NASA tests RS-25 engine No. 10001 for 500 seconds at Stennis

NASA teams tested RS-25 engine No. 10001 at the Stennis Space Center near Bay St. Louis, Mississippi, on Oct. 21, 2026.

The hot fire ran for 500 seconds, almost eight-and-a-half minutes, matching how long RS-25 engines fire during an SLS launch. The test used the developmental RS-25 engine at the Mississippi test center. NASA describes Stennis, near Bay St. Louis, Mississippi, as the site where all such engines are proven flightworthy before use, and operators from NASA, L3Harris, and Nova Space Solutions run the Stennis tests that prove RS-25 engines flightworthy before use.

Operators ran the firing on the Fred Haise Test Stand at Stennis, which is part of NASA’s Stennis Space Center near Bay St. Louis, Mississippi, where the Oct. 21 firing took place. Test teams include operators from NASA, L3Harris, and Nova Space Solutions.

NASA’s release lists the 111% power level for the Oct. 21 firing, and operators ran RS-25 engine No. 10001 at that power level during the test. NASA says 111% power matches the thrust required for new production engines to send the SLS rocket and Orion spacecraft to orbit.

Because engine No. 10001 is developmental, NASA says it will not fly, and the engine itself is developmental rather than flight hardware. The stated purpose of firing the non-flight developmental unit is to let NASA and contractor L3Harris Technologies gather critical data for better engine performance and reliability, and the test still supports data collection for engine performance and reliability.

Engineers aimed to acceptance-test RS-25 flight hardware for coming Artemis flights and to validate a new thermal protection system shielding the engine nozzle. NASA lists acceptance testing of RS-25 flight components for Artemis missions as a test objective, and the thermal protection system shields the RS-25 engine nozzle from the thermal environment around SLS during launch.

On each Artemis mission, four RS-25 engines generate as much as 2 million pounds of combined thrust to aid the SLS launch, and NASA says this combined thrust helps launch the SLS rocket. Stennis is the site where the engines are proven flightworthy before flight use, and every RS-25 engine undergoes testing and is proven flightworthy at NASA Stennis before use.