Return Table of Contents
ANALYSIS PROCESS
In order to determine the technical feasibility of deploying maglev in the United States, the NMI Office performed a comprehensive assessment of the state-of-the-art of maglev technology.
Over the past two decades various
ground transportation systems have been developed overseas, having operational
speeds in excess of 150 mph (67 m/s), compared to 125 mph (56 m/s) for
the U.S. Metroliner. Several steel-wheel-on-rail trains can maintain a
speed of 167 to 186 mph (75 to 83 m/s), most notably the Japanese Series
300 Shinkansen, the German ICE, and the French TGV. The German Transrapid
Maglev train has demonstrated a speed of 270 mph (121 m/s) on a test track,
and the Japanese have operated a maglev test car at 321 mph (144 m/s).
The following are descriptions of the French, German, and Japanese systems
used for comparison to the U.S. Maglev (USML) SCD concepts.
French Train a Grande Vitesse
(TGV)
The French National Railway's TGV is representative of the current generation of high-speed, steel-wheel-on-rail trains. The TGV has been in service for 12 years on the Paris-Lyon (PSE) route and for 3 years on an initial portion of the Paris-Bordeaux (Atlantique) route. The Atlantique train consists of ten passenger cars with a power car at each end. The power cars use synchronous rotary traction motors for propulsion. Roof mounted pantographs collect electric power from an overhead catenary. Cruise speed is 186 mph (83 m/s). The train is nontilting and, thus, requires a reasonably straight route alignment to sustain high speed. Although the operator controls the train speed, interlocks exist including automatic overspeed protection and enforced braking. Braking is by a combination of rheostat brakes and axle-mounted disc brakes. All axles possess antilock braking. Power axles have anti-slip control. The TGV track structure is that of a conventional standard-gauge railroad with a well-engineered base (compacted granular materials). The track consists of continuous-welded rail on concrete/steel ties with elastic fasteners. Its high-speed switch is a conventional swing-nose turnout. The TGV operates on pre-existing tracks, but at a substantially reduced speed. Because of its high speed, high power, and antiwheel slip control, the TGV can climb grades that are about twice as great as normal in U.S. railroad practice and, thus, can follow the gently rolling terrain of France without extensive and expensive viaducts and tunnels.
The German TR07 is the high-speed Maglev system nearest to commercial readiness. If financing can be obtained, ground breaking will take place in Florida in 1993 for a 14-mile (23 km) shuttle between Orlando International Airport and the amusement zone at International Drive. The TR07 system is also under consideration for a high-speed link between Hamburg and Berlin and between downtown Pittsburgh and the airport. As the designation suggests, TR07 was preceded by at least six earlier models. In the early seventies, German firms, including Krauss-Maffei, MBB and Siemens, tested full-scale versions of an air cushion vehicle (TR03) and a repulsion maglev vehicle using superconducting magnets. After a decision was made to concentrate on attraction maglev in 1977, advancement proceeded in significant increments, with the system evolving from linear induction motor (LIM) propulsion with wayside power collection to the linear synchronous motor (LSM), which employs variable frequency, electrically powered coils on the guideway. TR05 functioned as a people mover at the International Traffic Fair Hamburg in 1979, carrying 50,000 passengers and providing valuable operating experience.
The TR07, which operates on 19.6 miles (31.5 km) of guideway at the Emsland test track in northwest Germany, is the culmination of nearly 25 years of German Maglev development, costing over $1 billion. It is a sophisticated EMS system, using separate conventional iron-core attracting electromagnets to generate vehicle lift and guidance. The vehicle wraps around a T-shaped guideway. The TR07 guideway uses steel or concrete beams constructed and erected to very tight tolerances. Control systems regulate levitation and guidance forces to maintain an inch gap (8 to 10 mm) between the magnets and the iron "tracks" on the guideway. Attraction between vehicle magnets and edge-mounted guideway rails provide guidance. Attraction between a second set of vehicle magnets and the propulsion stator packs underneath the guideway generate lift. The lift magnets also serve as the secondary or rotor of a LSM, whose primary or stator is an electrical winding running the length of the guideway. TR07 uses two or more nontilting vehicles in a consist. TR07 propulsion is by a long-stator LSM. Guideway stator windings generate a traveling wave that interacts with the vehicle levitation magnets for synchronous propulsion. Centrally controlled wayside stations provide the requisite variable-frequency, variable-voltage power to the LSM. Primary braking is regenerative through the LSM, with eddy-current braking and high-friction skids for emergencies. TR07 has demonstrated safe operation at 270 mph (121 m/s) on the Emsland track. It is designed for cruise speeds of 311 mph (139 m/s).
Japanese High-Speed Maglev
The Japanese have spent over $1 billion developing both attraction and repulsion maglev systems. The HSST attraction system, developed by a consortium often identified with Japan Airlines, is actually a series of vehicles designed for 100, 200, and 300 km/h. Sixty miles-per-hour (100 km/h) HSST Maglevs have transported over two million passengers at several Expos in Japan and the 1989 Canada Transport Expo in Vancouver. The high speed Japanese repulsion Maglev system is under development by Railway Technical Research Institute (RTRI), the research arm of the newly privatized Japan Rail Group. RTRI's ML500 research vehicle achieved the world high-speed guided ground vehicle record of 321 mph (144 m/s) in December 1979, a record that still stands, although a specially modified French TGV rail train has come close. A manned three-car MLU001 began testing in 1982. Subsequently, the single car MLU002 was destroyed by fire in 1991. Its replacement, the MLU002N, is being used to test the sidewall levitation that is planned for eventual revenue system use. The principal activity at present is the construction of a $2 billion, 27-mile (43 km) maglev test line through the mountains of Yamanashi Prefecture, where testing of a revenue prototype is scheduled to commence in 1994.
The Central Japan Railway Company plans to begin building a second high-speed line from Tokyo to Osaka on a new route (including the Yamanashi test section) starting in 1997. This will provide relief for the highly profitable Tokaido Shinkansen, which is nearing saturation and needs rehabilitation. To provide ever improving service, as well as to forestall encroachment by the airlines on its present 85 percent market share, higher speeds than the present 171 mph (76 m/s) are regarded as necessary. Although the design speed of the first generation maglev system is 311 mph (139 m/s), speeds up to 500 mph (223 m/s) are projected for future systems. Repulsion maglev has been chosen over attraction maglev because of its reputed higher speed potential and because the larger air gap accommodates the ground motion experienced in Japan's earthquake-prone territory. The design of Japan's repulsion system is not firm. A 1991 cost estimate by Japan's Central Railway Company, which would own the line, indicates that the new high-speed line through the mountainous terrain north of Mt. Fuji would be very expensive, about $100 million per mile (8 million yen per meter) for a conventional railway. A maglev system would cost 25 percent more. A significant part of the expense is the cost of acquiring surface and subsurface ROW. Knowledge of the technical details of Japan's high-speed Maglev is sparse. What is known is that it will have superconducting magnets in bogies with sidewall levitation, linear synchronous propulsion using guideway coils, and a cruise speed of 311 mph (139 m/s).
U.S. Contractors' Maglev Concepts (SCDs)
Three of the four SCD concepts use an EDS system in which superconducting magnets on the vehicle induce repulsive lift and guidance forces through movement along a system of passive conductors mounted on the guideway. The fourth SCD concept uses an EMS system similar to the German TR07. In this concept, attraction forces generate lift and guide the vehicle along the guideway. However, unlike TR07, which uses conventional magnets, the attraction forces of the SCD EMS concept are produced by superconducting magnets. The following individual descriptions highlight the significant features of the four U.S. SCDs.
Bechtel SCD
The Bechtel concept is an EDS system that uses a novel configuration of vehicle-mounted, flux-canceling magnets. The vehicle contains six sets of eight superconducting magnets per side and straddles a concrete box-beam guideway. Interaction between the vehicle magnets and a laminated aluminum ladder on each guideway sidewall generates lift. Similar interaction with guideway mounted nullflux coils provides guidance. LSM propulsion windings, also attached to the guideway sidewalls, interact with vehicle magnets to produce thrust. Centrally controlled wayside stations provide the required variable-frequency, variable-voltage power to the LSM. The Bechtel vehicle consists of a single car with an inner tilting shell. It uses aerodynamic control surfaces to augment magnetic guidance forces. In an emergency, it delevitates onto air-bearing pads. The guideway consists of a post-tensioned concrete box girder. Because of high magnetic fields, the concept calls for nonmagnetic, fiber-reinforced plastic (FRP) post-tensioning rods and stirrups in the upper portion of the box beam. The switch is a bendable beam constructed entirely of FRP.
Foster-Miller SCD
The Foster-Miller concept is an EDS similar to the Japanese high-speed Maglev, but has some additional features to improve potential performance. The Foster-Miller concept has a vehicle tilting design that would allow it to operate through curves faster than the Japanese system for the same level of passenger comfort. Like the Japanese system, the Foster-Miller concept uses superconducting vehicle magnets to generate lift by interacting with null-flux levitation coils located in the sidewalls of a U-shaped guideway. Magnet interaction with guideway-mounted, electrical propulsion coils provides null-flux guidance. Its innovative propulsion scheme is called a locally commutated linear synchronous motor (LCLSM). Individual "H-bridge" inverters sequentially energize propulsion coils directly under the bogies. The inverters synthesize a magnetic wave that travels along the guideway at the same speed as the vehicle. The Foster-Miller vehicle is composed of articulated passenger modules and tail and nose sections that create multiple-car "consists." The modules have magnet bogies at each end that they share with adjacent cars. Each bogie contains four magnets per side. The U-shaped guideway consists of two parallel, post-tensioned concrete beams joined transversely by precast concrete diaphragms. To avoid adverse magnetic effects, the upper post-tensioning rods are FRP. The high-speed switch uses switched null-flux coils to guide the vehicle through a vertical turnout. Thus, the Foster-Miller switch requires no moving structural members.
Grumman SCD
The Grumman concept is an EMS with similarities to the German TR07. However, Grumman's vehicles wrap around a Y-shaped guideway and use a common set of vehicle magnets for levitation, propulsion, and guidance. Guideway rails are ferromagnetic and have LSM windings for propulsion. The vehicle magnets are superconducting coils around horseshoe-shaped iron cores. The pole faces are attracted to iron rails on the underside of the guideway. Nonsuperconducting control coils on each iron-core leg modulate levitation and guidance forces to maintain a 1.6-inch (40 mm) air gap. No secondary suspension is required to maintain adequate ride quality. Propulsion is by conventional LSM embedded in the guideway rail. Grumman vehicles may be single or multi-car consists with tilt capability. The innovative guideway superstructure consists of slender Y-shaped guideway sections (one for each direction) mounted by outriggers every 15-feet to a 90-foot (4.5 m to a 27 m) spline girder. The structural spline girder serves both directions. Switching is accomplished with a TR07-style bending guideway beam, shortened by use of a sliding or rotating section.
Magneplane SCD
The Magneplane concept is a single-vehicle EDS using a trough-shaped 0.8-inch (20 mm) thick aluminum guideway for sheet levitation and guidance. Magneplane vehicles can self-bank up to 45 degrees in curves. Earlier laboratory work on this concept validated the levitation, guidance, and propulsion schemes. Superconducting levitation and propulsion magnets are grouped in bogies at the front and rear of the vehicle. The centerline magnets interact with conventional LSM windings for propulsion and generate some electromagnetic "roll-righting torque" called the keel effect. The magnets on the sides of each bogie react against the aluminum guideway sheets to provide levitation. The Magneplane vehicle uses aerodynamic control surfaces to provide active motion damping. The aluminum levitation sheets in the guideway trough form the tops of two structural aluminum box beams. These box beams are supported directly on piers. The high-speed switch uses switched null-flux coils to guide the vehicle through a fork in the guideway trough. Thus, the Magneplane switch requires no moving structural members.
