For the Earth, the space age began 65 years ago. In October 1957, a Russian rocket launched the first satellite – “Sputnik” – into orbit. Since then there have been 6200 more successful rocket launches.
With their help, 13,100 satellites were transported into space. 8410 of them are still there and around 5700 are still working.
And that’s where we come to the problem: the other 2,700 or so satellites are or will be space junk – which is meticulously counted by the European Space Agency (ESA). The current figures were only collected in mid-May 2022.
“Other typical examples of space debris are disused upper stages of rockets, but an astronaut’s lost tool is also one of them,” says Manuel Metz, astrophysicist at the German Aerospace Center (DLR) and head of the department for space debris research there.
“Numerically, however, the largest contributors are debris from explosions, spacecraft breakup, or in-orbit collisions,” he explains.
More than 31,380 pieces of space debris – based on 630 such “registered events that led to fragmentation” – were last recorded by ESA. This scrap is said to weigh a total of 9,900 tons.
But not all parts are tracked and catalogued. In total, Esa estimates that there are 36,500 pieces of space junk larger than four inches, a million pieces between one and four inches in size, and 130 million objects between one millimeter and one centimeter.
However, at the high speeds at which the parts travel in space, even the smallest pieces become dangerous projectiles. Smaller impacts were common, dramatic collisions are rare.
“The first and only event to date in which two intact spacecraft collided occurred on February 10, 2009. The active American satellite ‘Iridium 33’ collided with the deactivated Russian satellite ‘Cosmos 2251’,” reports Metz. To date, almost 1,700 pieces of debris have been identified that arose from this collision alone.
In addition, there are a large number of small parts that are not recorded. “For space travel – be it for the active satellites or the ‘ISS’ space station – the increasing pollution of near-Earth space represents a not inconsiderable problem,” says the astrophysicist.
“In the worst case, collisions between satellites could trigger a chain reaction that produces more and more pieces of scrap.”
In order to minimize possible damage, disused satellites should be placed in a low-Earth orbit at an altitude of less than 600 kilometers. This is one of the principles for avoiding waste that the Inter Agency Space Debris Coordination Committee (IADC), an association of all space agencies, has agreed on. There they should burn up in the earth’s atmosphere in a good two decades – and no longer cause any damage in space.
Incidentally, Elon Musk’s company Space X has sent more than 2,000 of the currently active satellites into space. They should ensure fast Internet in all regions of the world.
From the outset, however, these “Starlink” satellites fly in a low-earth and waste-avoiding orbit at an altitude of around 550 kilometers. Amazon also wants to launch its own communication satellites into space, but is not as far along as Musk.