In recent years, the advent of reusable launch systems has revolutionised the space sector, demonstrating not only their operational feasibility but also a significant reduction in cost per mission. Although these advanced systems are now dominated by developments in the United States, Europe is beginning to actively invest in the research and development of similar technologies, with the aim of building its capacity to access space in a sustainable manner. This thesis proposes an innovative design methodology, together with a supporting Python tool, for the rapid dimensioning of advanced expendable or reusable launch vehicles. The design tool developed is designed to be highly flexible, allowing rapid iteration from high level design and mission requirements.