CALLISTO: Reusable rocket stage demonstrator: getting ready for implementation

Japan and Europe are finishing the work to introduce their new workhorse launch vehicles: H-3 and Ariane 6. While both vehicles are following an expendable design, reusable launch vehicle are successfully tested and operated in USA. This evolution has shown that reusability could be a solution for further improvement of competitiveness, versatility and sustainability of future launch system. In order to understand the specificities of reusable launch vehicles in terms of design, optimization and operations, and mature the required key technologies, CNES, DLR and JAXA have decided to join their competences in the project CALLISTO (Cooperative Action Leading to Launcher Innovation in Stage Toss - back Operations). The project aims at developing, building and testing a prototype vehicle which shall, without a technological precursor, demonstrate the mastering of flights and operations representative to a reusable launch stage. Along all project phases, data and knowhow are being gained about design, manufacturing, operations and maintenance solutions, which are essential for the development of future operational vehicles. The project team is now finalising the design and series of tests in order to be ready to start in the implementation in few months. The paper is giving an overview of the progress achieved at DLR in collaboration with CNES and JAXA.