A new study by University of British Columbia has found that re-entry of abandoned stages of rockets left in orbit from space launches have a 6 to 10 per cent chance of severely injuring or killing a human being in the next decade if appropriate actions are not taken by governments involved in space launches.
All countries who have been launching satellites need to take collective action and mandate that rocket stages are guided safely back to Earth after their use. While this could increase cost of launch, researchers are of the opinion that such a step has the potential to save lots of lives.
When objects such as satellites are launched into space, they use rockets, parts of which are often left in orbit. If these leftover rocket stages have a low enough orbit, they can re-enter the atmosphere in an uncontrolled way. Most of the material will burn up in the atmosphere, but potentially lethal pieces can still hurtle towards the ground.
In the Nature Astronomy paper, the researchers looked at more than 30 years of data from a public satellite catalogue, and calculated the potential risk to human life over the next 10 years, given the corresponding rate of uncontrolled rocket body re-entries, their orbits, and human population data.
Using two different methods, they found that current practices have a six to 10 per cent chance of one or more casualties over the next decade if each re-entry spreads, on average, dangerous debris over an area of 10 metres squared. While the calculations consider the probability of one or more casualties for people on the ground, Dr. Byers says they do not take into account worst case scenarios, such as a piece of debris striking an airplane in flight. In addition, they found the risk is borne disproportionately by the global south, despite major space-faring nations being located in the north, with rocket bodies being approximately three times more likely to land at the latitudes of Jakarta, Dhaka and Lagos than those of New York, Beijing or Moscow. This is due to the distribution of orbits used when launching satellites.
While the risk to any one individual is very low, the authors note that dangerous debris from space hitting Earth’s surface is far from unheard of, including a 12-metre-long pipe from a Long March 5B rocket that struck a village in the Ivory Coast in 2020, causing damage to buildings. And space launches are increasing, says co-author.