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Would it be possible to create a submersible boat engine using the combined principles of electrolysis of water, ramjet propulsion, and hydrogen-oxygen combustion similar to that used in rocket engines?

For example, the engine structure would be similar to that of a ramjet with a small intake opening in the front that lets in water and a wide bell shaped nozzle at the back where the explosive force would be expelled. In the middle of the chamber there would be two wires protruding with one being for positive voltage and the other being ground. The voltage between the two wires would be kept consistently high enough to trigger the electrolysis and there would be periodic voltage spikes (KV range) to create an arc to trigger combustion of the hydrogen and oxygen.

enter image description here I would think the advantage of this propulsion system would be a lack of moving parts that require waterproofing such as standard propellers and rotary motors. So would this be a feasible method of propulsion or am I missing something? My background is primarily electrical so I could be missing a critical chemistry/mechanical component of the process.

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    $\begingroup$ Would you please do even the smallest amount of research into just what is involved with electrolysis? Start with Wikipedia. And I wonder about your electrical background if you're going to talk about megavolt pulses for ignition. $\endgroup$
    – WhatRoughBeast
    Commented Jun 15, 2015 at 19:13
  • $\begingroup$ If it doesn't work for cars, it's not going to work for boats either. $\endgroup$
    – Kyle Kanos
    Commented Jun 15, 2015 at 19:48
  • $\begingroup$ I'm not so willing to dismiss this idea. It is basically a way to do electric propulsion, by turning electrical energy into heat. The ignition can be done one way or another. I'm not saying this is a good idea, but neither would I reject it out of hand. $\endgroup$
    – Mike Dunlavey
    Commented Jun 15, 2015 at 19:56

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This scheme would be terribly inefficient thermodynamically. Firstly, where is the energy needed to generate the electrical pulses coming from? Secondly, neither the process of electrolysis of seawater or the combustion of the resulting hydrogen and oxygen is 100% efficient.

Finally can this system really generate enough thrust to propel a boat?

If the goal is no moving parts, a better choice would be a magnetohydrodynamic drive. This uses the conductivity of seawater to generate thrust on the seawater by passing a current through the water in the presence of a large magnetic field. More on this at the Wikipedia page on magnetohydrodynamic drive .

But this type of system has inefficiency problems of its own as well. Not the least of which is again, the generator needed to generate electricity for the water current and magnetic field. A conventional propeller driven by a gas or diesel engine on a small boat or geared turbines or gas turbines on a large ship, is much more efficient.

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The energy required to split the water into oxygen and hydrogen is quite a bit less than the energy you would get back when you burn it (commercial electrolysis units run at about 70% efficiency). I think that makes this an inefficient method of propulsion.

If you just (electrically) heated an amount of water until it became steam you would reach the same effect. Possible, inefficient.

Sealing moving parts isn't that hard. The engine you propose would be very noisy, too...

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    $\begingroup$ Commercial electrolysis units run at about 70% efficiency. $\endgroup$
    – WhatRoughBeast
    Commented Jun 15, 2015 at 21:50
  • $\begingroup$ @WhatRoughBeast I am trying to figure out if this means you agree or disagree with me... $\endgroup$
    – Floris
    Commented Jun 15, 2015 at 23:52
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    $\begingroup$ It means I think you're understating the problem. $\endgroup$
    – WhatRoughBeast
    Commented Jun 16, 2015 at 0:09
  • $\begingroup$ @WhatRoughBeast OK edited... $\endgroup$
    – Floris
    Commented Jun 16, 2015 at 10:01

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