In 2018, low Earth orbit still had months of margin: if satellites stopped dodging one another, researchers estimate it could take 164 days before a catastrophic collision. By 2025, after the rise of megaconstellations, that margin had collapsed to just 5.5 days.

The most important number in low Earth orbit may not be the number of satellites overhead. It may be the amount of time left if the system that keeps them apart suddenly stops working. Researchers have proposed a CRASH Clock metric estimating orbital collision recovery margins. In 2018, if all satellite collision avoidance systems failed, approximately 164 days would elapse before a catastrophic collision cascade. By 2025, following the deployment of megaconstellations with thousands of satellites, this margin has compressed to just 5.5 days, indicating severely reduced orbital sustainability and increased collision risk.