Space debris is a bit like space itself: We know it s up there, but beyond that there s so much we know we don t know.
The statistics are fun, though, if a little misleading. It s a bit of a safari crunching the numbers, but here goes.
Since 1957, the year the Soviet Union sent Sputnik into space, there have been 4,900 space launches. So far so good.
In that time we have put 6,600 satellites in orbit and/or created "an on-orbit population of more than 18,000 tracked objects." Elsewhere, ESA cites "more than 17,000 orbital objects" being tracked and catalogued by the US Space Surveillance Network. And in a third document it s 22,000 objects. But you get the idea: It s a lot.
Of the 6,600 satellites, 3,600 remain in space, and less than a third (about 1,100) are operational.
Space Debris / Welraumschrott (NASA)
Sometimes space debris falls back down to Earth. Sometimes it even survives atmospheric reentry
So of the 18,000 tracked objects "only 1,100 are functional spacecraft," or six percent.
The rest is junk - but no ordinary junk.
It s the fastest junk out there, traveling at speeds between 40,000 and 56,000 km/h (25,000 - 35,000 mph). At those speeds, debris as small as one centimeter can have the force of a hand grenade upon impact with spacecraft.
