Space Shuttle Main Engine

Space Shuttle Main Engine ( SSME ) was the name of the main engine of a space shuttle, using the liquid oxygen as the oxidizer and liquid hydrogen as fuel. Both components were located in the large outdoor tank.

The SSME was built by Pratt & Whitney Rocketdyne and had a mass of 3.2 tonnes. The exhaust nozzle had a length of 2.87 meters and a maximum diameter of 2.39 meters. It was re-usable and should be able to be reused in a maximum thrust value of 55 % 109 times. This number, however, was never reached.

Because of its reusability and high efficiency as well as the complexity of the engine was very expensive. NASA gave the SSME price of around 50 million U.S. dollars each, which is roughly the cost of a complete Delta II launch vehicle.

Each orbiter was equipped with three main engines, whose focal length is about eight and a half minutes at the start. For another mission, the SSMEs were no longer required. The U.S. space shuttle used for maneuvering in orbit the Reaction Control System and the Orbital Maneuvering System.

In contrast to the solid rocket However, the thrust could be controlled in the liquid engines or they could be turned off in flight in the event of a malfunction. In several missions, the main engines were shut down shortly before the ignition of the solid rocket again and thus aborted the start. In the ascending phase of the Challenger during mission STS -51 -F, the average main engine switched due to a disturbance after five minutes of flight time automatically. Despite the lower thrust a so-called abortion was to orbit carried out and the most objectives are achieved when planned in a lower orbit than originally.

The SSMEs were among the most powerful engines in the history of space travel. Each engine produced over 2000 kN thrust. In the combustion chamber the temperature was 3300 ° C. The fuel with about 450 bar and the oxidizer with around 300 bar was promoted to the combustion chamber through turbopumps. The high pressure pumps operated at speeds of 35.360/min and 28.120/min. The components of the SSMEs therefore had to meet the highest requirements.

The first run of a SSMEs took place in October 1975. During testing there were numerous problems. In one test, an engine exploded and destroyed the test stand.

A derived from the SSME engine to be used in the main stage of the future manned American carrier system SLS.