A Novel Application of High Temperature Superconducting Cable for Seabed Coils in Ship Magnetic Deperming

The zero electrical resistivity of superconducting materials makes them ideal for long-distance electric-current transmission. In particular, high-temperature superconducting (HTS) materials require only moderate cooling power, and a few trials have successfully demonstrated their capability for power transmission. Utilizing a long extended HTS cable to generate an external magnetic field is an emerging application with unique challenges. Our study introduces a conceptual design of a flat seabed coil, proportional to a ship’s size, for the purpose of ship magnetic deperming. Magnetic deperming involves imposing a magnetic field on the ship’s hull to saturate the magnetization of its steel components. The required field is estimated to be 2,400 A/m, achievable by the flat seabed coils in shallow water. The deperming process requires an alternating magnetic field with decreasing peak intensity. We have designed the coil for the largest destroyer and submarine ships of the Japanese Maritime Self-Defense Force. The parameters required for the coil design were obtained from publicly-available information. Our design features three racetrack-shaped coils, each carrying a maximum current of 200 kA, spanning a total length of 1,200 m for a single coil, set flat at a depth of 12 m, and cooled by liquid hydrogen, using the currently available HTS materials and technologies.