Space Shuttle Components >> Propulsion Systems

The two SRBs, with their combined thrust of some 26 million newtons (about 5.8 million lb), provide most of the power for the first two minutes of flight. The SRBs take the space shuttle to an altitude of 45 km (28 mi) and a speed of 4,973 km/h (3,094 mph) before they separate and fall back into the ocean to be retrieved, refurbished, and prepared for another flight.

After the boosters fall away, the three main engines continue to provide thrust. These engines are clustered at the rear end of the orbiter and have a combined thrust of almost 5.3 million newtons (almost 1.2 million lb). The space shuttle's liquid-propellant engines are the world's first reusable rocket engines. They fire for only eight minutes for each flight, just until the shuttle reaches orbit, and are designed to operate for 55 flights. The engines are very large—4.2 m (14 ft) long, and 2.4 m (8 ft) in diameter at the wide end of the cone-shaped nozzle at the rear of the orbiter.

Another propulsion system takes over once the space shuttle's main engines shut down as the ship approaches the altitude at which it will begin orbiting around Earth, known as the orbital insertion point. Two orbital maneuvering system (OMS) engines, mounted on either side of the aft fuselage, provide thrust for major orbital changes. For more exacting maneuvers in orbit, 44 small rocket engines (known as the reaction control system), clustered on the shuttle's nose and on either side of the tail, are used. They have proven indispensable in performing the shuttle's important work of retrieving, launching, and repairing satellites in orbit.