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Hunter-Killer Satellite to Take Out Space Junk

Researchers at The Australian National University and Tohoku University in Japan have proposed a new way to deal with space junk – a “hunter-killer satellite”.

In a paper published in Scientific Reports (, the researchers propose that a satellite powered by superheated gas could shoot a beam of hot plasma at space junk from the opposite end of the satellite. This would allow the satellite to either 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,” said Prof Rod Boswell of the ANU Research School of Physics and Engineering. “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 2 years if it’s less than 500 km 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 km, however, Boswell says: “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.”

It’s difficult to test a concept like this on the ground, but Dr Kazunori Takahashi of Tohoku University in Japan 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. “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,” Boswell said.

“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,” 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.”