Space Shuttle Solid Rocket Booster

The Space Shuttle Solid Rocket Booster (SRB) is the rocket that provides 83% of liftoff thrust for the Space Shuttle. It is the largest and most powerful solid rocket ever flown, and the most powerful rocket motor of any type (solid or liquid) ever flown. Each SRB produces 1.8 times the liftoff thrust of the F-1 engine used in the Saturn V moon rocket (although note that the Saturn V used five F-1s, while the STS stack uses two SRBs).

The two reusable SRBs (or "motors", SRMs) provide the main thrust to lift the Space Shuttle off the pad and up to an altitude of about 150,000 feet (45.7 km). In addition, the two SRBs carry the entire weight of the external tank and orbiter and transmit the weight load through their structure to the mobile launcher platform. Each booster has a (sea level) liftoff thrust of approximately 2,800,000 lbf (12.45 MN) at launch. They are ignited after the three space shuttle main engines' thrust level is verified. The two SRBs provide 83 % of the thrust at lift-off. Seventy five seconds after SRB separation, SRB apogee occurs at an altitude of approximately 220,000 feet (67 km), after which they land on parachutes; impact occurs in the ocean approximately 122 nautical miles (226 km) downrange, after which the two are recovered.

The SRBs are the largest solid-propellant motors ever flown and the first of such large rockets designed for reuse. Each is 149.16 feet (45.5 m) long and 12.17 feet (3.7 m) in diameter.