Product Assurance Overview of Additive Manufactured Components for Space Applications
Creators: name:  D. ZUIN 
name:   S. LA LUNA 
name:   S. DOSSI 
name:   F. MAGGI 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: STRUCTURES
MATERIALS
ADDIDITVE MANUFACTURING

description: In the last decade, the new space economy has grown at an increasing pace: projections estimates a 300% rise in satellite launches for the next 6 years. Cost reduction is pivotal for boosting this trend, which affects all the aspects and subsystems of a satellite, including the propulsion segment. Within this framework, significant steps have been performed with the introduction of innovative manufacturing and technological processes for space applications. Additive manufactured propulsion components, together with the implementation of highly engineered materials such as metallic alloys, ceramics and other high temperature materials, are leading to thrust chamber designs which are more effective in the solution of structural and thermal problems. As an example, innovative regenerative channel design is possible with additive manufacturing technologies; thrusters can be manufactured with materials showing a continuous/discontinuous modification of mechanical and functional properties along the thrust chamber axis; the number of components for the thruster assembly can be drastically reduced, avoiding possible failure modes of the engine itself. On the other side, these new techniques applied to innovative materials pose a series of questions. Highly conductive metal alloys for thruster applications do require further research, since printing techniques for metal components are relatively new to the market and only few materials have reached high TRL values for space applications. These processes may cause non uniformity of the material deposition, leading to weak points on the structure with consequent leakages and safety issues. For this reason, product assurance of additively manufactured parts is pivotal to increase reliability of end-user products. Requirements of quality assurance for these parts affect different aspects of the AM product lifecycle: feedstock, machine processes, part post-processing are only few examples of AM process steps which can be impacted. The implementation of a part production plan containing requirements in terms of process verification and reverification affects the design of the AM parts For the verification of the AM process, a minimum set of test coupons has to be stated, considering different geometries and build directions; these test coupons shall undergo different tests, such as NDI, tensile tests, metallography tests, density tests and other. On the other side, process reverification requirements are related mainly to the machine which is implemented in the process: they are implemented when the machine is relocated, the machine software is updated, components of the machine are modified, repaired or altered (such as laser or powder plate support modification). In this paper, a state-of-the-art analysis for AM is performed, and different technologies are outlined and compared: 3d printing, direct energy deposition, powder bed melting, stereolithography, lamination methods are only some of the current existing technologies of interest in the AM panorama. A case study is introduced in order to make a comparison between these processes. A parallel analysis of the materials which are available for the AM processes is performed: for the analysis, metallic materials are considered. A final selection of the promising technologies for additive manufactured components for in-space propulsion applications is made. A detailed analysis of the quality assurance design drivers related to AM processes is outlined, where the criticalities associated to resolution of the final feature, post-processes required, technical features achievable with the technology (minimum thicknesses, hole diameters, inclination angles, other) are reported and analyzed.