Editing Azimuth thruster

{{short description|Steerable propulsion pod under a watercraft}}
{{Refimprove|date=September 2012}}
[[Image:Siemens Schottel Propulsor.jpg|thumb|right|[[Siemens AG|Siemens]] [[Schottel (company)|Schottel]] azimuth thrusters]]

An '''azimuth thruster''' is a configuration of marine [[propeller]]s placed in pods that can be rotated to any horizontal angle ([[azimuth]]), making a [[rudder]] redundant.  These give [[ship]]s better maneuverability than a fixed propeller and rudder system.

==Types of azimuth thrusters==
[[File:Oued el Kebir-IMG 9346.jpg|thumb|upright|Azimuth thrusters on the tug ''Oued el Kebir'' - note the [[Kort nozzle]]s]]

There are two major variants, based on the location of the motor:{{cn|date=November 2014}}

# [[Transmission (mechanics)|Mechanical transmission]], which connects a motor inside the ship to the outboard unit by [[gear]]ing.  The motor may be [[Diesel engine|diesel]] or [[Diesel-electric transmission|diesel-electric]].  Depending on the shaft arrangement, mechanical azimuth thrusters are divided into [[L-drive]] and [[Z-drive]].  An L-drive thruster has a vertical input shaft and a horizontal output shaft with one right-angle gear.  A Z-drive thruster has a horizontal input shaft, a vertical shaft in the rotating column and a horizontal output shaft, with two right-angle gears.
# [[Diesel-electric transmission|Electrical transmission]], more commonly called pods, where an electric motor is fitted in the pod itself, connected directly to the propeller without gears. The electricity is produced by an onboard engine, usually [[Diesel engine|diesel]] or [[gas turbine]]. Invented in 1955 by [[Friedrich W. Pleuger]] and [[Friedrich Busmann]] (Pleuger Unterwasserpumpen GmbH), [[ABB Group]]'s [[Azipod]] was the first product using this technology. 

The most powerful podded thrusters in use are the four 21.5 MW Rolls-Royce Mermaid units fitted to {{RMS|Queen Mary 2}}.<ref>{{cite web| url=https://www.wartsila.com/encyclopedia/term/mermaid-propulsion-unit| title=Mermaid propulsion unit| publisher=[[Wärtsilä]]| access-date=1 February 2020}}</ref>

Mechanical azimuth thrusters can be fixed installed, retractable or underwater-mountable. They may have fixed pitch propellers or [[controllable pitch propeller]]s. Fixed installed thrusters are used for tugboats, ferries and supply-boats. Retractable thrusters are used as auxiliary propulsion for dynamically positioned vessels and take-home propulsion for military vessels.  Underwater-mountable thrusters are used as dynamic positioning propulsion for very large vessels such as [[semi-submersible]] [[drilling rig]]s and [[drillship]]s.

==Advantages and disadvantages==
[[File:BPC Dixmude.jpg|thumb|The [[French Navy]] [[Mistral-class amphibious assault ship]] [[French ship Dixmude (L9015)|''Dixmude'']] manoeuvering in Jounieh bay; the wake at the stern is perpendicular to the ship, indicating the use of her azimuth thrusters.]]
Primary advantages are maneuverability, electrical efficiency, better use of ship space, and lower maintenance costs.{{Citation needed|date=October 2010}} Ships with azimuth thrusters do not need [[tugboat]]s to dock, though they may still require tugs to maneuver in difficult places.{{citation needed|date=October 2020}}

The major disadvantage of azimuth drive systems is that a ship with azimuth drive maneuvers differently from one with a standard propeller and rudder configuration, necessitating specialized pilot training.{{citation needed|date=October 2020}} Another disadvantage is they increase the draught of the ship.{{citation needed|date=October 2020}}

==History==
English inventor [[Francis Ronalds]] described what he called a ''propelling rudder'' in 1859 that combined the propulsion and steering mechanisms of a boat in a single apparatus. The propeller was placed in a frame having an outer profile similar to a rudder and attached to a vertical shaft that allowed the device to rotate in plane while spin was transmitted to the propeller.<ref>{{Cite book|title = Sir Francis Ronalds: Father of the Electric Telegraph|last = Ronalds|first = B.F.|publisher = Imperial College Press|year = 2016|isbn = 978-1-78326-917-4|location = London}}</ref>

The modern azimuth thruster using the Z-drive transmission was invented in 1951 by Joseph Becker, the founder of [[Schottel (company)|Schottel]] in Germany, and marketed as the Ruderpropeller.  Becker was awarded the 2004 [[Elmer A. Sperry Award]] for the invention.<ref name="sperry">{{cite web |url=http://www.sperryaward.org/awardbooklets/2004%20Sperry%20Award%20Booklet.pdf|title=Presentation of The Elmer A. Sperry Award for 2004|publisher=Sperryaward.org|access-date=24 November 2014}}</ref> This kind of propulsion was first patented in 1955 by [[Pleuger rudder|Pleuger]].<ref name="Pleuger">{{cite web|url=https://patents.google.com/patent/US2714866|title=Patent US2714866 - Device for propelling a ship|access-date=24 November 2014}}</ref>

In the late 1980s Wärtsilä Marine, Strömberg and the Finnish National Board of Navigation developed the [[Azipod]] thruster with the motor located in the pod itself.{{cn|date=November 2014}}

==See also==
* {{annotated link|Pleuger rudder}}
* {{annotated link|Cyclorotor}}
* {{annotated link|Voith Schneider Propeller}}
* {{annotated link|Saildrive}}
* {{annotated link|Z-drive}}
* {{annotated link|Outboard motor}}
{{commonscat|Azimuth thrusters}}

==References==
{{Reflist}}

{{DEFAULTSORT:Azimuth Thruster}}
[[Category:Marine propulsion]]