The National Aeronautics and Space Administration’s (NASA’s) Space Launch System (SLS) will be the most powerful rocket in history, launching crews of up to four astronauts in the Orion spacecraft to explore multiple, deep space destinations. The SLS is designed around an evolvable architecture that will support versions ranging from 77-metric-ton (77 ton) to 130 metric ton (143 tons) lift capability. The SLS core stage, more than 200 feet tall with a diameter of 27.6 feet, will store cryogenic liquid hydrogen and oxygen that will feed four RS-25 engines. The RS-25 served as the Space Shuttle main engines and operated with 100% mission success during 135 missions. The RS-25 is being modified to serve on the SLS by increasing its power from 491,000 to 512,000 pounds of vacuum thrust among many other improvements.