Nuclear power gives you more energy, but you're still limited by how much reaction mass you can carry.

The plans that work look like early 1960s NASA plans - build infrastructure in orbit, assemble nuclear power interplanetary craft in orbit, nuclear power is from planetary orbit to planetary orbit only. That was Wernher von Braun's "Man Will Conquer Space Soon" plan.[1]

The Apollo program, at US$20 billion, was the economy version. To the moon and back, no space station, no permanent infrastructure in space.

[1] https://www.youtube.com/watch?v=Sz7njI0wEIw

Then again, it's looking like the whole 'fail fast' approach is over anyway, with Starship grounded by red tape.

A full-stack Starship failure is seemingly too big/dramatic/risky to get away with doing repeatedly, especially admidst the politics of Twitter/X.

#seveneves

No. Nuclear is not worth it for starship, as the added engine weight limits the additional delta V and the additional challenges of handling nuclear material.

The obstacles faced by the NERVA project were immense, and the iterations achieved spectacular improvements in record time. That project that lasted for less than one decade and was done on a shoestring budget is not quite the equal of the Manhattan project, but it's not much below it. It achieved the highest density of power generation by maybe a factor of 100 compared to any other reactor in history.

All that stuff was pretty much lost. NASA is trying to revive this, but it will not have legs. We simply don't have the same pool of talent to recruit from. In the 60's there were lots of scientists and engineers that had first hand experience building nukes and nuclear reactors. Now this country has not built a reactor in 3 decades, with the exception of Vogtle.

[1] https://en.wikipedia.org/wiki/NERVA

>The short answer is no

>If we need the full performance advantage of nuclear propulsion, we should design a spaceship that is intended for it from the get-go. It never lands, only going from orbit to orbit, so there is no need for heat shielding, flaps, high thrust engines, thick steel structure or aerodynamic shaping requirements.

If that is the case, liquid hydrogen seems like an awful substance -- hard to produce and transport, hard to store and the mass required to support keeping it is not insubstantialy, all for a mass density of ~70g/L.

Why not just use water? Water is 1000g/L and can be stored without any real effort at all. If all you're doing is shooting it out the rear end of the rocket with as much energy as possible, it's mysterious why you would even consider liquid H2.

https://news.ycombinator.com/item?id=38086518 https://planetocracy.substack.com/p/mars-cyclers

https://en.wikipedia.org/wiki/Fission-fragment_rocket

So here is my science fiction theory: fusion will never be possible, but fission already is. So in the galactic civilization, rare uranium is the most valuable resource since it enables interstellar travel. Uranium is only produced in the collisions of neutron stars, so we are lucky to have any.

We should not squander our uranium for power generation when we can use solar for that. It's like not using oil or gasoline for heating.. we need it for transportation.

Nukes can totally function as the energy for rocket’s impulse. Very small and very directed nukes. The directed explosion plasma wave hits a pusher plate, where very specific plasma physics play out - the plate is not vaporized but merely receives an impulse - and then there are dampers to smoothen the blow.

Half of the interviewed experts were positive it would work and half were skeptical.

So, it’s sort of sad they had to wrap it up due to nuclear test ban before actually being able to run actual tests.

The best part? The bigger it is, the better. We could totally have gigantic nuclear space cruisers that go to Jupiter in like a week (I exaggerate because I forget the exact orbits but with ISP from nukes that bastard goes fast)

RIP New Caird

> Most significant for our purposes is methane as propellant. It is six times denser than liquid hydrogen, can be stored at 100K, which is compatible with liquid oxygen, and it can be produced using water and carbon dioxide. At high temperatures, it breaks down into hydrogen and carbon, turning it from a 16 g/mol molecule into a 3.25 g/mol plasma. That is how it achieves a specific impulse only mildly lower than what is achievable using liquid hydrogen. Zubrin lists its specific impulse as

>Previous calculations using hydrogen propellant revealed how volume-limited the Starship design was. There was no room for the bulky liquid hydrogen, and getting to orbit meant sacrificing the payload mass and volume advantages that the Starship is built around.

>These could be solved by using denser liquid methane as propellant for the nuclear propulsion system. The Isp will be lower, but the mass ratios become so much better that more deltaV is available overall.

I think all real-life actually-tested nuclear thermal rockets have used hydrogen as propellant, though use of other substances has definitely been proposed.

In deep space you don't really care about the volume of your fuel tank, so then it does make sense to use something light like hydrogen.

As an adult, Kerbal Space Program has taught me that it's incredibly difficult to lose the orbital velocity and get things into the Sun!

But the answer my teachers told me was "Well, even if rockets have a 99.5% success rate and a 0.5% failure rate, and only 1 out of every 200 rockets explodes during launch... then eventually a rocket carrying nuclear waste is going to explode and spread it everywhere"

As others have pointed out: Nuclear rockets don't have the thrust ratio necessary for take off, so presumably they'd be assembled and used in space. My question is: What level of risk does launching nuclear rocket parts/fuel into space pose?