History Development In 1987, the Finnish National Board of Navigation made a co-operation proposal to the multinational electrical equipment corporation ABB Group and the Finnish shipbuilder Wärtsilä Marine for the development of a new type of electric propulsion unit. Prior to this, the companies had been working together for decades in the field of diesel-electric propulsion systems and in the 1980s produced the first icebreakers with alternating current propulsion motors and cycloconverters. The development of the prototype started in 1989 and the first unit was ready for installation in the following year. The 1.5MW unit, dubbed "Azipod" (short for azimuthing electric podded drive) was installed on the 1979-built Finnish fairway support vessel Seili at Hietalahti shipyard in Helsinki, Finland. After the refit, the vessel's icebreaking performance was considerably increased and she was also found out to be capable of breaking ice astern (backwards). This discovery of a new operating mode eventually led to the development of the double acting ship concept in the early 1990s. When Seili was refitted with new propulsion system in the 2000s, the prototype unit was donated to Forum Marinum and put on display in Turku, Finland. Following the encouraging experiences from the prototype installation, the development of the Azipod concept continued and the next units were retrofitted on two Finnish oil tankers, Uikku and Lunni, in 1993 and 1994, respectively. Nearly eight times as powerful as the prototype, the 11.4MW Azipod units considerably increased the icegoing ability of the vessels that were already built with independent icebreaking capability in mind. Since the 1990s, the vast majority of ships capable of operating in ice without icebreaker escort have been fitted with Azipod propulsion system. The first three Azipod units were of so-called "pushing" type in which the propeller is mounted behind the gondola. In the subsequent installations, ABB adopted the more efficient "pulling" configuration similar to propeller-driven airplanes. The world's first cruise ship fitted with Azipod propulsion units, Elation, was delivered by Kværner Masa-Yards Helsinki shipyard in the spring of 1998. Even though the Azipod was initially developed for icebreaking vessels, cruise ships have become the largest group of ships by type to be fitted with Azipod propulsion system since the 1990s and the success of the electric podded propulsion units has paved the way for competitors such as the Rolls-Royce Mermaid. Among the vessels fitted with Azipod units are Royal Caribbean International's Voyager-, Freedom- and