Non-conventional propulsion devices

In this paper the application of non-conventional propulsion devices and the motives thereof with respect to merchant ships are considered. This is done from the viewpoints of efficiency, cavitation, vibrations, stopping, manoeuvring, safety and economics. The propulsion devices considered are: 1) controllable pitch propellers; 2) overlapping propellers; 3) contra-rotating propellers; 4) ducted propellers; 5) vertical axis propellers; and 6) high speed propulsion devices, including air propulsion.