Maglevs for ships

Several approaches have been devised for suppressing the rolling motion of ships at sea. Active systems that position a movable mass to provide a countering torque can rapidly damp the rolling, but the inherent friction not only is noisy but also produces constant wear. Researchers from the Korea Institute of Machinery and Materials recently demonstrated that the technology employed to reduce friction in magnetically levitated trains can do the same for ships. Indeed, their antirolling device is essentially a maglev train car on a short track that runs side to side across the ship’s midline. For the demonstration, the team built a 118-kg, small-scale model with the cross-sectional shape of a twin-hulled catamaran. A C-shaped, 4kg mass—the “train car”—wrapped around a 1-m-long rail along the top of the model; electromagnets at the bottom of the mass faced the rail from underneath and provided the levitating force. Mounted in the rail...