Hunter-killer satellite: new weapon in battle against space junk

Thursday 27 September 2018

It may sound futuristic, but researchers from The Australian National University (ANU) and Tohoku University in Japan have found a new way of dealing with space junk – and it involves a new type of satellite powered by superheated gas.

Space debris orbiting the earth has become a major problem in recent decades. If it collides with spacecraft it can cause serious damage, and create even more debris.

Now a study has found has found a satellite could be sent up to seek out and shift this debris. It would work by shooting out a beam of hot ‘plasma’ – or ionised gas – from the opposite end of the satellite.

This would allow the satellite to push the space junk down into a lower orbit so it eventually decays, or push it up to get it out of the way of other objects.

“Our tests show you can push plasma out one end of a satellite to thrust it towards the junk, and then push it out the other end to send that junk in the right direction,” Professor Rod Boswell from the ANU Research School of Physics and Engineering said.

“If you can throw the gas out as a plasma, or charged gas, you can throw it out very quickly and make much better use of the fuel. You throw out less of it, because it’s thrown out very fast.”

A piece of space junk will naturally decay within around two years if it’s below 500 kilometres from the Earth’s surface, because the atmosphere is still dense enough to cause friction, which causes the junk to gradually get slower and lower.

Above 500 kilometres, it presents a much tougher problem.

“It’s going to take a long time to come down. Space junk is regarded as a fairly major problem and the European Space Agency now requires European satellites to have some system that’ll get them out of the way once they’re no longer in use,” Professor Boswell said.

“They’re trying to mitigate this problem of tons of stuff flying around and potentially hitting other satellites when they’re not ready for it.”

It’s difficult to test a concept like this on the ground, but Dr Kazunori Takahashi succeeded in developing a sophisticated experiment in his space simulation facility at Tohoku University.

The next challenge for the team is to work out how to guide the satellite towards the debris once it’s been sent off into space.

“Doing it up in space is going to require even more work. I call this the hunter killer satellite because it would have to hunt out the space junk,” Professor Boswell said.

“From the ground you can calculate the orbit trajectory, so you know within a certain number of kilometres - but then it would have to find the junk with its own radar.”

The so-called “Sheppard” system would have a main plasma engine thrusting it towards the junk, as well as small thrusters to direct it properly during smaller manoeuvres.

“We’re now trying to make this system much cheaper and much more effective, because at the moment it’s a laboratory instrument so it’s a big clunky thing. So we’re working with Dr Kazunori and universities in America and New Zealand to make these things applicable to actual spacecraft,” Professor Boswell said.

“We’re gradually developing mission profiles to get these things in space. So you could do a test where you throw two satellites out, and have one as the target and one as the chaser.”

The research has just been published in the journal Scientific Reports.

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