The Reusability Flight Experiment – ReFEx: Details of the Protoflight-model Integration Campaign and Final Update Prior to Flight

Abstract

The Reusability Flight Experiment (ReFEx), is a technology demonstration mission of the German Aerospace Center (DLR), aimed at validating key technologies for aerodynamically controlled reusable launch vehicle (RLV) stages. Scheduled for launch in 2026 from the Koonibba Test Range (KTR) in South Australia, ReFEx will be carried by a VSB-30 sounding rocket to a trajectory representative of a returning RLV first-stage. The experiment seeks to autonomously guide the vehicle as far back as possible toward the launch site using only aerodynamic control surfaces, demonstrating fully autonomous flight control capable of critical heading changes and energy-efficient returns.ReFEx features a compact design, measuring 2.7 meters in length with foldable wings and a mass of approximately 400 kg. In the frame of the ReFEx project the advanced guidance, navigation, and control (GNC) systems, aerodynamic control strategies, and structural resilience under hypersonic and subsonic conditions shall be tested. One key aspect of the project is a rigorous pre-flight verification campaign, including structural integrity tests, avionics integration, and environmental simulations. By collecting flight data to validate aerodynamic models and control algorithms, ReFEx aims to enhance the development of future European reusable launch vehicles, contributing to more sustainable and cost-effective space access. This paper, which is the latest addition in a long series of updates on the project, focuses on the efforts to bring the final proto-flight model (PFM) of the experimental vehicle to completion in the PFM integration campaign, currently underway at the DLR Institute of Space Systems in Bremen, Germany. The work here was informed by the successful structural model (SM) campaign, which was completed at the end of 2023. Since then, lessons learned and modification from the SM campaign have been incorporated in the project. Once completed ReFEx will then be shipped to KTR, Australia and prepared for the flight experiment.