is 3.5 to 4 times superior and gives the system a unique advantage for the economical propulsion of ships." The efficiency of the system has however not been subjected to sufficient comparative engineering research. There have been only two turbosail-equipped vessels on which active research has been performed. The Cousteau group is the only organisation with a large body of data available on turbosails. Early development 1981–1982 : Moulin à Vent Cousteau and his research team mounted the invention on a catamaran christened Moulin à Vent (Windmill). The system consisted of a single turbosail mast, painted a navy blue. The research program for this vessel was designed to test efficiency of thrust with the propulsive system. Having proved the concept, the prototype development was ultimately abandoned in 1982 as Cousteau's group turned their attention to a larger vessel, the Alcyone. The Alcyone Cousteau's experience was turned to good use in designing a new vessel. Working with naval engineers, he designed an innovative hull of aluminum, both lightweight and strong. The catamaran-like stern gave it stability. The monohull forward was designed to split swells and improve ride in heavy seas. Two turbosails rose from her deck and two diesel engines provided the necessary suction forces. The ship was named Alcyone, the daughter of the wind. When the Alcyone was launched in 1985, it benefited from the development of the original turbosail Moulin a Vent. With two turbosails of reduced aspect ratio, the stresses placed on the metal of the sail surfaces was much reduced. Both sails also contained axial turbines for power generation, and with decreases in the cost of computers, also featured sensor driven controls to actuate the sails for optimal thrust. Practical experience with the ship saw the Cousteau group adopting the vessel as flagship and primary research platform in the 1980s. Computers optimized the functioning of turbosails and engines. To maintain a constant speed, the engines take over automatically when the wind dies down, and they stop completely when the wind is of sufficient strength when blowing in the right direction. A crew of five is required to maintain the ship. Further development With an interest in expanding adoption of the turbosail, it was suggested that tankers and other large vessels would soon install turbosails as a mean to decrease fuel consumption. The system was intended to power the Calypso II, which has yet to be built. See