[prestonh]

I havent researched the orbital dynamics much here, but wouldnt it be possible for the satellite fragments resulting from a collision at orbital speeds to have much greater speeds, possibly ending up in elliptical orbits with lower total drag? Seems like just waiting for orbits to decay after a Kessler syndrome like event wouldnt be feasible.

[jdsully]

An elliptical orbit would require the perigee to be even closer to the earth further increasing drag.

It is possible for small fragments to potentially be moved to higher orbits (with counter balancing mass being moved lower) But the conservation of momentum prevents the vast majority of fragments from suffering this fate.

Baring exceptionally bad luck a collision in LEO would usually decrease the time before the orbit decays. Remember a debris field has more surface area than an intact satellite.

[marcosdumay]

Yes, it is possible. If you get an explosion, many fragments will be in an elliptical orbit where they can stay longer than on LEO. But there is a trade-off here, the time during what a fragment is dangerous is exactly the same time it is in a high drag region, so if it's not feasible to wait for it to fall down, it is also not really dangerous either.