In 1978, NASA researcher Donald Kessler and his colleagues published a paper titled “Collision frequency of artificial satellites: The creation of a debris belt.”
The paper laid down a grim warning: a single collision between satellites that would escalate into a series of followup accidents, “each of which would increase the probability of further collisions, leading to the growth of a belt of debris around the Earth.”
“Under certain conditions, the belt could begin to form within this century and could be a significant problem during the next century,” the prescient paper warned.
Such a catastrophic series of cascading events, has since been dubbed “Kessler syndrome.” The term highlights the considerable risks of littering our planet’s orbit with many thousands of human-made objects, including multiple megaconstellations of satellites, as well as all the junk that gets left behind after they’re launched and decommissioned.
Not only does it put astronauts at risk, but Kessler syndrome could also greatly complicate future space exploration efforts by turning the planet’s orbit into a whirling vortex of death.
Now, an international team of researchers from Princeton University, the University of British Columbia, and the University of Regina, has attempted to quantify this risk by coming up with a new metric, called the “Collision Realization and Significant Harm (CRASH) Clock.”
“There is substantial potential for current or planned actions in orbit to cause serious degradation of the orbital environment or lead to catastrophic outcomes, highlighting the urgent need to find better ways to quantify stress on the orbital environment,” they wrote in a yet-to-be-peer-reviewed paper, first spotted by Gizmodo. “Here we propose a new metric, the CRASH Clock, that measures such stress in terms of the time it takes for a catastrophic collision to occur if there are no collision avoidance maneuvers or there is a severe loss in situational awareness.”
In the case of an extremely powerful solar storm shutting down satellite communications, or a different kind of “widespread disruptive event,” the researchers warn that it could take a mere 2.8 days for a collision to take place.
Put differently, if satellites were to suddenly lose their ability to track and avoid other objects in orbit, it would take less than three days for a potentially catastrophic crash to occur.
Such an event may sound implausible, but the researchers pointed out that countless satellites had to adjust their orbits following a strong solar storm in May 2024. The ensuing chaotic movements made “collision avoidance maneuvers extremely uncertain.”
The risks were considerably lower before the “megaconstellation era,” with a CRASH Clock of 121 days or around four months in 2018, a mere seven years ago,” the researchers concluded.
“While collisional cascades can take decades to centuries to develop, a single collision could create substantial stress on the orbital environment immediately, even if it does not lead to a runaway,” the paper reads.
In other words, it would be like watching a trainwreck in slow-motion.
“In the short term, a major collision is more akin to the Exxon Valdez oil spill disaster than a Hollywood-style immediate end of operations in orbit,” the researchers write. “Indeed, satellite operations could continue after a major collision, but would have different operating parameters, including a higher risk of collision damage.”
It’s true: the number of satellites being sent into orbit has skyrocketed since 2018, as companies race to build out enormous networks hundreds of miles above the surface. According to a recent study, the number of objects in low-Earth orbit almost doubled from 13,700 in 2019 to well over 24,000 in 2025.
For now, the main culprit is Elon Musk’s SpaceX. In October, the firm passed a major milestone of having launched 10,000 Starlink satellites. But thanks to their shelf life, the company is losing one to two satellites per day. As of October 30, the company has around 9,000 functioning satellites in orbit, representing over 60 percent of all active satellites currently orbiting the Earth.
While they’re designed to burn up completely during reentry, experts still worry that operating such enormous constellations could eventually lead to collisions.
Coincidentally, just today SpaceX admitted that it had lost contact with a Starlink satellite following a mishap, highlighting the increased dangers of a collision.
“The satellite is largely intact, tumbling, and will reenter the Earth’s atmosphere and fully demise within weeks,” the company tweeted. “The satellite’s current trajectory will place it below the International Space Station, posing no risk to the orbiting lab or its crew.”
While it has gained a considerable lead, SpaceX is only one of several players working on orbital constellations. Competitors including Amazon and the state-backed China Aerospace Science and Industry Corporation are looking to launch their own broadband constellations as well, meaning that the number of objects orbiting our planet is expected to rise exponentially over the coming years.
And it’s not just a massive increase in the risk of a potentially disastrous collision that we have to worry about. Experts have already warned that the constellations are proving to be a major disruption to astronomical observations. The many satellites could also be releasing harmful pollutants such as aluminum oxides while burning up during reentry, damaging the Earth’s upper atmosphere and ozone layer, leading experts to call for increased oversight and tighter rules.
More on space debris: Space Junk Now Almost Constantly Crashing Down to Earth
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