Solid Rocket Boosters (SRBs) are powerful engines used to provide the initial thrust needed to launch spacecraft, such as the Space Shuttle. They burn solid propellant, which is a mixture of fuel and oxidizer, to produce a large amount of gas that is expelled at high speed, propelling the rocket upward. Once ignited, SRBs cannot be turned off until all the fuel is consumed. They are typically jettisoned after a few minutes of flight, once the rocket has gained enough altitude and speed. This design allows for a simpler and more reliable launch system compared to liquid-fueled engines.