How Dangerous Is Space Debris?
The International Space Station recently made its latest move in a long-running game of cat and mouse with pieces of space debris. For years now, the ISS has been dodging collisions. Some of the latest maneuvers took place in April 2011 and January 2012. What may not be so obvious is that many of its “near-misses” are due to fragments from a single event in 2009 that shocked the aerospace community. On 10 February that year, the defunct Russian military communications satellite Kosmos 2251 struck the solar panel of Iridium 33, a commercial American communications satellite. The panel shattered and Iridium 33 tumbled out of control. Kosmos 2251 disintegrated.
The catastrophe created more than 2,000 pieces of space debris with sizes greater than 10 centimetres, and potentially hundreds of thousands of smaller fragments that cannot currently be tracked from Earth. To put the trackable debris into perspective, about 10% of all known space debris accumulated over the past 55 years comes from the 2009 Kosmos-Iridium collision. Fragments as small as a single centimetre have the potential to destroy whole satellites because of the speed at which they are travelling. This is because the energy of a collision is overwhelmingly determined by the speed at which things strike each other.