Screw Propeller

A rotating marine device whose blades push water backward to produce forward thrust. Its helical blade shape converts rotational motion into movement through water.

Propeller Pitch: The theoretical distance a propeller would advance in one revolution through a solid medium. Pitch sets how far each revolution would move the propeller without water slipping past its blades.
Newton's Third Law: The principle that every action force has an equal and opposite reaction force. A propeller accelerates water backward, and the corresponding reaction pushes the vessel forward.
Controllable-Pitch Propeller: A propeller whose blade angles can be adjusted while it rotates. Changing pitch lets ships adapt thrust to speed, maneuvering, and engine conditions.
John Ericsson: A Swedish-American engineer who developed marine screw propulsion and designed the ironclad USS Monitor. Ericsson’s screw-propelled vessel Princeton helped demonstrate the system’s maritime potential.
Waterjet Propulsion: A marine propulsion system that expels a high-speed jet of water to generate thrust. Waterjets replace exposed propeller blades with an internal pump and steerable outlet.
Angle of Attack: The angle between a moving surface and the fluid flow approaching it. A blade’s local angle of attack shapes the pressure forces that generate thrust.
Lift: A force perpendicular to the relative flow around a surface moving through a fluid. Propeller blades act like rotating hydrofoils, producing lift with a forward component.
Ducted Propeller: A propeller surrounded by a nozzle-shaped shroud that alters the flow around it. The duct can improve thrust at low speeds and protect the blades.
Francis Pettit Smith: A British inventor whose experimental screw propeller helped establish screw propulsion in the Royal Navy. Smith’s work supplied a competing design during the propeller’s early adoption.
Voith Schneider Propeller: A cycloidal marine propulsor whose vertical blades rotate around a vertical axis while changing pitch. Its rapidly adjustable thrust direction differs from the fixed-axis thrust of a conventional screw.

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