The term "mag-lev" refers not only to the vehicles, but to the railway system as well, specifically designed for magnetic levitation and propulsion. All operational implementations of mag-lev technology have had minimal overlap with wheeled train technology and have not been compatible with conventional rail tracks. Because they cannot share existing infrastructure, these mag-lev systems must be designed as complete transportation systems.
There are two particularly notable types of maglev technology:
- For electromagnetic suspension (EMS), electromagnets in the train attract it to a magnetically conductive (usually steel) track.
- Electrodynamic suspension (EDS) uses electromagnets on both track and train to push the train away from the rail.
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Electromagnetic Suspension
In current electromagnetic suspension (EMS) systems, the train levitates above a steel rail while electromagnets, attached to the train, are oriented toward the rail from below. The system is typically arranged on a series of C-shaped arms, with the upper portion of the arm attached to the vehicle, and the lower inside edge containing the magnets. The rail is situated between the upper and lower edges.
Magnetic attraction varies with the cube of distance, so minor changes in distance between the magnets and the rail produce greatly varying forces. These changes in force are dynamically unstable - if there is a slight divergence from the optimum position, the tendency will be to exacerbate this, and complex systems of feedback control are required to maintain a train at a constant distance from the track, (approximately 15 millimeters (0.6 in)).
The major advantage to suspended maglev systems is that they work at all speeds, unlike electrodynamic systems which only work at a minimum speed of about 30 km/h. This eliminates the need for a separate low-speed suspension system, and can simplify the track layout as a result. On the downside, the dynamic instability of the system demands high tolerances of the track, which can offset, or eliminate this advantage.
Electrodynamic Suspension
In electrodynamic suspension (EDS), both the rail and the train exert a magnetic field, and the train is levitated by the repulsive force between these magnetic fields. The magnetic field in the train is produced by either superconducting magnets or by an array of permanent magnets. The repulsive force in the track is created by an induced magnetic field in wires or other conducting strips in the track. A major advantage of the repulsive maglev systems is that they are naturally stable - minor narrowing in distance between the track and the magnets creates strong forces to repel the magnets back to their original position, while a slight increase in distance greatly reduces the force and again returns the vehicle to the right separation. No feedback control is needed.
Repulsive systems have a major downside as well. At slow speeds, the current induced in these coils and the resultant magnetic flux is not large enough to support the weight of the train. For this reason the train must have wheels or some other form of landing gear to support the train until it reaches a speed that can sustain levitation. Since a train may stop at any location, due to equipment problems for instance, the entire track must be able to support both low-speed and high-speed operation. Another downside is that the repulsive system naturally creates a field in the track in front and to the rear of the lift magnets, which act against the magnets and create a form of drag. This is generally only a concern at low speeds, at higher speeds the effect does not have time to build to its full potential and other forms of drag dominate.
The drag force can be used to the electrodynamic system's advantage, however, as it creates a varying force in the rails that can be used as a reactionary system to drive the train, without the need for a separate reaction plate, as in most linear motor systems. Alternately, propulsion coils on the guideway are used to exert a force on the magnets in the train and make the train move forward. The propulsion coils that exert a force on the train are effectively a linear motor: an alternating current flowing through the coils generates a continuously varying magnetic field that moves forward along the track. The frequency of the alternating current is synchronized to match the speed of the train. The offset between the field exerted by magnets on the train and the applied field creates a force moving the train forward.
Uses Within The Republic
By far the most popular Mag-Lev technology used throughout the Republican Star Cluster is the EMS variety for its relatively low maintenance costs associated with the tracks since most of the hardware required is on the train cars themselves.
The city of New Chicago on the planet Galileo has an extensive mag-lev network, with spokes reaching out to most of the smaller towns and all the way to College Park. It is of the EMS variety and all of the cars may work on any of the different lines. Additionally, the elevated trains that run through the city are also mag-lev though of a much smaller variety and a different "gauge" than the extra-city train lines.
Most of the cars used on this line were built by Independent Maglev in the city of Little Dallas on Kaesong. While Maglev Technologies on Penglai built the initial rail cars for the extra-city lines on Galileo, in later years they were also made by Independent.
Athena City also boasts an extensive Mag-Lev rail network, both above and below ground. Because Maglev Technologies had a great deal of experience with New Chicago, Athena City selected the company as the provider of its Mag-Lev cars.
The planet of Troy was another adopter of Mag-Lev technology, initially selecting Maglev Technologies as its provider but later switching to a home grown company called Troyer Maglev which is the exclusive supplier of its cars. The Troy Mag-Lev network connects all the cities and towns on world together at high speeds and a lower cost than using flying transport. It is operated by a consortium of the city and town's business councils as a way to provide tourism and trade dollars to the linked destinations.
Both Yamanashi and Kanagawa sport Mag-Lev networks between their cities as well with an extensive network connecting almost every city and town on Yamanashi. On Kanagawa, the networks typically only connect the more densely inhabited cities of the night side of the planet while the day side is connected only by roads due to its relatively sparse population. Both networks were constructed by Maglev Technologies though Kanagawa has since switched over to using Independent Maglev cars for its tracks.
Major Mag-Lev Companies
- Independent Maglev - Established in 2113 by a group of investors when New Chicago put out its requests for proposals for building a Mag-Lev network on Galileo.
- Maglev Technologies - Established in 2125 after seeing the success of the Galileo experiment and hoping to bring the technology to more of the colonial worlds.
- Troyer Maglev - Established in 2150 by a group of investors hoping to capitalize on the local angle when the network consortium put out an RFP for new cars in the same year. It primarily deals with the trains on Troy but also sells to some of the smaller networks throughout the Republican Star Cluster.
