Technical development perspective of reusable booster stages

This paper describes the recent investigations of a partially reusable space transportation system under study within the German future launcher technology research program ASTRA. It consists of dual booster stages, which are attached to the expendable Ariane 5 core (EPC) at an upgraded future technology level. The design of the reference liquid fly-back boosters (LFBB) is focused on LOX/LH2 propellant and a future derivative of the Vulcain rocket motor. The preliminary design study is performed in close cooperation between DLR and the German space industry. The paper's first part outlines the design progress of this reusable booster stage achieved since last year. The second part of the paper assesses a long-term, strategic scenario of the reusable stage's operation. The general idea is the gradual evolution of the above mentioned basic fly-back booster vehicle into three space transportation systems performing different tasks: Reusable First Stage for a small launcher application, successive development to a fully reusable TSTO, and booster for a super-heavy-lift rocket to support an ambitious space flight program like manned Mars missions. The assessment addresses questions of technical sanity, preliminary sizing and performance issues and, where applicable, examines alternative options.