Brace yourself for a chilling reality: the threat of space junk colliding with airplanes is on the rise, and it's not just a distant concern. Experts are sounding the alarm, warning us of a growing problem that extends beyond Earth's orbit.
Imagine a weekly occurrence where a spacecraft or its remnants plummet back into our atmosphere. Most of these are empty rocket stages, but some are dead satellites whose orbits have finally deteriorated, turning them into human-made meteors. While most disintegrate due to the intense heat and force of high-speed collisions, some debris can survive long enough to rain down, ranging from microscopic particles to entire propellant tanks. And this is where the real danger lies.
The risk of these stray pieces striking an aircraft is small but significant enough to capture the attention of experts. They're now grappling with the challenge of reducing this risk, as the potential consequences are dire.
We've been fortunate so far, but the increasing frequency of space debris re-entering Earth's atmosphere is a cause for concern. As satellite constellations and spacecraft operations become more commonplace, the likelihood of deorbiting space junk will only escalate.
According to a 2025 study by researchers at the University of British Columbia, there's a 26% chance that uncontrolled space debris will pass through some of the world's busiest airspaces within the next year. While the odds of actual impact are low, they're not negligible. By 2030, the chances of a commercial flight encountering falling space debris could be as high as 1 in 1,000, according to a 2020 study.
These odds might not seem daunting, but considering the vast number of planes crisscrossing our skies at any given moment, it's a gamble we can't afford to take lightly. The stakes are high, and the potential outcome is catastrophic. Commercial aircraft carry hundreds of passengers, and even a small piece of debris can cause a disaster, especially when it comes to jet engines.
Benjamin Virgili Bastida, a space debris system engineer at the European Space Agency, puts it into perspective: "Aircraft can be affected by much smaller pieces of debris. It's similar to flying through volcanic ash, where the tiny particles pose a risk." Virgili Bastida and his colleagues have published a paper in the Journal of Space Safety Engineering, highlighting the challenges of deciding when and where to close airspace due to falling space debris.
One notable incident occurred in November 2022 when the core stage of a Chinese Long March 5B rocket re-entered Earth's atmosphere. This was the fourth uncontrolled re-entry of a Long March 5B, and its ground track passed over Spain, leading to a flurry of airspace closures. While the Long March incident was an anomaly due to the rocket's massive size, it serves as a stark reminder of the potential dangers and the need for more precise warnings.
Despite a few close calls and airspace closures in recent years, we've been lucky. However, maintaining this luck without causing air-traffic gridlock requires a multi-pronged approach. Virgili Bastida and his team are investigating the threshold for risk and the appropriate response: "What is the level of risk that warrants action? At what point do we react?"
Other crucial aspects include limiting the amount of debris that reaches the altitudes where most planes fly, improving the accuracy of spacecraft re-entry predictions, and enhancing coordination between space agencies and air traffic controllers. These tasks are complex and challenging.
The uncertainty surrounding uncontrolled satellite re-entries is a significant hurdle. Even during a spacecraft's final orbits, the margin of error allows for several hours, translating to thousands of miles due to the high speeds involved. Air traffic controllers face a difficult choice: take no action and risk lives, or close vast areas of airspace, causing significant delays and economic losses.
For instance, the 2022 Long March 5B incident in Spain resulted in the closure of a 62-mile-wide strip of airspace for about 40 minutes, delaying, canceling, or rerouting more than 300 flights. Yet, the debris only spent about five minutes in the affected airspace, according to Virgili Bastida.
Ian Christensen, a space and aviation analyst at the Secure World Foundation, emphasizes the need for more specific and constrained airspace closures: "There's a desire to narrow down the windows and closures as much as safety allows." Christensen adds that both the FAA and the International Civil Aviation Organization are already working with space launch companies like SpaceX, ULA, and Blue Origin to develop more precise closures for rocket launches, which can be applied to returning debris as well.
To achieve this, space agencies and air traffic controllers need accurate information on when and where spacecraft will re-enter, how much debris will survive intact, and the specific areas of the sky it will fall through. Additionally, they need to assess the threat level posed by the debris to passing aircraft, taking into account factors like size, speed, and aircraft features.
The margin of error is large, in part, due to our limited understanding of the upper edge of the atmosphere, between 62 and 124 miles up. Satellites don't spend much time in this rarefied region, and most are already disintegrating due to the friction of the thin air. Virgili Bastida explains, "There's very little information on this region, so the models are just extrapolated."
To improve predictions, the European Space Agency's upcoming DRACO mission will measure in detail how a small satellite disintegrates during its descent into Earth's upper atmosphere. The goal is to gather data on the spacecraft's trajectory and the precise timing of component failures. DRACO's lead system engineer, Alex Rosenbaum, and his team are fitting the capsule with various materials and sensors to capture this data.
Meanwhile, the Inter-Agency Space Debris Coordination Committee, comprising 13 space agencies, conducts annual Re-Entry Campaigns. Members choose interesting test cases from among the defunct satellites due to re-enter Earth's atmosphere and pool their information and predictions. By comparing actual events with predictions, they refine their models.
The Re-Entry Campaigns and DRACO mission will help improve predictions and guide the design of satellites and rocket stages that disintegrate more completely at high altitudes. But once the data is available, someone will need to make critical decisions.
The key lies in effective communication and coordination between air traffic controllers, national aviation authorities, and space agencies. The Long March incident highlighted the importance of cross-border collaboration, as airspace closures concentrated aircraft into other areas, still under the remaining track.
Building a coordinated response is crucial, and it needs to happen before the next incident. This coordination will likely take the form of standards and guidelines, defining appropriate actions for specific situations. As Christensen puts it, "The aviation world is driven by standards, and we're seeing a lot of activity around standards in the space world as well."
Virgili Bastida remains optimistic, envisioning a future where re-entries are predicted in advance, allowing flight plans to bypass affected areas seamlessly. In the meantime, he assures travelers that the risk of being hit by space debris is extremely low, much lower than any other risk in normal life. "The sky is not going to fall on your head," he says, "but we're working on ways to make it even safer."
As we navigate this complex issue, it's a reminder that space exploration comes with its challenges and responsibilities. The collaboration between experts and agencies is crucial to ensuring the safety of air travel and managing the risks posed by space debris.
