Kessler syndrome is somewhat similar to a nuclear reaction (the math may be similar?): below a critical density, collisions are rare enough that orbital decay m

Kessler syndrome is somewhat similar to a nuclear reaction (the math may be similar?): below a critical density, collisions are rare enough that orbital decay means that the chance of the next collision is ~0. Above that critical density, a collision produces multiple pieces of debris which are then involved in further collisions. The chance of a collision goes up exponentially and the only solution is not launching anything until decay has cleared the orbit.