Naked Science Forum
Non Life Sciences => Technology => Topic started by: profound on 05/12/2012 20:56:00
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I just had an idea that of using electrolysis to generate thrust while in the bath and looking at the hot and cold taps.
basically you have 2 carbon electrodes sealed in a container filled with water.
you apply a current through this water and this causes electrolysis and increases pressure inside the vessel due to release of hydrogen and oxygen at each electrode and after the pressure has built up then a valve/nozzle is opened to release this very high pressure and hence generate thrust.
the electrolysis would be maintained to maintain the high pressure in the container which i understand can reach 10000 psi or more.
hence you do not need to BURN anything.
you merely pass current through a readily available compound such as water or any other suitable compound.
it does not have to be water but any compound which is low cost and can be electrolyzed.
advantage is it has no moving parts and even the water which may slosh around can be replaced by a jelly like substance and still allow electrolysis.
could be very useful in space travel and possibly for lift of from earth without the toxic fuels burning at present.
just imagine passing a 1000 amps or more in a sealed container and generating huge thrust from the released gases or passing 0.1 amp and generating smaller course correction thrusts.
any thoughts anyone?
Also as no one has ever mentioned this befre i claim exclusive rights to this idea for propulsion.
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Unfortunately, it would generate far, far less thrust than a gas turbine engine or rocket engine of similar mass. It would also require large amounts of electricity for little pay off in terms of thrust.
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Unfortunately, it would generate far, far less thrust than a gas turbine engine or rocket engine of similar mass. It would also require large amounts of electricity for little pay off in terms of thrust.
i understand it can achieve psi of over 10000.A lot more than turbuns,etc.
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The main question you are going to need to consider is where does the electrical energy for electrolysis come from in the first place?
The realistic efficiency of turning water into free hydrogen and oxygen is at best around 70% practically - so, you have already lost around a third of your stored energy before you do anything with it.
Also, if you then reignite the fuel/oxygen mixture it will potentially give you a fairly good recovery on the remaining energy in the system, but (as per your suggestion, IIRC) to let it simply increase the pressure without igniting is 'throwing away' even more of the energy, as the heat of combustion will provide by far the largest component in raising the pressure in a thruster.
Let's say the initial electricity used for electrolysing your water supply comes from one of the most efficient heat-engines there is - a fuel-cell. What can the fuel cell be run on? - well it's fair to say that for the best overall efficiency one might choose a F.C. that operates on Hydrogen (combining with free oxygen in the air, or a separate tank of it in space) - so that's a hydrogen-powered engine used to make electricity (what 80% efficient?) - to electrolyse water - to free hydrogen from oxygen - to create a weak pressure increase - to generate thrust from a nozzle.
In space, this would seem to do the job a lot better:
Ion Thruster (http://en.wikipedia.org/wiki/Ion_thruster)
As an aside, are rocket fuels really toxic anyway?
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Also, I've just realised I've wasted my time re-answering a question you've already asked verbatim on a different board, so I've merged the two topics into one. Please read the forum's AUP in detail before posting again, as this kind of 'copying & pasting' is not viewed well by the moderators.
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The main question you are going to need to consider is where does the electrical energy for electrolysis come from in the first place?
The realistic efficiency of turning water into free hydrogen and oxygen is at best around 70% practically - so, you have already lost around a third of your stored energy before you do anything with it.
Also, if you then reignite the fuel/oxygen mixture it will potentially give you a fairly good recovery on the remaining energy in the system, but (as per your suggestion, IIRC) to let it simply increase the pressure without igniting is 'throwing away' even more of the energy, as the heat of combustion will provide by far the largest component in raising the pressure in a thruster.
Let's say the initial electricity used for electrolysing your water supply comes from one of the most efficient heat-engines there is - a fuel-cell. What can the fuel cell be run on? - well it's fair to say that for the best overall efficiency one might choose a F.C. that operates on Hydrogen (combining with free oxygen in the air, or a separate tank of it in space) - so that's a hydrogen-powered engine used to make electricity (what 80% efficient?) - to electrolyse water - to free hydrogen from oxygen - to create a weak pressure increase - to generate thrust from a nozzle.
In space, this would seem to do the job a lot better:
Ion Thruster (http://en.wikipedia.org/wiki/Ion_thruster)
As an aside, are rocket fuels really toxic anyway?
hydrazine not toxic ...kazakstan littered with it.babies deformed.
normally burning hydrogen/oxygen or kerosene causes it nearly explode due to high temperature and thus create pressure.expulsion from nozzle chamber creates thrust/reaction mass.
my idea removes the need for creating this pressure by BURNING fuel.
pressure is created solely electrolysis in sealed chamber and once is high enough release in a controlled manner from valve/nozzle.
pressures of over 10000 psi are impressive and routinely achieved in industrial chemical electrolysis processes.
normal atmosphere pressure is 14.7 psi
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A quick would seem to indicate that hydrazine hasn't been used as a propellent in the Earth's atmosphere since W.W.II.
The key common component of all rocket (launch) fuels is their enormous exothermic release of energy as heat. And, for gases, an increase in heat holds an almost linear relationship to an increase in pressure (see 'Ideal Gas Law', as a guide) - Hence, if you are not burning the fuel* then really very little of the potential energy that your system has (inefficiently) unlocked will be recovered - a minuscule increase in pressure around ambient temperatures -versus- the enormous increase available in oxidizing (burning) the hydrogen available.
*The fuel that, in your design, has been created; via a convoluted and inefficient manner (itself powered by some unexplained source of electricity).
Perhaps, if there was a way to just combust say Li-H2 with Li-O2, it could make for a completely non-toxic launch method.... maybe it will catch on!
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"pressures of over 10000 psi are impressive and routinely achieved in industrial chemical electrolysis processes."
I doubt that.
Why bother?
Also, you can get high pressures but only at very low flow rates so it's a rather inefficient way to generate thrust.
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A quick would seem to indicate that hydrazine hasn't been used as a propellent in the Earth's atmosphere since W.W.II.
A more modern use for hydrazine is as a fuel for the Emergency Power Unit (EPU) on some modern American military aircraft. Nasty stuff and highly toxic.
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"pressures of over 10000 psi are impressive and routinely achieved in industrial chemical electrolysis processes."
I doubt that.
Why bother?
Also, you can get high pressures but only at very low flow rates so it's a rather inefficient way to generate thrust.
are you on some kind of incentive scheme to dismiss other people ideas?
you have totally missed the point and are incapable of reading a post and remembering it.
too much mtv I guess.
thankfully for all at least your ancestors did not prevail or we would be without fire and the wheel.
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My guess is that your conversion efficiency will drop with higher pressures and greater electrode separation. Of course, a loss of efficiency may be generation of heat which may or may not be desirable. Under very high temperatures, water will undergo thermal decomposition (http://en.wikipedia.org/wiki/Water_splitting#Thermal_decomposition_of_water).
It is unlikely that you will be able to achieve more than a few PSI with mixed gasses at low temperatures, so you will have to generate a system that separates the H2 and O2.
Thrust can be used either directly as in a rocket engine, or indirectly as in a turbine.
Wasting the energy of decomposition would waste a lot of energy.
If you first ran the gases first through a turbine, then they could still be combusted to provide additional heat and energy.
Unfortunately, like many things in physics/mechanics, one never truly gets something for nothing.
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"pressures of over 10000 psi are impressive and routinely achieved in industrial chemical electrolysis processes."
I doubt that.
Why bother?
Also, you can get high pressures but only at very low flow rates so it's a rather inefficient way to generate thrust.
are you on some kind of incentive scheme to dismiss other people ideas?
you have totally missed the point and are incapable of reading a post and remembering it.
too much mtv I guess.
thankfully for all at least your ancestors did not prevail or we would be without fire and the wheel.
In a way, I am on such an incentive scheme.
My incentives are that I don't want the forum cluttered with drivel and I don't want people to waste their time on things that won't work.
Does either of those motives trouble you?
I haven't missed the point of this assertion "pressures of over 10000 psi are impressive and routinely achieved in industrial chemical electrolysis processes."
It makes a clear testable claim
I'm sure that the claim is false.
I have two reasons for that. The first is simply that i would expect to have heard of it. It would have been in my professional field of interest.
The second is that raising pressures always involves doing work.
Electrolysis is used for making things- usually things that are difficult to make.
Making them under high pressure means doing more work (and hence using more energy and more money) than you need to.
I commented to the effect that I'd be surprised if someone was actually running some commercial electrolytic process under those conditions.
I said "I doubt that."
I can't be absolutely certain that someone somewhere isn't running such a process so I asked.
"Why bother?"
Then I pointed out another problem with the system- you can only get a high pressure at low flow rates.
That's rather inefficient as a means to generate thrust.
I think you may find that my ancestors were the ones who didn't bother making a square wheel * and, for the record, I'm 47: MTV was a bit after my time.
Now, did you actually have any valid points?
Can you , for example, give an instance of a commercial electrolysis that is done at 10,000 PSI?
Can you give a reason why someone would bother?
Can you show how it would be possible to get a high flow rate and a high pressure?
If not, do you understand why I'm going to dismiss your post?
(Btw, if you do have some actual data, please present them in sentences which can be parsed in English, and include some capital letters at the starts of them.)
*Unless they had funny shaped roads.
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One may use high pressures to do "cracking" of organic compounds, for example production of short chain hydrocarbons from long chain hydrocarbons, but that is completely a different issue.
It would be handy to fill H2 or O2 bottles directly at high pressure without the use of a compressor. However, I would imagine there are a couple of purification steps between electrolysis and filling tanks that would be easier to do at low pressures.
I'm having troubles finding the vapor pressure of liquid O2 and H2 at room temperature. I think it may be somewhere close to 10,000 PSI for Liquid Oxygen at room temperature. Certainly at high pressures, much more will remain dissolved in solution, and thus likely more mixing of the H2/O2 output.
One can get significant short-term thrust out of pressurized tanks of oxygen/nitrogen/hydrogen/air/etc. Welding bottles have been known to fly up to a mile or so when ruptured. However, far more energy would be recovered using stored hydrogen for combustion/fuel cells than would be gained from thrust alone.
There have been a few compressed air cars (http://en.wikipedia.org/wiki/Compressed_air_car) that have been experimented with. The compressed air is much cheaper to make than compressed pure oxygen or pure hydrogen.
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"I'm having troubles finding the vapor pressure of liquid O2 and H2 at room temperature. "
Good, because they don't have one.
http://en.wikipedia.org/wiki/Supercritical_fluid
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I think around the turn of the century a few cars were made that were powered by the evaporation of liquid air but it is a very inconvenient and if efficient way of storing energy.
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I think there was a resurgence of using air power at the next turn of the century.
http://scripophily.net/liaipoandauc.html
http://en.wikipedia.org/wiki/Compressed_air_energy_storage#Cars
I wonder if it will happen again around 2100.
On a more serious note, the problem with liquid air is that the nitrogen boils off first leaving liquid oxygen behind. Then you end up with an engine full of pure oxygen under pressure.
Add lubricating oil and you have an accident waiting to happen.
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I think you may find that my ancestors were the ones who didn't bother making a square wheel * and, for the record, I'm 47: MTV was a bit after my time.
I did not know you were in charge of clearing drivel.Could someone please give him the key to the internet so he clear the "drivel".
I have two reasons for that. The first is simply that i would expect to have heard of it. It would have been in my professional field of interest".
I had no idea you were some kind of knowledge gatekeeper where all knowledge passes through your mighty omniscient self.
My incentives are that I don't want the forum cluttered with drivel and I don't want people to waste their time on things that won't work.
Could you please come and clear my drive.it's cluttered with snow and other drivel and I don't want to waste my time driving my car as I know it won't work.
[truncated by Mod]
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So, no actual evidence to support your odd claim that "pressures of over 10000 psi are impressive and routinely achieved in industrial chemical electrolysis processes."
Just some random rubbish.
"I did not know you were in charge of clearing drivel."
I never said that I was.
"I had no idea you were some kind of knowledge gatekeeper where all knowledge passes through your mighty omniscient self."
I never said that I was.
[ditto]
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High-pressure electrolysis
Ultrahigh-pressure electrolysis is high-pressure electrolysis operating at 5000–10000 psi.[7] At ultra-high pressures the water solubility and cross-permeation across the membrane of H2 and O2 is affecting hydrogen purity, modified PEMs are used to reduce cross-permeation in combination with catalytic H2/O2 recombiners to maintain H2 levels in O2 and O2 levels in H2 at values compatible with hydrogen safety requirements.[8][9]
he US DOE believes that high-pressure electrolysis, supported by ongoing research and development, will contribute to the enabling and acceptance of technologies where hydrogen is the energy carrier between renewable energy resources and clean energy consumers.[10]
High-pressure electrolysis is being investigated by the DOE for efficient production of hydrogen from water. The target total in 2005 is $4.75 per gge H2 at an efficiency of 64%.[9] The total goal for the DOE in 2010 is $2.85 per gge H2 at an efficiency of 75%.[10] As of 2005 the DOE provided a total of $1,563,882 worth of funding for research.[9]
Mitsubishi is pursuing such technology with its High-pressure hydrogen energy generator (HHEG) project.[11]
This project will develop a prototype for a photovoltaic (PV)-powered, hydrogen fuel producer that supplies high-pressure gas (5,000 to 10,000 psi) to a hydrogen fuel dispenser for the depot-style fueling of commercial or agricultural vehicles, without additional compression or power conditioning equipment. The approach will be based on an innovative ultra-high pressure electrolysis system that has the potential to deliver hydrogen fuel at pressures exceeding 10,000 psi, directly from the electrolysis cell. Phase I will: (1) instrument and run a series of parametric tests on an ultra-high pressure electrolysis cell and document the efficiency of producing fuel grade hydrogen at pressures from ambient to 10,000 psi...
http://ecaaser3.ecaa.ntu.edu.tw/weifang/eBook/electrolysis/Prediction%20of%20production%20power%20for%20high-pressure%20hydrogen%20by%20high-pressure%20water%20electrolysis.pdf
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The ebook at http://ecaaser3.ecaa.ntu.edu.tw is specifically about finding more efficient ways to produce hydrogen for applications like fuel cells in vehicles.
They recover the energy for propulsion by combining the hydrogen and oxygen in a fuel cell, making electricity to drive the wheels.
They do not propose opening a tank of hydrogen to make a rocket-powered vehicle.
This would provide only a few seconds thrust for the vehicle, and create a severe fire/explosion hazard in enclosed spaces.
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Pressures of over 10000 psi are impressive and routinely achieved in industrial chemical electrolysis processes.
So, as your cut and paste confirms above, Ultrahigh-pressure electrolysis is neither routine nor operating above 10,000 psi.
As has been pointed out previously, pressure in isolation tells us nothing about a motor's ability to do work. Mass-flow and expansion are key to getting a heat engine to generate mechanical energy.
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Profound, other members have patiently pointed out to you the practical deficiencies in your imaginative proposal. I hope all would applaud the application of innovative thinking to problems. As you implied yourself it is such thinking that leads to advances in technology and ultimately to quality of life. However, the imagination must be balanced by skepticism and robust critique of any proposal.
Would you agree, in the light of the clearly documented weaknesses in your proposal, that it is not viable as a practical propulsion system?
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The ebook at http://ecaaser3.ecaa.ntu.edu.tw is specifically about finding more efficient ways to produce hydrogen for applications like fuel cells in vehicles.
They recover the energy for propulsion by combining the hydrogen and oxygen in a fuel cell, making electricity to drive the wheels.
They do not propose opening a tank of hydrogen to make a rocket-powered vehicle.
This would provide only a few seconds thrust for the vehicle, and create a severe fire/explosion hazard in enclosed spaces.
it does not have to be water but any compound which is low cost and can be electrolyzed.
so that it gives of carbon dioxide.
maybe you should read the post again.
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Profound, other members have patiently pointed out to you the practical deficiencies in your imaginative proposal. I hope all would applaud the application of innovative thinking to problems. As you implied yourself it is such thinking that leads to advances in technology and ultimately to quality of life. However, the imagination must be balanced by skepticism and robust critique of any proposal.
Would you agree, in the light of the clearly documented weaknesses in your proposal, that it is not viable as a practical propulsion system?
burning kerosene and oxygen can create a dangerous fire/explosion hazard.it is highly dangerous and can only create thrust for very short time periods.it is highly impractical.
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burning kerosene and oxygen can create a dangerous fire/explosion hazard.it is highly dangerous and can only create thrust for very short time periods.it is highly impractical.
In many situations, kerosene, diesel, or vegetable oil will burn, rather than explode. Unlike gasoline that is far more explosive. Your internal combustion engine creates the explosive environment with the high temperatures and pressures.
A kerosene based rocket would be inefficient near the ground. However, kerosene fuel for a turbine engines, and turbojets is reasonably efficient.
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Profound, other members have patiently pointed out to you the practical deficiencies in your imaginative proposal. I hope all would applaud the application of innovative thinking to problems. As you implied yourself it is such thinking that leads to advances in technology and ultimately to quality of life. However, the imagination must be balanced by skepticism and robust critique of any proposal.
Would you agree, in the light of the clearly documented weaknesses in your proposal, that it is not viable as a practical propulsion system?
burning kerosene and oxygen can create a dangerous fire/explosion hazard.it is highly dangerous and can only create thrust for very short time periods.it is highly impractical.
That's demontrably false.
Commercial air travel relies on burning kerosene the engines run for hours at a time and have long lifespans.
Since it's not true, it clearly doesn't support your argument.
Why did you post it?
Also, any news of the "pressures of over 10000 psi are impressive and routinely achieved in industrial chemical electrolysis processes."
or do you accept that it simply isn't true?
Apart from anything else it would be a bit odd. The voltage needed rises with the pressure so it would, for most purposes, be more efficient to run at near atmospheric pressure.
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Also, any news of the "pressures of over 10000 psi are impressive and routinely achieved in industrial chemical electrolysis processes."
or do you accept that it simply isn't true?
Apart from anything else it would be a bit odd. The voltage needed rises with the pressure so it would, for most purposes, be more efficient to run at near atmospheric pressure.
Profound did post a link here:
http://www.thenakedscientists.com/forum/index.php?topic=46355.msg404240#msg404240
Although, this appears to point towards a research article, and not necessarily indicating that it is routinely used in industry at this time. But, their theoretical efficiency of the high pressure electrolysis did indicate that it may in fact be competitive with low pressure electrolysis as far as energy consumption.
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He posted a link in response to my challenging his assertion that "pressures of over 10000 psi are impressive and routinely achieved in industrial chemical electrolysis processes."
But, since they are not using pressures above 10,000 PSI ad they are not an industrial process, they don't actually support his claim.
That's why I asked him if he had " any news" of the "pressures of over 10000 psi are impressive and routinely achieved in industrial chemical electrolysis processes."
It seems he hasn't- or , at least, he hasn't cited any.
It remains the case that electrolysis at higher pressures takes more energy than doing it at lower pressures, so unless you really need the high pressure, it's a non-starter.
http://en.wikipedia.org/wiki/Nernst_equation (http://en.wikipedia.org/wiki/Nernst_equation)
It may come to pass, at some stage in hefutre that with a "hydrogen economy" high pressure electrolysis will be used- but it would be insanely expensive to distribute the hydrogen at such high pressures.
100 PSI- sure, that's already done*
1000 PSI- possibly, but only for very specialist uses
10,000 PSI - not realistic.
*
http://www.hydrogenics.com/hydro/industrial (http://www.hydrogenics.com/hydro/industrial)
Of course, it's also important to realise that, just because it can get high pressures, doesn't mean it can be used as a means of propulsion. The flow rate at those pressures is still far too small to get much thrust.
It really is a non-starter.
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Sigh.
It may be true that high pressures can be made with electrolysis. But that's not what you need for propulsion; you need high pressures over large areas with the minimum amount of propellant.
When you let the gas out, you need some sort of hole. That's an area. If you use a nozzle it turns out it more or less doubles the thrust... at best.
Trouble is, as the gas expands out the nozzle, the gas cools. The hotter the gas is, the more thrust you get and the better the nozzle works, because the gas holds its pressure up better due to the heat.
Also, the hotter the gas is, the more pressure it gives for the same mass of gas in the chamber.
The net upshot is that you really, really, really want hot gas, and that's why virtually all practical engines use combustion to produce hot gas, gas that is as hot as possible.
There is a class of engines called 'cold gas thrusters'. They're used for attitude jets for rockets, but they have very low performance.
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I was thinking a bit.
If one had high pressure H2 and high pressure O2.
One could burn the hydrogen using a low pressure oxygen/nitrogen mix from the air. This would leave the pressurized oxygen to be used as one saw fit. Of course, with proper controls, there could be a market for it in the welding and medical industries.
Diesel engines inject fuel at high pressures, gasoline engines inject it at low pressures. It is possible one could gain a minimal amount of energy running the fuel through a pressure reduction turbine before injection. However, this effect would be quite minimal.
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If you want the maximum thrust, you just burn the oxygen with the hydrogen and use it to make steam, and stick the steam out a nozzle.
Of course, you get the same thrust as if you had just superheated the water (actually less thrust than that since the electrolysis is extremely inefficient)...
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Here's a rocket engine
http://en.wikipedia.org/wiki/F-1_(rocket_engine (http://en.wikipedia.org/wiki/F-1_(rocket_engine))
it delivers 41 Million Watts of power and weighs less than 10 tons.
Good luck with designing an electrolytic cell that can handle that much power and isn't ridiculously heavy.
Incidentally, since the cell voltage is pretty much determined by the chemical reaction and will be about 2 volts we can calculate the electrical current needed to deliver that sort of power.
It's about 20 million amps.
Typically cables handle about 1000 amps per square inch.
So you need cables with a cross section of about 20000 square inches. That's a square section cable about 350 cm on each side.
A metre of a cable like that would weigh about ten times much as the jet engine.
(Cooling the cell may also be a problem)
" Can Electrolysis Be Used As a Propulsion Method?"
No.
This really is a silly idea.
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Unfortunately, it would generate far, far less thrust than a gas turbine engine or rocket engine of similar mass. It would also require large amounts of electricity for little pay off in terms of thrust.
i understand it can achieve psi of over 10000.A lot more than turbuns,etc.
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19970041522.pdf
http://www.spacecraftresearch.com/files/ZeledonPeckSpace2011.pdf
you are both wrong again as these research papers prove.
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And how do you generate the electricity to electrolyse the water? Nuclear reactors have a reasonably high energy density but then you need a steam cycle driving a turbine and a generator and it all gets very heavy and complicated.
In a ship, you can use the turbine to drive the propellor directly or through an electric motor, but the whole machine won't fly. Better to electrolyse water on the ground, liquefy the hydrogen and oxygen, shove them into tanks in your flying machine, and recombine them in a rocket motor, just like we do already.
If you want a welding gas, electrolyse the water with an alternating current. The stochiometric mixture of hydrogen and oxygen is reasonably stable until ignited, when it turns back to water with the release of loads of heat. "Brown's Gas" welders are quite handy for work in a confined space - not as hot as acetylene but no carbon oxides are produced. Now the question is whether you can liquefy Brown's Gas and make a single-tank liquid rocket motor. Alas, no, because the two elements recombine explosively in the liquid state!