After sleeping on this, I realized that even though liquid hydrogen could be the working fluid for the (water) hammer, there would be no way to limit the reacti

After sleeping on this, I realized that even though liquid hydrogen could be the working fluid for the (water) hammer, there would be no way to limit the reaction, so we'd just end up with a hydrogen bomb. I also forgot to include one other link: https://en.wikipedia.org/wiki/Bubble_fusion https://en.wikipedia.org/wiki/Bubble_fusion The liquid metal is sort of like the moderator in fission, except in this case it just limits how much hydrogen can fuse by taking the place of the hydrogen in the center. Also the Carnot efficiency of a liquid hydrogen heat engine would be terrible because it's so cold. It would also be difficult to contain it if it got too hot and turned to gas. It looks like the compressibility of water is about 46.4 parts per million for every unit increase in pressure: https://en.wikipedia.org/wiki/Liquid#Volume https://en.wikipedia.org/wiki/Liquid#Volume And compressibility is roughly inversely proportional to density: https://en.wikipedia.org/wiki/Compressibility#cite_note-4 https://en.wikipedia.org/wiki/Compressibility#cite_note-4 Water is 4.6e-10 Pa^-1 and mercury is 3.7×10–11 Pa^-1 so I would guess that the compressibility of liquid lead is comparable to that of mercury. If we temporarily ignore the compressibility of hydrogen in the center of the bubble, then to find the maximum pressure we'd need to integrate the compression from outside in, based on the kinetic energy of incoming atoms starting from a certain velocity and exerting pressure on the atoms beneath as they come to rest. Something similar happens in a type II supernova when a large star runs out of fuel and no longer has the heat energy to hold itself up (think of the hot atoms in the core like the gas in a bubble). When the outer layers collapse inward, they form a fluid hammer where the pressure and temperature are so extreme that a large portion of the center of the star fuses all at once. https://en.wikipedia.org/wiki/Type_II_supernova https://en.wikipedia.org/wiki/Type_II_supernova I'm having trouble finding a simple formula for the maximum pressure of a collapsing fluid, but this simulation could probably tell us if the General Fusion reactor would actually work: https://cs.lbl.gov/assets/CSSSP-Slides/20160623-Nonaka.pdf https://cs.lbl.gov/assets/CSSSP-Slides/20160623-Nonaka.pdf