Every object in the shell orbits Earth on its own inclined circular path. Collision risk grows with the square of object count — twice as many tracked objects means roughly four times the chance of a collision per unit time, because every object is a potential target for every other object. That's the mechanism behind the Kessler syndrome: each collision doesn't just remove two objects, it fragments them into several new debris pieces, which raises N further and makes the next collision more likely still.
In Active Removal mode, a chaser spacecraft launches on a fixed schedule, rendezvouses with whichever tracked debris object currently poses the greatest risk (its size, i.e. cross-section), captures it and de-orbits it. Removing the single most dangerous object before it can fragment holds N — and therefore the collision rate — roughly flat instead of letting it run away.
- Satellites (large, colored) — start intact; a hit destroys them and scatters debris.
- Debris (small, gray) — every collision, satellite or debris, produces 4-9 new fragments.
- Collision rate is measured over the trailing simulated year.