Operators fired the engine for almost 11 minutes (650 seconds) on the A-1 Test Stand at Stennis Space Center near Bay St. Louis, Mississippi, providing valuable data to Aerojet Rocketdyne, lead contractor for the SLS engines, as it begins production of new engines for use after the first four SLS flights. Four RS-25 engines, along with a pair of solid rocket boosters, will help power SLS at launch. Engines for the rocket's first four Artemis program missions to the Moon already have been tested.

Operators now are focused on collecting data to demonstrate and verify various engine capabilities, evaluate new engine components manufactured with cutting-edge and cost-saving technologies, eliminate operating risks, and enhance engine production. The latest 650-second duration test represents the time three engines would have to fire to burn up propellant and power SLS to orbit, if the fourth engine shut down early during launch.

The longer time also allows operators to schedule and meet more performance objectives during a test. Operators fired the engine at 113% of its original power level for a period of time April 28 as well. RS-25 engines must fire at 111% to help power the launch of SLS; firing at 113% helps operators to test a margin of safety. The hot fire also marked the second test of a new NASA-designed thrust vector control (TVC) system used to gimbal engines for the test.

"Gimbaling" refers to how the engine must move to ensure proper flight trajectory. During the April 28 test, operators demonstrated the ability of the new TVC to move engines on both a tight circular axis and back-and-forth on a line. With the Artemis program, NASA will land the first woman and the first person of color on the Moon and establish sustainable exploration in preparation for missions to Mars.

SLS and NASA's Orion spacecraft, along with the commercial human landing system and the Gateway in orbit around the Moon, are NASA's backbone for deep space exploration. SLS is the only rocket that can send Orion, astronauts, and supplies to the Moon in a single mission. RS-25 tests at Stennis Space Center are conducted by an integrated team, including NASA, Aerojet Rocketdyne, and Syncom Space Services, the prime contractor of Stennis facilities and operations.