Rotor ship

, depicted with a backspinning cylinder in an airstream. The arrow represents the resulting sideways force that can be used to help propel a ship. The curly flow lines represent a turbulent wake. The airflow is deflected in the direction of spin. A rotor or Flettner ship is designed to use the Magnus effect for propulsion. The Magnus Effect is caused by a spinning body in a moving airstream, or a moving body which is spinning (such as a ball), which pulls the air round to one side of the object, using the skin friction, creating a difference in air pressure from one side to the other. This causes a sideways force on the object making the spinning body move towards the low pressure side where there is least resistance. On a ship, this sideways force is resisted by the hull, and a component of this force can be used to propel the ship forward, provided that the ship's direction is generally within the low pressure zone. A Magnus rotor used to propel a ship is called a rotor sail and is mounted with its axis vertical. When the wind blows from the side, the Magnus effect creates a forward thrust. The most common form of rotor sail is the Flettner rotor. Rotor sails have been reported to generate 5-20% fuel savings. ==History==

Pioneers The German engineer Anton Flettner was the first to build a ship which attempted to use the Magnus effect for propulsion. Buckau Assisted by Albert Betz, Jakob Ackeret, and Ludwig Prandtl, Flettner constructed an experimental rotor vessel; October 1924 the Germaniawerft finished construction of a large two-rotor ship named Buckau. The vessel was a refitted schooner which carried two cylinders (or rotors) approximately high, and in diameter, driven by an electric propulsion system of power. Buckau sailed from Danzig to Scotland across the North Sea in February 1925. The ship could tack (sail into the wind) at 20–30 degrees, Some sources claim that the ship had proved inefficient on these voyages, that the power consumed by spinning 15-metre tall drums was disproportionate to the propulsive effect when compared with conventional propellers. That view stands in contrast to others that claim that due to the impressive performance, Buckau was put into service to carry bulk cargo across the North Atlantic and the Baltic sea. On 31 March 1926, Buckau, now renamed Baden-Baden sailed to New York via South America, the 6,200 nautical mile voyage across the Atlantic used only 12 tons of fuel oil, compared with 45 tons for a motor ship of the same size without rotors, arriving in New York harbor on 9 May. The latter assessment seems to be more accurate, as the outcome of the Buckau experiment, resulted in the development of the next rotor ship, Barbara. Barbara In 1926, a larger ship with three rotors, Barbara was built by the shipyard A.G. Weser in Bremen. It proved to perform reliably "as a normal freighter in the Mediterranean between 1926 and 1929. By 1928, Flettner had secured orders for six new ships of the Barbara class. However, the global economic crash caused a decrease in consumer buying confidence. In addition to this, Marine Diesel Oil (MDO) and the related engine technology required to use it became readily and cheaply available. Fuel prices at that point meant that any savings achieved by the rotor were too small for shipping companies to consider the investment due to the lengthy payback period." Enercon launched the hybrid rotor ship E-Ship 1 on 2 August 2008. From 2010, it has been used to transport the company's turbine products and other equipment. Enercon claim "operational fuel savings of up to 25% compared to same-sized conventional freight vessels." The University of Flensburg is developing the Flensburg catamaran or Uni-Cat Flensburg, a rotor-driven catamaran. In 2007, Stephen H. Salter and John Latham proposed the building of 1,500 robotic rotor ships to mitigate global warming. The ships would spray seawater into the air to enhance cloud reflectivity. A prototype rotor ship was tested on Discovery Project Earth. The rotors were made of carbon fibre and were attached to a retrofitted trimaran A rotor system was retrofitted in 2018. In 2014 and 2015, Norsepower installed twin rotor sails on Finnish shipping company Bore's RoRo vessel M/V Estraden. In May 2018, the 1996 built cargo ship Fehn Pollux of the German-based Fehn Shipmanagement (Leer) was fitted with an 18-metre long Flettner rotor of the EcoFlettner type at the front. In 2018, Norsepower deployed rotor sails with the world's biggest shipping company, Maersk. The Maersk Pelican, an LR2 class tanker, has been fitted with two Norsepower Rotor Sails. The MV Afros (IMO 9746803) bulk carrier has operated four movable rotors over a year with positive results. In 2021, Norsepower installed five tilting rotor sails onto a Vale-operated iron ore carrier; the tilting design intended to allow maneuvering below bridges. In 2020 Sea-Cargo retrofitted the ro-ro vessel SC Connector with two 35-metre Norsepower tilting rotor sails. The system allows the rotors to be lowered to pass under bridges. According to the operator, the installation enables average fuel savings of around 25% and, under favourable conditions, allows the vessel to operate entirely on wind power. The SC Connector entered service with the new system in early 2021. Scandlines operates two hybrid ferries with rotorsail, M/F Copenhagen and M/F Berlin. In October 2023 Airbus announced that it had commissioned six ships with Flettner rotors for entry into service in 2026 to transport aircraft sections to its US assembly line. Stena Line commissioned the 'NewMax' Connecta RoRo ship in January 2026 to be used on the Belfast-Heysham routes. ==See also==