NASA selected the Centaur V upper stage, from the United Launch Alliance (ULA), to equip the Space Launch System (SLS) rocket on future missions of the Artemis program, replacing the canceled Exploration Upper Stage (EUS). The decision was formalized on March 6, 2026 through a justification document for exclusive contracting with ULA. The Centaur V will be used from Artemis IV, scheduled no earlier than early 2028, and also on Artemis V, with a reserve flight unit included in the agreement.
The choice occurred after the cancellation of the development of the SLS Block 1B and Block 2, announced on February 27, 2026, which standardized the SLS in a configuration close to the The Centaur V, already in operation on ULA’s Vulcan rocket since 2024 with four successful flights, offers compatibility with cryogenic propellants (liquid hydrogen and liquid oxygen) and RL10 engines similar to those of the ICPS.
The agency assessed that the Centaur V requires only relatively minor modifications to meet SLS performance requirements, leveraging existing infrastructure and ULA’s proven experience in integration and certification for human flight. Outras options, such as the New Glenn upper stage of Blue Origin, were discarded as they required extensive changes, additional testing, and unacceptable impacts on schedule and costs.
Decision justified by technical analysis
NASA has concluded that Centaur V represents the only viable solution at this time to meet the objectives of the Artemis program without significant delays. The document highlights that alternative alternatives do not meet performance parameters or require development of non-existent new hardware.
Modifications to the Centaur V include adaptations for integration with the SLS core stage and the Orion vehicle, maintaining familiarity with human certification processes already established by ULA.
The agency emphasizes that this approach preserves capabilities and flight history of the Centaur, which has decades of use in previous variants.
Schedule and impacted missions
Deliveries of the Centaur V stages are expected to occur at least nine months before launch, with the first expected to arrive more than a year from March 2026 and the second by the end of 2027. Artemis IV remains the first mission to utilize the new stage, with a focus on lunar orbit operations and preparation for subsequent landings.
The Artemis V will follow the same configuration, ensuring consistency in the SLS for manned missions planned for 2028. The reserve unit serves as a contingency for possible replacement needs or additional tests.
The adjustment aligns the program with goals for a higher release cadence, prioritizing immediate availability over more ambitious upgrades.
Benefits of SLS standardization
Standardization close to Block 1 reduces complexity and costs associated with the development of more advanced variants. The Centaur V offers greater propellant volume than ICPS, allowing greater flexibility for payloads on lunar missions.
The decision takes advantage of the ongoing production of the Centaur V for the Vulcan, minimizing the risk of supply chain disruptions. ULA maintains responsibility for interprogram integration, facilitating certifications and operations.
This path ensures that SLS remains viable for the Artemis campaign, with a focus on lunar landings and a sustainable presence at Lua.
Alternatives evaluated and discarded
Estudos descartaram o estágio do New Glenn por estar em fases iniciais, com apenas dois voos até o momento e necessidade de modificações extensas na estrutura e na infraestrutura terrestre, incluindo adaptações para o Vehicle Assembly Building.
Other commercial or development solutions would fail to meet propellant, performance, and timeline requirements. The analysis reinforces that only the Centaur V, with minor adjustments, fully complies with NASA specifications.
The exclusive choice reflects the urgency to maintain the Artemis schedule without compromising safety or scientific objectives.
Changes to program Artemis
The cancellation of EUS and configurations Block 1B and 2 represents a significant revision to the SLS architecture, driven by delays and increasing costs in previous development. NASA chose to prioritize stability and flight cadence over immediate greater capacity.
The transition to Centaur V maintains the SLS as the primary vehicle for crewed missions around Lua and lunar surface preparations. The agency continues to monitor progress for future adjustments if necessary.