Boeing is expected to spend 2.8 billion dollars on NASA’s brand-new Exploration Upper Stage (EUS), which is set to ride with the Space Launch System Block 1B version of the rocket, and this week showed off part of its hardware, or at least a render of it.
The current SLS configuration relies on the Interim Cryogenic Propulsion Stage, or ICPS, built by United Launch Alliance. The ICPS, essentially a modified second stage from ULA’s Delta rocket family, is tailored to work with the Orion spacecraft for the first three Artemis missions.
As its name suggests, the “interim” part is key – it’s a temporary solution, a placeholder until a more capable successor takes over.
The ICPS has proven its abilities on Artemis I, providing the necessary thrust to propel Orion into lunar orbit. However, its limitations in power and payload capacity make it inadequate for the more ambitious goals of Artemis IV and beyond, which aim to deliver heavier payloads, including components for the Lunar Gateway space station, and sustained lunar surface operations.
Enter the Exploration Upper Stage, the next-generation powerhouse designed to replace the ICPS starting with Artemis IV: That’s what Boeing is working on at NASA’s Michoud Assembly Facility. It’s one of the upgrades coming to the SLS rocket in its new Block 1B configuration, providing a boost in payload capacity & a stretch to the rocket’s height that necessitates a brand-new launch platform.
This week, the company announced it had completed the first thrust structure for this stage. It connects the four RL-10 engines to the rest of the upper stage and transfers the loads, or thrust, from the engines to the rocket. That’s an upgrade from the single RL-10, which powers the ICPS. Technically, the engine itself will also be upgraded: from the RL-10B-2, to the RL-10C-3.
The completed piece is not meant for flight; it’s for the structural test article that will be tested to ensure it meets all of NASA’s requirements and transfers the thrust in a way that doesn’t damage the upper stage. But, Boeing did say it’s already working on the first flight-worthy thrust structure as well.
Notably, Boeing didn’t share any pictures of the completed thrust structure, but instead just some computer-generated images showing what it would look like, potentially for proprietary reasons.
Despite the odd PR choice, Boeing’s progress on the EUS is a positive step for the Artemis program. The recent passage of the so-called “Big Beautiful Bill” by Congress has secured the SLS program’s future through Artemis V, silencing earlier uncertainties under the current administration, which had considered canceling SLS after Artemis III.
Moving forward, Boeing’s ability to deliver – and perhaps show – tangible progress will be crucial. For now, we’ll have to trust their word on the thrust structure and hope future updates come with real photos, not just rendered squares.
That progress will likely next come via actual hardware production photos and video from the facility at MAF, which has been outfitting large amounts of floor space for EUS assembly.
(Lead Image: EUS in action with SLS – render by NASA).
