麻豆传媒

After the party, there鈥檚 always the cleanup to take care of. It鈥檚 no different in space. Earth orbit is littered with derelict satellites, dead rockets and fragments of both that really ought to be tidied up听鈥� pushed into the atmosphere to safely incinerate.

The over the past 50 years. Of the 4300 currently in orbit, only 1200 still work and some of the rest are in pieces, following collisions and fuel or battery explosions. The result is that there are now whizzing around our planet. That鈥檚 in addition to the millions of smaller fragments of potentially lethal, fast-moving junk obstructing the space lanes.

But we still have no proven way of capturing and casting space rubbish into the atmosphere. But that could be about to change. An called RemoveDEBRIS, which will test various methods, is due to launch in early 2018.

The craft will fire a net to snare a simulated 鈥榙ead鈥� satellite and shoot a tethered harpoon at a mock target to see if, in microgravity, junk could be captured this way.

Testing these ideas in space is wise. But we will need to go further still to give us the best chance of success. Robot arms make more sense than nets and harpoons for capturing the most massive pieces of debris in some of the more crowded orbits. That鈥檚 why the European Space Agency is hoping to launch a space tug in the early 2020s, drawing on lessons from the RemoveDEBRIS test.

Called , it is developing a robot arm that could grip a massive, dead 鈥淓SA-owned satellite鈥� and use the tug鈥檚 engine to push it out towards a fiery end.

A likely target is the zombie satellite Envisat. On 8 April 2012, this Earth-observing object, about the size of a double decker bus, stopped responding. No one knows why. We do know, however, that it鈥檚 going years before the 8200-kilogram spacecraft鈥檚 orbit decays enough for it to burn up.

Until then it will tumble through low Earth orbit, out of control and possibly breaking up, presenting a major risk to other spacecraft.

But why use a tug which would have to burn up too when the reusable spacecraft revolution is just kicking off? Why not equip a reusable spaceplane with the robotics to do the job?

That is the thinking at GMV Aerospace & Defence in Spain, where engineers worked alongside Sierra Nevada Corporation of Nevada to thrash out how to use the latter鈥檚 spaceplane to deorbit Envisat.

In a fascinating , GMV says Dream Chaser has the fine-grained guidance, navigation and control needed to rendezvous with Envisat, use its thrusters to match the satellite鈥檚 complex tumble, grasp it with robot arms and stop it spinning.

Dream Chaser, aiming to fly in space for the first time in 2020, would then push Envisat into the upper atmosphere for burn up, separate from it and land.

These are just some of the many ideas being floated for the increasingly critical task of debris removal. The sooner we put them to the test the better 鈥� harnessing reusable spacecraft where we can 鈥� to ensure the orbital party can continue in safety.

Paul Marks is a science and technology writer based in London

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