Abstract: NASA’s Space Launch System (SLS) entered a new phase in 2017, completing major structural manufacturing on the core stage and delivering the first flight hardware to NASA’s Kennedy Space Center (KSC). The program is now transitioning to integration, assembly and testing in preparation for launch readiness in late 2019. Core stage prime contractor Boeing concluded welding of the major core stage components for Exploration Mission 1 (EM-1) with the liquid hydrogen flight tank, following complet…