• electric propulsion
• TANDEM
• Hall thruster
• additive manufacturing
• ceramic adhesives

This thesis aims to assess the feasibility of creating additively manufactured high-power Hall thruster components in metallic and ceramic materials. The work is part of a project assigned by the European Space Agency to the University of Pisa in collaboration with Aerospazio Tecnologie s.r.l. for the realization of the high-power nested Hall thruster called TANDEM. As an introduction, the main characteristics of Hall thrusters are discussed, analyzing their working principle and performance parameters. Then, a summary of the possible additive manufacturing technologies and joining methods to build the TANDEM accelerating channel and anode/propellant distributor assembly is presented. Additive manufacturing is of great interest for building electric thruster components because it reduces costs and production time with respect to the currently used subtractive methods. Joining methods are important, especially in joints with different materials, and are hard to realize in a fast and economical way in Hall thrusters assemblies due to the large thermal loads. Particular attention is given in the discussion to material extrusion additive manufacturing and ceramic adhesives, as they are chosen to be respectively the manufacturing and joining technique that are further deepened in the work. In particular, a ceramic adhesive, the alumina based Resbond 989, is analyzed and tested. Some solutions for the integration of the channel and anode-distributor of a typical Hall thruster, based on examples available in the literature, are presented, and their advantages and drawbacks are analyzed. Thermo-mechanical simulations are performed for the accelerating channel-anode assembly of the TANDEM thruster in order to calculate the arising stresses due to thermal loads. The metallic holder and the ceramic channel itself in the simulations are joined using Resbond 989. The thruster geometry and adhesive location are changed in order to analyze the different loading states in each condition. The solution with adhesive as an electrical insulator coating is also evaluated. According to simulations, the maximum stress that can develop in an adhesive joint in each configuration is on the order of 100 MPa, whereas in the case of adhesive insulation, it is one order of magnitude lower. Lastly, some adhesion and strength tests are conducted on metal to ceramic joints. The ceramic substrate of the joint is alumina, realized either by material extrusion or in cylindrical form, while the metallic one is AISI 304 stainless steel. The adhesion tests are performed by changing the surface treatments, the cure, and the ceramic substrate geometry. As a result, using 3D printed alumina plates is the best method for creating a ceramic-to-metal joint to be used in the shear tests. Ceramic plates have been printed in two dimensions: 15 𝗑 15 𝗑 3 mm^3 and 30 𝗑 15 𝗑 3 mm^3. The adhesive is applied, forming a single sided strap joint, and the cure is first performed in vacuum, then at room temperature. Thus, shear strength behaviour is tested on a tensile machine, and the corresponding stress deformation curves are extrapolated. The results show that the samples with small ceramic plates have a shear strength in the order of 1 MPa, while that of the ones with longer plates is one order of magnitude lower.