BRIEF NEWS: Housekeeping Spacecraft Proposed To Tackle Mounting Space Waste

9 August 2011

With more than 17,000 objects of a size greater than 10cm reside in low-Earth orbit, with the largest of these having the potential to create thousands more, a potential solution could be found in housekeeping spacecraft

The idea, published in the journal Acta Astronautica, claims it could inexpensively remove five to 10 of the largest objects per year of operation, which would involve launching a satellite to rendezvous with items such as spent rocket bodies.

The satellite would then affix a propellant kit and force the debris into the Earth's atmosphere where it would burn up.

"In our opinion the problem is very challenging and it's quite urgent as well," said Marco Castronuovo, the Italian Space Agency researcher who authored the paper. "The time to act is now; as we go farther in time we will need to remove more and more fragments," he told BBC News.

Dr Castronuovo proposes a scheme in which small satellites are deployed on seven-year missions, each with two robotic arms: one to intercept a rocket body or failed satellite and hang on, and another to affix an ion-engine thruster that will drive the debris out of orbit.

The satellites would then release the debris, hopping from one to the next in a choreographed dance with five to ten large objects per year.

"The proximity operations and maneuvering talked about here is not easy, but the technology is getting there for that; the idea that you go and attach yourself to something in orbit is becoming more credible," said Stuart Eves, principal engineer for Surrey Satellite Technology.

"People have come up with all sorts of daft ideas... that are really science fiction at the moment. Something like this is a lot more practical."

Nevertheless, the greater problem may be political, as any proposal struggles to be seen as a purely aimed at space junk, Dr Castronuovo said.

"This kind of approach could be seen as a threat to operative systems; if you have the power to go to an object in space and pull it down, nothing prevents you from going to an operative satellite and pulling it down, so it's really a delicate matter."

Kessler Syndrome

The new research identifies more than 60 objects at a height of about 850km, and two thirds of those weigh more than three tonnes each - many moving near a speed of 7.5km/s. Most of these largest threats are spent rocket bodies, and it is there that Dr Castronuovo thinks the effort should begin.

What is feared is a kind of chain reaction, called the Kessler syndrome after the NASA scientist who first described it in 1978, in which fragments hit other fragments, which in turn hit more, creating a cloud of debris that will make vast swathes of low-Earth orbit completely unusable.

The debris presents a risk not only to other man-made satellites in orbit, but occasionally also to the International Space Station and manned space missions.

Darrel Moore