In this paper some developments concerning the possibility of generating a rectilinear motion of bodies partially or totally submerged subject to vibration, without the use of propellers, are presented. The motion is obtained by a device equipped with counterrotating masses installed in the vessel that vibrates along the longitudinal direction. The hull has a suitably shaped stern. The study considers an analysis for evaluating the energy that the propulsion system consumes in relation to its performances. A further objective was to maximize the speed of the system while keeping certain parameters unchanged relating to the equations of motion of the device and suitably allocating the counterrotating masses. This result is obtained by using elliptical gears to transmit the motion from the driving motor to a double pair of counterrotating masses. Such a solution allows us to reach the variability of the angular velocity of the counterrotating masses during each revolution in accordance with certain laws that maximize the thrust applied to the vessel preferentially along a direction in respect of the opposite one, all being equal. Finally, a formulation to compute the propulsive efficiency of the device study and the results of the numerical simulations carried out are illustrated.
