New ‘CRASH Clock’ Warns of 2.8-Day Window Before Likely Orbital Collision

Last week, a Chinese spacecraft passed within just 655 feet (200 meters) of a Starlink satellite, narrowly avoiding a collision. According to a new study, such near misses are now happening all the time in low-Earth orbit, and the risk of disaster is shockingly high.

The findings, which have yet to be peer-reviewed, paint a disturbing picture. Based on the number of objects in LEO last June, a sudden loss of collision-avoidance capabilities would likely lead to a catastrophic crash within just 2.8 days.

Such a collision could set off a major debris-generating event that would cause more collisions and potentially initiate the first stage of Kessler syndrome. In this theoretical scenario, LEO becomes so congested with orbiters and debris that collisions between objects trigger a chain reaction, creating exponentially more debris. This would weaken the satellite networks we depend on and render some orbits useless for new satellites and missions.

Kessler syndrome would take decades to fully develop, but we certainly don’t want to set this process in motion if we can still avoid it. Some experts believe it’s already too late.

Countdown to crash

Before you hyperfixate on this worst-case scenario and stare blankly off into the void, let’s talk about the near-term risks. That’s what the authors of this study aimed to quantify with their new metric: the Collision Realization and Significant Harm (CRASH) Clock.

The CRASH clock measures stress on the orbital environment by calculating how long it would take for a catastrophic collision to occur if satellite operators lost the ability to perform avoidance maneuvers or suffered a significant loss of situational awareness.

The researchers’ calculations show the CRASH clock is currently at 2.8 days, a staggering difference from 2018, when it was at 121 days. But that was the pre-megaconstellation era. The number of objects in LEO has ballooned in recent years, jumping from about 13,700 in 2019 to nearly 24,200 in 2025.

According to the study, satellites across all low-Earth-orbit megaconstellations now pass within 0.6 miles (1 kilometer) of one another about every 22 seconds, providing ample opportunity for collisions.

Starlink on the brink

Starlink is by far the largest megaconstellation in LEO. Its 9,300 operational satellites make up the majority of all active Earth-orbiting satellites, according to Harvard University astronomer Jonathan McDowell, who tracks the number of spacecraft in LEO. That number is only going to grow as SpaceX continues to launch thousands of Starlinks each year.

The study found that Starlinks pass within less than 0.6 miles (1 kilometer) of another object every 11 minutes in the densest part of the constellation. Starlinks currently average 41 collision-avoidance maneuvers per satellite per year—that’s one maneuver every 1.8 minutes across the entire megaconstellation.

Historically, the number of collision-avoidance maneuvers made by Starlink has been doubling every six months, the researchers note.

Suddenly losing the ability to perform these maneuvers would be bad. Very bad. While it’s relatively unlikely, the researchers readily outline two situations that could disrupt this capability: a major solar storm and a catastrophic software issue.

It’s essential that we take these risks seriously, not just when it comes to Starlink, but the entire population of maneuverable spacecraft in LEO. The researchers hope the CRASH clock and the “dangerously high collision risks” it calculated encourage decision makers to change the current approach to satellite deployment and operation “immediately.”