NASA and Aerojet Rocketdyne, a Sacramento, CA-based GenCorp company, announced Oct. 17 that they successfully completed a series of hot-fire tests on an advanced rocket-engine thrust chamber assembly (TCA) using copper alloy additive manufacturing (AM) technology.

The testing, claimed to be an industry first, was conducted with cooperation between Aerojet Rocketdyne, NASA’s Space Technology Mission Directorate Game-Changing Development Program, and NASA’s Glenn Research Center under a Space Act Agreement.

The hot-fire tests used Aerojet Rocketdyne’s proprietary Selective Laser Melting (SLM) copper alloy enhanced heat transfer design chamber, which demonstrated a “significant increase in performance” compared to traditional combustion chamber designs and material systems.

“In all, NASA and Aerojet Rocketdyne conducted 19 hot-fire tests on four injector and TCA configurations, exploring various mixture ratios and injector operability points. At the conclusion of the tests, the injector and chamber hardware were found to be in excellent condition, and test data correlated with performance predictions,” Lee Ryberg, Lead Project Engineer on Aerojet Rocketdyne’s Additive Manufacturing development team, said in a statement announcing the successful testing.

Aerojet Rocketdyne told Aerospace Engineering that it has been “aggressively working the methodical development of AM” for several years, for a number of alloys. The specific copper alloy employed in this round of hot-fire tests is proprietary and has been in some phase of development and demonstration for about the past three years.

“SLM of copper can be pretty tricky, for the reasons…regarding the conductivity of Cu,” a company spokesperson shared. “So it can be a challenge to get a solid, well-managed microstructure that will result in good mechanical properties.”

Other materials the company is exploring for the AM technology include a few different nickel alloys, some titanium, a couple of steels, and some aluminum, the spokesperson said.

“This work represents another major milestone in the integrated development and certification of the materials characterization, manufacturing processes, analysis, and design-tool technologies that are required to successfully implement Selective Laser Melting for critical rocket engine components,” Jay Littles, Director of Advanced Launch Programs at Aerojet Rocketdyne, said in the statement. “Aerojet Rocketdyne continues to expand the development of novel material and design solutions made possible through additive manufacturing, which will result in more efficient engines at lower costs. We are working on a range of additive-manufacturing implementation paths—from affordability and performance enhancement to legacy products such as the RL10 upper stage engine. We also are applying the technology to next-generation propulsion systems, including the Bantam Engine family, as well as our new large, high-performance booster engine, the AR1.”

The traditional materials that could be replaced by SLM copper alloy technology depend on the specific application. “For some of our legacy products, this type of additively-manufactured copper combustion chamber could replace a brazed steel tube combustion chamber. Moving from brazed steel tube construction to an integral copper chamber would have benefits in terms of component cost, lead time, and even performance, depending on the configuration,” the spokesperson told Aerospace Engineering.

Performance improvements, for this application, can include improved thermal management within the combustion chamber, “which can relate to improved component durability and even combustion efficiency,” according to Aerojet Rocketdyne.

Full-scale demonstration is the next step in the technology’s development path.