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In mid-October, an unidentified object shattered the windshield of a crowded Boeing 737 flying at 36,000 feet over Utah, compelling the pilots to make an emergency landing. The online community was abuzz with theories that the aircraft had been struck by a fragment of space debris. The exact nature of what hit the plane remains unclear—most likely a relic of a weather balloon—but it seems the internet’s conjectures weren’t entirely unfounded.
This is because, while the likelihood of flights encountering space junk is still low, it is indeed on the rise.
Approximately three fragments of outdated space apparatus—obsolete rockets and inactive satellites—enter Earth’s atmosphere daily, as estimated by the European Space Agency. By the mid-2030s, this number could swell into the dozens. The rise correlates with the increasing number of satellites orbiting the Earth. Presently, around 12,900 functioning satellites are in orbit. Within a decade, it’s predicted there could be 100,000, based on analyst projections.
To reduce the potential for collisions in orbit, operators maneuver aging satellites to incinerate upon reentry into Earth’s atmosphere. However, the mechanics of this reentry phase are not fully comprehended, and the amount of debris that burns up versus what survives to reach the surface is uncertain.
“The frequency of such reentry incidents is on the rise,” remarks Richard Ocaya, a physics professor at the University of Free State in South Africa and a coauthor of a recent research paper discussing space debris risk. “We’re anticipating an exponential increase in the next few years.”
Up until now, space debris hasn’t caused any injuries to individuals—either airborne or terrestrial. Nonetheless, several near misses have been documented in recent years. In March of the previous year, a 0.7-kilogram metal fragment penetrated the roof of a residence in Florida. This object was later confirmed to be a remnant of a battery pallet discarded from the International Space Station. At the time of the incident, the homeowner’s 19-year-old son was in an adjacent room.
Additionally, in February of this year, a 1.5-meter-long piece of SpaceX’s Falcon 9 rocket landed near a warehouse outside Poland’s fifth-largest city, Poznan. Another fragment was discovered in a nearby woodland. A month later, a 2.5-kilogram part of a Starlink satellite plummeted onto a farm in Saskatchewan, Canada. Other occurrences have been reported in Australia and Africa. Many additional incidents may remain completely unnoticed.
“If you stumbled upon a pile of burned electronics in a forest, your first assumption wouldn’t be that it originated from outer space,” says James Beck, the director of Belstead Research, a space engineering research firm based in the UK. He cautions that our understanding of the hazards posed by space debris strikes is not comprehensive and that the risks might be significantly higher than what satellite operators admit.
For instance, SpaceX, operator of the largest mega-constellation, Starlink, asserts that its satellites are “engineered for demise” and fully incinerate upon reentry and descent through the atmosphere.
However, Beck, who has conducted numerous wind tunnel experiments using satellite replicas to simulate atmospheric conditions, claims the findings of these tests raise skepticism. Certain satellite components are constructed from resilient materials like titanium and specialized alloy composites that do not melt, even under the exceedingly high temperatures encountered during hypersonic atmospheric descent.
“We have collaborated with small-satellite manufacturers, and essentially, their primary challenge is the tanks survive,” Beck states. “For larger satellites—approximately 800 kilograms—we might anticipate seeing two or three remnants touchdown.”
Quantifying the threat posed by space debris can be complicated. The International Civil Aviation Organization (ICAO) notified MIT Technology Review that “the swift increase in satellite launches poses a novel challenge” to aviation safety, one that “cannot be measured with the same accuracy as more recognized risks.”
Nonetheless, the Federal Aviation Administration has calculated some initial figures regarding the risks to flights: In a 2023 evaluation, the FAA estimated that by 2035, the chance that one aircraft annually will endure a severe space debris impact stands at approximately 7 in 10,000. Such an event would either obliterate the aircraft instantly or result in a swift drop in cabin pressure, endangering everyone on board.
The risk to humans on the ground will be significantly greater. Aaron Boley, an associate professor of astronomy and a researcher focused on space debris at the University of British Columbia, Canada, mentions that if megaconstellation satellites “don’t completely disintegrate,” the possibility of a single human fatality or injury due to a space debris impact on land could rise to about 10% annually by 2035. This could imply a better than even chance that someone on Earth will be struck by space debris approximately every decade. In its report, the FAA estimated the odds even higher with similar assumptions, predicting that “one individual on the planet would likely be harmed or killed every two years.”
Experts are beginning to deliberate on how they might integrate space debris considerations into their aviation safety protocols. For instance, the German space situational awareness company Okapi Orbits, in collaboration with the German Aerospace Center and the European Organization for the Safety of Air Navigation (Eurocontrol), is investigating methods to modify air traffic management systems so that pilots and air traffic controllers can receive timely and precise warnings about potential threats from space debris.
However, forecasting the trajectory of space debris is also a difficult task. Recent advancements in AI have facilitated improved predictions of the routes of space objects in the vacuum, potentially lowering the chances of orbital collisions. Nevertheless, thus far, these algorithms cannot adequately account for the effects of the gradually thickening atmosphere encountered by space junk during reentry. Radar and telescopic monitoring can assist, but the precise impact location becomes apparent only with very brief advance notice.
“Even with highly accurate models, numerous variables are involved, making it difficult to identify a very precise reentry spot,” remarks Njord Eggen, a data analyst at Okapi Orbits. Space debris makes a complete orbit around the planet every hour and a half while in low Earth orbit, he points out, “so even with uncertainties spanning around 10 minutes, that can lead to significant ramifications regarding where it might land.”
For aviation companies, the challenge is not solely the risk of a potential impact, as disastrous as it could be. To prevent incidents, authorities are likely to temporarily restrict airspace in vulnerable areas, leading to delays and incurring costs. Boley and his associates published a study earlier this year estimating that busy aerospace regions such as northern Europe or the northeastern United States already face about a 26% annual probability of experiencing at least one disruption resulting from the reentry of a significant space debris object. Once all proposed constellations are fully operational, airspace closures due to space debris threats could become nearly as frequent as those caused by adverse weather conditions.
Given the unreliability of current reentry forecasts, many of these closures may prove to be unwarranted.
For instance, when a 21-metric-ton Chinese Long March mega-rocket was descending to Earth in 2022, predictions indicated that its debris might scatter over Spain and parts of France. Ultimately, the rocket impacted the Pacific Ocean. However, the 30-minute airspace restriction over southern Europe postponed and rerouted hundreds of flights.
In the meantime, international bodies are urging satellite operators and launch service providers to deorbit large satellites and rocket components in a controlled manner whenever feasible, by skillfully maneuvering them into remote ocean areas with leftover fuel.
The European Space Agency estimates that only about half of the rocket bodies reentering the atmosphere do so in a controlled manner.
Additionally, there are roughly 2,300 obsolete and uncontrollable rocket bodies still in orbit, gradually spiraling toward Earth without any means for operators to direct them safely into the sea.
“There is sufficient debris up there such that even if we change our practices, we will still witness all those rocket bodies eventually reenter,” says Boley. “While the chance of space debris colliding with an aircraft is minimal, the likelihood that debris will disperse and descend over heavily-trafficked airspace is not insignificant. That scenario is actually rather probable.”
