NASA reschedules final SLS Core Stage Green Run tests for December - NASASpaceflight.com

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NASA’s Space Launch System (SLS) Program rescheduled the final two tests that will culminate the Core Stage Green Run campaign for December after successfully repairing one of the liquid hydrogen (LH2) prevalves inside the engine section of the stage

The Artemis 1 core stage flight article is installed in the B-2 Test Stand at the Stennis Space Center in Southern Mississippi for the Green Run design verification campaign

Following the surgical clutch replacement, the fully-reconstructed valve assembly passed retesting and Core Stage prime contractor Boeing is now working to pick up preparations for the first of the two final critical tests: a Wet Dress Rehearsal (WDR) to prepare for a subsequent full-duration test firing of the stage

NASA reported on November 18 that in-place repairs of the engine four LH2 prevalve in the Core Stage were successful

Louis, Mississippi, successfully repaired a valve inside the core stage of the agency’s Space Launch System (SLS) rocket,” Kathryn Hambleton, Public Affairs Officer at NASA Headquarters, wrote in the agency’s Artemis blog

“The team designed an innovative tool to remove and replace the valve’s faulty clutch while the core stage remained in the B-2 test stand, and without removing the entire valve.”

Engineers worked in cramped quarters inside the Core Stage’s engine section to do the troubleshooting and repairs

The bottom of the LH2 propellant tank, the aft dome, takes up a significant part of the room inside the engine section, with the prevalves attached to the bottom of the tank in a small space above and around all the Main Propulsion System (MPS) equipment at the bottom of the engine section

(Photo Caption: The four LH2 prevalves on Core Stage-1 can be seen sticking out of the LH2 tank aft manifold in the upper right part of this image taken in September, 2019, at Michoud Assembly Facility during operations to mate the engine section (left) to the bottom of the hydrogen tank (right). A suspect clutch mechanism in one of the valves was recently repaired from inside the engine section with the stage installed vertically in the B-2 Test Stand.)

Engineers for Boeing and prevalve vendor Vacco had to position themselves on an erector set style work platform installed for access inside the engine section

Test case five performed a checkout of the Core Stage Main Propulsion System (MPS) and RS-25 engines late in the Summer which included a test of the TVC systems for all four engines

(Photo Caption: One of the RS-25 Core Stage engines is swung outwards by the stage’s hydraulically-powered TVC system in a gimbal test performed on August 31. Data from the TVC testing performed during Green Run test case five is still being discussed, but the issue is not holding up plans to run the final two test cases in December.)

In flight the Core Stage moves the four RS-25 engines for steering using hydraulic power; each engine has two TVC actuators connected to it, a pitch and a yaw actuator

The lab is located near the SLS avionics and software test lab which has operating sets of the Core Stage flight computers and avionics

With NASA and Boeing moving ahead towards the final Green Run tests in December, the issue doesn’t appear to be a showstopper to the new schedule for finishing the Stennis campaign; however, careful positioning of the engines by the stage TVC system is a crucial element of the Hot-Fire test