What is the primary energy source used in a liquid-fuelled rocket?

The primary energy source used in a liquid-fueled rocket is chemical energy. In these rockets, the propellant consists of a fuel and an oxidizer which, when combined and ignited, undergo a chemical reaction that releases a large amount of energy. This release of energy generates thrust as the high-temperature gases produced by the combustion are expelled out of the rocket engine nozzle, propelling the rocket in the opposite direction in accordance with Newton's third law of motion.

Chemical energy is essential in this context since it directly translates into kinetic energy, which allows the rocket to overcome gravitational pull and ascend. Other forms of energy like solid fuel, gas, or electrical energy do not apply in this scenario, as they either refer to different types of propulsion systems or do not produce the necessary thrust characteristic of liquid-fueled rockets. Thus, recognizing that chemical energy is fundamental to the performance of liquid-fueled rockets is crucial in understanding rocketry and propulsion technologies.