Optimization and Characterization of Additively Manufactured Injectors for a Small-Scale Gas/Gas Thruster

The growing demand for mega-constellations, in-orbit servicing, and lunar missions necessitates advancements in spacecraft propulsion. Cryogenic propellants, such as methane and oxygen, offer an alternative that is more efficient and environmentally friendly than conventional storable propellants. Injectors have a significant impact on the performance, combustion stability, and reliability of rocket engines. To design injectors that meet these demanding requirements, additive manufacturing can be used to enable innovative designs. While Inconel has often been used due to its high tensile strength and temperature resistance, copper-based alloys, which have only recently become available for additive manufacturing, may offer advantages due to their high thermal conductivity. In this paper, the design process of injectors for a small-scale gas/gas thruster is presented, focusing on manufacturability as well as injector performance. Additive manufacturing, namely laser power-bed fusion, yields the possibility to design components with complex internal geometries in an integral design, potentially reducing the number and mass of required components. However, the resulting parts exhibit anisotropic material properties, as well as surface properties depending on surface orientation. As the surface roughness directly impacts the flow characteristics in an injector, these special aspects of additive manufacturing are given particular consideration in the design. Four different injector types are manufactured and subjected to cold-flow testing.