NASA achieved a key milestone recently, completing an initial certification test series designed to pave the way for production of new RS-25 engines to help power NASA’s SLS (Space Launch System) rocket on future Artemis missions to the Moon, beginning with Artemis V.

“This certification test series for the redesigned engine sets the stage for a new chapter of spaceflight history for the RS-25 engines and future flights of the SLS rocket,” said Johnny Heflin, SLS liquid engines manager. “The newly redesigned RS-25 engines leverage advanced manufacturing techniques and innovative designs while increasing the engine’s performance as NASA aims establish a sustainable presence on the Moon and prepare for future missions to Mars.”

Engineers conducted a full-duration test of more than eight minutes (500 seconds) on an RS-25 certification engine manufactured by SLS engines lead contractor Aerojet Rocketdyne. The engine incorporates dozens of improvements to make production more efficient and affordable while maintaining high performance and reliability. The test series on the Fred Haise Test Stand at NASA’s Stennis Space Center near Bay St. Louis, Mississippi, is designed to verify that the new engines meet all Artemis flight requirements.

The stage is now set for a second – and final – certification series to begin in early fall. Data from the certification tests will confirm all is good to go in producing new engines for use beginning with the Artemis V mission to the Moon as NASA continues its effort to explore the secrets of the universe for the benefit of all.

Aerojet Rocketdyne is employing new manufacturing processes and techniques, including 3D printing, to produce the RS-25 more efficiently. NASA has awarded the company contracts to provide 24 new engines, which will help power six SLS launches. Four RS-25 engines fire simultaneously to produce more than 2 million pounds of combined thrust to help launch the rocket.

The recent certification series featured a dozen full-duration tests and plenty of highlights, including –

• Almost 110 minutes of cumulative hot fire duration. Each of the 12 tests fired for at least 8 minutes (500 seconds) and several for even longer to fully characterize engine performance. the 500-second tests simulate the same amount of time the engine must perform to lift SLS and astronauts aboard the Orion spacecraft to orbit. The engine approached 2 hours (6,570 seconds) of cumulative hot fire time during the series.
• Four long-duration tests. Operators conducted a pair of 10-minute tests, as well as 10-and-a-half minute and 12-minute hot fires, during the series. The 720-second test represented the longest-ever hot fire of a modified RS-25 engine.
• An aggressive gimbal test. Halfway through the campaign, operators conducted a gimbal test of the engine to ensure it will pivot as needed to maintain SLS stability and trajectory during flight. Operators moved the engine by as much as 6 degrees from center on a tight circular axis and in a back-and-forth pattern to demonstrate the gimbaling capability.
• A wide range of power levels. Operators fired the RS-25 engine from 80% to 113% power levels to test the performance of the engine in various scenarios The first four Artemis missions use modified space shuttle main engines that can power up to 109% of their rated level. New RS-25 engines will power up to the 111% level to provide additional thrust. Operators tested up to the 113% power level during a number of certification hot fires to learn about the engine’s capabilities and to provide a margin of operational safety.
• State-of-the-art components. The certification engine featured various components manufactured with advanced processes and techniques, including a main combustion chamber using hot isostatic pressure bonding, an improved nozzle brazing process, new flex hoses, and numerous 3D-fabricated components. The certification hot fires demonstrate the performance capabilities of the new components.

The initial certification series provided key data about the performance limits of the redesigned engine and components. “Testing new hardware always is a learning process, even on an engine as proven as the RS-25,” said Chip Ellis, manager of the RS-25 Engine Test Project at NASA Stennis. “The success of this series really is a testament to NASA’s commitment to ‘test as we fly’ and to the expertise of the test team.”

“This 12-test series demonstrated our confidence level that our new designs have the same reliability and performance as their predecessors,” said Aerojet Rocketdyne RS-25 Deputy Program Manager Mike Lauer. “We put the engine through a lot of different scenarios, and we are extremely pleased with the results.”

By the close of the series, operators were conducting weekly full-duration tests of the engine. Now, all eyes turn to the second certification series. With completion of that campaign, it is anticipated that all systems will be “go” to produce engines for future Artemis missions to the Moon and, eventually, Mars.