As human activities in space have increased, the accumulation of space debris has become a major problem. Currently, various broken satellites, rocket pieces, as well as thousands of tiny particles endanger spacecraft. Space junk poses two main dangers: firstly it can damage or destroy space vehicles, and secondly space junk could render low earth orbit unusable for decades or even centuries. As both space junk and the amount of satellites in orbit increase, the chances for low earth orbit to be plagued by the Kessler Syndrome increases.
The Kessler Syndrome hypothesizes a situation in which collisions in low earth orbit create – due to the density of satellites – a knock-on effect, with debris from one collision sparking others. This would result in the destruction of our satellite network, as well as the creation of a debris zone around the Earth, thus preventing future launches.
In order to counter the threat of space debris,( which NASA currently estimates at over 3000 tons) the space agency is considering installing a laser system on the International Space Station (ISS) to shoot down incoming garbage. Due to the lack of atmospheric friction, space junk in orbit travels at 36,000km, with even minute particles reaching deadly velocity. Currently most spacecraft, including the ISS have adequate shielding to withstand impacts by particles around 1cm. However, ground based tracking systems have identified over 700,000 pieces of debris in orbit that are larger than 1cm.
To counter this threat, the ISS is seeking install the Extreme Universe Space Observatory (EUSO) in 2017, which will allow the station to track debris. The EUSO is part of a pilot program that could eventually see the installation of a Coherent Amplification Network (CAN) laser system. This system would fire rapid pulses of ultraviolet energy at debris, heating the surface to plasma. This in turn would create thrust and could be used to direct debris away from the station and into the atmosphere. The proposed defence system would consist of an advanced monitoring system akin to EUSO, alongside a 100,000 Watt ultraviolet laser with a 100km range.
Another application of this technology would be the creation of a dedicated anti-debris satellite. Such a satellite would be equipped with a 500,000 Watt laser system capable of de-orbiting a piece of debris every five minutes, or approximately 100,000 pieces in a year.
Ideally such a satellite would operate at 1000km on a polar orbit, allowing it to cover the entire Earth. As most space junk orbits the Earth at an altitude of 800km, the satellite would slowly descend, zapping debris as it went. By descending some 10km a month, the satellite would be able to clean out debris at various altitudes over a 50 month period.