Electromagnetic propulsion
Encyclopedia
Electromagnetic propulsion (EMP), is the principle of accelerating an object by the utilization of a flowing electrical current and magnetic fields. The electrical current
is used to either create an opposing magnetic field
, or to charge a fluid, which can then be repelled. It is well known that when a current flows through a conductor
in a magnetic field, an electromagnetic force known as a Lorentz force
, pushes the conductor in a direction perpendicular to the conductor and the magnetic field. This repulsing force is what causes propulsion in a system designed to take advantage of the phenomenon. The term electromagnetic propulsion (EMP) can be described by its individual components: electromagnetic- using electricity to create a magnetic field (electromagnetism
), and propulsion- the process of propelling something. One key difference between EMP and propulsion achieved by electric motors is that the electrical energy used for EMP is not used to produce rotational energy
for motion; though both use magnetic fields and a flowing electrical current.
The science of electromagnetic propulsion does not have origins with any one individual and has applications in many different fields. The thought of using magnets for propulsion continues to this day and has been dreamed of since at least 1897 when John Munro published his fictional story "A Trip to Venus". Current applications can be seen in maglev trains and military railgun
s. Other applications that remain not widely used or still in development include ion thruster
for low orbiting satellites and magnetohydrodynamic drive
for ships and submarines.
made public his work with electromagnetic waves and alternating currents. A few years later Emile Bachelet proposed the idea of a metal carriage levitated in air above the rails in a modern railway, which he showcased in the early 1890s. In the 1960s Eric Roberts Laithwaite
developed the linear induction motor
, which built upon these principles and introduced the first practical application of electromagnetic propulsion. In 1966 James R. Powell
and Gordon Danby
patented the superconducting maglev transportation system, and after this engineers around the world raced to create the first high speed rail. From 1984 to 1995 the first commercial automated maglev system ran in Birmingham. It was a low speed Maglev shuttle that ran from the Birmingham International Airport to the Birmingham International Railway System.
Electromagnetic propulsion is utilized in transportation systems to minimize friction and maximize speed over long distances. This has mainly been implemented in high-speed rail systems that use a linear induction motor to power trains by magnetic currents. It has also been utilized in theme parks to create high-speed roller coaster
s and water rides.
Maglev:
In a maglev train the primary coil assembly lies below the reaction plate. There is a 1–10 cm (0.39-3.93 inch) air gap between that eliminates friction, allowing for speeds up to 500 km/h (310 mph). An alternating electric current is supplied to the coils, which creates a change in polarity of the magnetic field. This pulls the train forward from the front, and thrusts the train forward from the back.
A typical Maglev train costs three cents per passenger mile, or seven cents per ton mile (not including construction costs). This compares to 15 cents per passenger miles for travel by plane and 30 cents for ton mile for travel by intercity trucks. Maglev tracks have high longevity due to minimal friction and an even distribution of weight. Most last for at least 50 years and require little maintenance during this time. Maglev trains are promoted for their energy efficiency since they run on electricity, which can be produced by coal, nuclear, hydro, fusion, wind or solar power without requiring oil. On average most trains travel 483 km/h (300 mph) and use 0.4 megajoules per passenger mile. Using a 20 mi/gallon car with 1.8 people as a comparison, travel by car is typically 97 khp (60 mph) and uses 4 megajoules per passenger mile. Along with this there are no carbon dioxide emissions and the running of the train is significantly quieter than other trains, trucks or airplanes.
Assembly: Linear Induction Motor
A linear induction motor
consists of two parts: the primary coil assembly and the reaction plate. The primary coil assembly consists of phase windings surrounded by steel laminations, and includes a thermal sensor within a thermal epoxy. The reaction plate consists of a 3.2 mm (0.125 inch) thick aluminum or copper plate bonded to a 6.4 mm (0.25 inch) thick cold rolled steel sheet. There is an air gap between these two parts that creates the frictionless property an electromagnetic propulsion system encompasses.
Functioning of a linear induction motor begins with an AC force that is supplied to the coil windings within the primary coil assembly. This creates a traveling magnetic field that induces a current in the reaction plate, which then creates its own magnetic field. The magnetic fields in the primary coil assembly and reaction plate alternate, which generates force and direct linear motion.
The current thrust-to mass ratios of these systems are relatively low. Nevertheless, since they do not require propulsive mass, the vehicle mass is constant. Also, the thrust can be continuous with relatively low electric consumption. The biggest limitation would be mainly the electrical conductance of materials to produce the necessary values of the current in the propulsion system.
s at each side of the channel and source of power to send direct current
through the channel at right angles to magnetic flux in accordance with Lorentz force.
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
is used to either create an opposing magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
, or to charge a fluid, which can then be repelled. It is well known that when a current flows through a conductor
Electrical conductor
In physics and electrical engineering, a conductor is a material which contains movable electric charges. In metallic conductors such as copper or aluminum, the movable charged particles are electrons...
in a magnetic field, an electromagnetic force known as a Lorentz force
Lorentz force
In 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:...
, pushes the conductor in a direction perpendicular to the conductor and the magnetic field. This repulsing force is what causes propulsion in a system designed to take advantage of the phenomenon. The term electromagnetic propulsion (EMP) can be described by its individual components: electromagnetic- using electricity to create a magnetic field (electromagnetism
Electromagnetism
Electromagnetism is one of the four fundamental interactions in nature. The other three are the strong interaction, the weak interaction and gravitation...
), and propulsion- the process of propelling something. One key difference between EMP and propulsion achieved by electric motors is that the electrical energy used for EMP is not used to produce rotational energy
Rotational energy
The rotational energy or angular kinetic energy is the kinetic energy due to the rotation of an object and is part of its total kinetic energy...
for motion; though both use magnetic fields and a flowing electrical current.
The science of electromagnetic propulsion does not have origins with any one individual and has applications in many different fields. The thought of using magnets for propulsion continues to this day and has been dreamed of since at least 1897 when John Munro published his fictional story "A Trip to Venus". Current applications can be seen in maglev trains and military railgun
Railgun
A railgun is an entirely electrical gun that accelerates a conductive projectile along a pair of metal rails using the same principles as the homopolar motor. Railguns use two sliding or rolling contacts that permit a large electric current to pass through the projectile. This current interacts...
s. Other applications that remain not widely used or still in development include 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...
for low orbiting satellites and magnetohydrodynamic drive
Magnetohydrodynamic drive
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 which can then be directed by a magnetic field,...
for ships and submarines.
History
One of the first recorded discoveries regarding electromagnetic propulsion was in 1889 when Professor Elihu ThomsonElihu Thomson
Elihu Thomson was an American engineer and inventor who was instrumental in the founding of major electrical companies in the United States, the United Kingdom and France.-Early life:...
made public his work with electromagnetic waves and alternating currents. A few years later Emile Bachelet proposed the idea of a metal carriage levitated in air above the rails in a modern railway, which he showcased in the early 1890s. In the 1960s Eric Roberts Laithwaite
Eric Laithwaite
Eric Roberts Laithwaite was a British electrical engineer, known as the "Father of Maglev" for his development of the linear induction motor and maglev rail system.- Biography :...
developed the linear induction motor
Linear induction motor
A linear induction motor is an AC asynchronous linear motor that works by the same general principles as other induction motors but which has been designed to directly produce motion in a straight line....
, which built upon these principles and introduced the first practical application of electromagnetic propulsion. In 1966 James R. Powell
James R. Powell
James R. Powell is an American physicist notable — together with Dr. Gordon Danby — for his work on superconducting Maglev, for which he shared the Franklin Institute "Medal 2000 for Engineering"....
and Gordon Danby
Gordon Danby
Gordon T. Danby is an American physicist notable for his work on superconducting Maglev, for which he shared the Franklin Institute 'Medal 2000 for Engineering'.-References:...
patented the superconducting maglev transportation system, and after this engineers around the world raced to create the first high speed rail. From 1984 to 1995 the first commercial automated maglev system ran in Birmingham. It was a low speed Maglev shuttle that ran from the Birmingham International Airport to the Birmingham International Railway System.
Trains
Roller coaster
The roller coaster is a popular amusement ride developed for amusement parks and modern theme parks. LaMarcus Adna Thompson patented the first coasters on January 20, 1885...
s and water rides.
Maglev:
In a maglev train the primary coil assembly lies below the reaction plate. There is a 1–10 cm (0.39-3.93 inch) air gap between that eliminates friction, allowing for speeds up to 500 km/h (310 mph). An alternating electric current is supplied to the coils, which creates a change in polarity of the magnetic field. This pulls the train forward from the front, and thrusts the train forward from the back.
A typical Maglev train costs three cents per passenger mile, or seven cents per ton mile (not including construction costs). This compares to 15 cents per passenger miles for travel by plane and 30 cents for ton mile for travel by intercity trucks. Maglev tracks have high longevity due to minimal friction and an even distribution of weight. Most last for at least 50 years and require little maintenance during this time. Maglev trains are promoted for their energy efficiency since they run on electricity, which can be produced by coal, nuclear, hydro, fusion, wind or solar power without requiring oil. On average most trains travel 483 km/h (300 mph) and use 0.4 megajoules per passenger mile. Using a 20 mi/gallon car with 1.8 people as a comparison, travel by car is typically 97 khp (60 mph) and uses 4 megajoules per passenger mile. Along with this there are no carbon dioxide emissions and the running of the train is significantly quieter than other trains, trucks or airplanes.
Assembly: Linear Induction Motor
A linear induction motor
Linear motor
A linear motor is an electric motor that has had its stator and rotor "unrolled" so that instead of producing a torque it produces a linear force along its length...
consists of two parts: the primary coil assembly and the reaction plate. The primary coil assembly consists of phase windings surrounded by steel laminations, and includes a thermal sensor within a thermal epoxy. The reaction plate consists of a 3.2 mm (0.125 inch) thick aluminum or copper plate bonded to a 6.4 mm (0.25 inch) thick cold rolled steel sheet. There is an air gap between these two parts that creates the frictionless property an electromagnetic propulsion system encompasses.
Functioning of a linear induction motor begins with an AC force that is supplied to the coil windings within the primary coil assembly. This creates a traveling magnetic field that induces a current in the reaction plate, which then creates its own magnetic field. The magnetic fields in the primary coil assembly and reaction plate alternate, which generates force and direct linear motion.
Spacecraft
There are multiple applications for EMP technologies in the field of aerospace. Many of these applications are conceptual as of now, however, there are also several applications that range from near term to next century. One of such applications is the use of EMP to control fine adjustments of orbiting satellites. One of these particular systems is based on the direct interactions of the vehicle's own electromagnetic field and the magnetic field of the earth. The thrust force may be thought of as an electrodynamic force of interaction of the electric current inside its conductors with the applied natural field of the earth. To attain a greater force of interaction, the magnetic field must be propagated further from the flight craft. The advantages of such systems is the very precise and instantaneous control over the thrust force. In addition, the expected electrical efficiencies are far greater than those of current chemical rockets that attain propulsion through the intermediate use of heat; this results in low efficiencies and large amounts of gaseous pollutants. The electrical energy in the coil of the EMP system is translated to potential and kinetic energy through direct energy conversion. This results in the system having the same high efficiencies as other electrical machines while excluding the ejection of any substance into the environment.The current thrust-to mass ratios of these systems are relatively low. Nevertheless, since they do not require propulsive mass, the vehicle mass is constant. Also, the thrust can be continuous with relatively low electric consumption. The biggest limitation would be mainly the electrical conductance of materials to produce the necessary values of the current in the propulsion system.
Ships and Submarines
EMP and its applications for seagoing ships and submarines have been investigated since at least 1958 when Warren Rice filled a patent explaining the technology . The technology described by Rice considered charging the hull of the vessel itself. The design was later refined by allowing the water to flow through thrusters as described in a later patent by James Meng . The arrangement consists of a water channel open at both ends extending longitudinally through or attached to the ship, a means for producing magnetic field throughout the water channel, electrodeElectrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...
s at each side of the channel and source of power to send direct current
Direct current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...
through the channel at right angles to magnetic flux in accordance with Lorentz force.