Propellants are substances that produce thrust to propel vehicles, such as rockets and missiles, into the air or space. They work by rapidly releasing gas when ignited, creating a force that pushes the vehicle in the opposite direction, according to Newton's third law of motion. Common types of propellants include liquid fuels, like liquid oxygen and kerosene, and solid fuels, which are often used in fireworks and military applications. In the world of space exploration, propellants are crucial for launching spacecraft, like those used in NASA missions. The choice of propellant affects the efficiency, speed, and range of the vehicle. Understanding propellants helps engineers design better rockets and improve space travel technology.