Say you had a large bomb - take the 50 megaton Tsar Bomba. You then proceed to place it in the center of a spherical tank containing liquid hydrogen, and then detonate it. Could you start a fusion reaction inside of that tank (and roughly how big would that tank need to be)?

  • $\begingroup$ The fusion process is triggered by compression so just lighting a match isn’t enough. See nuclearweaponarchive.org $\endgroup$ Apr 2, 2018 at 2:58
  • $\begingroup$ The only thing that would work is to put it in a tank of U-238. $\endgroup$
    – JEB
    Apr 2, 2018 at 3:34
  • $\begingroup$ My apologies, I meant if I actually detonated the bomb, instead of just lighting a match. $\endgroup$ Apr 2, 2018 at 10:48
  • $\begingroup$ Only if the tank is made part of a new stage of the radiation implosion device itself, see here. $\endgroup$ Apr 2, 2018 at 18:16

2 Answers 2


The first ever thermonuclear device, Ivy Mike, contained a tank with liquid deuterium (heavier isotope of hydrogen, the main isotope, protium, has too small fusion cross-sections). The fusion reactions in this tank were ignited by a fission bomb.

Note, that the main problem for obtaining a significant yield from fusion reactions is to contain fusion fuel long enough for it to fuse, rather than being dispersed by the explosion prematurely (then this would be called a fizzle). So, while simply placing the bomb inside the tank with liquid deuterium will produce some fusion reactions, large yields require careful design such as Teller-Ulam configuration.


When the nuclear bomb is ignited, the liquid hydrogen in the tank would evaporate instantly. The evaporation heat of liquid hydrogen of a tank of any reasonable size is negligible compared to the energy released even by a small (Hiroshima) 15kT TNT fission bomb.

Note after comment by @rob: That there won't be any significant fusion of ordinary hydrogen with hydrogen has been answered here: Fusion: Why deuterium and tritium?

  • $\begingroup$ The question seems to be about nuclear reactions in the hydrogen, not about the hydrogen phase change. $\endgroup$
    – rob
    Apr 2, 2018 at 16:55
  • $\begingroup$ @rob - The answer is correct. The hydrogen will evaporate and dissipate. That there won't be any significant fusion of ordinary hydrogen with hydrogen has been answered here: physics.stackexchange.com/q/87972/129209 $\endgroup$
    – freecharly
    Apr 2, 2018 at 17:41

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