Mar 21, 2018 | By Benedict

Engineers at NASA's Marshall Space Flight Center in Huntsville, Alabama have developed and tested a new additive manufacturing technique called Laser Wire Direct Closeout (LWDC). The 3D printing method can be used to make rocket engine nozzles at a reduced cost in a shorter time.

(Image: NASA/MSFC/David Olive)

You might never own the kind of additive manufacturing equipment used by NASA, but the space organization’s 3D printing endeavors remain some of the world’s most fascinating. We’ve kept a close eye on its partially 3D printed RS-25 rocket engines for the Space Launch System, while its more out-there 3D printing projects are often equally interesting.

This week, engineers at NASA’s Marshall Space Flight Center revealed the development of a completely new additive manufacturing process. It’s called Laser Wire Direct Closeout, and it can be used to fabricate 3D printed rocket engine nozzles—both faster and more affordably than other metal additive manufacturing technologies.

As the name suggests, LWDC isn’t a powder bed additive manufacturing process. Rather, the 3D printing technique uses a process of freeform directed energy wire deposition to fabricate intricate metal parts. The technique has already been patented by NASA, and is purportedly capable of shortening fabrication times from months to just weeks.

(Image: NASA/MSFC/Emmett Given)

According to the NASA engineers, the 3D printing process is designed to precisely “close out” the coolant channels of the printed nozzle. These channels contain the high-pressure coolant fluid that protects the extremely thin walls of a nozzle from very high temperatures.

The kind of rocket engine nozzles used by NASA are actively cooled, or “regeneratively” cooled, which means a series of channels are fabricated within the nozzle, and propellant later used in the combustion cycle is routed through the nozzle to properly cool its walls. These channels, however, must be closed out, sealed, to contain the high-pressure coolant.

NASA’s new LWDC 3D printing process effectively seals up the coolant channels and forms a support “jacket” in place, 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.”

The 3D printing technology has already been used by Keystone Synergistic of Port St. Lucie, Florida, which used LWDC to make and test a nozzle of its own. The 3D printed rocket engine nozzle was hot-fire tested at the Marshall Space Flight Center for just over 1,040 seconds.

As part of the same research, NASA also developed an abrasive water jet milling process and a second 3D printing process that produces a near-net-shape liner for containing the jet-milled channels.

All of the new technologies were developed through NASA’s Small Business Innovation Research program, helping small businesses benefit from NASA’s vast technological capabilities.



Posted in 3D Printing Technology



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