A rocket engine is a device that works by expelling a high-speed jet of gas in one direction, which generates an opposite force, propelling the rocket in the opposite direction.
Rocket engines work on the principle of Newton's third law of motion, which states that for every action, there is an equal and opposite reaction. The rocket engine works by accelerating a mass of propellant (usually a mixture of fuel and oxidizer) out of the back of the engine at high speeds. The force generated by the expulsion of the propellant creates an opposite and equal force, which propels the rocket forward. The greater the force generated by the rocket engine compared to the force of gravity on the rocket, the greater the acceleration of the rocket into space.
There are two main types of rocket engines: liquid-fueled and solid-fueled. In liquid-fueled engines, the fuel and oxidizer are stored separately and then mixed and burned in the combustion chamber. The burning gases are then expelled through a nozzle at the back of the engine, which provides a high-speed jet of gas that generates thrust. See the figure below (credit: NASA).
Solid-fueled engines, on the other hand, have the fuel and oxidizer mixed together in a solid form, which burns and produces thrust as it is consumed. Solid-fueled rockets are simpler in design and require less maintenance than liquid-fueled rockets, but they cannot be shut off or throttled once they are ignited.
Rocket engines are essential for space travel, as they provide the necessary thrust to overcome Earth's gravity and propel spacecraft into orbit or beyond. They are also used in military missiles, scientific research, and other applications where high-speed propulsion is needed.
