New RL10C-X Rocket Engine To Debut On Vulcan In 2025

United Launch Alliance (ULA) and Aerojet Rocketdyne have announced a revamped version of the 60-year-old RL10 rocket engine called the RL10C-X will make its inaugural flight on the Vulcan Centaur rocket in 2025.

"We are targeting in the 2025 timeframe, subject to integrating it with the vehicle and assigning a mission to it." - Gary Wentz, Vice President of Government and Commercial Programs at ULA

A significant transformation for the RL10C-X lies in its manufacturing process. Jim Maus, Vice President of Program Execution and Integration at Aerojet, revealed, "It relies heavily on additive manufacturing."

While the current RL10 utilizes additive manufacturing for its injector, the RL10C-X takes it a step further by using additive manufacturing to produce the entire thrust chamber. This alteration results in cost reductions, a pivotal factor in ensuring the engine's continued competitiveness in the market. Specific figures regarding the cost reductions were not disclosed.

The RL10C-X incorporates a carbon-silicon nozzle, enhancing its specific impulse, a metric that measures efficiency. Other components of the engine, including its turbomachinery, remain unchanged from previous iterations of the RL10.

The RL10C-X was selected by ULA in 2018 to power the Centaur upper stage on the Vulcan rocket through a competitive procurement process, and ULA ordered 116 RL10C-X engines solidifying its commitment to the upgraded design in 2022.

Aerojet currently holds a contracted backlog of "north of 150" RL10 engines, encompassing both the RL10C-X and older versions. While the ULA order dominates the backlog, deliveries of the older RL10 design are expected to continue until 2026. The overall production of RL10 engines is projected to increase from the current 16 to 18 engines per year to 40 engines per year.

Following the retirement of the Atlas 5 and Delta 4 Heavy, the RL10 will power the Vulcan and the Space Launch System. The Exploration Upper Stage (EUS) of the Space Launch System, set to debut on Artemis 4 in the late 2020s, which is expected to use four RL10 engines. However, NASA has not yet determined whether the new RL10C-X engine will be utilized on the EUS.