The National Aeronautics and Space Administration (NASA)’s Marshall Space Flight Center announced in an official release that it has developed and used a new additive manufacturing (AM) technique to fabricate nozzles that can help the space agency develop rocket engine nozzles at a much faster rate and at a much cheaper cost than earlier.
Known as the Laser Wire Direct Closeout (LWDC) process, NASA Marshall’s new technology is an advanced version of additive manufacturing. It differs from the traditional 3D printing technologies in the sense that unlike traditional 3D printing technologies that use powder-based and fabricated in layers; this new technology uses a freeform directed energy wire deposition process to fabricate material in place. This new patented technology has the potential to not just reduce the total building time for nozzles but also build nozzles that are less expensive.
Speaking about how NASA has been experimenting with new manufacturing technologies for their rocket engines, Preston Jones, Director of the Engineering Directorate at Marshall, said “NASA is committed to revitalizing and transforming its already highly advanced manufacturing technologies for rocket engine”.
“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,” Preston added.
Adding more about the motivation behind developing advanced manufacturing techniques for rocket engines, Paul Gradl, a senior propulsion Engineer in Marshall’s Engine Components Development & Technology Branch said, “Our motivation behind this technology was to develop a robust process that eliminates several steps in the traditional manufacturing process,”
“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 laser wire direct closeout process was used to fabricate a nozzle and was tested by Keystone Synergistic of Port St. Lucie, Florida. 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. This co-developed and patented technology will be licensed and considered for commercial use in other industry applications.
Nozzles are quite complex from designing, aerodynamics and material consideration and even manufacturing point of view. All the various attributes affect each other and the entire process gets complicated. The laser wire direct closeout method has played a crucial role in development of the nozzle. Due to the exposure of high temperatures, the nozzle design demanded a heat dissipation method. By employing wire-based additive manufacturing technique the nozzle coolant channels, containing the high pressure coolant fluid protecting the walls from the high temperatures a nozzle must withstand, were accurately closed out.
Firstly, the nozzles are cooled by the propellant to be used in a further combustion cycle was directed through the nozzle to appropriately cool the nozzle walls to cool them down.
Secondly, for regenerative cooling of the nozzle, a set of cooling channels were to be fabricated within the nozzle which must be sealed to contain the high-pressure coolant. This was effectively achieved by the novel laser wire direct closeout technology.
Apart from the laser wire direct closeout process, the team tested two more technologies, namely Abrasive water jet milling process to build coolant channels and an Arc-based deposition technology to the near net shape liner to contain the water-jet milled coolant channels.
On the new technologies, Gradl added, “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.”