In recent years, the space sector has experienced significant growth, both economically and culturally. Investments in space technologies have surged with the emergence of new players and start-ups, marking the beginning of the New Space Economy. This development has led to increased demand for access to space. However, the high cost and relatively low reusability of current launch vehicles remain the main obstacles to further evolution of space exploration. The future of space exploration also depends on the development of reusable and sustainable spacecrafts. Therefore, the creation of a methodology for the design of Reusable Launch Vehicles (RLVs) is essential. In this context, this thesis is part of a research project at the Polytechnic of Turin aimed at developing a software tool for the conceptual design of space missions involving reusable vehicles.