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Comment by danpalmer | Hacker News Reader

I have never heard of fusion weapons research, or what they would even be. My understanding is limited but where I can see fission leading to weapons, I can't see the same for fusion.

Could you give some more detail? What form would a fusion weapon take? Is it about the laser technology?

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The first thermonuclear weapon (or H-bomb) test was successfully completed in 1952. That is, a nuclear bomb that uses a fission reaction to create the conditions for a more pworful fusion reaction, which is either the final step, or is used to power an additional fission step, amplifying the final explosion many times more.

The NIF experiment explained here, which uses a laser to generate X rays by heating the walls of a heavy metal hohlraum, and then uses these X-rays inside the hohlraum to compress a pellet of gas to ignite a fusion reaction is very similar to the conditions inside an H-bomb, which also generates X-rays (via a fission reaction) to compress and ignite a fusion reaction.

The weapons use is relatively simple - fusion reactions expel much more energy than fission reactions, and using the power of a fission reaction to compress and to ignite a fusion reaction inside a large amount of gas expels much more energy than simply exploding the power of the fission reaction outwards.

The NIF and some other facilities (eg the Sandia Lab Z machine) are for studying fusion plasmas in order to understand their behaviour in thermonuclear weapons first, and possible application in power generation as a distant second. That’s pretty explicit, it’s a way of keeping up nuclear weapons research and maintenance without detonating actual devices and breaching test ban treaties and causing various other messes.

JET, ITER, Wendelstein and other magnetic confinement facilities on the other hand are investigating fusion as a source of grid energy.

Thermonuclear bombs are fusion weapons (with a fission trigger).

Having relatively easily handled, high density energy sources would also probably lead to deployment of energy weapons.

Most modern weapon designs are actually fission-fusion-fission designs with most of the energy actually coming from the final fission step - the latter being driven by neutrons from the fusion step. Things get even more complicated with the fact that primaries are fusion boosted fission and the fusion step contains a fission "sparkplug".

Sure, but the fusion step is still important and somewhat poorly understood, so ICF experiments which mirror the conditions inside the fission-fusion step could be valuable for increasing yields.

Interestingly, a lot of recent developments in warhead design (e.g. the non-spherical primaries of the W-88) are actually about primary design - so I guess its possible this kind of research also feeds into the fusion boosting component of primaries.

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