Hundreds of miles above Earth, thousands of satellites and fragments of debris are racing around the planet at speeds exceeding 17,000 miles per hour. Most of the time, they pass safely by one another, guided by careful planning and constant maneuvering by satellite operators on the ground. But what happens if that choreography suddenly stops?
According to a new study, published on arXiv, the answer may be deeply unsettling: we might have only days before a catastrophic collision becomes likely.
Researchers analyzing the rapidly growing congestion in low Earth orbit (LEO) have introduced a new metric designed to measure just how fragile the orbital environment has become.
Their findings suggest modern satellite operations increasingly resemble a precarious “house of cards,” dependent on near-perfect coordination to prevent disaster.
The study, conducted by researchers from Princeton University, the University of British Columbia, and the University of Regina, proposes what they call the “CRASH Clock”—short for Collision Realization And Significant Harm.
The metric estimates, on average, how long it would take for a serious collision to occur if satellites suddenly stopped maneuvering or if tracking systems temporarily failed.
The results highlight just how dramatically Earth’s orbital environment has changed in only a few years.
“Our calculations show the CRASH Clock is currently 5.5 days, which suggests there is limited time to recover from a widespread disruptive event, such as a solar storm,” the researchers write.
That number marks a stunning shift from conditions before the rise of massive commercial satellite constellations. In 2018, before megaconstellations like Starlink began rapidly populating orbit, the same calculation yielded a CRASH Clock of 164 days—nearly half a year between potential catastrophic collisions under similar assumptions.
Today, that margin has shrunk to less than a week.
The change is largely driven by the explosive growth of satellite megaconstellations, networks composed of thousands—or eventually tens of thousands—of satellites designed to provide global broadband coverage and other services. While these systems bring enormous benefits, they also dramatically increase traffic in low Earth orbit.
Researchers analyzed satellite catalog data from mid-2025 to calculate the density of objects in space at various altitudes. They then estimated how often objects pass dangerously close to one another, assuming that collision-avoidance maneuvers suddenly ceased.
Results showed that in some of the most crowded orbital shells, close approaches within about 0.6 miles (one kilometer) occur roughly every 22 minutes. Across all of low Earth orbit, objects pass within that distance somewhere roughly every 36 seconds.
Those close approaches do not automatically produce collisions. However, they represent moments when operators often must execute avoidance maneuvers to maintain safety. Without those maneuvers, the probability of impact rises dramatically.
And collisions in orbit are uniquely destructive. Satellite collisions typically shatter spacecraft into thousands of high-speed fragments. Those fragments then threaten other satellites, potentially triggering additional collisions—a chain reaction known as the “Kessler Syndrome,” which could render portions of orbit unusable for decades.
The CRASH Clock does not predict that such a runaway cascade is imminent. Instead, it measures how dependent modern space operations have become on constant, precise management.
In practice, satellite operators perform numerous maneuvers to avoid danger. According to industry reports cited in the study, Starlink satellites alone executed more than 144,000 collision-avoidance maneuvers over just six months, from late 2024 to mid-2025.
That works out to roughly one maneuver every two minutes somewhere within the constellation.
These avoidance actions are successful, but they also reveal how little margin for error remains. A software failure, tracking outage, or major space-weather event could quickly overwhelm operators’ ability to respond.
Solar storms present a particularly concerning scenario. Strong geomagnetic events can dramatically increase atmospheric drag, forcing satellites to maneuver unexpectedly while simultaneously degrading tracking accuracy.
During the “Gannon storm” in May 2024, nearly half of all active LEO satellites reportedly had to maneuver within just three days, complicating collision risk calculations across the entire orbital population.
A larger event—like the famousCarrington Event of 1859, which dwarfed modern storms—could create widespread disruption lasting days, exactly the type of scenario where the CRASH Clock becomes critical.
Researchers emphasize that their metric is not meant to provoke alarm but to provide policymakers and operators with a clear, understandable measure of orbital stress. Much like environmental indicators track pollution or climate change, the CRASH Clock offers a way to monitor the health of Earth’s orbital environment over time.
“From a policy standpoint, however, there needs to be discussion concerning whether the Clock threshold should indicate possible or probable collisions,” the researchers write. “ We have highlighted possible collisions not to be alarmists, but to contextualize the stress and demands on space safety.”
The low Earth orbit environment is under pressure in other ways as well. Astronomers increasingly struggle with bright satellite streaks interfering with observations. Spacecraft reentries add metals and other materials to the upper atmosphere. Meanwhile, discarded rocket stages and defunct satellites continue to accumulate, increasing risks both in orbit and during uncontrolled reentries.
Satellite operators themselves have strong incentives to maintain a safe environment. Companies invest heavily in tracking, maneuver planning, and constellation design to minimize risks. However, researchers argue that reliance on flawless operations becomes dangerous as traffic density rises.
Importantly, the CRASH Clock analysis focuses specifically on collision risks among objects operating in low Earth orbit and does not address hazards that arise once satellites leave orbit. That distinction matters because the rapidly expanding satellite population is also driving a surge in spacecraft reentries.
As previously reported by The Debrief, a separate study last year estimated that, on average, roughly one or two Starlink satellites were reentering Earth’s atmosphere each day in 2025, underscoring that congestion in orbit is now coupled with growing activity at the end of satellites’ operational lives.
While most spacecraft burn up before reaching the ground, the increasing frequency of reentries adds another layer of operational and environmental risk beyond the collision scenarios examined by the CRASH Clock.
In effect, humanity’s growing presence in space now demands systems that can tolerate failure and not merely systems that work perfectly under ideal conditions.
The CRASH Clock offers a stark reminder that Earth’s orbital environment is finite. Every satellite placed into orbit consumes part of that resource, and every fragment of debris remains a hazard long after its mission ends.
Researchers conclude that the Clock should be viewed along a spectrum: long collision times indicate a healthy orbital environment, moderate times signal caution, and short times warn of increasing fragility.
At just 5.5 days, today’s value falls squarely in that caution zone.
Ultimately, space has become essential to modern life, supporting everything from GPS navigation and weather forecasting to communications and global commerce. Ensuring that this infrastructure remains sustainable may now depend on recognizing how crowded and vulnerable the space around our planet has become.
“We are already experiencing disruption of astronomy, pollution in the upper atmosphere from increasingly frequent satellite ablation, and increased ground casualty risks,” researchers conclude. “By these safety and pollution metrics, it is clear we have already placed substantial stress on LEO, and changes to our approach are required immediately.”
Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan. Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com