[Wuli]

Water weighs a lot (about 8.3 lbs per gallon), could it add to the amount of thrust needed to move and maneuver? There must be fuels with as great or greater energy capacity than water and less weight.

How many grams of Uranium would it take to power a small reactor to power a space ship for years? Would it’s reactor weigh more than all the weight needed for other fuels?

Our modern navies seem to think, for large ocean going vessels - aircraft carriers - and vessels with trips that last a very long time - strategic submarines, that nuclear power is the best? Why would space travel be any different?

[Svartalfiar]

Our modern navies seem to think, for large ocean going vessels - aircraft carriers - and vessels with trips that last a very long time - strategic submarines, that nuclear power is the best? Why would space travel be any different?

Nuclear power on a sea-faring vessel uses water (steam) to convert the radiation energy into mechanical energy, turning a propeller in the water. If you were to use a nuclear reactor in space, how are you going to change that energy into something you can use for thrust?

[thackney]

Turning a screw outside a ship in the vacuum of space isn't going to move anything.

Propulsion in space requires the ejection of mass for an equal force in the opposite direction. Or you can capture moving mass and use that momentum.

There was even some speculation of dropping nuclear weapons out the tail and using a shield to let it push the ship.