Though numbers vary, it is estimated that there are at least 8,000 trackable objects in near-Earth space. These objects are baseball size or larger and can be tracked by ground-based radars. Of these 8,000 items, only 400-500 are operational spacecraft. The rest is space junk! This space junk or orbital debris includes things such as hatches blown off space modules, garbage discarded into space from past space stations, or satellites that are no longer in use.
In addition to the 8,000 trackable objects, there are millions of flecks of paint, metal or plastic that are currently in space. Much of this smaller space junk has come from the explosion of rocket stages or the explosion of satellites and their parts. Unfortunately, the past 30 years of space exploration have generated a lot of junk that poses a significant threat to spacecraft now in orbit.
Man-made debris orbits at a speed of roughly 17,500 miles/hour (28,000 km/h)! Think of the damage even a small speck of paint could do if impact occurred at such high speeds. Even an object as small as 1 cm in diameter has enough kinetic energy to disable a medium-sized spacecraft!
Space junk is particularly a problem for long duration Earth-orbiting spacecraft, especially the International Space Station (ISS). On a list of hazards for the ISS compiled by the NASA Safety Office, the threat of impacts by micrometeorites and orbital debris ranked #6 out of 10 hazards. NASA uses mainly preventative measures when it comes to dealing with space junk, and that means heavy shielding of the ISS and other spacecraft.Url: