Aerothermal Databases and CFD Based Load Predictions

The RETALT (Retro Propulsion Assisted Landing Technologies) project aims at investigating launch system reusability technologies for two different Vertical Take-off Vertical Landing launcher configurations, namely RETALT1 and RETALT2. This paper describes and summarizes the CFD based aerothermal load predictions, aerothermal database generation and application for the RETALT1 configuration for the complete trajectory. Furthermore, an analysis of representative CFD (Computational Fluid dynamic) results is provided with the aim to show typical flow field phenomena and the resulting heating patterns occurring during the retro-propulsion phase. CFD results are then validated by comparison with the wind tunnel experiments carried out at different ground testing facilities in DLR Cologne

Hypersonic Retrograde Propulsion Experiments - A Basis for Validation of CFD within RETPRO

The paper focuses on wind tunnel tests of the hypersonic re-entry part of the RETPRO descent trajectory. The re-usable rocket launcher configuration is investigated including active retro-propulsion at Mach 5.3 and 7.0 in the Hypersonic Wind Tunnel (H2K) of DLR, Cologne. Results from high-speed Schlieren imaging, force and unsteady wall pressure measurements are output for CFD accuracy assessment and validation. Variations of the number of active engines, thrust coefficient, jet temperature and angle of attack are performed to gather detailed information on sensitivities of characteristic mean and dynamic flow features. It is shown that the dynamic behavior of the retro-propulsion flow field is significantly altered by the engine configuration. A stable quasi-steady mode with overlaying shock oscillation is found for the one engine case, while three engine operation leads to a turbulent flow field with random flipping between a short and a long jet penetration mode. The oscillation frequency and temporal characteristics of the retro-propulsion flow field are found to be sensitive to the thrust coefficient and jet reservoir temperature

Wind Tunnel investigations in CALLISTO - Reusable VTVL Launcher First Stage Demonstrator

In order to make access to space more affordable for both scientific and commercial activities the German Aerospace Center (DLR), the Japanese Aerospace Exploration Agency (JAXA), and the French National Centre for Space Studies (CNES) joined in a trilateral agreement to develop and demonstrate the technologies that will be needed for future reusable launch vehicles. In the joined project CALLISTO (Cooperative Action Leading to Launcher Innovation in Stage Toss back Operations), a demonstrator for a reusable vertical take-off, vertical landing rocket is being developed and built. The long-term objective of the project aims at paving the way to develop a reusable launcher first stage, and the joint efforts of the three agencies will culminate with CALLISTO demonstration flights from the ourou Space Center in French Guyana. The aerodynamic and aerothermal characteristics of the CALLISTO vehicle are investigated by DLR, including its challenging variety of configurations and large flight envelope with high angles of attack and subsonic, transonic and supersonic flight regimes. To cross-check the CFD data and for an enhanced understanding of the vehicle aerodynamics, a first test Champaign was performed in the Trisonic Wind Tunnel (TMK) at the DLR Department of Supersonic- and Hypersonic Flow Technologies in Cologne. Data has been generated for Mach numbers between 0.5 and 2.5. The experiments considered the ascent as well as the backwards orientated descent configurations of the vehicle with folded and deployed aerodynamic control surfaces at several deflection angles. The angle of attack was continuously varied for all configurations. The measurements of force and moment coefficients demonstrated the trimmability, stability and controllability of the vehicle for the planar fins deflection angles of up to 20° for all tested Mach numbers. Furthermore, the dependency of the aerodynamic coefficients on the Mach number was analyzed. Roll moment measurements showed efficient controllability of the roll angle. Investigations with oil film technique gave insight in the boundary layer separation of the body and the fins. This paper describes the tested configurations, the experimental methods and main results of the test campaign, focusing on the fin efficiency and on force measurements with tripping, including the subsonic regime

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

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

Onboard Guidance for Reusable Rockets: Aerodynamic Descent and Powered Landing

This paper describes a novel general on-board guidance strategy which can be applied toboth the aerodynamically-controlled descent and the powered landing phase of reusable rockets.The proposed guidance method is based on sequential convex optimization applied to a Cartesianrepresentation of the equations of motion. The contributions are an exploitation of convexand non-convex contributions, which are processed separately to maximize the computationalefficiency of the approach, the inclusion of highly nonlinear terms represented by aerodynamicaccelerations, a complete reformulation of the problem based on the use of Euler angle rates ascontrol means, an improved transcription based on the use of a generalized hp pseudospectralmethod, and a dedicated formulation of the aerodynamic guidance problem for reusable rockets.The problem is solved for a 40 kN-class reusable rocket. Results show that the proposedtechnique is a very effective methodology able to satisfy all the constraints acting on the system,and can be potentially employed online to solve the entire descent phase of reusable rockets inreal-time

SUPERSONIC BRAKING DEVICES FOR REUSABLE UPPER STAGES - OVERVIEW OF ROCKETHANDBRAKE

This paper provides an overview of the project ‘RocketHandbrake’, which investigates the reusability of upper stages re-entering the earth’s atmosphere at high angles of attack as a means for aerodynamic braking, using Supersonic Braking Devices. For a maximum benefit, this concept takes so-called Ariane Next and Vega E -like launchers as reference configurations. However, the project does not aim to develop those launchers completely, but to clarify and focus on the required aerodynamic control surfaces, the entailed aerodynamics and resulting flow physics, flight dynamics, control laws, and structures, based on and for those example configurations. Furthermore, the results of phase one of the project are described and the decision process for choosing the Ariane Next as baseline configuration for the next project phases is detailed. This includes first aerodynamic, and mission analyses of reusable Ariane Next and Vega E upper stages featuring supersonic braking device

eine verfassungsrechtliche Untersuchung unter besonderer Berücksichtigung der UN-Behindertenrechtskonvention

Softcover, 17x24Schüler und Schülerinnen mit Legasthenie und/oder Dyskalkulie haben in der Schule erhebliche Probleme und erreichen häufig nur niedrige Bildungsabschlüsse, weil sie aufgrund ihrer Beeinträchtigung nicht im geforderten Maß lesen, rechtschreiben und/oder rechnen können. Ob und inwieweit Legasthenie und Dyskalkulie in der Schule berücksichtigt werden müssen, ist pädagogisch und schulrechtlich sehr umstritten. Die Arbeit untersucht auf der Grundlage des Verfassungsrechts und der UN-Behindertenrechtskonvention, welche Rechte Schüler und Schülerinnen mit Legasthenie/Dyskalkulie haben. Sie kommt zu dem Ergebnis, dass Legasthenie und Dyskalkulie Behinderungen im Sinne des Art. 3 III GG und der UN-BRK sind. Daraus ergibt sich für die betroffenen Schüler und Schülerinnen ein umfassender Anspruch auf Nachteilsausgleich, sowohl bei den Prüfungsbedingungen als auch bei den Prüfungsinhalten. Im umfangreichen Verfahrensteil werden praktische Fragestellungen geprüft, wie z.B. das Verfahren zur Anerkennung der Behinderung in der Schule, die Ausgestaltung von Nachteilsausgleich, der Umfang des Datenschutzes und die Zulässigkeit von Zeugnisbemerkungen

Unsteady Aerodynamics of the Retropropulsion Reentry Burn of Vertically Landing Launchers

During the vertical descent and landing of a launcher first stage with the aid of retropropulsion, commonly two main propulsive deceleration maneuvers are performed: the reentry burn in high altitudes at hypersonic to supersonic speeds and the landing burn shortly before touchdown at transonic to subsonic speeds. In the frame of the EU-funded H2020 project Retro Propulsion Assisted Landing Technologies (RETALT), the unsteady aerodynamics of those retropropulsion phases were studied. This paper presents results of experiments performed in the Hypersonic Wind Tunnel Cologne on the hypersonic reentry burn. The exhaust plume was simulated with pressurized air. Proper orthogonal decomposition was performed on high-speed schlieren videos, and spectral analyses of the time histories of the resulting modes were compared to the frequency content found in high-frequency pressure measurements. Dominant frequencies were found in the proper orthogonal decomposition modes for one and for three active engines. In the pressure measurements, dominant frequencies could only be observed for three active engines. The normalized pressure fluctuations are in the range of 0.002–0.012. Additionally, a good scaling of the pressures on the base area and in the wake of the configuration with the total pressure downstream of the bow shock could be confirmed, in the sense that the ratio of the local surface pressure to the total pressure downstream of the bow shock match for varying freestream Mach numbers