- The configuration will consist of a core stage and an upper stage both powered by a liquid hydrogen and liquid oxygen propulsion system, and booster stages that will be open to competition.
- The core stage will be powered by the RS-25D/E engines from the Space Shuttle, and the upper stage will be powered by the J-2X engine (a derivative design of the Saturn V main engines).
- Solid Rocket boosters will initially be used for the booster stages during developmental flights, but the ultimate design of the booster stages will be determined as part of a competition.
- The initial lift capacity is 70 metric tons to LEO, with later versions providing as much as 130 mT. this is the most powerful U.S. launcher since the Saturn V (127 mT to LEO).
- The first developmental flight is targeted for the end of 2017.
This modular architecture was chosen because it leverages existing capabilities, and its evolvable development approach allows the high-cost development activities occur early in the program. Bolden stated that "the decision to go with the same fuel system for the core and the upper stage was based on a NASA analysis demonstrating that use of common components can reduce costs and increase flexibility."
NASA has already updated their websiste for the SLS, so more information is available there.