>>11680662>Anything less than nuclear is pointlessFTFY
Fission gets our energy costs down to post-scarcity levels, which allows us to economically build the number of D-D fusion reactors we'd need to replace them.
The ideal future is one where fissile elements are used in reactors that allow lightweight deep space missions, D-T fusion is used for early game fusion propulsion systems, and D-D fusion powers all our industries anywhere where solar is a meme (ie on the surface of any planet or moon, or in space beyond the asteroid belt. Solar is actually perfectly viable as long as you're in the inner solar system and have constant exposure to the Sun).
By the way, with fission reactors using a breeder cycle, continental and upper mantle crust on Earth contains enough uranium and thorium by mass that every kilogram of rock contains about 20x the useful energy content of that of a chunk of anthracite coal. Breeder reactors let you power the planet using superabundant rocks that otherwise has effectively no value, and since the fuel extraction process already pays for itself, you can tweak it very slightly and also extract all of the rare earth metals and copper and silver and whatever other elements you want at the same time, meaning the cost of these materials drops down to basically zero, just like the energy.
Never forget that while D-D fusion lets you power everything using 1/4000th of the hydrogen on Earth, fission breeders let you power everything by using any igneous rock on the planet, and as an added bonus extracts every elemental resource along the way as a byproduct. Finally, this trick with fission breeders works on Mercury, Venus, the Moon, asteroids, and Mars, as well as on every solid object beyond the asteroid belt where the rocky mantle is within reach through the ice sheets.
