A new study led by the University of British Columbia (UBC) has found that the re-entry of abandoned stages of rockets left in orbit from space launches have a six to ten percent chance of severely injuring or even killing a human being over the next decade. According to the experts, governments need to take collective action and mandate that rocket stages are guided back to Earth safely after their use. While this would increase the costs of launches, it could potentially save lives.
“Is it permissible to regard the loss of human life as just a cost of doing business, or is it something that we should seek to protect when we can? And that’s the crucial point here: we can protect against this risk,” said study lead author Michael Byers, an expert in Political Science at UBC.
When objects such as satellites are launched into space, they use rockets, parts of which are of frequently left unattended in orbit. If these leftovers have a low enough orbit, they can re-enter the Earth’s atmosphere in an uncontrolled way, with potentially lethal pieces hurtling toward the ground.
By using over 30 years of data from a public satellite catalogue, the scientists calculated the potential risk to human life over the next decade of uncontrolled rocket body re-entries, and found that current practices have a six to ten percent chance of one or more casualties, if each re-entry spreads, on average, dangerous debris over a ten meters squared area.
Although major space-faring nations are located in the north, this risk will be borne disproportionately by the global south, with rocket bodies being about three times more likely to land in Jakarta, Lagos, or Dhaka than New York, Moscow, or Beijing, due to the distribution of orbits used when launching satellites.
“Risks have been evaluated on a per-launch basis so far, giving people the sense that the risk is so small that it can safely be ignored,” said study co-author Aaron Boley, an associate professor of Physics and Astronomy at UBC. “But the cumulative risk is not that small. There have been no reported casualties yet, and no mass casualty event, but do we wait for that moment and then react, particularly when it involves human life, or do we try and get in front of it?”
While technology and mission designs which can largely remove these risks already exist – such as having engines that reignite, as well as extra fuel to guide the rocket parts safely to remote ocean areas – they are quite expensive. Currently, there are no multilateral agreements mandating companies to make such changes.
“Those national governments whose populations are being put at risk should demand that major spacefaring states act, together, to mandate controlled rocket re-entries, create meaningful consequences for non-compliance, and thus eliminate the risks for everyone,” the authors concluded.
The study is published in the journal Nature Astronomy.