NASA Cancels Expensive Exploration Upper Stage Following Cost and Schedule Overruns

NASA has officially cancelled the development of the Exploration Upper Stage, a project originally intended to allow the Space Launch System (SLS) to carry larger payloads to the Moon. The decision follows a period of significant cost increases, with contract values for these efforts ballooning from nearly $2.8 billion to $5.9 billion.

Administrator Jared Isaacman directed the agency to replace the cancelled stage with United Launch Alliance’s Centaur V upper stage. This shift is part of a broader effort to streamline lunar exploration and prioritize returning astronauts to the Moon's surface over the construction of a lunar orbit space station.

In addition to the upper stage cancellation, NASA has issued a stop-work order for Mobile Launcher 2. This second launch platform, intended for the SLS Block 1B rocket, suffered from severe schedule delays and cost overruns. A 2024 report from NASA’s Office of Inspector General indicated the platform could have cost up to $2.5 billion and might not have been ready until 2029.

NASA now plans to standardize on a "near Block 1" version of the SLS to increase the flight rate for upcoming missions. Hardware from the halted Mobile Launcher 2 project will be repurposed as critical spares for Mobile Launcher 1, which supports the Block 1 version of the rocket used for the Artemis 1 and 2 missions.

The decision to move away from the Exploration Upper Stage comes as NASA seeks to avoid the "staggeringly and stupidly expensive" costs associated with the Boeing-contracted project. The agency's new direction focuses on utilizing the best available technology to ensure the United States can return to the lunar surface more efficiently.

While the core SLS program remains funded through legislative action, including the 2025 "One Big Beautiful Bill Act," Administrator Isaacman has signaled that the rocket is not the long-term solution for frequent deep-space transportation. He indicated that the current architecture will be used for planned crewed lunar missions before eventually transitioning to more capable commercial heavy-lift options.