Orbital re-entries of human-made space objects: Drawbacks for the upper atmosphere and the safety of people

The controlled and uncontrolled orbital re-entries occurred from 2010 to 2023 were reviewed. Excluding five Space Shuttle orbiters, the total mass re-entered into the atmosphere exceeded 4400 metric tons. In the five-year period 2019-2023, controlled re-entries accounted for nearly 62 % of the returned mass, including 31 % from Falcon 9 second stages alone, while uncontrolled re-entries of intact objects and large debris were responsible for the remaining 38 %. In 2023, the orbital re-entry mass dispersed as gas and particulate in the upper atmosphere was close to 600 metric tons.

The ground casualty probability associated with the uncontrolled re-entry of satellites, orbital stages and large debris varied, on an annual basis, from 0.8 % in 2010 to 3.5 % in 2023, assuming the complete demise of all objects of less than 300 kg. In 2023, 70 % of the casualty probability was associated with orbital stages, 20 % with satellites and 10 % with large fragments.