Magnetohydrodynamic drive
Encyclopedia
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
. The working principle involves electrification of the propellant (gas or water) which can then be directed by a magnetic field, pushing the vehicle in the opposite direction. Although some working prototypes exist, MHD drives remain impractical and exist mostly in the world of science fiction.
. Pushing the water out the back accelerates the vehicle in the forward direction.
The physics equation describing this propelling force is Fmag = I (L × B) where L is the vector in the direction of the current 'I' and its length is the distance the current travels, B is the magnetic field, and × denotes the cross product
.
MHD is attractive because it has no moving parts, which means that a good design might be silent, reliable, efficient, and inexpensive.
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. Such a large generator is not required when an engine directly drives a propeller.
are based on magnetohydrodynamic principles. In these the working fluid is usually a plasma
or a thin cloud of ion
s. Some of the techniques include various kinds of ion thruster
, the magnetoplasmadynamic thruster
, and the variable specific impulse magnetoplasma rocket
.
. Way, on leave from his job at Westinghouse Electric
, assigned his senior year undergraduate students to develop a submarine with this new propulsion system. In 1991, another prototype, the Yamato 1
, was completed in Japan
by the Ship & Ocean Foundation (later known as the Ocean Policy Research Foundation). The ship was first successfully propelled in Kobe
harbour in June 1992. Yamato 1
is propelled by two MHD thrusters that run without any moving parts.
universe, the sub-light impulse engines
are MHDs according to the Star Trek: The Next Generation Technical Manual
, where the working fluid/propellant is the plasma generated by nuclear fusion
reactors.
The "Oregon", a ship in the Oregon Files
series of books by author Clive Cussler
, has a magnetohydrodynamic drive. In Valhalla Rising, Clive Cussler
writes the same drive into the powering of Captain Nemo
's Nautilus
.
The film adaptation of The Hunt for Red October
popularized the magnetohydrodynamic drive as a "caterpillar drive" for submarine
s, 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
.
Propulsor
A propulsor is a mechanical device that gives propulsion. The word is commonly used in the marine vernacular, and implies a mechanical assembly that is more complicated than a propeller. The Kort nozzle and Pump-jet are examples....
is a method for propelling seagoing vessels using only electric and magnetic fields with no moving parts
Moving parts
The moving parts of a machine are those parts of it that move. Machines comprise both moving and fixed parts. The moving parts have controlled and constrained motions....
, using magnetohydrodynamics
Magnetohydrodynamics
Magnetohydrodynamics is an academic discipline which studies the dynamics of electrically conducting fluids. Examples of such fluids include plasmas, liquid metals, and salt water or electrolytes...
. The working principle involves electrification of the propellant (gas or water) which can then be directed by a magnetic field, pushing the vehicle in the opposite direction. Although some working prototypes exist, MHD drives remain impractical and exist mostly in the world of science fiction.
Ship propulsion
An electric current is passed through seawater in the presence of an intense magnetic field, which interacts with the magnetic field of the current through the water. Functionally, the seawater is then the moving, conductive part of an electric motorElectric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
. Pushing the water out the back accelerates the vehicle in the forward direction.
The physics equation describing this propelling force is Fmag = I (L × B) where L is the vector in the direction of the current 'I' and its length is the distance the current travels, B is the magnetic field, and × denotes the cross product
Cross product
In mathematics, the cross product, vector product, or Gibbs vector product is a binary operation on two vectors in three-dimensional space. It results in a vector which is perpendicular to both of the vectors being multiplied and normal to the plane containing them...
.
MHD is attractive because it has no moving parts, which means that a good design might be silent, reliable, efficient, and inexpensive.
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. Such a large generator is not required when an engine directly drives a propeller.
Spacecraft propulsion
A number of experimental methods of spacecraft propulsionSpacecraft propulsion
Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. There are many different methods. Each method has drawbacks and advantages, and spacecraft propulsion is an active area of research. However, most spacecraft today are propelled by forcing a gas from the...
are based on magnetohydrodynamic principles. In these the working fluid is usually a plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
or a thin cloud of ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
s. Some of the techniques include various kinds of ion thruster
Ion thruster
An ion thruster is a form of electric propulsion used for spacecraft propulsion that creates thrust by accelerating ions. Ion thrusters are categorized by how they accelerate the ions, using either electrostatic or electromagnetic force. Electrostatic ion thrusters use the Coulomb force and...
, the magnetoplasmadynamic thruster
Magnetoplasmadynamic thruster
The Magnetoplasmadynamic thruster is a form of electrically powered spacecraft propulsion which uses the Lorentz force to generate thrust...
, and the variable specific impulse magnetoplasma rocket
Variable specific impulse magnetoplasma rocket
The Variable Specific Impulse Magnetoplasma Rocket is an electro-magnetic thruster for spacecraft propulsion. It uses radio waves to ionize and heat a propellant and magnetic fields to accelerate the resulting plasma to generate thrust...
.
Prototypes
The first prototype of this kind of propulsion was built and tested in 1965 by Steward Way, a professor of mechanical engineering at the University of California, Santa BarbaraUniversity of California, Santa Barbara
The University of California, Santa Barbara, commonly known as UCSB or UC Santa Barbara, is a public research university and one of the 10 general campuses of the University of California system. The main campus is located on a site in Goleta, California, from Santa Barbara and northwest of Los...
. Way, on leave from his job at Westinghouse Electric
Westinghouse Electric (1886)
Westinghouse Electric was an American manufacturing company. It was founded in 1886 as Westinghouse Electric Company and later renamed Westinghouse Electric Corporation by George Westinghouse. The company purchased CBS in 1995 and became CBS Corporation in 1997...
, assigned his senior year undergraduate students to develop a submarine with this new propulsion system. In 1991, another prototype, the Yamato 1
Yamato 1
Yamato 1 is a boat built in the early 1990s by Japanese conglomerate "The Mitsubishi Group" through their subsidiary company Mitsubishi Heavy Industries, Ltd at Wadasaki-cho Hyogo-ku, Kobe. It uses a MagnetoHydrodynamic Drive , driven by a liquid helium-cooled superconductor, and can travel at 15...
, was completed in Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
by the Ship & Ocean Foundation (later known as the Ocean Policy Research Foundation). The ship was first successfully propelled in Kobe
Kobe
, pronounced , is the fifth-largest city in Japan and is the capital city of Hyōgo Prefecture on the southern side of the main island of Honshū, approximately west of Osaka...
harbour in June 1992. Yamato 1
Yamato 1
Yamato 1 is a boat built in the early 1990s by Japanese conglomerate "The Mitsubishi Group" through their subsidiary company Mitsubishi Heavy Industries, Ltd at Wadasaki-cho Hyogo-ku, Kobe. It uses a MagnetoHydrodynamic Drive , driven by a liquid helium-cooled superconductor, and can travel at 15...
is propelled by two MHD thrusters that run without any moving parts.
Fiction
In the Star TrekStar Trek
Star Trek is an American science fiction entertainment franchise created by Gene Roddenberry. The core of Star Trek is its six television series: The Original Series, The Animated Series, The Next Generation, Deep Space Nine, Voyager, and Enterprise...
universe, the sub-light impulse engines
Impulse drive
In the fictional Star Trek universe, the impulse drive is the method of propulsion that starships and other spacecraft use when they are travelling below the speed of light. Typically powered by deuterium fusion reactors, impulse engines let ships travel interplanetary distances readily...
are MHDs according to the Star Trek: The Next Generation Technical Manual
Star Trek: The Next Generation Technical Manual
Star Trek: The Next Generation: Technical Manual is a paperback reference guide detailing the inner and other workings of the fictional Federation starship Enterprise-D and other aspects of technology that appeared in the television series Star Trek: The Next Generation.Authored by Rick Sternbach...
, where the working fluid/propellant is the plasma generated by nuclear fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
reactors.
The "Oregon", a ship in the Oregon Files
The Oregon Files
The Oregon Files are a group of novels written by author Clive Cussler and co-author Craig Dirgo and later co-author Jack Du Brul. The books follow the mysterious "Corporation" and its leader Juan Cabrillo. The "Oregon Files" come from the name of the ship on which the Corporation is based, the...
series of books by author Clive Cussler
Clive Cussler
Clive Eric Cussler is an American adventure novelist and marine archaeologist. His thriller novels, many featuring the character Dirk Pitt, have reached The New York Times fiction best-seller list more than seventeen times...
, has a magnetohydrodynamic drive. In Valhalla Rising, Clive Cussler
Clive Cussler
Clive Eric Cussler is an American adventure novelist and marine archaeologist. His thriller novels, many featuring the character Dirk Pitt, have reached The New York Times fiction best-seller list more than seventeen times...
writes the same drive into the powering of Captain Nemo
Captain Nemo
Captain Nemo, also known as Prince Dakkar, is a fictional character featured in Jules Verne's novels Twenty Thousand Leagues Under the Sea and The Mysterious Island ....
's Nautilus
Nautilus (Verne)
The Nautilus is the fictional submarine featured in Jules Verne's novels Twenty Thousand Leagues Under the Sea and The Mysterious Island . Verne named the Nautilus after Robert Fulton's real-life submarine Nautilus...
.
The film adaptation of The Hunt for Red October
The Hunt for Red October (film)
The Hunt for Red October is a 1990 thriller film based on the novel of the same name by Tom Clancy. It was directed by John McTiernan and stars Sean Connery as Captain Marko Ramius and Alec Baldwin as Jack Ryan...
popularized the magnetohydrodynamic drive as a "caterpillar drive" for submarine
Submarine
A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...
s, an undetectable "silent drive" intended to achieve stealth
Stealth technology
Stealth technology also termed LO technology is a sub-discipline of military tactics and passive electronic countermeasures, which cover a range of techniques used with personnel, aircraft, ships, submarines, and missiles, to make them less visible to radar, infrared, sonar and other detection...
in submarine warfare
Submarine warfare
Naval warfare is divided into three operational areas: surface warfare, air warfare and underwater warfare. The latter may be subdivided into submarine warfare and anti-submarine warfare as well as mine warfare and mine countermeasures...
. 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
Pump-jet
A pump-jet, hydrojet, or water jet, is a marine system that creates a jet of water for propulsion. The mechanical arrangement may be a ducted propeller with nozzle, or a centrifugal pump and nozzle...
.
See also
- Lorentz forceLorentz forceIn physics, the Lorentz force is the force on a point charge due to electromagnetic fields. It is given by the following equation in terms of the electric and magnetic fields:...
, relates electric and magnetic fields to propulsion force - MagnetohydrodynamicsMagnetohydrodynamicsMagnetohydrodynamics is an academic discipline which studies the dynamics of electrically conducting fluids. Examples of such fluids include plasmas, liquid metals, and salt water or electrolytes...
- ElectrohydrodynamicsElectrohydrodynamicsElectrohydrodynamics , also known as electro-fluid-dynamics or electrokinetics, is the study of the dynamics of electrically charged fluids. It is the study of the motions of ionised particles or molecules and their interactions with electric fields and the surrounding fluid...