Change the mass of your ship/missile to increase/decrease the chance to intercept.
Use gravygravity from nearby objects to aid your acceleration and hinder your enemies. a)This may require being able to predict the enemiesenemy's most likely path/course of action.
Defensive positioning. Place your forces in such a way that even with the lower thrust there is no incoming vector that could not be intercepted before planet fall.
Use stealth to hide your forces and only launch intercept forces when the target is within the threat envelope.
