NASA’s Stennis Space Center has completed upgrades to a critical system needed to test RS-25 engines that will power the new Space Launch System (SLS) rocket on Artemis missions to the Moon.

Engineers and operators on the Fred Haise Test Stand at Stennis recently completed testing of an upgraded thrust vector (TVC) system needed to gimbal RS-25 engines during testing. Gimbaling is the term for moving an engine a few degrees along a tight circular axis to direct the thrust and “steer” the SLS rocket on a proper trajectory during launch.

Two hydraulic actuators are used to push and pull the engine several degrees and direct the thrust in a particular direction. The upgrades completed to the TVC system were performed to increase the speed of the actuators in returning an engine from a gimbaled angle back to the null position with the engine pointing directly down.

“We did this to make sure that if we ever encounter any failure scenarios during hot fire tests, we have enough speed in the system to get back to home before we cut the engine,” said David Carver, lead engineer of electrical test operations. “This is important because if we cut the engine while it is gimbaled out to say six degrees, it could cause potential damage … to the engine or nozzle.”

Stennis engineers used a mass simulator to test TVC system upgrades. The mass simulator is designed to be the approximate size and shape of the RS-25 engine and nozzle, including its weight of about 8,000 pounds.

Using this simulator allows engineers to check the control system to ensure there are no clearance issues between the engine and test stand. It is also used to ensure the timing and responses from the system are correct. The simulation allows engineers to orchestrate different scenarios to see how the TVC system reacts.

Stennis Space Center, located near Bay St. Louis, Mississippi, currently is preparing to conduct certification tests for production of new RS-25 engines for future Artemis missions. Stennis already has tested engines for the first four Artemis missions. Every RS-25 engine that will help power the SLS rocket at launch will be tested at Stennis, including those that return the first woman and first person of color to the Moon and those that power eventual missions to Mars.