Liquid propellants are fuels used in rocket engines that exist in a liquid state. They are typically composed of a fuel and an oxidizer, which are stored separately and mixed in the combustion chamber. When ignited, the chemical reaction produces high-pressure gases that propel the rocket forward. Common examples of liquid propellants include liquid oxygen and kerosene. These propellants offer several advantages over solid propellants, such as better control over thrust and the ability to shut down and restart the engine. Liquid propellants are widely used in various space missions, including those involving NASA and other space agencies, due to their efficiency and reliability.