The Space Launch System is an extra large and heavy launch vehicle capable of reaching far beyond the earth's orbits and potentially onto Mars. It's being designed by NASA to replace the Space Shuttle after its retirement. The NASA Authorization Act of 2010 envisions the transformation of the Ares I and Ares V vehicle designs into a single launch vehicle usable for both crew and cargo.

SLS will use a new expendable version of the liquid-oxygen/liquid-hydrogen Space Shuttle Main Engine (SSME). The initial capability of the core elements, without an upper stage, should be for between 70 tons and 100 tons into low-Earth orbit (LEO) in preparation for transit for missions beyond low-Earth orbit. With the addition of integrated upper Earth Departure Stage the total lift capability of the Space Launch System should be 130 tons or more.