NASA Conducts Hot Fire of RS-25 Engine
- NASA successfully conducted a hot fire test of RS-25 engine No. 2063 on January 22, 2026, at the Stennis Space Center.
- The test was conducted to ensure the engine is ready for flight and cleared the way for its installation on the SLS core stage for the Artemis IV mission.
- Engine No. 2063 was originally installed for the Artemis II mission but was removed due to a hydraulic leak in the main oxidizer valve actuator, which was later replaced.
- The hot fire test demonstrated the engine’s readiness for flight and was conducted at up to 109% of its rated power level, with teams from NASA, L3Harris Technologies, and Sierra Lobo, Inc. participating in the operation.
- The successful test paves the way for the Artemis IV mission, which is scheduled to launch as soon as February and will send four astronauts around the Moon and back on a crewed mission under the Artemis campaign.
NASA successfully conducted a hot fire of RS-25 engine No. 2063 on Jan. 22 at the Fred Haise Test Stand at NASA’s Stennis Space Center near Bay St. Louis, Mississippi, clearing the way for the engine to be installed for the agency’s Artemis IV mission.
The RS-25 engines help power NASA’s SLS (Space Launch System) rocket that will carry astronauts to the Moon under the Artemis campaign.
Engine No. 2063 originally was installed on the SLS core stage for the Artemis II mission but was removed in 2025 after engineers discovered a hydraulic leak on the engine’s main oxidizer valve actuator, which controls propellant flow into the engine combustion chamber.
Following standard NASA procedures, teams removed the engine from the core stage and replaced the actuator.
Because NASA requires any significantly modified or repaired engine to undergo hot fire testing before flight, teams at NASA Stennis fired the engine for five minutes (300 seconds), at up to 109% of its rated power level in a test known as a confidence test that demonstrates the engine is ready for flight.
The test was conducted by a team of operators from NASA, L3Harris Technologies, and Sierra Lobo, Inc., the NASA Stennis test operations contractor. NASA Stennis provides critical data to L3Harris, the prime engines contractor for the SLS rocket.
With the successful test complete, engine No. 2063 is scheduled to be installed on the SLS core stage for Artemis IV. All RS-25 engines for NASA’s Artemis missions are tested and proven flightworthy at NASA Stennis before flight.
NASA is targeting as soon as February to send four astronauts around the Moon and back on Artemis II, the first crewed mission under the Artemis campaign. During launch, the SLS rocket will use four RS-25 engines, along with a pair of solid rocket boosters, to help lift the Orion spacecraft and the crew away from Earth using more than 8.8 million pounds of thrust.
Under the Artemis campaign, NASA is returning humans to the Moon for economic benefits, scientific discovery, and to prepare for crewed missions to Mars.