A new study reveals that Earth-orbiting satellites could begin colliding with one another in less than three days during a worst-case emergency, such as an extreme solar storm. This potential cascade of collisions could render low Earth orbit (LEO) unusable. The findings are based on a newly developed metric called the 'Collision Realization And Significant Harm (CRASH) Clock.'
The CRASH Clock indicates that the time until the first potential collision has drastically decreased. In late 2025, the estimated value was approximately 2.8 days, with a 30% probability of a collision within 24 hours of an emergency rendering satellites inoperable. This contrasts sharply with an estimated 128 days in 2018.
This accelerated risk is primarily attributed to the rapid increase in the number of active satellites, particularly 'megaconstellations' like SpaceX's Starlink. As of May 2025, there were at least 11,700 active satellites around Earth, a 485% increase from the roughly 2,000 in LEO at the end of 2018.
While satellite operators typically manage to avoid collisions, a loss of control due to technical glitches, cyber attacks, or significant solar storms would prevent such avoidance. The CRASH Clock models the distribution of spacecraft in LEO to predict the time until the first collision if all spacecraft became inoperable.
Researchers acknowledge that the initial findings, currently in preprint and not yet peer-reviewed, might slightly overestimate the clock's brevity. However, the observed rapid rate of change in these timeframes is considered highly concerning. The CRASH Clock's value is expected to decrease further as more satellites are deployed, continuing a trend of increasing orbital stress.
The most probable trigger for a CRASH Clock scenario is a powerful solar storm, which can disrupt satellite systems with radiation. If satellites remain offline longer than the CRASH Clock's value, multiple collisions could occur, potentially leading to the Kessler Syndrome. This theoretical scenario describes a cascading increase in space junk that could make LEO unsafe for operations. While the timeframe for Kessler Syndrome is uncertain due to numerous variables, experts warn that humanity may be approaching the early stages of an irreversible collision cascade.