ESA

Debris lost in space.

A dramatic illustration of the dangers of space debris is given in the film Gravity. It may have taken someartistic license with scienceto craft a good story, but its main premise is plausible. What Gravity showed was the worst case scenario, known as the Kessler syndrome, where a collision between two objects generates a cloud of smaller debris, which triggers a chain reaction of further catastrophic collisions, thereby rapidly increasing the amount of debris. This could make the low Earth orbit unusable for spacecrafts.

Most of those are useless fragments of once-useful objects, which were created by explosions, collisions or missile tests. For instance, an accidental collision between the Iridium-33 and Kosmos-2251 satellites in 2009 caused them to shatter into 2,200 (recorded) fragments. Smaller space debris is much harder to track, but NASA estimates that up to 500,000 objects larger than 1cm, and 135 million particles over 1mm in size may now be orbiting the Earth.

NASA

Catalogued objects in Low Earth Orbit (LEO) larger than 10 cm.

Space debris is becoming a serious issue, and many space agencies have started working on solutions. One approach being taken by JAXA, Japans space agency, is to use a magnetically charged 700m-wide net made from aluminium and steel wires. If used at the right height it will attract floating space debris to it. When enough has been caught, the system can be ordered to fall out of its orbit back to Earth. During that process the debris, along with the net, will burn up as it enters Earths dense atmosphere. JAXA will be doing a test launch of the system next month.

The other approach is to remove existing inactive satellites from orbit. A prime target for this experiment would be the European ENVISAT satellite which stopped functioning in 2012 and now drifts uncontrolled in orbit. At an altitude of 800km and with mass of more than 8,000kg, the ENVISAT satellite would take more than 150 years to deorbit that is, drop out of its orbit naturally.

Throughout that time the satellite would be at risk of colliding with other objects and generating further debris. A more sustainable solution is to remove future satellites from orbit after they have served their purpose, thereby mitigating the growth of the amount of space debris. This is why international guidelines have been proposed which will restrict post-mission deorbiting time to 25 years for all new satellites.

Most satellites designed today take will take longer to deorbit, and new technical solutions are necessary to meet the guidelines. This is where Surrey Space Centre (SSC) working with the European Space Agency (ESA) have developed aGossamer Sail for Satellite Deorbiting. The idea is to attach a large and very light, or gossamer, sail to a satellite, which can be deployed after its mission is over.

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Half A Million Pieces Of Debris Are Orbiting Earth — Here's How We're Going To Clean Them Up