**Quote from Mal on 11/09/10 at 19:05:37:**I was thinking that if there was a away to calculate the critical collisional velocity (based on certain assumptions, I guess) then if a collision happens it could be flagged as either disruptive or accretional - if it's disruptive then both objects are deleted from the system, but if it's collisional then both objects are merged instead and now have a mass equal to the sum of the two components and an orbit determined by the collisional parameters of the two bodies.

The latter is how it works now. I don't know how to compute the critical velocity. I imagine that the energy lost in the collision would need to leave the objects with velocities less than escape velocity. A lot might depend on whether or not it was a glancing blow, or a head-on collision. If you can figure out a formula, I could try to incorporate it.