Thrust chambers have historically been difficult to manufacture. They require extensive tooling and labor, and are expensive with long lead times. Thrust chambers were designed for manufacture using conventional machining. As a result, designs required multiple pieces to ensure machine tool access to each surface. The individual pieces would then be joined and assembled into a single thrust chamber. These joining operations typically required process development due to the complexity of the parts and the need for joining to provide a seal between parts. A faster, more reliable and affordable manufacturing method was desired.

Additive manufacturing, including selective laser melting, provides the ability to fabricate what used to be an assembly as a single part. Unlike conventional machining, access to each surface is not required. A modular, regeneratively cooled thrust chamber was developed that exploits this manufacturing capability.

The additively manufactured thrust chamber enables complex design features that cannot be fabricated with conventional machining. These features improve overall performance of the thrust chamber regenerative cooling, and also significantly lower the manufacturing cost and lead-time.

The thrust cell is sized per the requirements of the engine (thrust, chamber pressure, mixture ratio, etc.). Thermal analysis is performed to generate the optimum regenerative cooling channel design (height, width, spiral, wall thickness, pressure drop, etc.). Thermal structural analysis is performed to ensure the design meets the structural requirements. The detailed design is generated within the requirements and limitations of the additive manufacturing process and machine.

The resulting thrust chamber functions the same as one that was conventionally machined; however, the additively manufactured thrust chamber typically has more uniform thermal conditions and heat transfer due to the complex geometry possible with additive manufacturing. This innovation can be expanded to include other parts of the thrust chamber, including the injector assembly.

This work was done by Wendel Burkhardt of WASK Engineering for Marshall Space Flight Center. NASA is seeking partners to further develop this technology through joint cooperative research and development. For more information about this technology and to explore opportunities, please contact Ronald C. Darty at This email address is being protected from spambots. You need JavaScript enabled to view it.. MFS-33171-1

NASA Tech Briefs Magazine

This article first appeared in the April, 2017 issue of NASA Tech Briefs Magazine.

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