Korea Aerospace Research Institute: Trends in 3D Printed Rocket Launchers

Researchers from the Korea Aerospace Research Institute examine the fine details of 3D printing rocket parts, releasing the findings of their study in ‘Technology Trends in Additively Manufactured Small Rocket Engines for Launcher Applications.’

As so many space startups today become involved in the manufacturing of launch vehicles, 3D printing often plays a major role in production—offering all the classic benefits such as affordability, speed in manufacturing, the ability to innovate like never before, and best of all, no middleman. Space X, Rocket Lab, and of course NASA too have all put 3D printing in the headlines whether in showing off 3D printed thrusters, or entire rockets.

SuperDraco engine of SpaceX

In this study, the researchers fabricated an existing valve housing for a rocket engine, investigating the future potential of such technology, as well as how cost could be reduced for projectile engines. Looking to the SpaceX SuperDraco, the research team followed AM progress in aerospace. Further, they discuss Rocket Lab’s Rutherford engine, used for the Electron projectile which eventually reached space orbit in 2018. The engineers were able to 3D print nearly all the parts, sending an engine with a ground thrust of 24 kN and a ground specific thrust of 311 seconds successfully into space.

AM engine specifications made in USA.

Peter Beck, CEO of the private spaceflight company Rocket Lab, holding a Rutherford engine and standing next to an Electron Rocket

The turbopump is one of the most complex parts of the engine, leaving the researchers to note that much more time must be spent on this component for design, analysis, and verification. Divided into many different parts, and each with a separate manufacturing method, the turbopump makes up 45 percent of the cost of the entire engine.

“Accordingly, attempts to incorporate AM technology into the production of turbopumps have been made in various forms in various countries,” stated the researchers. “The turbopump requires a differentiated AM strategy because the shape of the main parts is complicated and there are shape constraints required to implement the function.”

SpaceX, acting as the precursor and inspiration to many in terms of projectile startups—and additive manufacturing processes, demonstrated the benefits of such progressive, forward thinking in production. NASA, using 3D printing for decades already, has continued to fabricate parts for a variety of projects, including production of smaller turbopumps. In developing tasks such as the Low Cost Upper Stage Project and the Additive Manufacturing Demonstrator Engine, NASA continues to demonstrate and recognize reduction in cost, more efficient schedules, and flexibility in design.

Currently, the ESA is planning to build a methane engine (Prometheus), while Sweden’s GKN is said to be producing turbine disks and casings via additive manufacturing. And as variety of countries and organizations engineer new aerospace components, Japan is developing an H-3 projectile—featuring an expander-bleed engine—instead of a previous ‘fuel-rich’ multistage engine. IHI is currently creating a 3 ton-class methane expander engine. While they may be saving on time and cost, there are also claims that increased surface roughness affected performance:

“In the case of the turbopump under development, the pump head was raised by up to 15% or more by improving the roughness of the impeller,” stated the researchers.

Turbine blisk for PROMETHEUS engine

FIG 13

“The only engines that succeeded in launching using additive manufacturing were SpaceX’s SuperDraco and Rocket Lab’s Rutherford Engine by the end of 2019,” concluded the researchers.

“Currently, most of the materials used for the additive manufacturing of projectile engine parts were Inconel 718, and some companies used Ti-6Al-4V or copper alloy.”

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Manufacturing map of IHI 3-ton class turbopump