In May 2021, a hole was found in a robotic arm aboard
the International Space Station (ISS). The suspected culprit was a
piece of rogue space junk. While thankfully no astronauts were
injured, it has re-focussed attention on the growing problem of
orbital debris.
How did we get here?
It’s easy to forget that just seven decades ago the Moon
was the only thing orbiting the Earth. On 1 January 2021 there
were 6,542 satellites in orbit. Tellingly, only just over half of
them were active. That’s a lot of useless metal careering around
the planet at 28,000 kph — ten times faster than a bullet.
How bad is the problem?
Very bad and getting worse. Estimates suggest there are
currently half a million pieces of debris the size of a marble or
larger and 100 million pieces of debris above one millimeter
across. Yet only 27,000 pieces are actively tracked by the US
Department of Defense.
What is Kessler syndrome?
It’s a catastrophic chain of events in which a satellite is
shattered by a piece of space junk (or a collision with another
satellite) and the resulting debris destroys more satellites creating
more junk and so on in a never-ending cascade. It’s a domino
effect – one piece falls and then takes the rest with it – and is
named after NASA scientist Donald Kessler, who outlined the
dangers back in 1978.
What can we do about it?
Better regulation of new launches would help, as right
now it’s a bit of a free-for-all. There are existing regulations in
place to try and mitigate the dangers, such as a 25-year de-orbit
rule for missions in low-Earth orbit. However, ESA’s Space
Debris Environment Report says that less than 60 per cent of
those flying in low-Earth orbit currently stick to the rules.
Colin Stuart. Space Junk: Is it a disaster waiting to happen?
Internet: <www.sciencefocus.com> (adapted).