A recent incident involving a Boeing 737, which had its windshield cracked while flying at 36,000 feet over Utah, has reignited discussions about the risk of space debris affecting commercial flights. The aircraft was forced to make an emergency landing, and while it is suspected that the impact was caused by a remnant of a weather balloon, it underscores a growing concern in aviation safety regarding space junk.
While the probability of a plane being struck by space debris remains low, the risk is increasing. According to estimates from the European Space Agency, approximately three pieces of old space equipment, including defunct satellites and used rockets, re-enter the Earth’s atmosphere each day. Projections suggest that by the mid-2030s, this number may rise significantly due to the expanding number of satellites in orbit.
Currently, there are around 12,900 active satellites orbiting Earth, a number expected to swell to 100,000 within the next decade. To mitigate the risk of collisions, satellite operators are encouraged to direct aging satellites to burn up upon re-entry. However, the physics involved in this process is not fully understood, leading to uncertainty about how much debris survives the descent.
“The number of such landfall events is increasing,” noted Richard Ocaya, a professor of physics at the University of Free State in South Africa. He co-authored a paper examining the risks associated with space debris and expressed concern about a potential exponential increase in such incidents in the coming years.
Despite no reported injuries from space debris strikes to date, there have been alarming close calls. In March 2022, a 0.7-kilogram piece of metal penetrated the roof of a Florida home, confirmed to be a remnant from the International Space Station. Fortunately, no one was hurt, but the incident highlights the latent dangers posed by space debris.
In February 2023, a 1.5-meter fragment of SpaceX’s Falcon 9 rocket crashed near Poznan, Poland, while another piece weighing 2.5 kilograms fell on a farm in Saskatchewan, Canada. Similar incidents have occurred in Australia and Africa, with many strikes going unnoticed due to their low profile.
As James Beck, director of Belstead Research, pointed out, many people may not immediately associate burnt electronics found in forests with space debris. He emphasized that the risks might be underestimated, particularly by satellite operators who claim their devices are designed to disintegrate upon atmospheric re-entry.
The International Civil Aviation Organization (ICAO) acknowledges that the rapid expansion of satellite deployments presents challenges for aviation safety that cannot be quantified as precisely as traditional flight hazards. The Federal Aviation Administration (FAA) has indicated that by 2035, there may be a 7 in 10,000 chance that an aircraft will experience a catastrophic collision with space debris, which could lead to an immediate loss of air pressure and endanger all onboard.
The risk to people on the ground is even more significant. Aaron Boley, an associate professor at the University of British Columbia, estimates that if satellites do not completely disintegrate upon re-entry, there could be a 10% annual chance of a human being injured or killed due to space debris by 2035. The FAA’s analysis suggests that the likelihood of one person being harmed by falling debris could rise to every two years.
In response to these growing threats, companies like Okapi Orbits are working with the German Aerospace Center and Eurocontrol to improve air traffic control systems. The goal is to provide real-time alerts to pilots and air traffic controllers regarding potential space debris hazards.
However, accurately predicting the path of space debris remains a challenge. Although artificial intelligence has improved trajectory predictions, the algorithms struggle to account for atmospheric effects that alter the debris’s descent. As Njord Eggen, a data analyst at Okapi Orbits, noted, even minor uncertainties in predicting the re-entry trajectory can lead to significant consequences for potential impact sites.
For aviation authorities, the implications are not limited to the potential for catastrophic strikes. To prevent accidents, airspace closures may become necessary in regions at risk, resulting in costly delays. Boley and colleagues previously estimated that busy airspace areas, such as northern Europe and the northeastern United States, currently face a 26% chance each year of experiencing disruptions due to space debris re-entries.
As satellite constellations become more prevalent, space debris hazards may become as common a reason for airspace closures as adverse weather conditions. The unpredictability of current re-entry predictions can lead to unnecessary airspace restrictions. For instance, when a 21-metric-ton Chinese Long March rocket was re-entering the atmosphere in 2022, predictions suggested it would scatter debris over parts of Spain and France. Ultimately, the rocket landed safely in the Pacific Ocean, but the precautionary airspace closure disrupted hundreds of flights.
International regulators are advocating for satellite operators to manage the end-of-life processes of large satellites and rocket bodies more effectively. The European Space Agency estimates that only about half of the rocket bodies re-entering the atmosphere do so in a controlled manner. Approximately 2,300 old rocket bodies remain in orbit, gradually descending without the means to ensure safe re-entry.
“There’s enough material up there that even if we change our practices, we will still have all those rocket bodies eventually re-enter,” Boley pointed out. While the probability of a space debris collision with an aircraft is relatively low, the likelihood of debris falling over busy airspace is significantly higher. The urgent need for effective strategies to manage and mitigate space debris has never been clearer.
