A Magnetohydrodynamic drive or MHD propulsor , is a method for propelling seagoing vessels using only electric and magnetic fields with no moving parts, using magnetohydrodynamics .

An electric current is passed through seawater in the presence of an intense magnetic field. Functionally, the seawater is then the moving, conductive part of an electric motor . Pushing the water out the back accelerates the vehicle.

MHD is attractive because it has no moving parts, which means that a good design might be silent, reliable, efficient, and inexpensive.

Click here for a video of the experiment

The movie The Hunt for Red October popularized the magnetohydrodynamic drive as a caterpillar drive for submarines , an undetectable "silent drive" intended to achieve stealth in submarine warfare . In reality, the current traveling through the water would create gases and noise, and the magnetic fields would induce a detectable magnetic signature. In the novel, of which the movie was an adaptation, the caterpillar was a pumpjet .

The major problem with MHD is that with current technologies it is more expensive and much slower than a propeller driven by an engine. The extra expense is from the large generator that must be driven by an engine.

Design

The first job here is to make a salt solution (brine). The simplest method is get an old coffee mug or container that is able to hold boiling water. Boil the kettle and fill it to about 3/4 full with the boiled water. I used some old sea salt lumps I found at the back of the cupboard and empty a quantity in and stir, continue to pour and stir, pour and stir until you cannot dissolve anymore. You will know when you get to this point when a crystal of salt remains at the bottom of the mug. This is called a saturated solution. Leave to cool

Connections

Simply take your double ended crocodile clips and attach them to a PP9 9 volt battery. I used this particular battery so that I could have a good voltage and also the fact it was rechargeable. On the other ends I attached a screw each, you can use thick copper wire if you want, but this is Kitchen Table Science and this is what I had at hand.

You are now ready to do the experiment

Take some of the salt solution and place it in a saucer, I did this to demonstrate as it was very close to the magnet, you may want to do it with an old egg cup. Place the old hard disc magnet on a flat surfaceand then place the saucer on top of it. Place the two screws and hold them about 1 inch apart, you should now have movement...if not check the connections and if there is any charge left in it.....simple