Magnetohydrodynamics

[Kaziarl]

What is it?

I watched The Hunt for Red October the other day, in which this concept was a prominent part of the movie. The new Russian Typhoon class sub had a Magnetohydronynamic drive system, aka Caterpillar Drive, which had no moving parts and rendered the sub virtually silent.

However, they didn't really explain how it worked, which is understandable in a feature film due to time constraints. But it did get me curious. Is there anything in current science, theoretical or otherwise, that relates to this concept? Or is it total Hollywood asshatery?

 

[Jadzia]

Basically is a branch of fluid dynamics which tries to model the behaviour of liquids which respond to magnetic fields.

Magnetic liquids, aka ferrofluids.

A magnet will draw the ferrofluid out of a dish. It forms a ball surrounding the magnet.

[yt]http://www.youtube.com/watch?v=ob7aXIoySvo[/yt]

In the presence of a magnetic field, the fluid develops poles which cause it to repel itself to some extent. While this could motivate fractal-like formations, surface tension of the ferrofluid prevents things getting too intricate, and gives the fluid a relatively smooth surface.

[yt]http://www.youtube.com/watch?v=Gso_XVxa-rE[/yt]

Ferrofluids enjoy climbing up the arms of magnetised spirals. Some people have made art with them.

[yt]http://www.youtube.com/watch?v=me5Zzm2TXh4[/yt]

 

[Asbo Zaprudder]

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

Simple demo here that anyone can build:

http://www.youtube.com/watch?v=Trvd2XOIeXY

 

[T'Girl]

I remember the movie and always wondered if something like the Caterpillar Drive would work in reverse to generate power in a hydro-electric dam. Instead of those very expensive turbine generators.

 

[Kaziarl]

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

Simple demo here that anyone can build:

http://www.youtube.com/watch?v=Trvd2XOIeXY

So, you get a strong enough electromagnetic field, the right set up, and the engine could conceivably work, atleast for propulsion. Two questions come to mind, and i'll probably think of another while typing them.

1) How much power would that take?
2) Would it really be "Silent"?
3) Would speed be controlled by regulating power like a dimmer light switch? (oversimplified, but I'm sure the basic idea is there)


edit: btw, thanks alot Jadzia... now i want to get my hands on some of that ferrofluid and play with it. lol.

 

[Jadzia]

http://www.rapidonline.com/Educatio...sign/Materials/Ferrofluid/71907/kw/ferrofluid

 

[Asbo Zaprudder]

I remember the movie and always wondered if something like the Caterpillar Drive would work in reverse to generate power in a hydro-electric dam. Instead of those very expensive turbine generators.

I doubt it would work very efficiently with fresh water, which is a hundred times poorer conducter than brine (5 siemens per metre for sea water as opposed to typically 0.05 S/m for fresh water; the conductivity of Copper is 60000000 S/m).

I wonder if a 3-phase linear induction motor would work with the sea water acting as the passive conductor -- no need to pass a current directly. Perhaps the induced eddy currents would produce much less electrolytic outgassing and noise. You'd still have the problem of a pulsing EM signature as regards stealth.

 

[Kaziarl]

http://www.rapidonline.com/Educatio...sign/Materials/Ferrofluid/71907/kw/ferrofluid

haha, thanks . thats like dangling a Hershey bar in front of a chocoholic :P