Mechanical Design and Optimization of thrust chamber components for CH4/LOX liquid rocket engines

In recent years launching companies have been concentrating their resources toward developing reusable rocket solutions with the aim to both improve performances and drastically reduce the costs, transforming spaceflight from an exclusive, exorbitant endeavour into a more accessible and economically viable one. In order to support this ambitious goal, innovative manufacturing techniques must be explored to meet the demands for high performance, cost reduction and shorter production timelines. Additionally, allowing scalability of such technologies plays a strategic role in the development of future rocket engines, enabling next-generation launch vehicles to increase their payload capacity together with orbit insertion capabilities. Within this framework, the present thesis explores the field of liquid rocket propulsion and has been carried out in collaboration with Avio S.p.a. This initiative focuses on designing and optimizing a subscale thrust chamber for a CH₄/LOX liquid rocket engine, utilizing cutting edge hybrid additive manufacturing technologies that integrates Powder Bed Fusion (PBF) and Directed Energy Deposition (DED). At first, this study provides an overview of the current state of additive manufacturing techniques, contextualizing the methods that will be employed during the manufacturing phase of the project while also proposing alternative techniques for applying the chamber coolant channel closeout. Subsequently the thesis delves into the mechanical optimization of the injector head and combustion chamber components through the commercial CAD software DS Catia. The objective was to develop the design for 3D printing, reducing weight and tailoring the models suitable for subsequent structural simulations. Further analysis were conducted using the commercial software MSC Marc Mentat and MSC Apex to evaluate the structural integrity of the components under pressure and thermal loads that the engine encounters in its extreme operating conditions. The pressure loads were determined in accordance with the expected working conditions to be achieved, while the thermal loads, reflect the most demanding scenario: the firing test. The simulations output was essential in verifying and optimizing specific design aspects related to the building process and the integration of the two AM techniques. The entire study played a crucial role in preparing the components, through models and technical drawings, to successfully undergo the manufacturing phase, and subsequently in meeting the testing milestones and advancing the Technology Readiness Level (TRL) of bimetallic thrust chambers.