A study has estimated that dangerous space collisions will occur every five to nine years in our satellite and spacecraft orbit route if space junk is not effectively cleared soon. 

According to a report by the BBC, the study -- carried out for the Inter-Agency Space Debris Coordination Committee and announced at the Sixth European Conference on Space Debris -- suggests this estimate is an optimistic one, with conditions deteriorating over the next 200 years.

Space junk is an accumulation of debris orbiting the Earth -- anything from disused satellites to rocket parts discarded in-flight. Most of these are too small to do any damage (around 100 million particles are smaller than 1cm in diameter). However, according to Nasa's Orbital Debris Office, the number of particles exceeding 10cm is about 21,000, with 500,000 sized between one and ten centimetres bobbing around. Space junk from the Chinese satellite that collided with and threw a small Russian spacecraft off course earlier this year, is estimated to have weighed just 0.8g.

The study included six separate investigations by the ESA, Nasa and the UK, Italian, Indian and Japanese space agencies. Each came to broadly the same conclusions that objects sized 10cm and bigger will increase in number in the Earth's orbit over the next 200 years. Those located between 700km and 1,000km will collide more frequently, with the average increase set at 30 percent.

To avoid the "catastrophic collisions", the study suggests we stop exploding useless fuel and pressure tanks in space, and says we need to start complying with the "25-year-rule". This commonly held space etiquette rule states that when disposing of aircraft parts, solar activity and atmospheric drag projections have to estimate that its lifetime in space will be "no longer than 25 years after completion of mission". As an object orbits it will be eaten away at, the forces being exerted on it helping tear away pieces as it circles the Earth. 

However, according to a 2011 book on Nasa's Meteroid and Orbital Debris Programs, "the fact that waivers are sometimes granted at various stages of mission planning calls this status into questions", and points out that the rulebook is not a legal one. (Worrying then, because another rule states: If a space structure is to be disposed of by reentry into the Earth's atmosphere, the risk of human casualty will be less than 1 in 10,000. Hopefully that's more than a recommendation.)

A few proposals for dealing with the space junk accumulation have already been touted. In 2012 Astrium UK announced it was investing in harpooning satellites. The harpoons would be attached to satellites in orbit and fire away when a target nears, dragging it down till it disintegrates in the atmosphere. The company is rapidly improving on the technology, and it's now able to fire over 10m.

In February 2012 reported about the Swiss Federal Institute for Technology in Lausanne (EPFL) prototype satellite CleanSpace One, a £6.9 million project that could see the satellite pick up and store space junk before hurling itself into the atmosphere to burn up. 

Meanwhile, Darpa announced an initiative last year that will see amateur astronomers being provided with the equipment needed to help locate and track the growing number of space junk objects in orbit.

Source: BBC


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