>>14265484It's hard to say. The biggest issue is the fact that all near future tech nuclear propulsion systems create significant radiation hazards which are difficult to work around. In the far future things like aneutronic fusion could be possible, and of course in the far future spacecraft will end up being so huge that fully shielding the reactors will be very easy anyway, not to mention that after a certain period of living in enclosed environments surrounded by deadly outdoor conditions people will naturally care less about the "risks" of having nuclear power all over the place.
But anyway, sticking to near future stuff. You've got your nuclear thermal propulsion, nuclear electric propulsion, and on the outside edge of near future you've got pulsed microfission.
Nuclear thermal offers some GREAT advantages for propulsion in situations with low gravity and/or high stage delta V. In a nutshell, the biggest advantage of NTP is that you can design engines to run off of freely available volatiles like water, CO2, nitrogen, methane if you're on Titan, etc. Your propulsive Isp goes down to somewhat below that of the best chemical engines, but you can refill your rocket thousands of times faster with an equal power supply compared to splitting water to make hydrogen propellant or chemical bipropellants for a typical engine. A water propelled nuclear rocket launch vehicle for Callisto could easily be refilled and reflown once a day, offering routine access to orbit as well as high capacity transport of cargo (such as additional propellant) to installations in space, effectively opening up the entire Jovian moon system for exploration and settlement.
The problem with nuclear thermal is that it generates a lot of neutron flux which is both a direct radiation hazard and also activates materials into being radiation sources through neutron absorption.
Nuclear electric propulsion is "ion drives but you ionize your gasses by hitting them with radiation"
