p = 300 - 0.125d

p = energy from detonation (in megatons of TNT)
d = distance traveled in tens of kilometres.

Because of d being 10*distance traveled, shorter range battles will produce more explosive effect.
This formula can be used to show the amount of explosive energy lost over time.
If d < 0.05 (0.5 km distance), one third of p is directed at the firing ship.