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NASA improves 3D-printing for faster, cheaper nozzles

20 Mar 2018

Patented Laser Wire Direct Closeout method cuts manufacturing time and cost for thin-but-rugged rocket nozzle production.

Engineers at NASA's Marshall Space Flight Center in Huntsville, Alabama, have developed a new laser-additive manufacturing technique for rocket nozzle fabrication that can greatly reduce costs and development time.

Thus a new process called Laser Wire Direct Closeout was developed by NASA to achieve these two objectives. LWDC is a different from most 3-D printing technologies, which are powder-based and fabricated in layers. Instead, it uses a freeform-directed energy wire deposition process to fabricate material in place. This new NASA-patented technology can reduce build time from several months to several weeks.

"NASA is committed to revitalizing and transforming our already highly advanced manufacturing technologies for rocket engines," said Preston Jones, director of the Engineering Directorate at Marshall. "What makes this development project special is that three separate, advanced manufacturing technologies are used together to build a better nozzle and prove it out through hot-fire testing.”

The LWDC method employs a wire-based additive manufacturing process to precisely close out the nozzle coolant channels, which contain the high pressure coolant fluid that protects the walls from the high temperatures a nozzle must withstand.

Channel cooling

Nozzles are actively cooled, or regeneratively cooled, meaning the propellant later used in the combustion cycle is routed through the nozzle to properly cool the walls so they do not overheat. To regeneratively cool the nozzles, a series of channels are fabricated within the nozzle, but these must be sealed, to contain the high-pressure coolant. NASA's new patented process using the LWDC technology closes out the coolant channels and forms a support jacket.

"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 during operation.”

After Marshall co-developed and patented the LWDC process, Keystone Synergistic of Port St. Lucie, Florida, used the technology to fabricate and test a nozzle. Through hot-fire testing at Marshall, engineers put this nozzle through its paces, accumulating more than 1,040 seconds at high combustion chamber pressures and temperatures. Now, this technology is being licensed and considered in commercial applications across the industry.

The second technology tested as part of this campaign was an abrasive water jet milling process to form the coolant channels advanced by Ormond, LLC of Auburn, Washington, while a further technology developed was an arc-based deposition technology to additively manufacture the near net shape liner that would contain the water jet milled channels.

Business partnerships

All three technologies were developed through NASA’s Small Business Innovation Research program, working to bring together the agency with its industry partners to advance manufacturing. With projects such as these, Marshall says it is "stimulating small business to maximize the return on America’s investment in space technology and exploration".

Gradl added, "One of the things I get excited about is advancing and proving 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."

Video

The following NASA video shows the LWDC technology in action:

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