NASA is reportedly considering replacing the planned upper stage of its Space Launch System with hardware derived from United Launch Alliance’s Vulcan Centaur rocket, a change that could alter the trajectory of the Artemis moon program if it is confirmed. The reported move, first detailed by Bloomberg, would swap out the long-delayed Exploration Upper Stage in favor of Vulcan-based technology built by the Boeing-Lockheed Martin joint venture. If confirmed, the shift would mark a major departure from NASA’s original SLS upgrade roadmap as the agency targets lunar landings around 2028.
What the Reported Vulcan Decision Changes
For years, NASA’s plan to grow the SLS called for a transition from the current Block 1 configuration to a more powerful Block 1B variant. That upgrade centered on the Exploration Upper Stage, a new second stage designed to give the rocket enough muscle to carry both the Orion crew capsule and large co-manifested payloads, such as habitat modules, on a single flight. The Block 1B debut was originally targeted for the mid-2020s, but persistent schedule slips and ballooning costs have kept it from reaching the launch pad, raising questions inside and outside the agency about whether the design still fit NASA’s evolving plans for Artemis.
Replacing that upper stage with Vulcan Centaur hardware would represent a sharp departure from that blueprint. According to Bloomberg, NASA is said to be tapping the Boeing-Lockheed venture’s Vulcan technology for the top of the moon rocket. Vulcan Centaur uses a Centaur V upper stage powered by RL10 engines, a propulsion system with decades of flight heritage. Grafting that proven stage onto the SLS core could, in theory, bypass years of development work still needed for the Exploration Upper Stage while preserving enough lift capacity for Artemis missions, though it would force engineers to requalify the combined stack for crewed flight.
NASA’s Broader Artemis Restructuring
The reported Vulcan selection did not emerge in isolation. Earlier this year, NASA announced it would standardize the SLS configuration, increase Artemis launch cadence, and refine the program’s overall architecture. That announcement added a new mission to the manifest and signaled that the agency was rethinking how it sequences flights and hardware upgrades. Reading between the lines, the decision to lock in a single SLS variant rather than chase a series of progressively more powerful blocks suggested that the Exploration Upper Stage was already on thin ice, as managers sought to simplify production lines and reduce recurring costs.
The agency has also said the additional flight would not slow its return to the moon. NASA is still aiming for 2028 for one or even two lunar landings, even as it inserts a new mission into the sequence. Fitting a Vulcan-derived upper stage onto the SLS could, in theory, help meet that timeline because the Centaur V design draws on well-characterized RL10 engine performance and existing upper-stage heritage. Waiting for the Exploration Upper Stage to clear its own qualification campaign could push later Artemis missions further to the right on the calendar, potentially complicating the agency’s public commitments and partner schedules.
Vulcan’s Existing NASA Track Record
The Vulcan Centaur is not a newcomer to NASA’s stable of rockets. The agency formally added the vehicle to its NASA Launch Services (NLS) II contract through a modification, making it available for NASA missions under that contract. That step gave Vulcan a formal procurement pathway within NASA, separate from any SLS work, and established the technical and safety review baseline that the agency requires before trusting a rocket with high-value payloads. In practice, this means NASA program managers already have interfaces, documentation standards, and risk models for Vulcan missions, reducing the institutional friction that can accompany a new launch vehicle.
NASA’s own program documentation describes Vulcan variants ranging from zero to six solid rocket boosters, giving the vehicle a wide performance envelope depending on mission needs. That flexibility matters for the SLS discussion because the Centaur V upper stage at the heart of every Vulcan configuration is the component most relevant to the reported swap. Its hydrogen-oxygen RL10 engines, manufactured by Aerojet Rocketdyne (now part of L3Harris), have accumulated hundreds of flights across Atlas and Delta rockets over several decades. No other upper-stage engine in the current U.S. inventory comes close to that reliability record, an attribute that weighs heavily in NASA’s calculus when human lives and multibillion-dollar spacecraft are at stake.
Tensions Behind the Hardware Swap
The reported decision creates an unusual dynamic for Boeing and Lockheed Martin. Boeing is the prime contractor for the SLS core stage, including work on the Exploration Upper Stage that now appears to be sidelined. Lockheed Martin builds the Orion crew capsule that sits atop SLS. Both companies are also co-owners of United Launch Alliance, the joint venture that manufactures and operates Vulcan Centaur. In effect, the same parent companies that stood to profit from the Exploration Upper Stage would still capture revenue through ULA if Vulcan hardware takes its place, though the internal budget flows, contract structures, and workforce implications would differ substantially across the organizations.
Most coverage of the Artemis program treats the SLS and its commercial alternatives as a binary choice between government-directed and commercially built rockets. That framing misses the real tension here. The question is not whether NASA should use a commercial vehicle instead of SLS; it is whether NASA should use a commercial upper stage on top of an SLS core stage, creating a hybrid architecture that has no direct precedent in the agency’s human spaceflight history. That approach carries integration risk: mating a Centaur V to the SLS core would require new structural adapters, avionics interfaces, and software modifications, all of which would need to be verified through extensive ground testing and analysis. Any misstep could erode the schedule gains that motivated the swap in the first place.
Risk, Oversight, and What Comes Next
Beyond engineering, the reported shift toward Vulcan hardware raises policy and oversight questions. Lawmakers who backed SLS in part to sustain a geographically diverse industrial base may scrutinize how workshare moves if the Exploration Upper Stage is shelved. NASA will have to demonstrate that a Vulcan-derived solution not only preserves safety margins but also delivers tangible savings and higher launch cadence compared with staying the course. That case will likely lean on the fact that Vulcan is already embedded in NASA’s acquisition system and that its performance characteristics are well understood, even if the configuration atop SLS is novel.
For United Launch Alliance and its owners, the development also underscores how deeply intertwined commercial and government launch markets have become. The same company that sells Vulcan for science missions under NASA’s launch services contract could end up providing critical hardware for the agency’s flagship human spaceflight program. As Bloomberg’s professional channels and related support resources continue to track the financial and industrial impact of the decision, NASA will be under pressure to show that blending a government-owned rocket with a commercially derived upper stage can deliver on Artemis’s promise: regular, sustainable trips to lunar orbit and, eventually, the surface, without repeating the cost overruns and delays that have dogged earlier exploration efforts.
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*This article was researched with the help of AI, with human editors creating the final content.
