The RS-25, also known as the Space Shuttle Main Engine, is the world’s most reliable rocket booster engine.
As the nation shifts its vision toward deep space destinations, repurposed and modified RS-25 engines will support initial missions of NASA’s 70-metric ton Space Launch System (SLS). On the SLS, expendable versions of the engine will be used in a cluster of four to provide thrust for the launch vehicle’s core stage. While engines on the shuttle ran at 491,000 pounds vacuum thrust (104.5-percent of rated power level), the power level was increased for SLS to 512,000 pounds vacuum thrust (109 percent of rated power level) to augment the vehicle's heavy lift capability.
A total of 16 RS-25 flight engines are stored at NASA's Stennis Space Center. Teams began hot-fire testing in 2015.
