Upcoming DLR reusability flight experiment

After the successful hypersonic flight experiments SHEFEX I and II, the German Aerospace Center (DLR) is now investigating the realization of the Reusability Flight Experiment (ReFEx). This successor mission shall be launched on a Brazilian VSB-30 sounding rocket in 2021 and shall achieve a reentry velocity of more than Mach 5. The main goal is the demonstration of a controlled autonomous re-entry flight from hypersonic velocity down to subsonic range and to test key technologies required for future reusable booster systems. So far, two Concurrent Engineering (CE) studies were conducted to investigate the feasibility of this sophisticated project. The required subsystems, including sensors and actuators as well as their interfaces have been defined and different options were assessed regarding matters like the scientific output, complexity, risk, and cost. The current configuration of ReFEx has a re-entry mass of about 450 kg, a length of 2.7 m, and a wingspan of 1.1 m. This paper provides a system overview, addresses systems engineering aspects and main challenges regarding the mission realization. For example, to meet the VSB-30 launcher flight stability requirement, the wings of the ReFEx experiment were designed foldable. Therefore, special attention was paid to a passive and reliable lock mechanism for the wings.