For the first time in 40 years, a NASA human-rated rocket has completed all steps needed to clear a Critical Design Review (CDR). The agency’s Space Launch System (SLS) is the first vehicle designed to meet the challenges of the journey to Mars and the first exploration class rocket since the Saturn V.

SLS will be the most powerful rocket ever built and, with the agency's Orion spacecraft, will launch America into a new era of exploration to destinations beyond Earth's orbit. The CDR provided a final look at the design and development of the integrated launch vehicle before full-scale fabrication begins.

The CDR examined the first of three configurations planned for the rocket, referred to as SLS Block 1. The Block I configuration will have a minimum 70-metric-ton (77-ton) lift capability and be powered by twin boosters and four RS-25 engines.

The next planned upgrade of SLS, Block 1B, would use a more powerful exploration upper stage for more ambitious missions with a 105-metric-ton (115-ton) lift capacity. Block 2 will add a pair of advanced solid or liquid propellant boosters to provide a 130-metric-ton (143-ton) lift capacity. In each configuration, SLS will continue to use the same core stage and four RS-25 engines.

The SLS Program completed the review in July 2015, in conjunction with a separate review by the Standing Review Board, which is composed of seasoned experts from NASA and industry who are independent of the program. The program briefed the results of the review in October to the Agency Program Management Council, led by NASA Associate Administrator Robert Lightfoot, as the final step in the CDR process.

This review is the last of four reviews that examine concepts and designs. The next step for the program is design certification, which will take place in 2017 after manufacturing, integration and testing is complete. The design certification will compare the actual final product to the rocket's design. The final review, the flight readiness review, will take place just prior to the 2018 flight readiness date