When two objects collide at orbital speed (closing velocities of
7–14 km/s), neither
survives. The 2009 Iridium-33 / Kosmos-2251 crash produced
~2,300 tracked fragments —
and far more too small to track, each still lethal.
What happens to the debris? It spreads along the original orbital plane into a shell.
Atmospheric drag is the only cleanup, and it is brutally slow at altitude:
| 300 km | reenters and burns up in months |
| 500 km | years — a decade |
| 800 km | decades to centuries |
| 1,000+ km | effectively permanent (millennia) |
Use
⏩ FAST-FORWARD after a cascade to watch this decay statistically, and the
altitude histogram to see which shells die and which stay poisoned.
This sim propagates the catalog on the GPU with
J2 secular precession (orbit planes
drift as in reality), dims satellites crossing Earth's shadow, and — when online — uses
live CelesTrak orbital elements, so the Starlink shells, the ISS and the named debris
clouds are the real ones. Collision ranges are exaggerated so decades unfold in minutes.