By: City AM
March 17, 2021
In 1978 NASA scientist Donald J. Kessler proposed a theoretical scenario in which the density of objects in low Earth orbit due to space pollution becomes high enough that collisions between objects starts to cause a chain reaction whereby each collision generates more space debris, which then increases the likelihood of further collisions. One implication of the ‘Kessler effect’ is that the distribution of debris in orbit could render space activities and the use of satellites difficult for generations to come.
Last week Elon Musk’s SpaceX launched 60 new Starlink satellites into orbit, adding to the 6,000 satellites that are currently circling our tiny planet. Of these 6,000 satellites, approximately 60% are now defunct space junk, according to The Union of Concerned Scientists. But defunct satellites are only a small part of the problem of pollution in space. Over 34,000 items of space junk larger than 10cm in size have been mapped, and there are millions of items of smaller debris that are still large enough to damage a telecom satellite. This number is also growing as the frequency of satellites being sent into orbit accelerates.
A consequence of all of this space junk is that hundreds of collision avoidance manoeuvres are performed each year, including by the International Space Station (ISS) where astronauts live. Removing this debris is expensive. In 2020 the European Space Agency signed a $105 million contract with Swiss startup ClearSpace to ‘snare’ large items of space debris and move them closer to the Earth’s atmosphere where they will burn up. Clearspace is developing a robot-like spacecraft that will have four arms.