The American space agency NASA has officially terminated the long-standing and problematic Exploration Upper Stage (EUS) project, developed by Boeing for the lunar rocket SLS. Instead, as reported by agency sources, NASA has chosen a solution from the United Launch Alliance (ULA) consortium. The agency intends to use a modified version of the Vulcan Centaur rocket as the new upper stage for heavier missions in the Artemis program, starting with the Artemis IV flight. The decision is a response to chronic delays and rising costs of the Boeing project.
End of Boeing's Project
NASA has officially terminated work on the Exploration Upper Stage (EUS), an advanced upper stage for the SLS rocket, which had been developed by Boeing for years. The project was criticized for delays and budget overruns.
New Supplier: ULA
The agency turned to the commercial sector, choosing a solution from the United Launch Alliance (ULA) consortium. NASA intends to use a modified version of the Vulcan Centaur rocket as the new upper stage for Artemis missions.
Impact on the Artemis Program
The decision concerns future, heavier lunar missions, starting with Artemis IV. The new stage is to provide greater payload capacity and precision than the currently used interim ICPS stage, enabling the achievement of the program's advanced goals.
Reasons for the Change
The direct cause for abandoning the EUS project was chronic delays and uncontrolled cost increases. NASA determined that available commercial technologies offer a faster and likely cheaper alternative.
The American space agency NASA has made a radical decision to definitively close the long-standing and problematic project of the advanced upper stage Exploration Upper Stage (EUS), which was being developed by the Boeing corporation for the flagship lunar rocket Space Launch System (SLS). The information about the project's termination, based on sources within the agency, was first reported by the Ars Technica portal. This decision results in the official closure of a chapter that for years had been a bottleneck for the entire program. The Artemis program, officially announced in 2017, is the successor to the legendary Apollo program of the 1960s and 70s. Its goal is not only to return humans to the Moon but also to establish a sustained presence through the construction of the Gateway orbital station and a surface base, which requires regular, advanced supply and crewed missions. The direct cause of this radical change was chronic delays and uncontrolled cost overruns of the EUS project. This stage was essential for missions Artemis IV and beyond, as it was supposed to provide significantly greater payload capacity and trajectory precision than the currently used Interim Cryogenic Propulsion Stage (ICPS). In response, NASA turned to the commercial sector, where proven technologies are already available. As reported by Bloomberg and Reuters agencies, NASA has chosen a solution from the consortium United Launch Alliance (ULA). It involves delivering a modified version of the Vulcan Centaur rocket, which is to serve as the upper stage for the heavier variants of the SLS rocket, known as Block 1B. This decision is a significant blow to Boeing, which loses a key element of its involvement in the Artemis program, while strengthening ULA's position in the space market. The new solution, although technically different, is to meet the same requirements as the abandoned EUS: to launch heavier payloads, such as Gateway station modules or the crewed lunar lander, onto the appropriate trajectory towards the Moon. Switching to a commercially available platform like Vulcan Centaur is expected to accelerate the schedule and potentially lower the costs of future missions. NASA's decision reflects a broader trend in U.S. space policy, involving greater use of ready-made solutions from private contractors, as also seen in the International Space Station supply program or the Commercial Crew program. Final confirmation and contract details with ULA are to be announced by the agency in the near future.