Space debris plummeting back to Earth could be a growing problem for aircraft, researchers warned in a new study.
The study authors, all affiliated with Canada's University of British Columbia, said that the probability of space debris hitting an airplane is small, but the risk is rising due to increases in both space debris reentries and flights. The study focused on rocket bodies, which pose a greater risk because of their size.
"While the probability of a strike is low, the consequences could be catastrophic," the researchers said in the study, which was published in Scientific Reports. The study builds on work by the authors presented at the annual International Orbital Debris Conference.
The study authors worked to determine the odds of a rocket body reentering in an airspace. They found that high-density regions immediately around major airports have an 0.8% chance per year of being affected by an uncontrolled reentry, but in "larger but still busy" airspace areas like those found in the northeastern United States or around major cities Asia, the risk rose to 26%.
Space debris and risks to airplanes
The odds of debris striking an aircraft is small, the study authors said, but a collision between a commercial plane and space debris could "lead to mass casualties."
The risk will only grow as space debris remains in orbit, the study authors warned. Trackable objects in orbit have doubled in the last decade. The number of daily flights has also nearly doubled since 2000. Large reentries occur almost weekly, the study authors note.
"Over 2,300 rocket bodies are already in orbit and will eventually reenter in an uncontrolled manner," the study noted. "Airspace authorities will face the challenge of uncontrolled reentries for decades to come."
Closing airspace to avoid collisions
The study authors highlighted an incident in 2022, when a 20-ton rocket body was set to reenter the atmosphere. Predictions the night before the reentry showed that it may land over southern Europe. European space and air traffic industries issued a safety bulletin recommending that authorities implement airspace restrictions. Spanish and French authorities wound up closing part of their airspace. It was the first time airspace was closed for an uncontrolled reentry.
The closures delayed 645 aircraft for about 29 minutes, including diverting some planes that were in the air. Airspaces in Italy, Portugal and Greece that did not close saw an "unexpected increase in air traffic" from diverted flights, creating "different, operational risks" than those posed by the falling space debris.
"The incident highlighted, among other things, a lack of preparation for this eventuality and a lack of harmonization of responses among states," the study authors noted.
The rocket body eventually fell in the Pacific Ocean. The study authors argued that better than closing airspace would be if all rocket missions required controlled reentries, with charted flight paths and scheduled landings. Fewer than 35% of launches currently have controlled reentries, the study authors said.
"Uncontrolled rocket body reentries are a design choice, not a necessity," the study noted. "If controlled reentries were used by all operators, the risks to people and aircraft would be greatly reduced."
