[LINK] "Orbiting Dust Storm Could Remove Space Junk"

[rfmcdonald]

Another Alasdair Wilkins io9 link, this one pointing to a proposal for a way to dispose of the huge volume of debris--waste, fragments, and the like--produced by decades of space travel in Earth orbit.

Gurudas Ganguli at the US Naval Research Laboratory and a few pals describe a novel way of getting it down.

Their idea is to increase the drag on the stuff above 900 km so that their orbits decay more rapidly. That sounds perfectly sensible but their method is likely to be controversial.

Their scheme is to release some 20 tons of tungsten dust at an altitude of 1100km, creating a thin shell of particles that will entirely envelop the Earth. These tungsten particles will be just 30 micrometres across but still capable of packing a punch, tungsten being 1.7 times denser than lead.

Ganguli and co say that the dust's interaction with the atmosphere will cause its orbit to decay slowly. But within 10 years or so, it should drop below the critical 900 km level. After that, it will deorbit more quickly.

However, the crucial point is that the tungsten particles will naturally collide with any debris it encounters, taking this junk with it. The dust and the debris will then burn up in the Earth's atmosphere over the next 25 years or so.

So over period of 35 years, the orbits up to 1100km will be scrubbed clean. Ganguli and co call it a "dust snow plow".

There are problems. As Facebook's John pointed out last night, objects smaller than 10 centimetres haven't been tracked because the frequency of the radar used is in the 10 centimetre range. Microwave radar, or even ladar, is necessary to determine what exactly is in orbit. The impact of tungsten dust on functioning objects already in orbit also has to be considered, the author notes, while the impact on astronomical observations is unknown and it's apparently possible that the tungsten band could simply widen to "form a cloud several hundred kilometres thick!"