Re: Fusion rocket engines - the gist
Cruise missiles like this are air breathing and so have no real upper bound on reaction mass: as long as you can heat the air you can keep going. Nuclear power therefore good option for this: you use air to cool reactor and also to drive missile, giving you really no limit on range, and thus a specific impulse which is for all useful purposes infinite. Exhaust tends to be a bit radioactiv though. One idea for Pluto was that it could fly around over enemys cities dumping fallout once it had used all its warheads I think.
Biting the hand that feeds IT
