This clears a key facility-readiness gate for EUS hot-fire testing by validating the new water-cooled diffusers/fairings and the stand’s ability to run all 11 pumps simultaneously at maximum load. The activation generated performance data that will be used to finalize the test complex configuration before EUS hardware arrives for Green Run. The demonstrated 14-million-gallon recycled-water run indicates the stand can sustain the thermal management demands of four RL10 engines, reducing the risk of test-stand-driven schedule slips once the campaign starts.