31–40 of 155 posts
Earlier quoted context omitted.
Name me a country willing to give Elon Musk control of fissile material, however indirect.
Starship and the booster already collectively carry 70 kiloton-tnt-equivalent masses of liquid methane and oxygen. As a weapon of mass destruction, it's hard to beat relativistic impact.
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.
Aren't SpaceX launch explosions big enough already?
I don't know why you're downvoted. I think it's a legitimate question. When I was in high school I asked " Why don't we just shoot our nuclear waste into the sun? ". 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…
Or just used as an upper stage! See https://en.wikipedia.org/wiki/Saturn_C-5N, for instance, and a bunch of even more ridiculous Soviet designs.
Amazingly, this project (nuclear third stage for Saturn V) was actually under serious development. This to be used on a rocket stack which had had two major incidents in 13 launches; it really was a very different safety culture back then.
I only skimmed the article; but as I understood it the liquid hydrogen here is being used strictly as ejecta. It is not being combusted, the way that it is used in the space shuttle boosters. 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…
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.
I only skimmed the article; but as I understood it the liquid hydrogen here is being used strictly as ejecta. It is not being combusted, the way that it is used in the space shuttle boosters. 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…
> 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 only skimmed the article; but as I understood it the liquid hydrogen here is being used strictly as ejecta. It is not being combusted, the way that it is used in the space shuttle boosters. 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…
For specific impulse. When you have unlimited power, you want the lightest possible molecular mass exhaust for the best total delta V.
Earlier quoted context omitted.
Niger Central African Republic Cambodia Bolivia Palau Laos There are in fact a lot of countries that would be thrilled to give Elon fissile material in exchange for investment.
I'm going to go out on a limb and say Niger, CAR, Palau, etc don't have access to highly enriched uranium.
https://en.wikipedia.org/wiki/List_of_countries_by_uranium_r...
AFAIK, the only nuclear rocket that makes sense is landing a reactor on an icy comet and using it to shoot super heated steam wherever you want thrust. #seveneves
Aren't SpaceX launch explosions big enough already?
I don't know why you're downvoted. I think it's a legitimate question. When I was in high school I asked " Why don't we just shoot our nuclear waste into the sun? ". 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…
Aren't SpaceX launch explosions big enough already?
I don't know why you're downvoted. I think it's a legitimate question. When I was in high school I asked " Why don't we just shoot our nuclear waste into the sun? ". 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…
But even without a crash can, it's of less concern to public health than the radioisotopes in coal.
