Space shuttle main engines (SSMEs) for the orbiters were originally built by Rocketdyne in Canoga Park, California. Clustered in a set of three at the back of each orbiter, the SSMEs burned propellants from the large, orange external tank mounted on the orbiter's underside. The SSMEs helped to push the shuttle up to orbit.

Engineers at the Rocketdyne Operations Support Center (ROSC) in Canoga Park remotely monitored the SSMEs during launch and for the first eight and a half minutes of every shuttle flight, checking pressures, temperatures, and other readouts until the shuttle reached orbit. If something went wrong, Rocketdyne staff could provide recommendations to launch control in Florida or Mission Control in Houston.