What pressure would be needed to cause fusion of water?

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Discussion Overview

The discussion revolves around the theoretical pressure required to induce fusion of water's constituent elements, hydrogen and oxygen, within a highly compressed and indestructible container. Participants explore the implications of such a scenario, including energy calculations and the nature of fusion reactions, while considering the feasibility of extreme compression and the resulting physical phenomena.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant speculates on the extreme pressure and density required for fusion, citing a specific density value and questioning whether this would lead to fusion of hydrogen and oxygen.
  • Another participant emphasizes that pressure alone is insufficient for fusion, suggesting that additional factors must be considered, referencing the Lawson criterion.
  • A participant challenges the precision of the density value provided, questioning the exothermic nature of the proposed reaction.
  • Concerns are raised about the feasibility of compressing water to such extreme levels, with one participant suggesting that the container would rupture due to molecular bond stretching.
  • Another participant introduces the concept of zero point energy and tunneling reactions, proposing that fusion could occur even at low temperatures and pressures under certain conditions.
  • One participant discusses potential fusion products from oxygen and the energy implications of these reactions, while expressing uncertainty about the processes involved.
  • Another participant argues that the extreme pressure would lead to a violent explosion, suggesting that the energy released would be comparable to a nuclear explosion.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the feasibility of inducing fusion in water under extreme pressure, the nature of the reactions involved, and the energy implications. The discussion remains unresolved, with no consensus reached on the viability of the proposed scenario.

Contextual Notes

Limitations include the lack of consensus on whether the fusion reaction is exothermic, the assumptions regarding the indestructibility of the container, and the dependence on specific definitions of fusion processes. The discussion also highlights unresolved mathematical steps related to energy calculations and the conditions necessary for fusion.

prodigylock
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TL;DR
Theoretically, what pressure would water need to be subjected to force the oxygen and hydrogen to fuse into heavier elements and how much energy would it release.
So in a DnD story, someone made a bomb by putting 3375ft^3 of water into a 0.5ft radius sphere and caused it to make a nuke. I was thinking if this was possible then what would actually happen, so I spent an afternoon looking for the answer and only got the pressure and density.
6445773,7307163375188090110591252 kg/m^3
186976087900000000000000000 PSI
Would the pressure result in the hydrogen and or oxygen fusing and if so how much energy would all of it make if this indestructible sphere disappeared at one point.
 
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prodigylock said:
Summary:: Theoretically, what pressure would water need to be subjected to force the oxygen and hydrogen to fuse into heavier elements and how much energy would it release.

So in a DnD story, someone made a bomb by putting 3375ft^3 of water into a 0.5ft radius sphere and caused it to make a nuke. I was thinking if this was possible then what would actually happen, so I spent an afternoon looking for the answer and only got the pressure and density.
6445773,7307163375188090110591252 kg/m^3
186976087900000000000000000 PSI
Would the pressure result in the hydrogen and or oxygen fusing and if so how much energy would all of it make if this indestructible sphere disappeared at one point.
Welcome to the PF. :smile:

This is where you need to start -- it's not just pressure that is involved in starting a fusion reaction...

https://en.wikipedia.org/wiki/Lawson_criterion
 
6445773,7307163375188090110591252

Good heavens. If Sister Mary Albert saw you write something with that ridiculous precision, she'd rap your knuckles with her ruler.

Have you established that this reaction is even exothermic?
 
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prodigylock said:
So in a DnD story, someone made a bomb by putting 3375ft^3 of water into a 0.5ft radius sphere and caused it to make a nuke.
How could you possibly compress water by that much?

The container would expand as molecular bonds stretched, resulting in rupture of the containment.

If you calculate the energy needed to compress the water, you will find that it needs as much energy as is released by a nuclear bomb.
 
I forgot to mention but this theoretical container is indestructible.

As I couldn't find a source on a Liquid adiabatic process I couldn't calculate if the compression would generate enough heat to make plasma and cause the sphere to become ignited.

It should not be exothermic since the only way would be with beta decay but that would take too long on this scale to sustain the reaction but I'm not that good with this(hence the reason I asked here) so that's what I wanted to find out what would happen.
 
Well if it's not exothermic, where does the energy come from for the kaboom?
 
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The energy for the kaboom came from quick math and assumptions and that's why I wanted to explore the idea further. As far as I have read the oxygen from the water might be able to fuse into si-28 and an alpha particle. Later through the Triple-Alpha process, it would make 2 gamma rays and some carbon-12. So that would produce some energy and one of these might fuse with the protium but I'm not too sure about that.
 
Vanadium 50 said:
Well if it's not exothermic, where does the energy come from for the kaboom?
You don´ t need any energy. Well, zero point energy.
Even at zero pressure, a water molecule in vacuum, you will have small but nonzero rate of tunnelling, mostly for the two simple reactions:
p+p=d+e+e
p+p+e-=d+νe
Note that p-p fusion has the lowest Coulomb barrier. Whether it takes place due to pure zero point energy (pure pycnonuclear fusion), with appreciable contribution of heat or mainly as thermonuclear fusion, it is preferred.
Of course, as either the pressure/zero point energy or temperature is increased, higher Coulomb barrier reactions will contribute:
p+16O=17F+γ
16O+16O=32S+γ
16O+16O=28Si+α
16O+16O=31P+p
et cetera
Therefore, seal water in a pressure vessel and since heat generated by pycnonuclear fusion cannot escape, it slowly heats up to thermonuclear.
The original premise is water compressed to density of about 6400 kg/l, making about 700 kg/l of protium. At that density and no temperature, what is the lifetime of protium to pycnonuclear fusion?
 
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The container is a massive bomb without any fusion already. Just release the interior which is under some ridiculous pressure and it will explode violently. At this density you can forget molecular bonds or even atoms. The electron degeneracy pressure will be ~1018 Pa, giving that bomb an energy of the order of 1016 J or a few megatons of TNT equivalent.

Any plausible mechanism to compress the material will probably heat it up a lot, too. You end up with a pressure and density way higher than in the core of the Sun. Might be enough for a lot of hydrogen fusion, followed by more fusion reactions later.
 

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