The idea behind the rotor is that as wind passes a spinning cylinder, the air flow accelerates on one side while decelerating on the other. This creates a thrust perpendicular to the wind direction.

The technology has the potential for fuel savings of up to 20 percent on routes with favorable wind conditions.

The design was pioneered by Flettner and utilized a process known as the Magnus effect for propulsion. Named after German physicist Heinrich Gustav Magnus who investigated the effect in 1852, the principle was initially used to illustrate how balls or artillery can curve away from their principle flight path depending on the airstream that surrounds the object.

[Source: New Atlas. 16 March 2017. Rich Haridy]