I find this interesting w.r.t your post on 'should shots have mass' Eric, IIRC, which I doubt I do, isn't mass weight X speed or something? Somewhere along the lines of a small object travelling at a high velocity can cause the same damage as a large object traveling at a slow speed...
I'm not sure how you could calculate costs for such but should shot speed be adjustable as well as shot weigh/nrg?
Force = Mass X Acceleration.
Since shots are fired or impact in a single cycle, the acceleration can be though of as the shot's velocity (or relative velocity) per cycle per cycle. So yes, bottom line, faster shots carry more force, more kinetic energy. So do more massive shots. If we gave control of either or both to the firing bot, the amount of accleration (recoil) they expereinced as a result of firing the shot (or the target expereicned as a result of being impacted) would be a function of both.
Costs would be proportional to the mass and speed. For existing shot types, I think I would make the mass implicit as a function of the payload amount (which means things like nrg shots would become less massive as they age) and the cost of firing the shot at the default speed would be the same as is today - the basic user defined per shot cost plus the cost of the payload. There may be loopholes in this approach that require tweaking, but you get the idea.
What I would probably do is make the cost of firing a shot at increasingly higher velocities increase at some seriously exponential rate, perhaps 2^X. Firing a shot at twice the defalut velocity costs four times the per shot cost. Three times the default is 8 times the shot cost and so on.
You could only directly set the mass of a shot for the new shot type, say shots of type -8 by specifying the amount of shell/mass it should contain as payload. Firing shots of this type, even at the default velocity should provide a decent enough recoil for propulsion.
