When rockets launch into space, many will drop parts no longer needed to complete their mission. Most of these parts are abandoned, and they eventually return to Earth in an uncontrolled way. In the past, the risk these falling rocket pieces pose to humans has been treated as negligible; so far, no deaths from falling rocket bodies have been documented. But rocket launches are increasing. The year 2021 saw 135 successful rocket launches—the most in history.
In a new study published in Nature Astronomy, researchers estimate that if current practices continue, there’s about a 10 percent chance of one or more casualties in the next decade from a falling rocket body.
“It’s a statistically low risk, but it’s not negligible, and it’s increasing — and it’s totally avoidable,” Michael Byers, lead author and a professor of political science at the University of British Columbia, tells The Verge’s Justine Calma. “So, should we take available measures to eliminate casualty risks? I think the answer should be yes.”
To make their calculation, researchers examined 30 years of satellite data. They found that during that time period, more than 1,500 rocket bodies deorbited—or departed deliberately from orbit. Of those, more than 70 percent deorbited in an uncontrolled manner.
Where rocket bodies fall can be difficult to predict, because there are so many variables at play, reports Jackson Ryan for CNET. But researchers found that those living in the Global South face more of a risk, per the paper. Rocket bodies are three times more likely to land at the latitudes of Jakarta, Dhaka and Lagos than at the latitudes of New York, Beijing or Moscow.
“We think this has to stop,” Byers tells New Scientist’s Jonathan O’Callaghan. “We have modern rockets that can avoid uncontrolled re-entries, rather than playing Russian roulette with the Ivory Coast and India. Who’s to say the next piece won’t come down in central Mumbai?”
In addition to the danger they pose upon reentry, rocket bodies left orbiting in space can be a collision hazard for satellites, and they can explode from fuel left on board, per the paper. In 2020, the researchers estimated that more than 60 percent of launches resulted in a rocket body being left in orbit.
“The only way to make sure your rocket isn’t going to blow up is to de-orbit it,” Jonathan McDowell at the Center for Astrophysics, Harvard and Smithsonian tells New Scientist.
The authors argue that though the technology exists to return rocket bodies safely, launching sites and companies are reluctant to take on the costs associated with making those changes.
“This problem is solvable with political will and current technology,” Byers tells Vice’s Chloe Xiang. “Our paper is just one piece of this larger puzzle as to how we achieve the sustainable development of space.”