Mag-train propulsion prototype funded: magnetic repulsion to drive train

November 07, 2000

Albuquerque, N.M. -- More powerful than an ordinary locomotive and expected to climb steep mountains without losing traction, Seraphim -- a simpler, less expensive US alternative to the magnetically levitated (maglev) trains of Europe and Japan -- is now funded for development at the Department of Energy's Sandia National Laboratories.

The fiscal year 2001 Transportation Appropriations Bill passed by Congress and signed into law by President Clinton on Oct. 23 allocates $2 million to Sandia for further motor testing and design of its Seraphim technology, which relies upon magnetic repulsion to push a vehicle forward. (In mid-September, Sandia received a FY 2000 appropriation of $1 million, to build a full-scale prototype of its Seraphim motor.)

The same 2001 bill allocates an additional $2 million to the Colorado Intermountain Fixed Guideway Authority (CIFGA), a state planning agency, to perform cost and technical analyses on an essentially silent, magnetically powered, monorail transit system for the Denver metropolitan area. CIFGA's and Sandia's intent is to develop an urban 21st century system robust enough to reach from the Denver International Airport through downtown Denver to the more mountainous western suburbs. A Seraphim-based system is expected by backers to decrease new highway construction, vehicle noise, atmospheric pollution, and other environmental degradations attendant on more highways and automobiles. Miller Hudson, Executive Director of CIFGA, a state-planning agency developing the monorail project, said, "We are pleased that the Federal Transit Administration is funding the Seraphim prototype. We believe there is a nearly perfect match between what we need in Colorado and what Sandia is developing."

Los Angeles, Seattle, Atlanta, San Francisco, Albuquerque...?

Other regions in which Seraphim could be used as part of a cost-effective transit system include Los Angeles, Seattle, Atlanta, San Francisco, and other locations "where the terrain and distances make it important to travel at high average speeds within existing rights-of-way," says Bruce Kelley, project leader of the Sandia effort. Kelley adds that a transit system using Seraphim "would also enable an all-weather, high-speed connection to be established between Albuquerque and Santa Fe along the I-25 right-of-way, when the traffic density and economics justify such a connection."

Key parts of the work to be completed in the year ahead include analyses of system energy efficiency, construction costs, and operating costs. Should these analyses lead to a system design that is economically attractive to one or more transit agencies, a working system could be riding the rails at the Pueblo, Colo., Transportation Technology Center in about 5 years.

The science behind Seraphim was originally developed for the Strategic Defense Initiative (colloquially referred to as Star Wars) of the Reagan years, and uses magnetic forces to hurl projectiles at 20 times the speed of sound. A challenge for Seraphim researchers was to moderate the force of propulsion. Seraphim -- an acronym for Segmented Rail Phased Induction Motor -- relies upon electromagnetic forces to push a transit vehicle forward and to provide braking. The motor generates vertical forces in addition to the horizontal propulsion forces and thus is considered a form of "maglev" but the completed vehicle probably will rely on wheels -- a far cheaper technology -- for support.

Is levitation necessary?

"Conventional magnetic levitation is possible, and fascinating to the public, but costly," says Barry Marder, principal inventor of Sandia's Seraphim technology. "The main limitation to high-speed trains is air resistance, not rolling friction. So why add all the complexity needed for levitation? The TGV train in France has demonstrated that wheels are perfectly good at speeds up to 250 miles per hour." The TGV is a French acronym for "Train a Grande Vitesse."

Sandia researchers will design and test a prototype motor that can power a test vehicle at speeds up to 125 MPH. This should permit actual transit at average speeds of 60-70 MPH, including stops, over grades of up to 8 1/2 percent even in periods of snow and ice accumulation. Conventional transit systems are limited to grades of a few percent in good weather conditions, because the reliance on friction between steel wheels and steel rails limits the grade a conventional transit vehicle can safely climb.

A five-year stop at the station

In the mid-1990s, Sandia researchers demonstrated a Seraphim motor prototype that accelerated a two-foot tall aluminum plate to 34 miles per hour in only 12 feet as it traveled along rails. However, no funding was available to build a motor suitable for testing on a vehicle.

Now, after a five-year stop at the station, the propulsion system will roll the next mile in its development.

Preliminary cost studies have shown that a Seraphim-powered transit system with the equivalent carrying capacity of 6-8 highway lanes could be deployed for $12-$22 million per mile depending on corridor geography and construction conditions. This cost compares favorably with the cost of an equivalent capacity of new highway lanes in many urban areas.

The system, operated on a guideway such as an elevated monorail, would operate within existing rights-of-way and provide significant congestion mitigation for corridors where the cost of building additional highway lanes is prohibitive.

How it works

The Seraphim motor works by sequentially powering a series of electromagnetic coils mounted on the vehicle. The powered coils, by a well-known principle of physics, induce associated eddy currents and magnetic fields of opposite direction in passive coils incorporated in the guideway. The resultant repulsion of the magnetic fields accelerates the transit vehicle. Sensors monitor the location of the coils on the vehicle with respect to the coils in the guideway and control the sequential firing of the powered coils to produce either acceleration or braking. Compared to the original satellite launcher, the challenge in designing a Seraphim motor for transit applications is making it operate efficiently at low speeds.

A number of transit applications and amusement park rides use conventional linear induction motors (LIMs) for propulsion. One example is the low-speed shuttle trains used at Dallas-Fort Worth International Airport, which operates at about 30 MPH. A conventional LIM-powered vehicle was tested in the 1970's by the Federal Railroad Administration at the Transportation Technology Center in Pueblo, Colo. This vehicle reached speeds up to 250 MPH, and proved the viability of LIMs for high-speed transit. The Seraphim motor is a modular, high-performance extension of LIM technology that could enable cost-effective, energy efficient transit system deployment within existing transportation rights-of-way.

For 2001, says Kelley, expect continued development of Seraphim's motor and controls, as well as work on the safety, surety, and systems controls aspects of the project.

Sandia is a multiprogram DOE laboratory, operated by a subsidiary of Lockheed Martin Corp. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major research and development responsibilities in national security, energy, and environmental technologies.
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DOE/Sandia National Laboratories

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