Superconducting paddle wheels, screws, and other propulsion units for high-speed ground transportation

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Abstract
High-speed ground vehicles magnetically suspended above a continuous aluminum guideway by superconducting coils can have a clearance of 0.1–0.3 m. To take full advantage of the large clearance, a propulsion system with a comparable clearance is needed. Two such systems based upon physically moving static magnetic fields produced by superconducting coils are proposed. With the use of a prime mover such as a gas turbine or a diesel engine, these systems avoid power collection problems and should result in a lower-weight propulsion unit. A numerical analysis of each has been made to determine the thrust, the lift force, and the efficiency as a function of various parameters. The mechanical efficiency of the paddle wheel appears to have a maximum of ∼60% at 483 km/h (300 mph), while that of the superconducting screw is (1-slip) for an infinitely long machine. End effects will degrade the efficiency somewhat for a screw of finite length.