NASA has successfully cleared a repaired RS-25 rocket engine for flight after a critical hot-fire test. The engine, designated No. 2063, completed a full-duration, 300-second test on January 22 at the Fred Haise Test Stand at NASA’s Stennis Space Center near Bay St. Louis, Mississippi. This “confidence test,” conducted at up to 109% of its rated power, verified its readiness for the Artemis IV mission.
This particular engine has a unique history. It was originally installed on the core stage for the upcoming Artemis II mission, the first crewed flight of the SLS (Space Launch System) rocket. However, in 2025, engineers identified a hydraulic leak in the engine’s main oxidizer valve actuator, a crucial component that controls propellant flow. Following standard procedures, teams removed the engine from the rocket, replaced the faulty actuator, and prepared it for rigorous re-testing at Stennis.
The successful test was executed by a collaborative team of operators from NASA, L3Harris Technologies—the prime engines contractor for SLS—and Sierra Lobo, Inc., the Stennis test operations contractor. The data gathered confirms the repair was effective and the engine performs flawlessly under flight-like conditions.
With this milestone complete, engine No. 2063 is now scheduled to be reinstalled on the SLS core stage that will launch the Artemis IV mission. This process underscores NASA’s strict protocol: any engine that undergoes significant modification or repair must pass a full hot-fire test before being approved for flight. All RS-25 engines for the Artemis program are tested and proven flightworthy at Stennis.
The RS-25 engines are integral to NASA’s deep space exploration plans. During launch, four of these engines, combined with two solid rocket boosters, will generate a combined 8.8 million pounds of thrust to lift the SLS rocket and Orion spacecraft. NASA is currently targeting February for the Artemis II mission, which will send four astronauts on a journey around the Moon and back.
Under the broader Artemis campaign, these powerful engines will help NASA return humans to the lunar surface for scientific discovery, economic benefits, and to develop the technologies necessary for future crewed missions to Mars.
