A Study on Configuration of Propellers for Multirotorlike Hybrid AerialAquatic Vehicles This paper presents a study on the configuration of propulsion systems for multirotorlike hybrid vehicles that travel in both, aerial and aquatic medium, hereafter called Hybrid Unmanned Aerial Underwater Vehicles (HUAUVs). Following, we evaluate the impact of diameter and shape of propellers, and the medium in which the robot moves, on thrust generation and energy consumption. Sets of counterrotating propellers (CRPs) and single propellers propulsion systems were experimentally evaluated in air and under the water. One of our conclusions is that aerial counterrotating propellers, used in the stateoftheart hybrid vehicles, are relatively inefficient in the air, and even more in the water, and this energy loss must be taken into account during the platform project. Furthermore, we also demonstrate that aquatic screwlike propellers are more efficient in the water than aerial ones, equally contradicting the current literature. Moreover, since aquatic propellers provide more thrust with smaller diameters, they improve our capacity to miniaturize hybrid vehicles.

Motorpropeller Matching of Aerial Propulsion Systems for Direct Aerialaquatic Operation Electric aerial propulsion systems are commonly used for many smallscale unmanned aerial vehicles (UAVs), providing a light and powerful method of generating thrust. In the emerging area of aerialaquatic vehicles, most existing prototypes rely on such systems to propel themselves in both air and water. As the density of water is three orders of magnitude larger than that of air, a spinning aerodynamic body in the medium will experience significantly higher torque at the same speed. This results in aerial propulsion systems to be heavily mismatched underwater, as the required torque is higher than the drive torque that a typical aerial motor can provide. Here, an indepth investigation of such offdesign operation is conducted. Based on numerical simulation, we identify the feasible operating range of such systems and present an evaluation framework that identifies a motorpropeller combination from a component database that maximises underwater performance while ensuring aerial thrust requirements are met.