NASA Develops New 3D Printing Method for Fabricating Rocket Engine Nozzles

Rocket engine nozzles are complex and expensive to manufacture, due to the fact that they operate in extreme temperatures and pressures from the combustion process. Additive manufacturing, however, like with so many other aerospace components, can cut down on some of the cost and time involved in manufacturing the nozzles, as a team of engineers at NASA’s Marshall Space Flight Center showed when they developed a new 3D printing technique for nozzle fabrication.

Laser Wire Direct Closeout (LWDC) uses a freeform-directed energy wire deposition process to fabricate components, and it has the potential to reduce build time from several months to several weeks.

“NASA is committed to revitalizing and transforming its already highly advanced manufacturing technologies for rocket engines. What makes this development project even more unique is there were three separate, state-of-the-art, advanced manufacturing technologies used together to build a better nozzle and prove it out through hot-fire testing — an example of why Marshall continues to be a worldwide leader in manufacturing of propulsion technologies,” said Preston Jones, Director of the Engineering Directorate at Marshall.

Nozzles are actually quite complex components, despite their simple appearance; the use of additive manufacturing in GE’s famed fuel nozzle was groundbreaking in that it brought the technology to bear in commercial aircraft, earning it a mention among the most significant objects ever 3D printed. 3D printing the fuel nozzle saved on weight and costs, as well as simplifying the design, all critical considerations in the aerospace industry.

Rocket nozzles are actively, or regeneratively, cooled, meaning that the propellant later used in the combustion cycle is routed through the nozzle to cool the walls so that they do not overheat. To regeneratively cool the nozzles, a series of channels is fabricated within the nozzle. Those channels must then be sealed to contain the high-pressure coolant. The new LWDC process uses wire-based additive manufacturing to close the channels and form a support jacket, reacting structural loads during engine operation.

“Our motivation behind this technology was to develop a robust process that eliminates several steps in the traditional manufacturing process,” said Paul Gradl, a senior propulsion engineer in Marshall’s Engine Components Development & Technology Branch. “The manufacturing process is further complicated by the fact that the hot wall of the nozzle is only the thickness of a few sheets of paper and must withstand high temperatures and strains during operation.”

After the process was developed and patented by Marshall, it was used by Keystone Synergistic Enterprises to fabricate and test a nozzle. Engineers put the nozzle through hot-fire testing at Marshall, accumulating more than 1,040 seconds at high combustion chamber pressures and temperatures. The technology is now being licensed and considered for commercial applications across the industry.

Two other technologies were tested at the same time: an abrasive water jet milling process to form the cooling channels developed by Ormond, LLC, and an arc-based deposition technology to additively manufacture the near net shape liner that would contain the water jet milled channels. All three technologies were developed through NASA’s Small Business Innovation Research program, which works to bring the agency together with industry partners to advance manufacturing.

“One of the things I get excited about is advancing and proving out new technologies for our application with industry partners that a private space company can then use as part of their supply chain. That was the objective behind some of this — we formulated the concept, worked with external vendors, and now we’re partnering to infuse this new technology throughout industry to improve advanced manufacturing,” said Gradl.

NASA has been working for some time on bringing additive manufacturing into rocket engine production, building up a record of successful tests of various components and technologies as 3D printing continues to find its way into end-use applications in a demanding industry.

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[Source: NASA]