Up to 10% risk of returning rocket casualties over 10 years

July 13 () –

Reentry of derelict rocket stages left in orbit has a 6 to 10 percent chance of seriously injure or kill a human being in the next decade.

It is the conclusion of a new study from the University of British Columbia (UBC), whose authors call on governments to take collective action and require that rocket stages be safely guided back to Earth after use, which that could increase the cost of a launch, but potentially save lives.

“Is it permissible to look at loss of human life as just a cost of doing business, or is it something we should try to protect when we can? And that’s the crucial point here: we can protect ourselves against this risk,” he says. it’s a statement the lead author, Dr. Michael Byers, a professor in the UBC department of political science.

When objects like satellites are launched into space, rockets are used, parts of which are often left in orbit. If these leftover rocket stages are in a low enough orbit, they can re-enter the atmosphere in an uncontrolled manner. Most of the material will burn in the atmosphere, but potentially lethal pieces can still fall to the ground.

In the paper, published in Nature Astronomy, the researchers analyzed more than 30 years of data from a public satellite catalog and calculated the potential risk to human life over the next 10 years. given the corresponding rate of uncontrolled re-entries of rocket bodies, their orbits, and human population data.

Using two different methods, they found that current practices have a 6 to 10 percent chance of one or more casualties over the next decade if each re-entry spreads, on average, hazardous debris over an area of ​​10 square meters. While the calculations consider the probability of one or more casualties for people on the ground, Dr. Byers says that they don’t take into account worst-case scenarios, such as a piece of debris hitting a plane in flight.

In addition, they found that the global south disproportionately bears the risk, despite the fact that the main spacefaring nations are located in the north, and rocket bodies are about three times more likely to land in Jakarta latitudes. , Dhaka and Lagos than in New York, Beijing or Moscow. This is due to the distribution of orbits used when launching satellites.

While the risk to any individual is very low, the authors note that hazardous space debris hitting the Earth’s surface is far from unknown. including a 12-meter-long tube from a Long March 5B rocket that hit a village in Côte d’Ivoire in 2020, causing damage to buildings.

And space launches are increasingsays co-author Dr. Aaron Boley, associate professor in the department of physics and astronomy. “Until now, the risks have been assessed by launch, giving people the feeling that the risk is so small that it can be safely ignored. But the cumulative risk is not that small. No casualties or events have yet been reported. with mass casualties, but Do we wait for that moment and then react, particularly when it comes to human lives, or do we try to get ahead of it?”

Technology and mission designs now exist that can largely eliminate this risk, including having restartable engines, as well as additional fuel, to guide rocket bodies safely to remote areas of the ocean. But these measures cost money and there are currently no multilateral agreements that force companies to make these changes, says Dr. Byers.

Examples of such international collective action exist, says Dr. Byers, including the mandatory transition from single to double hulls on oil tankers after the Exxon Valdez spill and the phasing out of chlorofluorocarbons to protect the ozone layer in the 1980s. “Both required some cost to change practice, but in response to new scientific analysis, there was a collective will to do so, and in both cases, they were wholly successful. What we are proposing is entirely feasible and therefore there is no excuse to delay action on this matter.”

Future research directions will include adding to models, which currently assume all rocket bodies are the same size, says co-author Ewan Wright, a doctoral student in interdisciplinary studies.

“While some have the mass of an average washing machine, others have masses of up to 20 tons. This affects the amount of material that burns in the atmosphere, and adding this detail would improve our models. However, very little is known about how the bodies of the rockets are burned, so it is important to have a better understanding of the ‘victim area’ of lethal debris reaching the ground“, said.