Space junk, not meteorites, remains biggest threat to spacecraft

tech.hindustantimes.com:

Dodging the kind of meteorite strike that forced Russia to plan a space station rescue mission is nearly impossible, yet the greater threat to spacecraft is actually the man-made debris in orbit, experts say.

Russian announced on Wednesday a February mission to the International Space Station to pick up crew members left stranded after a strike damaged the capsule that was to take them home.

Didier Schmitt, the European Space Agency's head of human and robotic exploration, said it was not rare for tiny meteorites to hit the space station.

The micrometeorites can be travelling at speeds from 10 to 30 kilometres (6-18 miles) a second -- "much faster than a shotgun bullet," Schmitt said.

That is why, when the space station's large observation window is not in use, it is shuttered with "very, very thick layers of protective materials," he said.

The small meteorites come from so far away in the distant universe and at such high speeds that they cannot realistically be tracked, he said.

But space agencies do monitor known meteor showers, such as one expected in early August.

NASA has previously said that the Geminid meteor shower in December was unlikely to have hit the Soyuz capsule, as the hull was penetrated from a different direction.

While meteorites might sound scary, the biggest threat to spacecraft is believed to be from orbital debris -- disused satellites and other human-made objects spinning around Earth known as "space junk".

That is because colliding space junk creates even more debris, leading to a "runaway chain reaction" of cascading collisions littering orbit with tiny, dangerous objects, NASA says.

There are half a million pieces of debris the size of a marble and 100 million pieces measuring around one millimetre in