The propeller is the most common type of ship propulsion. This is an impeller with a longitudinal axis of rotation, consisting of blades mounted on a hub and forming a helical surface. The main function of the propeller is to convert the rotation of the propeller shaft into a force that propels the ship. Most propellers have a one-piece construction where the blades are cast or stamped together with the hub. Typically, propellers are completely submerged in water. Propellers vary in design, number of blades, diameter, pitch, material, and other parameters. The more intensively the engine power and speed of ships grow, the higher the requirements for the geometry and material of propellers.