The Space Launch System (SLS) is an American Space Shuttle-derived super heavy-lift expendable launch vehicle, which has been under development by NASA in the United States since its announcement in 2011. It has been planned to become the primary launch vehicle of NASA's deep space exploration plans throughout the 2010s, including the planned crewed lunar flights of the Artemis program and a possible follow-on human mission to Mars. The SLS program has replaced the Constellation program's Ares V launch vehicle program of 2005, which never left the development phase. SLS is intended to replace the retired Space Shuttle as NASA's flagship vehicle. Following the cancellation of the Constellation program, the NASA Authorization Act of 2010 envisioned a single launch vehicle usable for both crew and cargo. In 2013, SLS was projected to possibly be the most capable super-heavy lift vehicle ever built. (Wikipedia)