A strange, black artefact appeared in a paddock nestled in Australia's Snowy Mountains back in July. It's a place used to raging bushfires, so you could mistake it for a tree turned to cinder. Yet it came from outer space. Some reports suggest it is a stray piece of a SpaceX Dragon capsule that broke up in the Earth's atmosphere upon re-entry. Some of it stands upright after spiking into the Australian soil like a javelin. Clearly you wouldn't want to have been standing there at the time.
More recently, a large chunk of spacecraft thought to be part of China's failed Long March 5B rocket launch crash landed in Borneo.
This is not the first time pieces of space junk have returned to Earth with a bang, but what are chances of it damaging people or property? According to Prof Don Pollacco, director of the University of Warwick’s Centre for Space Domain Awareness, even this event was a rare beast.
“The surface of the Earth is mostly water - the chances of this happening on land is really low,” he says. The chances of anyone being hurt by it? “You'd have a better chance of winning the lottery,” Pollacco says.
It has happened, though, albeit at sea. Five Japanese sailors were injured when wreckage from a Soviet spacecraft hit a freighter off the coast of Siberia back in 1969.
Another hairy moment came in 1977 when a Soviet surveillance satellite crashed into Northern Canada. It carried a nuclear reactor on board and only 0.1 per cent of the hazardous fuel was ever recovered. Some of the radioactive material made it into a lake and the Canadian government eventually received three million Canadian dollars from the Soviets to pay for the clean-up operation.
Dangerous space junk falls may be rare, but that doesn't mean space junk isn't a threat.
“The danger isn't deorbiting and landing on someone,” Pollacco says. “The danger is in damaging other satellites or stopping us launching into space.”
The region immediately around us in space is fast turning into a junkyard. There are tens of thousands of pieces larger than 10 centimetres across up there. For objects smaller than one centimetre across, the tally runs into the hundreds of millions.
Bits of old rocket, parts of defunct satellites and even flecks of paint and frozen fuel. Twelve accidental fragmentation events typically occur in space every year as hardware breaks apart and adds to the growing problem. The tiniest objects can still wreak significant havoc.
“Objects in Low Earth Orbit are moving at 25,000 miles per hour,” says Pollacco. “Even a pea-sized object packs a lot of energy – if it hit something it would disable a satellite. It's something we're going to have to get used to.”
That's because the number of satellites being hurled into space is skyrocketing. Companies like SpaceX and Amazon are launching mega-constellations into Low Earth Orbit to beam down the internet to remote places where traditional underground cables can't reach.
One report estimates that we'll launch 1,700 satellites a year between now and 2030. The rapid expansion of space capabilities comes on the back of the advent of reusable rockets. The cost of getting something into Low Earth Orbit has dropped from around $60,000 per kilogram to just $2,400.
So, what can we do about it? Bodies like the European Space Agency and NASA are advocating debris removal.
“There are a number of companies working on this and running demo missions,” says Pollacco. The plan is to dock with a decommissioned spacecraft and haul it down into Earth's atmosphere to meet a fiery end.
Pollacco sees big problems, though.
“The reality is someone has to pay for this.” He points to a swarm of Russian satellites in a spacecraft graveyard some 800 kilometres above the surface of the Earth. “They weren't decommissioned properly and they're dangerous – they even still contain propellant,” he says. “Is Russia going to pay to remove them? No.”
Even then it's a sticking plaster approach. Removing the thousands of large, dead satellites does nothing about the hundreds of millions of pea-sized satellite killers.
“It's not practical to deorbit those,” Pollacco says. “In the end you just have to know where it all is.”
What's the worst case scenario?
“You create a finer and finer cloud of satellite killing debris that would take decades to deorbit,” Pollacco says. Eventually that could create such an obstacle that it affects our ability to put anything new into space.
“If your risk of collision during launch is above a certain amount then you don't launch – we won't be able to get off the Earth,” he says.
We plan to go back to the Moon later this decade and to Mars in the decades ahead, but we could end up firmly rooted to terra firma.
It seems that space junk falling on our heads may be the least of our problems.
Read more about space junk:
