Aerojet Rocketdyne RS-25E to Power Future NASA Moon Missions

NASA and Aerojet Rocketdyne—the California-based manufacturer of rocket, hypersonic, and electric propulsive systems for the space, defense, civil and commercial sectors—have completed a series of certification tests of the new RS-25E rocket engines by which future iterations of United Launch Alliance’s (ULA) Space Launch System (SLS) will be powered.

The test series was undertaken for purpose of ensuring the new engine maintains the standards of robustness and reliability established by its predecessor.

Aerojet Rocketdyne president and CEO Eileen P. Drake stated: “With the completion of this 12-test campaign, we have cleared a major milestone in our RS-25 production restart program. The test series went very smoothly, raising our level of confidence that the new hardware designs and manufacturing processes will yield highly-producible, reliable engines.”

The SLS core stage is powered by four Aerojet Rocketdyne RS-25 liquid-fuel cryogenic rocket engines—known also as Space Shuttle Main Engines (SSME)—each producing some 418,000 lbf thrust at liftoff. The next three SLS flights, after the fashion of Artemis I, will be liberated from Earth’s surly bonds by legacy Space Shuttle Main Engines upgraded with modern flight controllers. However, subsequent launches, starting with NASA’s planned 2029 Artemis V mission, will be borne moonward by quartets of Aerojet Rocketdyne’s newly-certified RS-25E engine.  

Redesigned to deliver improved performance and lower costs, the RS-25E features simplified component designs made possible by manufacturing advances the likes of 3D printing. At the time of this writing, Aerojet Rocketdyne’s RS-25E is the world’s only high-performance, liquid hydrogen, staged combustion cycle engine. The first RS-25E engines are slated to be delivered to NASA in 2024.

Conducted on the historic Fred Haise Test Stand at NASA’s Stennis Space Center between 08 February and 22 June 2023, the recently-completed RS-25E test series comprised firings ranging in duration from five-hundred seconds—an interval consistent with the nominal SLS flight profile—to 720-seconds. Test engines were evaluated across thrust outputs of 80 to 111-percent-rated-power. To demonstrate an operational margin of safety, engines were occasionally pushed as high as 113-percent-rated-power.

In addition to thrust generation and resiliency, the certification campaign vetted the RS-25E engine’s redesigned nozzle, demonstrated engine gimballing at angles ranging from one to six degrees off-center, and showcased the new optimized flexible fuel and oxidizer feed lines. The longer-duration tests and gimbal demonstrations are relevant to a number of flight scenarios and help expand the RS-25 performance database.

Over the decades since its early 1960s inception, Rocketdyne’s RS-25, by dint of numerous revisions and upgrades, has been rendered increasingly safe, reliable, and powerful. As the SLS and the entirety of its constituent components are expendable, every launch of the platform burns up four RS-25 engines. The inevitable expenditure of the final legacy RS-25 will herald the SLS’s retrofitting with the newly-certified RS-25E rocket engines—an variant some 11-percent more powerful and thirty-percent less costly than the heritage RS-25 it replaces.

In summer 2023, NASA and Aerojet Rocketdyne will endeavor to certify yet another new rocket engine model by way of a similar testing campaign.

On 20 December 2020, it was announced that Lockheed Martin would acquire Aerojet Rocketdyne for $4.4-billion. However, the deal, which was expected to close in 2022’s first quarter, was opposed by Raytheon Technologies. In time, the U.S. Federal Trade Commission (FTC) sued to block the proposed acquisition, alleging it occasioned the elimination of the U.S.’s largest independent maker of rocket motors. In February 2022, Lockheed withdrew from the deal.

In December 2022, L3Harris Technologies agreed to buy Aerojet Rocketdyne for a cash payment of $4.7-billion.

At a special 16 March 2023 meeting, Aerojet Rocketdyne Holdings, Inc. announced that 99.7-percent of its stockholders had voted in favor of L3Harris’s acquisition of the company. The two firms expect to finalize the deal in 2023.

Whether or not the FTC again opposes Aerojet Rocketdyne’s acquisition remains to be seen.

FMI: www.rocket.com