Italian boffins to robo-grapple space junk

Italian scientists have devised what they reckon is a viable plan to deal with the menace of large chucks of space debris: a robotic satellite which will grapple the junk, attach a propellant kit and dispatch it to a fiery death in the Earth's upper atmosphere.

Marco Castronuovo and colleagues from the Agenzia Spaziale Italiana have identified over 60 major threats at an altitude of roughly 850km, the BBC explains. Two-thirds of these weigh in at over three tonnes apiece, and many are whizzing along at up to 27,000 km/h (16,800 mph).

Among these are the priority targets: 41 large rocket bodies in a similar orbit which could collide, provoking a "cascading" collision effect as more and more pieces are added to the circling junk pile.

Castronuovo told the BBC: "In our opinion the problem is very challenging and it's quite urgent as well. The time to act is now; as we go farther in time we will need to remove more and more fragments."

The team's abstract in the journal Acta Astronautica explains: "The selected concept of operations envisages the launch of a satellite carrying a number of de-orbiting devices, such as solid propellant kits. The satellite performs a rendezvous with an identified object and mates with it by means of a robotic arm. A de-orbiting device is attached to the object by means of a second robotic arm, the object is released and the device is activated."

The scientists say their method could effectively and economically deal with 35 rocket bodies over seven years. Castronuovo is aware of the potential political sensitivity of the plan, given that his robosat grappler could potentially be used to deorbit working space hardware.

He said: "It's difficult from a political point of view; many of these objects belong to nations that are not willing to co-operate or do not allow access to their objects even if they are at the end of their operative life, and there is no international regulation on who should remove the objects that are left in space.

"If we start concentrating on the spent rocket bodies – which do not have sensitive equipment on board – it should not pose any problem to the owner to give permission to remove them; and there's no doubt they are not operative anymore."

The Italian plan is radically different to the Japan Aerospace Exploration Agency (JAXA) proposal, unveiled earlier this year, which suggests an orbital fishing trip with a really big net to clear the heavens of rubbish. ®