A brief history of the Flettner ship, an archetype of sustainable marine propulsion design

The Magnus effect, discovered by Heinrich Gustav Magnus (1802 - 1870) in 1852, is a physical phenomenon responsible for the variation of the trajectory of a rotating body in a moving fluid due to lift, the force generated on the cylinder, creating a difference in side-to-side air pressure. This physical phenomenon was investigated by Martin Kutta (1867 – 1944) and Nikolay Yegorovich Zhukovsky (1847 – 1921). The first scholar who dealt with putting the Magnus effect into practice was the German inventor and aeronautical engineer Anton Flettner (1885 - 1961), who studied a rotor inserted on a ship - which he then took on the name of “Flettner ship” - specially designed to use the Magnus effect for propulsion. The economic crisis which swept the world at the end of the First World War, and which inevitably followed the maritime boom which took place in 1914-18 was the cause of many changes which occurred in naval construction, changes dictated by the need to improve and at the same time improve the maritime transport making it more efficient and cheaper. The German engineer Anton Flettner, assisted by Albert Betz (1885 – 1968), Jakob Ackeret (1898 – 1981), Ludwig Prandtl (1875 – 1953) and Albert Einstein (1879 – 1955), began his experiments around the 1920s XX century and built an experimental rotor with the idea of reviving naval propulsion by the action of the wind. Climate change, which today has become a topic of great interest, requires greater efforts to direct scientific and technological research towards new proposals that can reduce the phenomenon of environmental and above all maritime pollution. In this brief note we want to retrace the history of an innovative idea that is still current today and which sees a renewed attention towards a marine propulsion system that is very topical today.