[HPsquared]

Orbital inclination is the big one. A polar orbit intersecting an equatorial orbit would have a very high relative velocity.

On the other hand two orbits in the same inclination, with one being slightly eccentric, their relative velocity is much lower.

[wkat4242]

It doesn't matter though. Even if they hit at 0.01% of their orbital velocities, that's still 100km/hr. So it's like a full highway speed car crash. No way two sats colliding will survive that.

And remember the collision speed can range from 0 to 200% of their ground velocities. Getting that close to zero is extremely unlikely.

[bagels]

Two objects at the same inclination can still have very high relative velocity if on different planes.

[HPsquared]

Ah, so like the "phase" of the inclination? orbital plane being a vector quantity (angle between the Earth's rotational axis and the normal vector of the satellite's orbital plane)

[bagels]

Yes. Find a visualization of starlink orbital shells. They are all in one of just a couple inclinations, lots of crossings