Options for future European reusable booster stages: evaluation and comparison of VTHL and VTVL costs

Abstract As the space industry evolves towards more cost-effective solutions, the development of reusable launch vehicles has become a crucial focus for reducing launch costs. This study addresses the problem of identifying the most cost-effective reusable booster stage design for future European launch systems, comparing vertical takeoff, horizontal landing (VTHL) and vertical takeoff, vertical landing (VTVL) methods. Conducted under the ENTRAIN (Europe’s NexT Reusable Ariane) study by the German Aerospace Center (DLR), the research provides a detailed analysis of both recurring and non-recurring costs associated with various design configurations. The study explores different design degrees of freedom, including engine cycles, propellant combinations, and staging velocities, using a parametric cost model to evaluate the trade-offs involved in each configuration. Findings indicate that reusable configurations can achieve significant cost reductions across a wide range of market scenarios, and offer slight total cost benefits even for the smallest herein considered launch markets. The results further show that the hydrogen-fueled configurations investigated within ENTRAIN offer lower costs compared to the hydrocarbon-fueled alternatives. In addition, the study highlights the sensitivity of launch costs to factors such as market conditions, reuse cycles, and refurbishment efforts, offering insights for future European space launcher development.