WASHINGTON — A new edition of a 60-year-old rocket engine, with performance and value improvements, is anticipated to make its debut in 2025 on the Vulcan Centaur rocket.
At a Nov. 27 briefing, executives with United Launch Alliance and Aerojet Rocketdyne, an L3Harris Technologies company, said they expected that the RL10C-X engine, the most recent upgrade to the RL10, to make its first flight on a Vulcan launch a while in 2025.
A significant change for the RL10C-X is the way it is manufactured. “It relies heavily on additive manufacturing,” said Jim Maus, vice chairman of program execution and integration at Aerojet. The present RL10 uses additive manufacturing to provide its injector, however the RL10C-X will use additive manufacturing to provide your complete thrust chamber.
That change offers cost reductions “that has been one among the enablers for us continuing to be viable within the marketplace,” he said, but didn’t quantify those reductions.
The engine also uses a carbon-silicon nozzle that he said improves its specific impulse, a measure of efficiency. Other elements of the engine, including its turbomachinery, are unchanged from existing versions of the RL10.
Maus said the RL10C-X goes through certification now, and he expected it first fly on a Vulcan Centaur a while in 2025. Gary Wentz, vice chairman of presidency and industrial programs at ULA, confirmed that timeline. “We’re targeting within the 2025 timeframe,” he said, “subject to integrating it with the vehicle and assigning a mission to it.”
ULA chosen the RL10C-X in 2018 to power the Centaur upper stage on Vulcan in what it described on the time as a “competitive procurement,” although versions of the RL10 have been used on Atlas and Delta launch vehicles for many years. ULA ordered 116 RL10C-X engines in 2022 for future Vulcan launches.
Aerojet has a contracted backlog of “north of 150” RL10 engines, Maus said, including the RL10C-X and older versions. While that backlog is dominated by the ULA order of RL10C-X engines, he said deliveries of the older RL10 design are projected to proceed to 2026, with overall RL10 production ramping up from a current 16 to 18 engines a yr to 40 a yr.
After the retirement of the Atlas 5 and Delta 4 Heavy, the RL10 will likely be utilized by Vulcan in addition to the Space Launch System. That rocket’s Interim Cryogenic Propulsion Stage uses a single RL10 while the Exploration Upper Stage (EUS), set to make its debut on Artemis 4 within the late 2020s, will use 4 RL10 engines. Maus said NASA has yet to make your mind up if will use the brand new RL10C-X engine on the EUS.
The businesses held the briefing to mark the sixtieth anniversary of the primary use of the RL10 on an Atlas-Centaur rocket. The engine has been used on a wide range of vehicles since then, from the Saturn 1 to the DC-X suborbital experimental vehicle.
Maus credited that longevity to the performance of the engine, whose high specific impulse comes from its use of liquid hydrogen and liquid oxygen propellants and an expander cycle that drives the engine’s turbomachinery without having to burn propellants.
“We proceed to deliver very high reliability, very high performance, and the engine itself could be very versatile,” he said. “It’s great to be at 60 years, with a really long and brilliant future ahead.”