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Magnetic levitation (maglev) is a relatively new transportation technology in which noncontacting vehicles travel safely at speeds of 250 to 300 miles-per-hour or higher while suspended, guided, and propelled above a guideway by magnetic fields. The guideway is the physical structure along which maglev vehicles are levitated. Various guideway configurations, e.g., T-shaped, U-shaped, Y-shaped, and box-beam, made of steel, concrete, or aluminum, have been proposed.
Figure 1 depicts the three primary functions basic to maglev technology: (1) levitation or suspension; (2) propulsion; and (3) guidance. In most current designs, magnetic forces are used to perform all three functions, although a nonmagnetic source of propulsion could be used. No consensus exists on an optimum design to perform each of the primary functions.
The two principal means of levitation are illustrated in Figures 2 and 3. Electromagnetic suspension (EMS) is an attractive force levitation system whereby electromagnets on the vehicle interact with and are attracted to ferromagnetic rails on the guideway. EMS was made practical by advances in electronic control systems that maintain the air gap between vehicle and guideway, thus preventing contact.
Variations in payload weight, dynamic loads, and guideway irregularities are compensated for by changing the magnetic field in response to vehicle/guideway air gap measurements.
Electrodynamic suspension (EDS) employs magnets on the moving vehicle to induce currents in the guideway. Resulting repulsive force produces inherently stable vehicle support and guidance because the magnetic repulsion increases as the vehicle/guideway gap decreases. However, the vehicle must be equipped with wheels or other forms of support for "takeoff" and "landing" because the EDS will not levitate at speeds below approximately 25 mph. EDS has progressed with advances in cryogenics and superconducting magnet technology.
Figure 2 and Figure 3
"Long-stator" propulsion using an electrically powered linear motor winding in the guideway appears to be the favored option for high-speed maglev systems. It is also the most expensive because of higher guideway construction costs.
"Short-stator" propulsion uses a linear induction motor (LIM) winding onboard and a passive guideway. While short-stator propulsion reduces guideway costs, the LIM is heavy and reduces vehicle payload capacity, resulting in higher operating costs and lower revenue potential compared to the long-stator propulsion. A third alternative is a nonmagnetic energy source (gas turbine or turboprop) but this, too, results in a heavy vehicle and reduced operating efficiency.
Guidance or steering refers to the sideward forces that are required to make the vehicle follow the guideway. The necessary forces are supplied in an exactly analogous fashion to the suspension forces, either attractive or repulsive. The same magnets on board the vehicle, which supply lift, can be used concurrently for guidance or separate guidance magnets can be used.
Maglev and U.S. Transportation
Maglev systems could offer an attractive transportation alternative for many time sensitive trips of 100 to 600 miles in length, thereby reducing air and highway congestion, air pollution, and energy use, and releasing slots for more efficient long-haul service at crowded airports. The potential value of maglev technology was recognized in the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA).
Before the passage of the ISTEA, Congress had appropriated $26.2 million to identify maglev system concepts for use in the United States and to assess the technical and economic feasibility of these systems. Studies were also directed toward determining the role of maglev in improving intercity transportation in the United States. Subsequently, an additional $9.8 million were appropriated to complete the NMI Studies.
What are the attributes of maglev that commend its consideration by transportation planners?
Faster trips - high peak speed and high acceleration/braking enable average speeds three to four times the national highway speed limit of 65 mph (30 m/s) and lower door-to-door trip time than high-speed rail or air (for trips under about 300 miles or 500 km). Still higher speeds are feasible. Maglev takes up where high-speed rail leaves off, permitting speeds of 250 to 300 mph (112 to 134 m/s) and higher.
Maglev has high reliability and less susceptible to congestion and weather conditions than air or highway travel. Variance from schedule can average less than one minute based on foreign high-speed rail experience. This means intra and intermodal connecting times can be reduced to a few minutes (rather than the half-hour or more required with airlines and Amtrak at present) and that appointments can safely be scheduled without having to consider delays.
Maglev gives petroleum independence - with respect to air and auto because of Maglev being electrically powered. Petroleum is unnecessary for the production of electricity. In 1990, less than 5 percent of the Nation's electricity was derived from petroleum whereas the petroleum used by both the air and automobile modes comes primarily from foreign sources.
Maglev is less polluting - with respect to air and auto, again because of being electrically powered. Emissions can be controlled more effectively at the source of electric power generation than at the many points of consumption, such as with air and automobile usage.
Maglev has a higher capacity than air travel with at least 12,000 passengers per hour in each direction. There is the potential for even higher capacities at 3 to 4 minute headways. Maglev provides sufficient capacity to accommodate traffic growth well into the twenty-first century and to provide an alternative to air and auto in the event of an oil availability crisis.
Maglev has high safety - both perceived and actual, based on foreign experience.
Maglev has convenience - due to high frequency of service and the ability to serve central business districts, airports, and other major metropolitan area nodes.
Maglev has improved comfort - with respect to air due to greater roominess, which allows separate dining and conference areas with freedom to move around. The absence of air turbulence ensures a consistently smooth ride.
The concept of magnetically levitated trains was first identified at the turn of the century by two Americans, Robert Goddard and Emile Bachelet. By the 1930s, Germany's Hermann Kemper was developing a concept and demonstrating the use of magnetic fields to combine the advantages of trains and airplanes. In 1968, Americans James R. Powell and Gordon T. Danby were granted a patent on their design for a magnetic levitation train.
Under the High-Speed Ground Transportation Act of 1965, the FRA funded a wide range of research into all forms of HSGT through the early 1970s. In 1971, the FRA awarded contracts to the Ford Motor Company and the Stanford Research Institute for analytical and experimental development of EMS and EDS systems. FRA-sponsored research led to the development of the linear electrical motor, the motive power used by all current maglev prototypes. In 1975, after Federal funding for high-speed maglev research in the United States was suspended, industry virtually abandoned its interest in maglev; however, research in low-speed maglev continued in the United States until 1986.
Over the past two decades, research and development programs in maglev technology have been conducted by several countries including: Great Britain, Canada, Germany, and Japan. Germany and Japan have invested over $1 billion each to develop and demonstrate maglev technology for HSGT.
The German EMS maglev design, Transrapid (TR07), was certified for operation by the German Government in December 1991. A maglev line between Hamburg and Berlin is under consideration in Germany with private financing and potentially with additional support from individual states in northern Germany along the proposed route. The line would connect with the high-speed Intercity Express (ICE) train as well as conventional trains. The TR07 has been tested extensively in Emsland, Germany, and is the only high-speed maglev system in the world ready for revenue service. The TR07 is planned for implementation in Orlando, Florida.
The EDS concept under development in Japan uses a superconducting magnet system. A decision will be made in 1997 whether to use maglev for the new Chuo line between Tokyo and Osaka.
The National Maglev Initiative (NMI)
Since the termination of Federal support in 1975, there was little research into high-speed maglev technology in the United States until 1990 when the National Maglev Initiative (NMI) was established. The NMI is a cooperative effort of the FRA of the DOT, the USACE, and the DOE, with support from other agencies. The purpose of the NMI was to evaluate the potential for maglev to improve intercity transportation and to develop the information necessary for the Administration and the Congress to determine the appropriate role for the Federal Government in advancing this technology.
In fact, from its inception, the U.S. Government has aided and promoted innovative transportation for economic, political, and social development reasons. There are numerous examples. In the nineteenth century, the Federal Government encouraged railroad development to establish transcontinental links through such actions as the massive land grant to the Illinois Central-Mobile Ohio Railroads in 1850. Beginning in the 1920s, the Federal Government provided commercial stimulus to the new technology of aviation through contracts for airmail routes and funds that paid for emergency landing fields, route lighting, weather reporting, and communications. Later in the twentieth century, Federal funds were used to construct the Interstate Highway System and assist States and municipalities in the construction and operation of airports. In 1971, the Federal Government formed Amtrak to ensure rail passenger service for the United States.