Orbital debris, more commonly known as space junk, is an unavoidable byproduct of human space exploration. Not only do we rubbish our earthly environment with all sorts of crap, but since the dawn of orbital spaceflight in the 1950s, humans have been littering the skies above as well.
On September 14 this year, astronauts of the space shuttle Atlantis contributed a few bolts to Earth’s orbit while completing installation of new solar arrays for the International Space Station. These days NASA tries to tether everything used during a spacewalk — but accidents do happen. NASA and the US Air Force track all space-faring garbage larger than ten centimetres and the addition of these few tidbits in September brought the count to 9,925.
Orbital debris consists of a wide menagerie of hazardous items, detrimental to astronauts, spacecraft, and expensive satellite equipment. Newer spacecraft, such as the International Space Station, are reinforced against orbital debris hazards but there are still many more at risk.
1996 is recorded as the first confirmed occurrence of a collision between cataloged space junk and Cerise – a French military reconnaissance satellite. The impact tore away some 4.2 metres of gravity gradient stabilisation boom from the craft. It is interesting to note that there are lawyers who track orbital debris — yes, there are expensive legal responsibilities resulting from your space junk damaging someone else’s satellite.
There are believed to be over 100,000 manmade objects zipping around the Earth at a speed of around 28,000 km/h, and the smaller items can be just as troublesome as larger ones — they’re just harder to track. Where NASA can warn astronauts and shuttle pilots to move out of the way of an impact with some of the larger pieces, it is almost impossible to avoid collisions with smaller debris. Fragments such as paint flakes can dent a craft or scratch the shuttle windshield, while clouds of smaller particles which can cause sandblasting.
Dumping waste from the space shuttle has urine, toothpaste, and shaving cream floating in the skies above us. After an Indonesian satellite was struck with urine and fecal matter, NASA decided that discarding human waste in space is probably not the greatest idea. Other hazards include trash thrown from the Russian space station Mir, rubble from explosions, spent booster rockets from launches since 1958, equipment discarded while repairing the Hubble Telescope, and some 2000 satellites no longer in use.