For explosion you want a chain reaction that consumes your entire piece of U-235.

fission of uranium-235 (U-235) can be represented as follows: U₂₃₅ + n₁ → Ba₁₄₁ + Kr₉₂ + 3n₁


But for nuclear rocket, you want your U-235 to be reticulated in graphene tape and to fission one atom at a time.

This means you don’t get the 3n at the end of the above equation.

You gotta put in the n that makes a very tiny particle of U-235 fission and yield its heat energy.

To get your n you want Polonium on tape and Beryllium on another tape, and then smash those two tapes together in a tamper that lets the neutrons out.

So your atoms of U-235, on another tape will fission, and drive your reaction mass (Copper and Tungsten) out of the nozzle at high speed (F = mass times velocity squared).

V here would be a few orders of magnitude larger than the speed of sound in air.

mass comes out as hot plasma — bits and pieces of atoms.

You can’t run my drive in Earth’s atmosphere. You must take itto space, before you run it.

You can pre-lift your reaction mass (heavy atoms on graphene tape).

Load the reels or spools into the rocket so they feed into the nozzle.

This rocket will take you to the outer planets and their moons.

You will not live long enough to go inter-stellar.

But Jupiter may have a moon or two worth going to.

And there could be items in the asteroid belt worth venturing onto (Psyche)