Supersonic Braking Devices for Upper Stage Recovery - Design and Aerodynamic assessment of RocketHandbrake

Abstract

Reusability in spaceflight represents a major challenge from a technical perspective, with an economical cost savings promise. Multiple European projects (e.g. RETALT, RETPRO, Themis, SALTO and CALLISTO) investigated and keep investigating reusability of first stages. While retro propulsion became a standard approach for first stage deceleration, for upper stages it comes with large fuel consumptions due to their high orbital velocities and energy level. Complementing these research efforts, the project “RocketHandbrake” investigates upper stage reusability, using Supersonic Braking Devices (SBD) for aerodynamic braking with the objective to reach full reusability of future European launch vehicles. SBD´s enable high angle of attack reentries, resulting in significant drag forces that are used for an atmospheric deceleration. However, this concept comes with the mass penalty for the SBD as well as the required thermal protection system (TPS). The ESA funded study "Supersonic Braking Devices for Upper Stage Recovery – RocketHandbrake", led by DLR together with Polaris and Deimos, aims to understand the key technologies required for a reusable upper stage configuration under a multitude of aspects, and to improve prediction tools for the concept. Based on a reference launcher configuration defined at the beginning of the project, the SBD are defined, analyzed and tested. Hereby a close collaboration between the different design areas of aerodynamics, thermal, structures, mechanisms and GNC is required to enable a feasible mission profile and a coherent design to be able to handle unsteady effects and thermal issues. This paper presents the work performed by DLR in RocketHandbrake during the detailed design and analysis phase up to the final wind tunnel testing at DLR´s Trisonic Wind Tunnel Cologne (TMK) in the context of aerodynamic analysis. Initially, the Supersonic Braking Devices are rescaled on the first phase´s outcomes, providing the new outer mold line for the numerical analysis. An Aerodynamic Database (AEDB), as well as a smaller Aerothermal Database (ATDB) is generated. The wind tunnel model is designed, manufactured and subsequently tested. As a final step, the aerodynamic analyses are combined and evaluated.