SLS Driving Objectives: I. Safe: a) Human-rated to provide safe and reliable systems for human missions. b) Protecting the public, NASA workforce, high-value equipment and property, and the environment from potential harm. II. Affordable: a) Maximum use of common elements and existing assets, infrastructure, and workforce. b) Constrained budget environment. c) Competitive opportunities for affordability on-ramps. III. Sustainable: a) Initial capability: 70 metric tons (t), 2017-2021. 1) Serves as primary transportation for Orion and exploration missions. 2) Provides back-up capability for crew/cargo to ISS. b) Evolved capability: 105 t and 130 t, post-2021. 1) Offers large volume for science missions and payloads. 2) Modular and flexible, right-sized for mission requirements. | Space Launch System (sls) Safety Mission Assurance And Risk Mitigation by Todd May, Paperback | Indigo Chapters