Read our related editorial: Even space is now brimming with trash
SPACE weapons are destructive enough, but out-of-control satellites can be worse. So says a space scientist who has calculated that last week鈥檚 collision between a US Iridium satellite and the defunct Russian craft Cosmos 2251 delivered far more destructive energy than China鈥檚 anti-satellite missile test in 2007.
In 2003 Hugh Lewis at the University of Southampton in the UK calculated the debris field created in a hypothetical collision of an Iridium satellite with a 1-kilogram object (Acta Astronautica, vol 54, p 191). Now he has used that knowledge to work out what is likely to have happened in last week鈥檚 collision.
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To obliterate a spacecraft, a collision has to impart at least 40,000 joules of energy for every kilogram of the craft鈥檚 mass. In China鈥檚 space-weapon test, a missile destroyed a satellite by imparting 350,000 joules per kilogram. The impact added 3000 tennis-ball-sized pieces of debris to the 10,000 objects already in low-Earth orbit. Last week鈥檚 42,120-kilometre-per-hour collision was even more energetic. It imparted 50 megajoules per kilogram of the satellites鈥� mass, to produce what Lewis expects to be a debris field with an extra 10,000 fragments (shown in red). Worse, many will move in the Iridium craft鈥檚 orbit, which crosses orbits of other Iridium craft at the poles. This, says Lewis, will greatly increase the chance of another Iridium collision.
鈥淢uch of the debris will cross the orbits of other Iridium satellites at the Earth鈥檚 poles鈥�
Read our related editorial: Even space is now brimming with trash
