propulsi

Propulsi is the mechanism by which a vehicle or object is moved by generating a net external impulse. In engineering, propulsion systems convert stored or captured energy into thrust or linear force, enabling motion through a surrounding medium or in vacuum.

Propulsion methods are commonly divided by the medium and the physics of thrust. Reaction propulsion, such as rocket engines and electric ion thrusters, expels reaction mass at high speed to produce thrust. Contact or flow-based propulsion, such as propellers and water jets, transfers momentum to a fluid or uses wheels and tracks to convert torque into forward motion. Electric propulsion uses electrical energy to accelerate propellant or to drive motors, while biological propulsion describes natural systems that move using muscles and appendages.

Key performance concepts include thrust (the forward force produced), specific impulse (an efficiency measure for rocket-like systems, defined as thrust per unit propellant flow), propellant mass flow rate, and propulsive efficiency. Environmental and energy considerations drive choices among chemical, electric, or hybrid systems.

Historically, propulsion began with human-powered methods (oars, sails) and animal power, followed by steam propulsion for ships and land vehicles. The invention of propellers and steam turbines expanded marine and aerial propulsion. The 20th century saw jet and rocket propulsion propel aircraft and spacecraft. In recent decades, electric and hybrid propulsion have become prominent, with ongoing research into sustainable fuels and advanced concepts such as ion or plasma propulsion for space missions.

Applications of propulsion span aviation, shipping, automotive engineering, underwater vehicles, and space exploration. Ongoing developments focus on improving efficiency, reducing emissions, and enabling long-duration spaceflight with high specific impulse and low propellant mass.