Space shuttle main engine

The space shuttle orbiter has three main engines (SSMEs), constructed by Rocketdyne. They are very sophisticated power plants that burn liquid hydrogen and liquid oxygen from the space shuttle external tank. They are used for propulsion during its ascent, in addition to the two more powerful solid rocket boosters. Each engine can generate almost 1.8 MN (400,000 pounds) of thrust at liftoff. The engines are capable of generating a specific impulse (Isp) of 453 seconds in a vacuum, or 363 seconds at sea level. The engines are removed after every flight and taken to the space shuttle main engine processing facility (SSMEPF) for inspection and replacement of any necessary components.

A much longer and detailed article at Wikipedia: [1]

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