Exploring Magnetohydrodynamic Water Propulsion for Silent Submarines

[taylaron]

Submarine propulsion

Regarding nuclear powered submarines, they produce electric energy through the use of a generator that is being powered by steam from a “boiler” –for simplicity-
Would this energy be enough to power a submarine using magnetohydrodynamic water propulsion? Using electricity to power a device that uses the electricity to move water through this “chamber” that runs the length of the ship?

Article found on magnetohydrodynamic water propulsion found at:
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This could be the key to “silent” submarines if possible.
I’m no physicist and am simply curious wither a submarines electrical output is enough to move enough water for a submarine to move significantly.
I know Honda experimented on magnetohydrodynamic water propulsion, and failed. But they don’t have nuclear power plants aboard their boats do they…..

I also know that they use electrolysis to make pure water and oxygen for their extended underwater travels. Magnetohydrodynamic propulsion expels water flow, hydrogen, and oxygen (from separating the hydrogen and oxygen in the water).
They could use this electrolysis for their oxygen and water supply. Neat and efficient.
The bad thing is, if it was possible, it would already be done. I’m afraid my perspectives on the required energy are way off.


Thank you everybody

 

[taylaron]

anybody?
some input would would be great.

 

[Morbius]

Submarine propulsion

Regarding nuclear powered submarines, they produce electric energy through the use of a generator that is being powered by steam from a “boiler” –for simplicity-...
The bad thing is, if it was possible, it would already be done. I’m afraid my perspectives on the required energy are way off.

taylaron,

Have you been watching "Hunt for Red October"?

The generators in subs are sized to provide the electrical needs of the sub,
but that doesn't mean they can't be sized to convert the entire turbine
output to electricity - as in a land-based commercial power plant.

The question I would have would be if magnetohydrodynamics would be
"gilding a lilly". One would have to know what the real noise makers are
on a sub.

Certainly propellors CAN be noise makers, but the Navy has put a lot of
work into making propellors as quiet as possible. The machining of propellors
is done very precisely. Toshiba got into trouble several years back when it
was discovered that they sold machining equipment with proprietary US
technology to Russia; which used that equipment to make quieter props for
Russian subs.

http://lubbers-line.blogspot.com/2005/10/toshiba-and-russian-espionage-again.html

However, suppose the turbine were the noisiest device on the sub. Then it
wouldn't make sense to go with MHD; because you would still have the
turbine noise.

I would bet that the U.S. Navy is making subs as quiet as possible within the
limits of current technology.

Dr. Gregory Greenman
Physicist

 

[3trQN]

Japan successfully ran a Prototype MHD Ship the Yamoto 1 Apparently.

 

[Astronuc]

Japan successfully ran a Prototype MHD Ship the Yamoto 1 Apparently.

While true, the speed was limited to 15 km/h (8 knots), they did not have to be concerned with 'noise' and I am quite sure they used conventional marine power systems rather than a nuclear plant, and the ships had a relatively limited demonstration period.

As Morbius indicated, the Navy is constantly looking for ways to make submarines quieter, as well as more reliable and less costly. The US Navy has certainly looked into MHD.

 

[taylaron]

i've seen the hunt for red october and i was assuming that the "caterpiller drive" was some sort of MHD engine. although i don't recall them ever calling it that.

thank you all for your help.

and happy new year

 

[taylaron]

so does MHD technology pose any usefullness in the near future? in your opinion.

 

[Morbius]

i've seen the hunt for red october and i was assuming that the "caterpiller drive" was some sort of MHD engine. although i don't recall them ever calling it that.

taylaron,

In the movie, "Hunt for Red October", I believe Ryan is told that the
catepillar is an MHD device by the "sub-driver" [ former sub captain ]
Oliver Wendell "Skip" Tyler; that he came to the USA to see.

Dr. Gregory Greenman
Physicist

 

[taylaron]

thanks morbius for your help

 

[sanman]

The coupling effect for MHD seems very poor.

 

[taylaron]

helping depth problems...

I know this is going off topic but,
For submersible vehicles for underwater exploration, they have a definite depth limit due to the integrity of the hull correct? the inside of these vehicles are full of air and pose a problem with implosion/folding when going too deep. Because you can't compress liquids, why not build a vehicle that is filled with a non-conductive liquid? Because water is a conductor, if the thing is filled, it will naturally fry the electronics. But if it was filled with a liquid that doesn’t conduct electricity. wouldn’t this dramatically help the maximum depth problem? I am merely curious, I don’t know if they're already doing this.
Thank you for your time.

 

[LURCH]

I would bet that the U.S. Navy is making subs as quiet as possible within the
limits of current technology.

Dr. Gregory Greenman
Physicist

Up until recently, you would have one that bet. However, the Germans appear to have beat us out with theirhttp://www.marineforce.net/class-212A.html" .

It is now the worlds quietest submarine, which nicely illustrates your point about the chief source of noise being something other than the propeller. The new Germans sub uses a propeller, just like nuclear powered American subs, but because it uses hydrogen fuel cells rather than a reactor, it is much quieter, because it does not have "the noise of the reactors cooling system", according to one interview I saw on, TLC.

 

[Morbius]

It is now the worlds quietest submarine, which nicely illustrates your point about the chief source of noise being something other than the propeller. The new Germans sub uses a propeller, just like nuclear powered American subs, but because it uses hydrogen fuel cells rather than a reactor, it is much quieter, because it does not have "the noise of the reactors cooling system", according to one interview I saw on, TLC.

LURCH,

More likely the noise of the TURBINE and reduction GEARS!

The Navy submarine cooling systems are very quiet - can't elaborate here.

The noise is from mechanical sources - a fast spinning turbine, and the gearing that
it takes to reduce the speed to much slower speeds of the sub's propellor.

I would bet the German subs use low RPM motors to turn the propellor, thus eliminating
the need for reduction gearing.

The German subs are quiet - but they are SLOOOOWWW compared to a US nuclear
sub. They may be able to sneak up on a nuke - but they most certainly can't run from
a nuke.

Dr. Gregory Greenman
Physicist

 

[russ_watters]

Up until recently, you would have one that bet. However, the Germans appear to have beat us out with theirhttp://www.marineforce.net/class-212A.html" .

It is now the worlds quietest submarine, which nicely illustrates your point about the chief source of noise being something other than the propeller. The new Germans sub uses a propeller, just like nuclear powered American subs, but because it uses hydrogen fuel cells rather than a reactor, it is much quieter, because it does not have "the noise of the reactors cooling system", according to one interview I saw on, TLC.

That's just a slightly better diesel sub - diesel subs are always the quietest subs (an electric motor running off a battery is very quiet), but they have a pretty severe drawback in that they require air to run the engines to charge the batteries.

The US very likely still holds the title when it comes to subs that can stay underwater for long periods of time (months rather than days).

[edit: Wik says 3 weeks. That would surprise me. Perhaps it is 3 weeks if they don't move...]

 

[berkeman]

I know this is going off topic but,
For submersible vehicles for underwater exploration, they have a definite depth limit due to the integrity of the hull correct? the inside of these vehicles are full of air and pose a problem with implosion/folding when going too deep. Because you can't compress liquids, why not build a vehicle that is filled with a non-conductive liquid? Because water is a conductor, if the thing is filled, it will naturally fry the electronics. But if it was filled with a liquid that doesn’t conduct electricity. wouldn’t this dramatically help the maximum depth problem? I am merely curious, I don’t know if they're already doing this.
Thank you for your time.

Like, fill the submarine with oxygenated Flourinert?

http://en.wikipedia.org/wiki/Flourinert

Then train all the submariners to breath the stuff, and give them special glasses so that they can focus on the displays and see still. Kind of like (what was the name of that movie...something like The Deep or The Chasm?...with the John Glenn actor guy?)

 

[Morbius]

The US very likely still holds the title when it comes to subs that can stay underwater for long periods of time (months rather than days).

[edit: Wik says 3 weeks. That would surprise me. Perhaps it is 3 weeks if they don't move...]

Russ,

I think you were correct the first time - it's more like months.

The Trident SSBN "boomers" certainly can stay submerged for months - that's how they
hide. The basic limitation on how long a Trident can remain at sea, and remain submerged
is how much food they can carry.

The sub can make it's own fresh water and oxygen from seawater.

A good book on life on a Trident is:

"Big Red: The Three-Month Voyage of a Trident Nuclear Submarine"
by Douglas C. Waller

https://www.amazon.com/dp/0380820781/?tag=pfamazon01-20

Dr. Gregory Greenman
Physicist

 

[LURCH]

Russ,

I think you were correct the first time - it's more like months.

The Trident SSBN "boomers" certainly can stay submerged for months - that's how they
hide. The basic limitation on how long a Trident can remain at sea, and remain submerged
is how much food they can carry.

The sub can make it's own fresh water and oxygen from seawater.

A good book on life on a Trident is:

"Big Red: The Three-Month Voyage of a Trident Nuclear Submarine"
by Douglas C. Waller

https://www.amazon.com/dp/0380820781/?tag=pfamazon01-20

Dr. Gregory Greenman
Physicist

The "three weeks' was for the German sub.

 

[taylaron]

rover suggestion

Like, fill the submarine with oxygenated Flourinert?

http://en.wikipedia.org/wiki/Flourinert

Then train all the submariners to breath the stuff, and give them special glasses so that they can focus on the displays and see still. Kind of like (what was the name of that movie...something like The Deep or The Chasm?...with the John Glenn actor guy?)

sounds like the movie "the abyss" by james cameron.
in this movie i think they use liquid oxygen or something along those lines to "breathe a liquid for insane depths."
but i was talking about mini remote controlled subs. i suggest filling one up with a non conductive liquid and sealing it shut. wouldent this let the rover go much deeper?

 

[taylaron]

nuclear power and fuel cells

hey,
in a submarine nuclear power plant, one of the forms of radiation is alpha radiation correct and it is identical to helium correct? but does it have orbiting electrons?
it doesn't say so in wikipedia's

Alpha particles (named after the first letter in the Greek alphabet, α) are a highly ionizing form of particle radiation that have low penetration. They consist of two protons and two neutrons bound together into a particle identical to a helium nucleus; hence, it can be written as He2+. The alpha particle mass is 6.644656×10-27 kg, which is equivalent to the energy of 3.72738 GeV.

Alpha particles are emitted by radioactive nuclei such as uranium or radium in a process known as alpha decay. This sometimes leaves the nucleus in an excited state, with the emission of a gamma ray removing the excess energy. In contrast to beta decay, alpha decay is mediated by the strong nuclear force. Classically, alpha particles do not have enough energy to escape the potential of the nucleus. However, the quantum tunnelling effect allows them to escape. When an alpha particle is emitted, the atomic mass of an element goes down by roughly 4.0015 amu, due to the loss of 4 nucleons. The atomic number of the atom goes down by 2, as the atom loses 2 protons, becoming a new element. An example of this is when radium becomes radon gas due to alpha decay.

although it does say it consists of 2 protons and 2 neutrons. no electrons? or did they leave those out for some strange reason?

i think this is where I am wrong
dispite that probability, i'll go on with my idea

couldent you take those helium particles and strip the elctrons from them like in the process used by fuel cells? or the same thing by using the beta emissions (high energy, high speed electrons) to produce electricity.

i think I am really screwed up here...

 

[zeta]

It's probably not wise me blowing what little captial I have at this forum being a newb and all, but I put in an SBIR proposal after grad school for a propulsion system, based around manipulating the dipole moments of water using electric field gradients. The system as proposed was too small to be practical and I suppose what was gained in noise suppresion was lost in creating a massive EM signature :)

 

[Morbius]

although it does say it consists of 2 protons and 2 neutrons. no electrons? or did they leave those out for some strange reason?

tayaron,

No - the alpha particles that come out of a radioactive nuclide DON'T have electrons.

That's why alpha radiation is so harmful - the fact that the alpha particle doesn't have
electrons, means that it is charged. It's actually "doubly charged" - there are 2 protons;
i.e. 2 "+" charges, without electrons to balance that out.

The alpha particle is a charged particle, and as it traverses through matter, there is an
attractive force between the alpha and the electrons. The alpha also has a lot of
energy, so it can, in essence; "pull" electrons away from where they were. That leaves
an ion where the alpha has pulled an electron away.

That's why high energy alpha radiation is "ionizing radiation". It "messes up" the
electron structure of the material through which it traverses. If that material happens
to be proteins or DNA of a living organism - the organism is damaged - potentially
lethaly, as in the case of the spy that was "poisoned".

Fortunately, because alpha particles react so strongly, they lose their energy rather
quickly - so they don't have much of a range and can be easily shielded. You can
shield yourself from alphas with a sheet of paper. The alpha will deposit all its energy
in the paper, and come to rest.

Alpha particles can't get through the dead layer of skin on your body. So alpha particles
outside the body are no problem. But if they ever get IN you - like the spy - then you
have problems.

Obviously in a submarine reactor; alpha particles are ZERO problem. The sub reactor
has enough shielding to stop the gamma, and alphas can be stopped by a sheet of paper.

Dr. Gregory Greenman
Physicist

 

[theCandyman]

While we're on the subject of electrons, do plasma ions have all of their electrons stripped? All I keep reading is that plasmas are made of positivly charged ions and electrons. I don't know if that means the ions are just missing one electron or all of them (for cases other than Hydrogen).

 

[Astronuc]

While we're on the subject of electrons, do plasma ions have all of their electrons stripped? All I keep reading is that plasmas are made of positivly charged ions and electrons.

In the case of a hydrogen plasma, the electrons are free of the protons (H as 1 p (d or t) and 1 e). Plasma infers that a gas is ionized. Remember the binding energy of a ground state electron in H is 13.6 eV - but plasmas are heated into the keV range - at least on earth. The electrons and nuclei have more kinetic energy than binding energy.

In He, the first ionziation energy is 24.6 ev, as compared to alpha particles which have kinetic energy of several MeV. However, alpha particles collide with surrouding matter, which is ionized, and quickly loose kinetic energy until they slow down and stop where they pickup two electrons.

When an alpha particle is emitted form a nucleus, the charge on the nuclear decreases by 2e. Two electrons then leave the atom and go off in search of a positive charge. Meanwhile the alpha particle is picking up two electrons from some other atom, to there is a cascade of moving electrons.

To have a reliable electric current, one would need a lot of alpha decays, and that is not practical for an electrical source for that and several other reasons.

 

[berkeman]

sounds like the movie "the abyss" by james cameron.
in this movie i think they use liquid oxygen or something along those lines to "breathe a liquid for insane depths."
but i was talking about mini remote controlled subs. i suggest filling one up with a non conductive liquid and sealing it shut. wouldent this let the rover go much deeper?

Yes! That was the movie. But it was oxygenated Flourinert. Even though I'm a scuba diver, I don't think I could acclimate to breathing a liquid.

 

[Morbius]

While we're on the subject of electrons, do plasma ions have all of their electrons stripped? All I keep reading is that plasmas are made of positivly charged ions and electrons. I don't know if that means the ions are just missing one electron or all of them (for cases other than Hydrogen).

Candyman,

Depends on how hot the plasma is.

If you have an atom with atomic number Z, you can strip off one electron, and
have an ion that consists of a nucleus with a charge of +Z, and an electron cloud
of charge -(Z-1) for a net charge of +1.

The quantity Z* [ "Z-star"] tells you what the effective ionization level is. The
higher the Z* the more ionized the atoms.

Dr. Gregory Greenman
Physicist

 

[sid_galt]

Russ,
The basic limitation on how long a Trident can remain at sea, and remain submerged
is how much food they can carry.

This is not related to nuclear physics but do you have any idea why the Trident does not just fish for food to give potentially unlimited time underwater until the fuel is exhausted?

 

[theCandyman]

How would you like to eat fish everyday for years on end?

 

[Morbius]

This is not related to nuclear physics but do you have any idea why the Trident does not just fish for food to give potentially unlimited time underwater until the fuel is exhausted?

sid,

A Trident submarine doesn't exhaust its fuel for 20 years!

In fact the Trident doesn't even have a hatch over the reactor to facilitate refueling the sub.
After 20 years, when it is time to refuel the reactor, the Navy actually cuts a hole in the
hull of the sub and repairs the hull after refueling. The sub will probably only be refueled
once, and at most twice; in its lifetime.

I confirmed this with the crew when I toured a Trident, the U.S.S. Georgia at what was
then called Subase Bangor in Washington state about 10 years ago. The Georgia has
recently undergone a conversion from a ballistic missile sub to a guided missile sub;
SSBN --> SSGN:

http://www.navy.mil/navydata/fact_display.asp?cid=4100&tid=300&ct=4

In regards to fishing, I doubt that they want to open the hull to bring anything inside.
You also don't want to have anything "passing through" the pressure hull; otherwise
you are asking for trouble.

The sub could fish on the surface, but a Trident stays underwater pretty much thourgh out
the mission in order to avoid detection by satellite.

Dr. Gregory Greenman
Physicist

 

[IAMOLBG]

what about a small submarine. What would it take for something like that to reach fairly high speeds. It's be submerged for only hours to a day. Manned though. It would be nice if it wasn't nuclear because of size limitations and health hazards.

 

[taylaron]

you will need to provide the energy to displace the water around the craft; the energy required for that at 'high speeds' (more specific please) I am afraid would be too much at current practical energy/kg metric. a slipstream craft would be best, although the issue is packing enough power in the given space to achieve the minimum speed is a concerning issue. whither its using a propeller or some other method will effect your efficiency. and that's just to propel the device, you need power for the passengers as well. small, sounds relatively large to me.

 

[chayced]

Slight change in topic, but I am amazed that the US hasn't invested in Stirling engines for sub propulsion. It seems pretty logical to me, you have primary coolant providing heat directly to the heat engine with a piston and hydrogen between it and the circ water. Maybe it's cost, maybe its size requirements.

Read about a Swedish company that builds Stirling powered submarines, but they are liquid 02 cooled and probably have a high temperature differential.

Oh and the 20 year lifespan of a reactor core is based around alternating at sea times of low power and in port periods of shutdown. If a boat is running at high power for extended periods of time that number can quickly fall. Then again if a boat was driven that hard for that long, it would be time for a complete overhaul anyway.

 

[mgb_phys]

Read about a Swedish company that builds Stirling powered submarines, but they are liquid 02 cooled and probably have a high temperature differential.

They aren't liquid oxygen cooled, they burn diesel fuel and the liquid oxygen is just a compact way of storing O2. The stirling engine can run from the diesel and stored O2 while submerged - the exhaust is dissolved directly into the sea water.
When the O2 runs out you still have a regular diesel electric boat. I assume they could also carry plants to make more LOX while at sea and surfaced. The advantage is that you get much better submerged endurance combined with diesel electric quiet, and you don't have any of that icky nuclear stuff to dispose of.

Nuclear boats are never completely quiet because of the coolant circuit. The Polaris boats were described by an-ex submariner technician as sounding like a "pair of skeletons ****ing in a metal trash can" - I assume they have improved since then.

 

[taylaron]

downside to that technique is you can track a submarine that is cooled by the surrounding water by measuring the surrounding temperature of the water. kind of like a hunting dog does a scent. without using the surrounding water to dissipate the heat from the source, you would need a lot of liquid He or O2 or N2 to do anything practical.

 

[chayced]

I believe the Stirling's in question were liquid oxygen cooled, just diesel and oxygen fired. It would be a waste to do it otherwise. Guess my comment was a bit ambiguous.

The coolant loop in a nuclear sub is only loud at high driven flowrates. In a natural circulation mode the loudest thing would be the reduction gear and main engine followed by the generators and pumps.

So yes, they have improved since the Polaris boats. From what I understand Trident boats are silent and easier to find by looking for the quiet spot than by looking for the noise they make. Until sonar technology improves its pretty pointless in making a quieter boat, unless of course it can go quietly at high speeds.

 

[mgb_phys]

The Swedish boats are only 1300Hp and supposedly because the exhaust dissolves into the sea water the temperature diffuses away form the boat quickly. Yes - it would make sense to arrange the cold side of the Stirling to be the LOX pre-heater.

I don't know how a nuclear boat cools the condensers but with a 30-50MW reactor something has to dump a lot of heat.