Space Debris and Re-Entry: Growing Risks for Aviation
Debris from SpaceX rocket seen in the skies over the Bahamas
Experts from Kenya’s space agency are investigating a 500kg metallic ring that crashed to Earth on Monday, highlighting growing concerns about space debris amid increasing space traffic. The object fell in Mukuku village, Makueni County, approximately 50km (31 miles) southeast of Nairobi. Fortunately, no injuries were reported. According to the Kenya Space Agency (KSA), preliminary assessments indicate that the debris is a separation ring from a rocket launch vehicle. These components are usually designed to either burn up upon re-entry or land in remote, uninhabited areas like the ocean. Since about 75% of Earth's surface is covered by water and much of the land is uninhabited, the risk to any individual is several orders of magnitude lower than the everyday risks commonly accepted in daily life. However, the growing number of launches by private space companies and the increasing space activities conducted by private actors are gradually raising the overall risk level (1). In an official statement, the KSA confirmed that authorities had secured the area and retrieved the object for further analysis. Officials also commended local villagers for promptly reporting the incident. The agency is working with other entities to determine the exact origin of the debris. There is speculation that it may be from an Ariane 5 L541 rocket or an Atlas/Centaur-167 rocket. However, as of the time of writing, no official statement has been released confirming its owner (2).
The metallic fragment of a space object found in Mukuku Village, Makueni County, Kenya
The risks associated with space debris depend on its mass and terminal velocity upon impact. While small fragments may not pose a significant threat to people on the ground, they can be catastrophic if they collide with an aircraft due to their high velocity. Estimating the number of such fragments remains a challenge, making current risk assessments uncertain and potentially conservative. The Federal Aviation Administration (FAA) has directed SpaceX to conduct a mishap investigation following the loss of its Starship vehicle during launch operations on January 16 from the company's Texas-based Starbase facility. Debris from Starship 7 landed in the Atlantic near the Turks and Caicos Islands, with reports of fragments found on land. Despite precautions, Flight 8 suffered the same fate as its predecessor. In both circumstances, the FAA activated a Debris Response Area, temporarily slowing aircraft outside the affected zone and halting departures where necessary. Several aircraft requested diversions due to low fuel while waiting to avoid the impacted areas. A Debris Response Area is only activated when a space vehicle experiences an anomaly that results in debris falling outside identified aircraft hazard zones. This measure allows the FAA to direct aircraft away from the area and prevent new entries, ensuring airspace safety. Closing airspace as a precautionary measure, as was done in Europe in 2022 due to a reentering Long March 5B rocket, reduces the risk of collision but carries economic consequences and further safety implications due to flight delays and rerouted traffic (3). Authorities face, therefore, a difficult dilemma: closing airspace helps prevent potential debris impacts, but it also disrupts aviation. With more than 2,300 rocket bodies currently in orbit expected to eventually reenter uncontrollably, airspace officials will likely have to navigate this challenge for decades to come. Uncontrolled rocket body reentries are a design choice, not a necessity. With reignitable engines and better mission planning, operators can guide reentries to remote ocean areas. However, fewer than 35% of launches currently follow this controlled approach, and even when they do, these reentry systems can sometimes fail (4). A Falcon 9 rocket’s second stage recently crashed in Poland (5) after an uncontrolled re-entry. Originally, the rocket was intended to perform a controlled descent into an uninhabited region of the Pacific Ocean. However, due to a propulsion anomaly, it instead reentered Earth’s atmosphere over densely populated areas of Europe. While such incidents can occur, they raise important questions about international risk management. Policymakers and aerospace business leaders criticise the FAA (5) for being "risk intolerant," they are not just discussing domestic policy but also the global implications of spaceflight safety. The United States should not have sole authority to decide the acceptable risk level for re-entries, especially when they affect other nations. The country's withdrawal from key international forums, such as the World Health Organization (WHO), the Paris Agreement, and the UN Human Rights Council (UNHRC), raises concerns about its commitment to multilateral cooperation and its reliability in other international bodies. Why isn’t the International Civil Aviation Organization (ICAO) involved in investigating space-related incidents that impact international airspace under its jurisdiction? Furthermore, when an uncontrolled re-entry occurs, public safety must take priority. Instead of silence, there should be a mandatory international alert system to inform governments and the public, ensuring proper precautions can be taken. As space activity increases, international cooperation and transparent risk communication will be crucial in preventing potential disasters. The increasing frequency of uncontrolled space debris reentries is a growing concern. While the probability of debris striking an aircraft is low, the potential consequences of such a collision could be catastrophic. As space activity expands, ensuring better risk mitigation and regulatory oversight will become increasingly urgent.
BIBLIOGRAPHY
1) Ewan Wright, Aaron Boley, Michael Byers, Improving casualty risk estimates for uncontrolled rocket body reentries, JOURNAL OF SPACE ENGINEERING 11 (2024) 74-79
2)The possible reentry in Kenya on 2024 Dec 30
https://planet4589.org/space/misc/kenya/index.html
3) Charlotte Hook, Ewan Wright, Michael Byers, Aaron Boley, Uncontrolled reentries of space objects and aviation safety, ACTA ASTRONAUTICA 222 (2024) 69-80
4) Wright, E., Boley, A. & Byers, M. Airspace closures due to reentering space objects. Sci Rep 15, 2966 (2025). https://doi.org/10.1038/s41598-024-84001-2
https://www.nature.com/articles/s41598-024-84001-2
5) SpaceX rocket debris crashes into Poland
https://www.bbc.com/news/articles/c62z3vxjplpo