A Magnetohydrodynamic drive or MHD propulsor, is a method proposed for propelling seagoing vessels. An electric current is passed through seawater in the presence of an intense magnetic field. Functionally, the seawater is the moving, conductive part of an electric motor. Pushing the water out the back accelerates the vehicle.

MHD is attractive to engineers because it has no moving parts, which means that a good design might be silent, reliable, efficient and inexpensive. Also known as a caterpillar drive for submarines, this was popularised in the movie The Hunt for Red October as being a "silent drive," an undetectable stealth superweapon in submarine warfare. In reality, the current traveling through the water would create a great amount of gases, and thus noise. USS Los Angeles A submarine is a specialized watercraft that can operate underwater. ... Red October redirects here; for the Bolshevik October Revolution, see October Revolution. ...

In the 1990s, Mitsubishi built several prototypes of ships propelled by an MHD system. These ships were able to reach speeds of 15 km/h despite projections of higher ones; // Events and trends The 1990s are generally classified as having moved slightly away from the more conservative 1980s, but keeping the same mind-set. ... The Mitsubishi companies, or the Mitsubishi Group of Companies or the Mitsubishi Group is a large group (keiretsu) of independently operated Japanese companies which share the Mitsubishi brand name. ...

Japan began sea trials of a prototype magnetic ship. Yamato 1 is propelled by two MHD (magnetohydrodynamic) thrusters that run without any moving parts. When completed, the MHD ship should be able to attain speeds of more than 100 knots (125 miles or 200 kilometers per hour), with little noise. This is several times the top speed of today’s ships, which are slowed down by turbulence created by the ship’s propellers. MHD works by applying a magnetic field to an electrically conducting fluid. The electrically conducting fluid used in the MHD thruster of the Yamoto 1 is seawater. [1]

The major problem with MHD is that with current technologies it is more expensive than a propeller driven by an engine. The extra expense is from the large generator that must be driven by an engine. Such a large generator is not required when an engine directly drives a propeller.

If fuel cells become common, MHD propulsors may have lower costs in some applications than electric motors driving propellers. A fuel cell is an electrochemical device similar to a battery, but differing from the latter in that it is designed for continuous replenishment of the reactants consumed; i. ...

A number of experimental methods of spacecraft propulsion are based on magnetohydrodynamic principles. In these the working fluid is usually a plasma or a thin cloud of ions. Some of the techniques include various kinds of ion thruster, the magnetoplasmadynamic thruster, and the variable specific impulse magnetoplasma rocket. A remote camera captures a close-up view of a Space Shuttle Main Engine during a test firing at the John C. Stennis Space Center in Hancock County, Mississippi Spacecraft propulsion is used to change the velocity of spacecraft and artificial satellites, or in short, to provide delta-v. ... The word plasma has a Greek root which means to be formed or molded (the word plastic shares this root). ... An ion is an elementary particle or system of elementary particles with a net electric charge. ... An ion engine test An ion thruster is one of several types of spacecraft propulsion that uses beams of ions for propulsion. ... Magneto-Plasmadynamic (MPD) thrusters are a form of electric Propulsion which use the Lorentz force (a force exerted on charged particles by magnetic and electrical fields in combination) to generate thrust. ... VASIMR test bed The Variable specific impulse magnetoplasma rocket (VASIMR) is a hypothetical form of spacecraft propulsion that uses radio waves and magnetic fields to accelerate a propellant. ...

See also

• Lorentz force, relates electric and magnetic fields to propulsion force

In physics, the Lorentz force is the force exerted on a charged particle in an electromagnetic field or just magnetic field. ...

External links

• Magnetohydrodynamic and the Mitsubishi Yamato
• Magnetohydrodynamic Water Propulsion
• MHD Propulsion
• Popular Science: Science Year by Year: Discoveries and Inventions from the Last Century that Shape our Lives (2001), New York: Scholastic, p. 208-209.