NASA selects Centaur for new SLS upper stage

The agency announced Feb. 27 it would not pursue development of the Block 1B version of the SLS, which was to start flying on Artemis 3 and use the EUS in place of the Interim Cryogenic Propulsion Stage, or ICPS, used on the Block 1 version. The ICPS was used on Artemis 1 in 2022 and will be used on Artemis 2 and 3.

In a procurement filing published March 6, NASA determined that the Vulcan Centaur 5 upper stage is the only option to replace the Exploration Upper Stage, or EUS, that was to be used on SLS launches after Artemis 3.

The filing, formally known as a Justification for Other than Full and Open Competition, allows NASA to proceed with a sole-source contract to ULA for Centaur upper stages that will be used on the Artemis 4 and 5 missions, along with a flight spare. The filing redacted the estimated cost to NASA to procure the stages.