SLS Exploration Upper Stage Passes Critical Design Review

The Critical Design Review for the Exploration Upper Stage (EUS) was completed, clearing SLS Block 1B development to proceed to hardware fabrication. The EUS, powered by four RL10C-3 engines, would increase SLS payload capacity from 27 to 38 metric tons to trans-lunar injection — enabling Orion to carry co-manifested Gateway payloads. The EUS cost, originally $962M in 2017, would later balloon to nearly $2.8 billion before cancellation in 2026.