Magnetic levitation

A Magnetic levitation train or maglev is a train-like vehicle that is suspended in the air above the track, and propelled forward using the repulsive and attractive forces of magnetism. Because of the lack of physical contact between the track and the vehicle, the only friction is that between the carriages and the air. Consequently maglev trains can travel at very high speeds with reasonable energy consumption and noise levels (systems have been proposed that operate at up to 650 km/h, which is far faster than is practical with conventional rail transport). Whilst the very high maximum speeds make maglev trains potential competitors to airliners on many routes, the enormous cost of constructing the tracks has limited maglev vehicles largely to demonstration projects.

There are two primary types of maglev technology: One that relies on superconducting magnets and a newer, potentially more economical system that uses permanent magnets.

Japan and Germany are active in maglev research producing several different approaches and designs. In one design, the train can be levitated by the repulsive force of like poles or the attractive force of opposite poles of magnets. The train can be propelled by a linear motor on the track or on the locomotive or both. Massive electrical coils are placed along the track in order to produce the magnetic field necessary to propel the train, leading some to speculate that the cost of constructing such tracks would be enormous.

Other systems make use of permanently magnetic materials that can be used to line the tracks if the motor is mounted on board the locomotive. However, the weight of a super electromagnet on the train is a major design and operational issue. A very strong magnetic field is required to levitate a massive train, hence maglev research is tightly related to superconductor research for an efficient electromagnet. The effect of a powerful magnetic field on the human body is largely unknown. For the safety of the passengers, shielding might be needed, which would add additional weight to the train. The concept is simple, but the engineering and design aspects are complex.

Transrapid (a German maglev company, which has a test track in Emsland, Germany), constructed the first operational maglev railway in the world, from Shanghai, China to the airport. It opened in 2002.

See also: High speed rail