Wind-Powered Rotor Ships Were Maritime Breakthrough of the 20s: Time Machine (March 1925)
This from a hundred years ago in Popular Mechanics.
With a proven record of supplying clean, natural energy to mariners ever since they first took sails to sea, wind power is an attractive—if inconsistent—alternative to diesel engines, which consume gallons of oil. In March 1925, Popular Mechanics featured an innovation called the "rotor ship," invented by German engineer Anton Flettner. The vessel was hailed as "the first new development in sailing ships since the earliest navigators discovered they could utilize the wind's power." Buckau, the first of the rotor ships, featured two hollow towers of steel, 10 ft. in diameter and 65 ft. tall, mounted on pivots powered by 9-hp motors. The towers utilized the Magnus effect—wind currents striking a rotating cylinder exert a force approximately at right angles to the direction of the wind. After an initial jumpstart from the motors, the cylinder's motion caused the ship to advance, PM reported. Its designers claimed the vessel outran other sailing ships as well as freight steamers.