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 field, which can then be repelled. 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: electromagneticusing electricity to create a magnetic field, and propulsionthe process of propelling something. When a fluid (liquid or gas) is employed as the moving conductor, the propulsion may be termed magnetohydrodynamic drive. 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 application 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". can be seen in maglev trains and military railguns. 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.
History
One of the first recorded discoveries regarding electromagnetic propulsion was in 1889 when Professor Elihu Thomson 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 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.
In the USSR at the beginning of 1960th at the Institute of Hydrodynamics, Novosibirsk, Russia, prof. V.F. Minin laid down the experimental foundations of electromagnetic accelerating of bodies to hypersonic velocity.
Uses
Trains
thumb|[[SCMaglev on the Yamanashi test track in Japan in November 2005]]
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 coasters and water rides.
Maglev
In a maglev train the primary coil assembly lies below the reaction plate.
A typical Maglev train costs three cents per passenger mile, or seven cents per ton mile (not including construction costs). 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. 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 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, electrodes 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.
Elevators
Cable-free elevators using EMP, capable of moving both vertically and horizontally, have been developed by German engineering firm Thyssen Krupp for use in high rise, high density buildings.
See also
- Coilgun
- Magnetohydrodynamics
- Railgun