Aerojet Rocketdyne recently completed work on the four RS-25 engines that will help power NASA's Space Launch System (SLS) rocket on the Artemis IV mission. Artemis IV is the ambitious plan that will see astronauts live and work in Gateway, the first lunar space station in history. The mission will help prep future human missions to Mars and will include multiple launches and spacecraft dockings in lunar orbit, including the debut of NASA's larger, more powerful SLS rocket.