Overview of system study on recovery methods for reusable first stages of future European launchers

Abstract

The design of a reusable launch vehicle implies the need to provide for a means to safely retrieve the component to be re-used. Following economic considerations, reusable launch vehicle concepts tend to be designed such that large parts, like entire stages, are to be recovered. These are usually significant in size and weight and have acquired a considerable amount of energy during their primary mission. This poses the challenge of how to recover them in a way that makes it available for further re-uses. In the past and present, different methods were and are used. Depending on the selected recovery method, the system design is very different necessitating different technologies and competencies to be acquired for a successful design. Two major classes of recovery methods can be distinguished: those recovery methods ending with a vertical landing of the reusable stage and those ending with a horizontal landing. Both have their own benefits and drawbacks. In 2016, The German Aerospace Centre DLR has initiated a large in-house study with the aim of investigating, in a comparative manner on system level, both classes of recovery methods on a system level for two-stage-to-orbit launch vehicles with a reusable first stage and an expendable upper stage to be operated within a European context. Fuel choice and engine cycle were major design parameters that were considered during the study. The present paper presents the framework of this study describing the adopted study logic, providing an overview of the major findings obtained at the end of the first study phase and gives an outlook to the work of the second study phase. It ends with providing a view of a possible demonstrator and technology roadmap toward the realization of an operational two-stage-to-orbit launch system with a reusable first stage.