A rotor ship, or Flettner ship, is a type of ship designed to use the Magnus effect for propulsion.[not verified in body] The Magnus effect is a force acting on a spinning body in a moving airstream, which acts perpendicularly to the direction of the airstream.[not verified in body] Rotor ships typically use rotor sails powered by a motor to take advantage of the effect.[not verified in body] German engineer Anton Flettner was the first to build a ship which attempted to tap this force for propulsion.[not verified in body]
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||This section possibly contains original research. (October 2015)|
A rotor or Flettner ship is a type of ship designed to use the Magnus effect for propulsion. The Magnus effect is a force acting on a spinning body in a moving airstream, which acts perpendicularly to the direction of the airstream. Rotor ships typically use rotor sails — spinning bodies that are essentially vertical cylinders — powered by a motor to take advantage of the effect. These types of propulsion cylinders are now commonly called Flettner rotors. Rotor ships have unique points of sail.[clarification needed]
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German engineer Anton Flettner was the first to build a ship which attempted to tap this force for propulsion. Flettner's first idea was to produce the propulsion force using a belt running round two cylinders; later[when?] Flettner decided that the cylinders would be better rotated by individual motors, thus avoiding power losses from the main engine. Flettner applied for a German patent for the rotor ship[clarification needed] on 16 September 1922.
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 15 metres (50 ft) high, and 3 metres (10 ft) in diameter, driven by an electric propulsion system of 50 hp (37 kW) power. In 1926, a larger ship with three rotors, the Barbara, was built by the shipyard A.G. Weser in Bremen.
Following completion of its trials, the Buckau set out on her first voyage, from Danzig to Scotland across the North Sea, in February 1925. The rotor ship could tack (sail into the wind) at 20-30 degrees, while a vessel with a typical sail rig[clarification needed] cannot tack closer than 45 degrees to the wind; hence, the rotors did not give cause for concern in stormy weather.
It was found[according to whom?] at the time[when?] that the rotor system could not compete economically with the diesel engines that were also being developed for ships in this era. Flettner turned his attention to other projects, and the rotors were dismantled. The Baden Baden was destroyed in a Caribbean storm in 1931.
Several types of rotor ships can be distinguished. Rotor sail-only ships exist, as do rotor sail-assist (hybrid) ships, and within each of these major categories, further subcategories exist. Wind Ship Development Corporation has two types of sail-assist designs, for use with different sizes of ships. In practice, most rotor ships have a system with an electric motor that allows the initial start and eventual stop of the rotor by crew. Rotor's rotational speed (i.e., RPM) and direction of spin can also be controlled.
Due to the rising cost of fossil fuels, as well as environmental concerns, there has been renewed interest in the concept in the later 20th century, starting with Jacques-Yves Cousteau's Alcyone in 1983.
The German wind-turbine manufacturer Enercon launched and christened a new rotor ship, E-Ship 1 — see opening image, this article — on 2 August 2008. The ship is being used to transport turbines and other equipment to locations around the world; the maiden delivery of turbines for Castledockrell Windfarm arrived in Dublin Port on 11th Aug 2010. On 29 July 2013, Enercon provided a press release claiming a potential for "operational fuel savings of up to 25% compared to same-sized conventional freight vessels." after 170,000 sea miles; actual performance figures were not provided.[this quote needs a citation] 
The THiiiNK Holding organization describes an improved version of the Flettner Rotor that is retractable and supplemented by an additional control surface. The page claims that "The system has been developed and tested both in tank tests and in full-scale sea trials." The design improvement claims include improved rotor performance (by 50% or more), and an improved internal rate of return (IRR) compared to a standard rotor (up to 55%).
In 2009 the Finland-based maritime engineering company Wärtsilä unveiled a concept for a cruiseferry that would utilise Flettner rotors as means of reducing fuel consumption. This concept has been developed in association with the Finnish ferry operator Viking Line, (the ship, M/S Viking Grace, was built 2011–2012, without the rotors).
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 and successfully propelled the vessel stably through the water at a speed of six knots. The focus of the experiment was based on the ability for the boat to move emissions free for a specialized purpose, leaving it unclear[according to whom?] whether or not the efficiency of the rotors was on parity, inferior to, or superior to conventionally propelled vessels.
|This section requires expansion with: science and engineering (versus hobbyist) basis for related concepts. (October 2015)|
|This section needs additional citations to secondary or tertiary sources (October 2015)|
- Anon. (2015). "Flettner rotor". Thiiink Holding. Retrieved 12 October 2015. [Includes text descriptions, and videos of the Magnus effect, the The Flettner principle, and of the Buckau Flettner Rotor Test 1925, the E-Ship 1 Flettner vessel, and the UNI-CAT Flettner vessel.]
- Gilmore, C.P. (1984). "Spin Sail: Harnesses Mysterious Magnus Effect for Ship Propulsion," Popular Science (January), pp. 70-73, Chicago, IL, USA: Bonnier Corporation, see  accessed 13 October 2015.
- Greenslade, Jr., Thomas B. (1971). "A Forgotten Magnus Effect Demonstration," The Physics Teacher Vol. 9, 43-44, see  [The Flettner Rotorship], accessed 13 October 2015.
- Bowen, Frank (1936). Winchester, Clarence, ed. "Rotor ships: Why the application of the rotor to ship propulsion, after having proved satisfactory, did not remain long upon the high seas". Shipping Wonders of the World 1 (13): 398–399. Retrieved 12 October 2015. [illustrated description of rotor ships]
- Gilmore, C.P. (1984). "Spin Sail: Harnesses Mysterious Magnus Effect for Ship Propulsion," Popular Science (January), pp. 70-73, see , accessed 13 October 2015.
- Kennedy, John (2010). "Discovery: State-of-the-art cargo ship to dock with haul of wind turbines". Silicon Republic (online, August, 10). Retrieved 12 October 2015.
- Anon. (2012). "PM E-Ship1 Ergebnisse DBU" (PDF). Enercon.de. Archived from the original (PDF) on June 7, 2014. Retrieved 2015-10-12.
- Anon. (2015). "Flettner rotor". Thiiink Holding. Retrieved 12 October 2015.
- Anon. (2015). "Folding Flettner Rotor Wing". Thiiink Holding. Retrieved 12 October 2015.
- Reinikainen, Kari (2009). "Wind and lng [liquified natural gas] power Wartsila’s cruise ferry design". Cruise Business Online (22 June). Retrieved 2010-01-19.
- Latham, John (2007). "Futuristic fleet of 'cloudseeders' (15 February)". BBC. Archived from the original on 2012-07-25. Retrieved 2012-07-25.
- Salter, Stephen; Sortino, Graham; Latham, John (2008). "Sea-going hardware for the cloud albedo method of reversing global warming". Phil. Trans. R. Soc. A 366 (1882, 13 November): 3989–4006. Bibcode:2008RSPTA.366.3989S. doi:10.1098/rsta.2008.0136. PMID 18757273. Retrieved 2009-07-27.
- Downie, Neil A. (2001). Vacuum bazookas, electric rainbow jelly, and 27 other Saturday science projects, Princeton, NJ, USA: Princeton University Press, ISBN 9780691009865.[page needed]
|Wikimedia Commons has media related to Rotor ships.|
- Center for the Study of Technology article
- Photograph of Baden Baden in NY harbour
- Enercon press release for the launch of E-Ship 1[dead link]