The future drive for boats: MHD drive without propellor

[Pirate88179]

A VERY important point, marine life is very sensitive to pollution, looks like this is dead in the water as far as propulison goes!

For electricity generation the pollution would not be a problem provided all generated potential was removed through very low resistance circuits.

I would not be too concerned, every boat and ship out there uses, and have used for many years, zinc or magnesium sacrificial anodes to prevent deterioration with the salt water.  These, of course, have to be replaced as they get "dissolved" over time while doing their job.  Don't get me wrong, I am not saying that just because we are already polluting the oceans in this manner now, it is ok to do more in the future.  I just don't think the amount of material released would anywhere compare to the costs (in terms of pollution) of all of the diesel fuel now being burned by the many ships at sea.

Bill

[ChileanOne]

Hello!

I have been reading about uses for the jealously kept secret MHD technology for years, in the online website of one of the few civilian MHD researcher, Dr. Jean Pierre Petit. He has many wonderfull divulgative comic books and one of them deals directly with the MHD propulsion for marine purposes, and also develops the theoretical views for the MHD flying machine (a "rip off" copy of this information was recently patented for a MHD propulsed drone, by a guy at Florida Tech).

The link for the comic book is here, it's completely worth the try.

http://www.savoir-sans-frontieres.com/JPP/telechargeables/English/the_silence_barrier.htm

I'll add some interesting snapshots:

[spinner]

The only downside, which shouldn't be flippantly overlooked, is the electrode and electrolyte chemical reactions, which could be a major pollution and toxicity issue for marine life if this form of propulsion was broadly introduced. If using non-inert electrodes, then they will disintegrate, and form various salts of the electrode metals suspended in the remaining electrolyte.

You're quite right, this really is a serious issue (sea pollution in many ways). But it is not the only one!

Replacing a power plant of e.g. a common power boat with an adequate MHD means replacing hundreds of (diesel, petrol) kWatts with hundreds of kilo!Amperes of electricity - as MHD concept is much much worse in Energy conversion efficiency (electricity to thrust) than a common mechanical interface (boat/ship propeller)....
It means you need a lot more powerful energy source (at least 10-times! for the same effect of thrust.)
Where to get a lot of electricity on a boat? Diesels? Nuclear generators? FE maybe..?

MHD in it's basics works mostly just as a water electrolyzer. The dynamic thrust (motion) is just a secondary, by far inferior effect.
Principle is known for >150 years, and so far I saw it being seriously "implemented" only in some movies (The hunt for the Red October?, Caterpillar drive?). It was presented as a silent (sonar undetectable) drive .... How about the chemical trace, which would be left behind a MHD driven submarine? 

Even when using inert electrodes in sea water, to avoid electrode disintegration due to ionic reactions, there will still be generation of chlorine gas, which is highly toxic, (and is usually not formed when non-inert electrodes are used).

It seems there is always a price to pay for our actions, and it's not always payable with money. Let's hope the price of this possible technology is negligible.
It is a very interesting concept, as most simple concepts are.
Cheers

Yes, Chlorine would be just one of the mostly unwanted side effects of MHD in a sea (salt waters). (MHD in a rivers/lakes is practically useless).
A five minutes cruising with a MHD-powered boat in a small bay would *probably* cause death of all marine life organisms in that bay....

How about a co-generation of power/thrust (burning the H2/O produced by the Electrolysis)?
Underwater gas explosions are mostly not really an efficient method to be used for continuous thrust.... Water pulse-jets? Ha...

Arcing water with HV (making "plasma" detonations)? Even less efficient....

So far, the 'antic' water propeller is still the most energy efficient device for water thrust we know....

[hartiberlin]

Well, can we have some numbers ?

Has the thrust produced by water arc explosions ever been measured ?

I guess it could be pretty huge versus used electrical power.
Especially if you use some setups like Peter Graneau used.
So this is then more like a water explosion where the steam is propelling the boat.
So it will also work in normal lake water where there is not much salt in the water.

Regards, Stefan.

[spinner]

Well, can we have some numbers ?
Has the thrust produced by water arc explosions ever been measured ?

Numbers for a water arc explosions efficiency? I don't have any. I think the correct figures are not exactly widely available.... God knows why?                                         

I guess it could be pretty huge versus used electrical power.
Especially if you use some setups like Peter Graneau used.
So this is then more like a water explosion where the steam is propelling the boat.

Sorry, I'll look at P.G.'s work...
In the mean time, steam explosions in water (as a thrust mechanism) are not very efficient... (If used directly (gas to fluid mechanical force conversion), without an usuall mechanical linkage)....

So it will also work in normal lake water where there is not much salt in the water.
Regards, Stefan.

The MHD efficiency depends on conductivity of the water (overall system efficiency) . Make it a low resistance, and it will act as a great medium... A great medium for a power conversion.... Of course, pouring tons of chemical substances like KoH into the water to get a suitable conductivity is not very efficient, no?
That's why a naturally Natrium rich water is more suitable....

Salt water has much higher conductivity (greater effect & lover losses) than a high resistance "potable" water (speaking about MHD)

But if you're counting on other mechanisms, like cavitation, hydroxy - explosions, etc... just build a decent proof of a concept modell....
Good Luck.
Cheers!