That's nice. I once had a very long talk with an engineer about why we simply didn't dust off the plans for the Saturn Vs and start reusing them. After all, it's a known technology, with a proven track record, so it should be easy to duplicate. Additionally, with things like carbon fiber to save weight, we could get more carrying capacity out of the same design. Seems simple, right? Wrong. First of all, just changing the materials, would require a lot of engineering time. Because if a spar is no longer carrying a 10 lb load, you might not need it to be as large, or you might need it to be larger, because it has to better support the panel it's attached to, as they don't have the same qualities as the original materials, and might not be able to handle certain forces as well, so the spar has to compensate for that. Then you've got all the electronics involved in the rocket, none of which are made any more. Now, of course, you're not going to want to run the capsule on the antique computer it had, but one can't simply slap in a new PC and call it "Done." You're changing the weight balance of the capsule, which has to be pretty precise. Then there's the electronics attached to various things like pumps and engines. What did they do? How did they work? Who made the damned things? Would it make more sense to replace it with a modern Matisui G37Z chip? Will that have the same power requirements? Don't forget there's some 15 miles of wiring in the CM, modern wiring is going to have different weight characteristics, even if you used the same materials, simply because the machines used to make such things are so much better today. What all that boils down to is you wind up putting nearly as much, if not more, work into building a clone of something, as you would in designing something from scratch. And the scratch version would be far more capable than the upgraded design of the original. That's why Musk and Bezos didn't bother with the original blueprints for the Saturn Vs to build their rockets, even if they did take advantage of the data from NASA's programs. Now, to talk about your nuclear rocket, that's adding a whole 'nother layer of complexity to things. First of all, "nuclear" is a scary word, so you're going to have to convince people (which is going to take time and money, and is never going to win over everyone) that the thing is safe. And you're going to have to design in added safety features as part of this, so that's going to add weight, increase the complexity of the thing, and add cost. That's if you can get the public and Congress to go along with your ideas to begin with. Can it be done? Yeah, IF we have a succession of Presidents who are bold visionaries, willing to take risks, strong arm the shit out of Congress, and are willing to push for something that might not come to fruition during their term in office. I can't name one politician in any party with that kind of vision when it comes to space. Not one. And you'd need at least two of them to get it all done.
You do know you don't use nuclear thermal rocket engines to actually lift off from Earth don't you? The reactors don't go critical until well out in space. And we've been launching space probes with RTG power sources containing highly lethal plutonium for years.
None of that has anything to do with the complexity of designing the rockets. And yes, I know quite well that we've been sending RTGs into space for quite some time now. Most of the public doesn't know that until the thing gets to space, though Michu Kaku still shows up to protest every launch. If you're going to send humans to Mars and beyond with nuclear powered rockets, you're going to have to get the public onboard with the idea, if you don't want the nutters cock blocking you before you finish the first CAD drawing.
Actually the heart of the Saturn V is the F-1 rocket engine and it is STILL arguably the most advanced rocket engine of its type ever built. Upgradeable from 1.5 million lbs. of thrust to 1.8 million. And believed to be reusable (as many as ten times). It is truly one of the great engineering achievements of the 20th century.