NASA Stennis proves water systems ready for Artemis IV upper stage trials

by Clarence Oxford
Los Angeles CA (SPX) Feb 13, 2026
A major water system activation at the Thad Cochran Test Stand (B-2) has moved NASA Stennis Space Center a step closer to Green Run testing of the exploration upper stage for the Artemis IV mission. The Jan. 30 activation exercised new cooling hardware and pushed the site's high pressure industrial water network to full capacity in preparation for operating the more powerful upper stage.

The exploration upper stage is a four engine liquid hydrogen and liquid oxygen in space stage for the Block 1B configuration of NASA's Space Launch System rocket. During Green Run, teams at NASA Stennis will check and operate all stage systems and finish with a full duration hot fire of the four RL10 engines, replicating flight like conditions. The Jan. 30 milestone focused on making sure the stand can handle the thermal and acoustic environment created by the upgraded stage.

As part of the stand modifications, engineers added water cooled diffusers that act as a heat shield to manage super hot exhaust from the four RL10 engines. They also installed water cooled fairings that guide the engine exhaust to align with diffuser walls and protect key structures. A new purge ring delivers cooling water and gaseous nitrogen to shield a flexible seal that allows the engines to gimbal during testing.

NASA Stennis integrated these new elements with the existing flame deflector and acoustic suppression equipment originally used for core stage testing ahead of the Artemis I launch. The combined system is designed to protect the stand while managing extreme temperatures, forces and noise generated during multi engine firings. The Jan. 30 run provided a first full systems look at how the legacy and new hardware perform together.

The activation also exercised the high pressure industrial water system at its maximum planned load. Typical RS 25 engine tests at NASA Stennis draw on a subset of the complex's 10 diesel driven pumps and single electric pump. Exploration upper stage operations will require all 11 pumps running simultaneously to supply the diffusers, fairings, purge ring and other cooling and suppression systems.

During the Jan. 30 exercise, about 14 million gallons of water circulated through the test complex. A 66 million gallon reservoir feeds the stand through an underground 96 inch diameter pipe that distributes water to cooling components across the structure. After use, water flows into the flame deflector, through a concrete flume and into the stand's catch pond, then drains back to the canal via a ditch for reuse in future operations.

Engineers collected detailed pressure, flow and timing data during the run to refine operating procedures for the upcoming test series. "We will use the data gathered to set the final timing of when valves are cycled, determine our redline pressures, and select the operating pressure," said Nick Nugent, NASA Stennis project engineer. "This exercise also put the water system under a full load prior to the final stress test. It is always good to give the system a good shake down run prior."

The exploration upper stage structure is being built by Boeing at NASA's Michoud Assembly Facility in New Orleans. The four RL10 engines that will power the stage are manufactured by L3Harris Technologies. Before the stage and engines arrive at NASA Stennis for Green Run, teams will conduct a 24 hour stress test across all facilities in the test complex to demonstrate readiness for the full campaign.