The following thesis, carried out in collaboration with the company Pro S3 s.r.l., consists in the study of the propulsion system of a quadricopter drone, with the aim of developing four propellers for vertical take-off and a propeller for horizontal flight. The Skywalker X8 drone must operate at an altitude of 4000 m. The theories used are: Simple Impulsive Theory, Extended Impulsive Theory, Vortex Theory, Blade Element Theory, and Linearized theory of the actuator disk. Firstly, the drone characteristics and the operating environment, characterized by a density of 0.86 kg/m^3, are exposed; the density is of central importance because, by calculating the Reynolds number, it contributes to the determination of the flow.