NASA contract confirms selection of ULA's Centaur 5 as new upper stage for the SLS rocket

NASA selected United Launch Alliance Centaur 5 as the upper stage for its Space Launch System rocket starting with the Artemis 4 mission. The selection was disclosed in contract documents published on Friday. The news came one week after NASA Administrator Jared Isaacman announced plans to standardize the SLS fleet to a near Block 1 configuration. Isaacman said the idea is to reduce complexity to the greatest extent possible, accelerate manufacturing, pull in the hardware and increase launch rate. NASA intends to issue a sole source contract to ULA. An eight page supporting document from the Marshall Space Flight Center was published to document the reasoning. The Centaur 5 was developed as the upper stage of ULA Vulcan rocket. The launch vehicle flew four times since its debut in January 2024 and the upper stage performed well across all flights. Among the reasons are the decades long heritage of the RL10 engine, the ability of the Centaur 5 to use the interfaces available on the Mobile Launcher 1 along with liquid oxygen and liquid hydrogen, and the experience of ULA teams working with Exploration Ground Systems. NASA also noted common features with the Centaur 3 upper stage, which has achieved certification to launch humans as part of the Commercial Crew Program. The agency said this approach uses current support infrastructure and will use with relatively minor modifications an existing ULA upper stage. All other alternative solutions fail to meet the performance requirements, would require significant modifications to hardware that is still under development or would require the development of new hardware that does not currently exist. A time constraint factored into the decision. The Kennedy Space Center need date for processing is projected to be nine months prior to a launch and an award to another source would cause unacceptable delays to current launch schedules.