>(and probably feasible)

I personally disagree, a nuclear salt water rocket is literally a continuous explosion and nothing close has been physically built. I think most feasible rockets would be more advanced variations of nuclear thermal rocket.

Ideally a pulsed nuclear thermal rocket, which can significantly amplify the specific impulse of a nuclear thermal rocket by a factor of 2x to 7x (Isp of 2000 s to 7000 s). I think this engine is the most promising next technological development for nuclear spacecraft propulsion because it is an advancement of the already developed and tested nuclear thermal rocket.

https://en.wikipedia.org/wiki/Pulsed_nuclear_thermal_rocket

However, in the far far future, then yes, perhaps the engineering challenges with a nuclear salt water rocket can be addressed we would have torch drives like in The Expanse.