Azimuth thruster

There are two major variants, based on the location of the motor:[citation needed] The most powerful podded thrusters in use are the four 21.5 MW Rolls-Royce Mermaid units fitted to RMS Queen Mary 2.

Underwater-mountable thrusters are used as dynamic positioning propulsion for very large vessels such as semi-submersible drilling rigs and drillships.

[citation needed] 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.

[2] The modern azimuth thruster using the Z-drive transmission was invented in 1951 by Joseph Becker, the founder of Schottel in Germany, and marketed as the Ruderpropeller.

[4] 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.

Siemens Schottel azimuth thrusters
Azimuth thrusters on the tug Oued el Kebir - note the Kort nozzles
The French Navy Mistral-class amphibious assault ship Dixmude manoeuvering in Jounieh bay; the wake at the stern is perpendicular to the ship, indicating the use of her azimuth thrusters.