The Exploration Upper Stage (EUS) is being developed as a large second stage for Block 1B of the Space Launch System (SLS), succeeding Block 1’s Interim Cryogenic Propulsion Stage. It will be powered by four RL10-C3 engines burning liquid oxygen and liquid hydrogen to produce a total of 440 kN (99,000 lbf) thrust. As of February 2015, the SLS Block 1B will provide thrust of 105 t (103 long tons; 116 short tons). The EUS is expected to first fly on Artemis IV in 2025.
Video credit: Aerojet Rocketdyne