For some reason (that I haven’t figured out yet) thermonuclear bombs are just so much more efficient than any other proposed fission or fusion reaction.
It’s strange that controlled fusion is an energy sink, but whatever black magic is happening inside an H-bomb manages to unlock so much “free” energy.
> It’s strange that controlled fusion is an energy sink, but whatever black magic is happening inside an H-bomb manages to unlock so much “free” energy.
E=mc^2. The proportion of the original mass converted to energy in fusion is higher than it is for fission.
The trouble with fusion is that you need really high temperatures and pressures to sustain it. You can easily sustain a fission reaction at a few hundred degrees C, or even lower than that if you wanted to (but the general goal is to boil water to run a steam turbine so >100°C is what you want).
Fusion requires millions of degrees, which would vaporize most things you might want to use as a container, so instead they use strong magnetic fields and then you spend a lot of energy maintaining the magnetic field. A bomb doesn't care about that because sustained operation isn't required and vaporizing everything in the vicinity is kind of the idea.
Moreover, efficiency isn't really the issue. The efficiency of fission is already absurd. Fission of a given mass of uranium generates the same amount of energy as burning 2.7 million times that amount coal -- by mass, it's even more by volume.
The main advantages of fusion are that hydrogen is a lot more common than uranium (though uranium is still pretty available) and that the byproduct of fusion is helium (a non-radioactive noble gas with general usefulness), whereas some of the fission byproducts are variously radioactive or have limited known commercial applications.
Fusion is ridiculously efficient and effective power source. The problem with it is that it is very hard to created conditions where fusion can happen. The one reliable way we have that doesn't take more energy in than it outputs, is to detonate a fission bomb and use the x-rays to compress a fusion secondary.
The history of fusion research for the past 70 years is trying to figure out a cost-effective way to trigger enough fusion to make net energy without a nuke. So far, we've got bupkis. (The magnetic containment approaches using high-temperature superconductors seem promising, but we won't know they actually work until we've built them.)
Even the cleanest bombs (97%+ fusion rather than fission) turned out to be too dirty for basically everything civilian (unlocking gas reservoirs - too radioactive; landscaping to replace enormous amounts of conventional explosives - too radioactive).
Not really? How do you define efficiency here?
Thermonuclear bombs literally create lots of heat, and don’t tend to drive anything that produces work. It’s the opposite of efficient.
Just like lighting gasoline on fire and claiming that that’s more efficient than a combustion energy…
I’m talking about net energy. Harnessing it is a whole different story.
Not really making nukes take a ridiculous amount of energy and you only get to use it once where the energy to create ITER gets split across its operating lifespan.
Further fission here requires a fission first stage which represents a huge additional energy input.
GPT pro says 3 to 30x energy release compared to the entire supply chain input for a megaton class weapon.
I trust the argument. You can look into it yourself. Long story short, it is massively energy positive compared to controlled fusion.
I really don’t trust that LLM estimate, they are really bad at that kind of thing but for the sake of argument let’s take that as a baseline.
ITER is supposed to be a 10-20x return on energy provided (10x being the safe bet) which mean it may or may not be better depending on the specific bomb design, but it’s not massively better.
People talk about fusion as useless but the current best design in construction was constructed in
What if we used them to run Tesla turbines
In order to trigger an H bomb, you first trigger a regular fission bomb to generate the necessary energy to trigger the second fusion stage.
So, fission bombs are the black magic.
I think there’s a lot more to it than that, like the heavy uranium tamper, “FOGBANK”, and radiation implosion (whatever that means).
It’s a much more efficient version of inertial confinement fusion like at the NIF.
The efficiency is higher because the device is bigger. To oversimplify a bit, the surface area through which energy is radiated away grows slower than the volume containing the fuel. So heavier fuel "pellets" in bombs (ones in the kilogram to ton range) have a much easier time burning efficiently than the tiny milligram scale fuel pellets at NIF. Tiny fuel pellets cool down too fast. Likewise, multi-megaton fusion bombs are more efficient than the "little" sub-megaton bombs that the US favors (for reasons of compactness/deliverability) in its nuclear weapons stockpile.