
Sticky satellites
Most space debris wasn’t designed to be collected, so docking with it in space is a big challenge. A team of researchers in Germany is working on a solution inspired by the sticky feet of geckos.
Gecko feet stick to walls because of van der Waals forces – weak interactions between atoms’ electrical charges. The plan is to launch a satellite with a surface coated in a synthetic, gecko-inspired material that will stick to passing debris.
Alternatively, the sticky material could be attached to a line and cast out, capturing debris like a chameleon’s tongue catches insects. The satellite could then drag the object back into Earth’s atmosphere, where it would burn up on re-entry.
Robotic tentacles
Several groups have proposed using robotic arms, claws or tentacles to grab space junk in orbit.
For example, the European Space Agency is developing a 500kg (1100lb) craft equipped with four tentacle-like robotic arms. Its mission – to capture the defunct PROBA-1 satellite – is scheduled to launch in 2029.
Space harpoons
An alternative proposal involves equipping a satellite with a harpoon, which can shoot out at 20 metres per second (66 feet per second), skewering space debris with a barbed spear.
A trial of the system, led by researchers at the University of Surrey, successfully harpooned a test target in orbit. Despite this, space harpoons haven’t been deployed to capture real space debris yet.
Laser cannons
Rather than going to the trouble of docking with space junk, why not blast it out of orbit?
In 2015, researchers in Japan proposed mounting a 500,000-watt laser on a satellite to patrol low Earth orbit and blast debris into smaller chunks, which would return to Earth more rapidly.
An alternative solution, researched by NASA in 2011, would use a laser on Earth to knock space junk out of the way of working satellites.
Space lassos
Engineers didn’t have clean up in mind when they built the satellites in orbit today, but all that could change in the future.
The Japanese Space Agency have been developing a space lasso, also known as an electrodynamic tether, which could be attached to new satellites prior to launch.
The 700m (almost 2,300ft) conductive cable would be unwound at the end of the satellite’s lifespan and be caught by Earth’s magnetic field, dragging the craft to a fiery end on re-entry.
This article is an answer to the question (asked by Alfie Hughes, Stoke-on-Trent) 'How can we clean up space junk?'
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