Solid rocket engines are propulsion systems that use solid propellant to produce thrust. The propellant is a mixture of fuel and oxidizer, which burns when ignited. This combustion generates hot gases that expand and are expelled through a nozzle, propelling the rocket forward. Solid rocket engines are known for their simplicity and reliability, making them popular in various applications, including space launches and military missiles. Unlike liquid rocket engines, which require complex fuel and oxidizer pumps, solid rocket engines are easier to handle and store. They are often used as boosters in larger launch systems, such as the Space Shuttle, to provide additional thrust during liftoff. Once ignited, solid rocket engines burn until all the propellant is consumed, making them a one-time-use technology.