Aerojet Rocketdyne Completes Altitude Hot Fire Test Series for 3D Printed Rocket Engine

California rocket and missile propulsion manufacturer Aerojet Rocketdyne said it has fully tested its 3D printed RL10C-X upper-stage rocket engine, hoping to help launch the Vulcan Centaur rocket as soon as 2022. The altitude hot fire test series put this next-generation engine through the rigors of a typical spaceflight mission. Using a test chamber that simulates the vacuum of outer space, the RL10C-X, which produces roughly 24,000 pounds of thrust, was tested in a flight-like configuration to demonstrate the engine’s capability to complete a typical mission profile, including multiple restarts.

The RL10C-X engine demonstrated full mission capability, said the company. The novel rocket engine is the next evolution of the company’s RL10 upper-stage engine and contains major components – including the injector and combustion chamber – produced with the company’s 3D printing technology. Aerojet has been actively working over the last decade to develop additive manufacturing (AM) platforms to build components that can reliably withstand the extreme operating environment of a rocket engine, which experiences high pressures and temperature gradients ranging from minus 423 degrees Fahrenheit to more than 5,000 degrees Fahrenheit.

Aerojet Rocketdyne’s RL10 has been a premier high-performance upper-stage engine for decades. Image courtesy of Eileen Drake via Twitter/Aerojet Rocketdyne.

Company CEO Eileen Drake said they have chosen to incorporate 3D printing techniques into the RL10 and other propulsion systems to make them more affordable while taking advantage of the technology’s inherent design and performance capabilities. In turn, they have managed to reduce engine component lead time by 35% and 50% and overall engine cost by 25% and 35%.

The 3D printed components in the RL10C-X make up the very core of the engine. Aerojet said the injector mixes the liquid hydrogen and liquid oxygen propellants and delivers them to the thrust chamber where they are burned, creating hot gases that produce thrust as they exit the engine. Aerojet selected these components because they offer the greatest cost reduction potential while delivering excellent performance and reliability.

“Successfully completing this test series validates our approach to incorporating 3D printing technology into the RL10 program in order to reduce cost while maintaining the engine’s unmatched performance,” said Drake. “The RL10 has been a workhorse in the industry for nearly six decades, and the RL10C-X will help ensure the engine maintains this leadership position well into the future.”

The RL10 engine has undergone nine major upgrades. In addition to orbiting hundreds of satellites and sending spacecraft to explore every planet in our solar system, the engine powered the DC-X vertical takeoff and landing vehicle in the 1990s and has demonstrated a deep-throttling capability for NASA down to 10% of rated thrust, making it ideal for the large lunar lander and future Mars lander applications.

The U.S. Air Force Space & Missle Command and Aerojet Rocketdyne advanced engine development on the RL10C-X. Image courtesy of Aerojet Rocketdyne via Twitter.

Built upon the RL10, the RL10C-X was developed in conjunction with the U.S. Air Force and American spacecraft launch service provider United Launch Alliance. It will power the Centaur upper stage of the ULA’s go-to launcher of the future, the Vulcan Centaur rocket. During the recent test series, the engine successfully demonstrated both long-duration operation and engine ignition at extreme in-flight conditions. Aerojet’s Space Business Unit Senior Vice President Jim Maser said the test series completed more than 600 seconds of run time in only two test runs. To date, the RL10C-X development program has accumulated more than 5,000 seconds of full engine hot-fire time and 32 starts.

In April 2019, the first RL10C-X prototype engine core made entirely of 3D printed components soared through the initial round of testing. All 3D printed engine components and the entire engine system remained in excellent condition, with significant life remaining after the hot fire testing.

3D printed RL10C-X prototype rocket engine soars through the initial round of testing. Image courtesy of Aerojet Rocketdyne.

In its adoption of AM techniques, the Aerojet team has followed a deliberate and proven development path that began with 3D printing and testing of subscale components. Then it progressed to a full-scale, additively manufactured thrust chamber assembly for the RL10 rocket engine built from a copper alloy using selective laser melting (SLM) technology. Later in 2019, the team incorporated and successfully tested a new re-generatively cooled nozzle that was 3D printed from a nickel-based alloy that led to testing a full-scale engine system at sea level.

Like dozens of other space companies, Aerojet has leveraged AM to achieve significant cost reductions, part weight optimization, faster build times, complex geometries, and in-house, on-demand builds. The continued adoption of additive technologies in the space industry can create price pressures on the costs of spacecraft manufacturing and help lower entry barriers for a wide range of startups. 3D printing is slated to help grow the space ecosystem and play a key role in enabling the future of human space travel and interplanetary colonization.