A new research metric called the "Collision Realization And Significant Harm (CRASH) Clock" estimates that a catastrophic satellite collision could occur in less than three days if all spacecraft in low Earth orbit (LEO) simultaneously lost the ability to perform collision avoidance maneuvers. The findings highlight an increased risk driven by the rapid growth of satellite constellations, though the research has not yet completed peer review.
Key Findings
The CRASH Clock metric models the time until the first collision in LEO if all spacecraft become inoperable and unable to maneuver. According to the study:
As of late 2025, the estimated CRASH Clock value is approximately 2.8 days.
- There is a 30% probability of a major collision occurring within the first 24 hours of a control failure.
- In 2018, the same scenario would have allowed an estimated 121 to 128 days.
The study was led by Sarah Thiele, formerly at the University of British Columbia and now at Princeton University, and has been published on the preprint server arXiv.
Contributing Factors
The decrease in estimated time is attributed to the significant increase in the number of operational satellites. As of May 2025, there were at least 11,700 active satellites in LEO. This represents a 485% increase from the approximately 2,000 satellites in orbit at the end of 2018.
The rise is largely due to "megaconstellations" such as SpaceX's Starlink. Researchers note that in LEO, close approaches (within 1 kilometer) between satellites occur approximately every 22 seconds across all megaconstellations. Within the Starlink constellation alone, these close approaches occur every 11 minutes, and each Starlink satellite performs an average of 41 course corrections per year.
Potential Triggers
The study identifies several scenarios that could lead to a loss of collision avoidance capability:
- Solar storms: These can heat and expand Earth's upper atmosphere, increasing drag on satellites and disrupting tracking accuracy. Storms can also interfere with or disable satellite navigation and communication systems. The May 2024 Gannon Storm forced more than half of all operational LEO satellites to expend fuel for orbital adjustments.
- Technical glitches or cyber attacks: Any event that prevents command and control of satellites would halt active collision avoidance.
Operators typically receive one to two days of warning before a solar storm. The study notes that extreme space weather events comparable to the 1859 Carrington Event could cause disruptions lasting longer than two days.
Context and Limitations
The researchers acknowledge that the initial findings may slightly overestimate the speed of the risk, as the work is currently in preprint and has not yet been peer-reviewed. However, they describe the observed rate of change in the CRASH Clock's value as concerning and expect the metric to decrease further as more satellites are deployed.
Kessler Syndrome
If satellites remain inoperable for longer than the CRASH Clock's estimated time, multiple collisions could occur. This could theoretically lead to the Kessler Syndrome, a scenario in which cascading collisions generate enough debris to make LEO unsafe for future operations. The timeframe for such an event remains uncertain due to numerous variables.