Space junk

Space debris, also known as space junk, are any of the tens of thousands of small artificial objects in orbit around Earth that are a result of the planet's space programs over the years. They consist of everything from entire spent rocket stages and defunct satellites to small screws, fragments of metal, flecks of paint, and other small particles. There is (or was) also a glove astronaut Ed White lost on the first American space-walk, a camera Michael Collins lost near the spacecraft Gemini 10, garbage bags, droplets of radioactive coolant from a Russian nuclear powered spaceship, a wrench and a toothbrush (yes, a toothbrush).

Debris are most concentrated in low Earth orbit, though some extends out past geosynchronous orbit.

Space debris has become a growing concern in recent years, since collisions at orbital velocities can be highly damaging to functioning satellites and can also produce even more space debris in the process. Most satellites are now armored to deal with this hazard. Also astronauts on EVA are vulnerable, see Extra-vehicular_activity.

Proposals have been made for ways to "sweep" space debris back into Earth's atmosphere, including automated tugs, laser brooms to vaporize or nudge particles into rapidly-decaying orbits, or huge aerogel blobs to absorb impacting junk and eventually fall out of orbit with them trapped inside. However, currently most effort is being devoted to prevention of collisions by keeping track of larger debris, and prevention of more debris: satellites are deliberately deorbited at the end of their useful lifespan, or moved to "graveyard orbits" where no valuable functioning satellites are present.

The United States Military tries to keep track of most of those objects, to be able to differentiate a debris from a space missile attack. In 1987 it had a recording of each one of 7,000 objects with size bigger than 10 cm. There is an approximate number of 50,000 pieces of debris from sizes ranging from 1 to 10 cm, and at something as 10 to 100 billion paint chips (size less than 1 cm) in orbit.

See also Near-Earth object.