Solid propellant systems are a type of rocket propulsion that uses a solid mixture of fuel and oxidizer. Unlike liquid propellants, which require tanks and pumps, solid propellants are pre-loaded into the rocket and ignite when needed. This makes them simpler and more reliable for many applications, such as launching satellites or military missiles. The solid propellant burns uniformly, producing hot gases that expand and exit through a nozzle, generating thrust. These systems are commonly used in spacecraft like the Space Shuttle boosters and in various military applications. Their design allows for easy storage and handling, making them a popular choice in aerospace engineering.