Originally built by Rocketdyne in Canoga Park, California, the space shuttle main engines (SSMEs) worked together with the solid rocket boosters to push the shuttle from launch pad to orbit. Powered by liquid hydrogen and liquid oxygen from the large, orange external tank, the three SSMEs propelled the shuttle with over one and a half million pounds of thrust. When the SSMEs finished firing eight and a half minutes after launch, their work for the entire shuttle mission was done. The external tank that fed propellants to the SSMEs detached from the orbiter and fell into the ocean.
After the orbiter’s return to Earth, the SSMEs were removed for service. Because the SSMEs could be swapped between orbiters, NASA maintained nine engines ready to fly on any launch day—three for the shuttle to be launched, three for an alternate orbiter in case a rescue mission was needed, and three to use as spares. A total of 51 SSMEs flew over the course of the shuttle program—35 of them on Endeavour.
Because the SSMEs are still the most advanced, efficient large rocket engine in the world, NASA plans to reuse the SSMEs on the Space Launch System, which will push space travel beyond Earth orbit and out into the solar system.
The Science Center's SSME
The Science Center's SSME, on loan from NASA, is built from components that have been used in several different engines. The SSME's gimbal bearing, the part that connected the engine to the orbiter and allowed the engine and nozzle to move to steer the orbiter during the first 8.5 minutes of each flight, was used on the first five shuttle missions ever flown. The nozzle, which is the cone-shaped part of the engine that sticks out from the back of an orbiter when the engine is installed, flew on shuttle missions STS-6 (first shuttle spacewalk flight), STS-7 (took first American woman into space, Sally Ride), STS-8 (took first African American astronaut to space, Guion Bluford, and was also the first night launch), STS-41B (first landing of spacecraft at launch site), and STS-32 (mission that collected footage for use in the IMAX film Blue Planet.