NASA has confirmed the selection of United Launch Alliance’s (ULA) Centaur 5 as the upper stage for its Space Launch System (SLS) rocket, beginning with the Artemis 4 mission, which is scheduled for launch no earlier than early 2028. This decision marks a shift from the agency’s previous plans to utilize the Interim Cryogenic Propulsion Stage (ICPS) and the Exploration Upper Stage (EUS).
The Centaur 5 was developed specifically for ULA’s Vulcan rocket, which has successfully completed four flights since its debut in January 2024. NASA Administrator Jared Isaacman announced the move towards a “standardization of the SLS fleet” during a briefing on February 27, emphasizing the need to reduce complexity and enhance manufacturing efficiency.
Reasons for the Selection
NASA’s decision, detailed in contract documents released on March 7, is driven by several factors. The agency highlighted the decades-long heritage of the RL10 engine, which has proven reliability, and the Centaur 5’s compatibility with the Mobile Launcher 1 (ML1) and its propulsion systems, which utilize liquid oxygen and liquid hydrogen.
Additionally, the Centaur 3’s certification for human launches under the Commercial Crew Program provides a foundation of common features with the Centaur 5. NASA stated, “This approach leverages current support infrastructure and will use, with relatively minor modifications, an existing ULA upper stage.”
Time Constraints and Other Considerations
NASA indicated that a time constraint influenced its decision to award a sole source contract to ULA. The agency noted that the processing need date at the Kennedy Space Center is projected to be nine months before a launch. Selecting another contractor could lead to unacceptable delays, as it would involve a lengthy procurement process and potential rework of existing hardware.
Concerns were also raised regarding the alternative upper stage from Blue Origin’s New Glenn rocket. NASA expressed that adopting the New Glenn Stage 2 would necessitate significant modifications to both the stage and the existing infrastructure, which could lead to additional costs and schedule risks.
Impact on Future Missions
The original plan to utilize the EUS aimed to enable more ambitious lunar missions, allowing for the delivery of up to 11 metric tons more mass to the lunar surface. However, delays and cost overruns associated with the EUS led to the current pivot towards the Centaur 5. A report from NASA’s Office of Inspector General highlighted that the SLS Block 1B program has faced ongoing challenges, with projected costs escalating significantly.
As NASA moves forward with the Centaur 5, the future of the EUS remains uncertain, particularly in light of the agency’s new direction for the SLS rocket.
This article was produced by NeonPulse.today using human and AI-assisted editorial processes, based on publicly available information. Content may be edited for clarity and style.
