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Aerothermal loads are a design driving factor during launcher development as the thermal loads directly in- fluence TPS design and trajectory. Recent developments in reusable launch vehicles (RLV) (e.g. SpaceX, Blue Origin) have added the dimension of refurbishment to the challenges the thermal design must con- sider. For disposable launchers the heat flux due to base heating during ascent needs to be considered for aft thermal protections system (TPS) and structural design. With the current European long term strategy[1] moving towards a reusable first stage - aerothermal loads may significantly change. In order to advance knowledge on RLV relevant technologies the German Aerospace Center (DLR), the Japan Aerospace Exploration Agency (JAXA) and the French Space Agency (CNES) entered into a collaboration agree- ment. This allows a significant increase of the organisational knowledge at a technical and economic level. This collaboration includes in particular a vertical take-off and vertical landing (VTVL) reusable subscale launcher first stage demonstrator. The vehicle is called CALLISTO, which stands for Cooperative Action Leading to Launcher Innovation in Stage Toss back Operations [2]. For the CALLISTO vehicle the high- est heat fluxes are mainly due to heating from hot exhaust gases and heated air in proximity of the aft bay and on the exposed structures like legs and fins. The development of the plume extension is different for the considered re-entry, when compared to Falcon 9, or the studies presented in [3, 4]. As shown by Dumont et al.[5] the plume remains relatively concentrated at the aft end of the vehicle due to high atmospheric pressure and only very low fractions of actual exhaust gas species enclosing the vehicle. In the current study we conducted computational fluid dynamics (CFD) studies in order to determine the aerothermal loads on the vehicle during descent through the landing approach corridor. Further the sensitivity of the plume-vehicle interaction to angle of attack, chemistry and turbulence modeling are investigated.

The current European long term strategy aims at moving towards reusable launch vehicles (RLV) for the first stages of launchers. In accordance with this strategy the German Aerospace Center (DLR) has entered into a collaboration with the Japan Aerospace Exploration Agency (JAXA) and the French Space Agency (CNES) for the development of RLV relevant technologies. A part of this collaboration is a vertical takeoff and vertical landing (VTVL) reusable subscale launcher first stage demonstrator - the Cooperative Action Leading to Launcher Innovation in Stage Toss back Operations (CALLISTO). The CALLISTO vehicle is to return to the launch pad using retro propulsion and an Aproach and Landing System (ALS) with extendable landing legs. This development leads to additional aerothermal design questions compared to traditional launchers. In the case of CALLISTO the highes heat fluxes are due to heating from hot exhaust gases of the aft bay section. This especially affects the unfolded ALS during the final phase of the landing approach. The arising heat fluxes, therefore, influence the structural design and the thermal protection system (TPS) of the ALS. In this study we conduct computational fluid dynamics (CFD) investigations using Reynolds averaged Navier Stokes (RANS) methods of the aerothermal loads on the ALS during the landing phase. We use the Spalat-Almaras turbulence model and frozen chemistry for the simulations. We analyse the flow field as well as the surface distributions. We investigat the necessity of simulations including the plume for these analyses. We use analyses of the flow fields as well as the surface distributions to investigate the influence of angle of attack, angle of roll, atmospheric conditions, flight speed and thrust level.

CALLISTO is a demonstrator for a first stage of a reusable vertical take-off, vertical landing rocket and is developed and build within a collaboration of DLR, CNES and JAXA [1]. DLR is leading the aero science team [2] and is in charge of the aerodynamic and aerothermodynamic characterisation of the vehicle. Within this task, experimental work has been carried out at two different wind tunnels on two different models in order to determine the aerodynamic coefficients and uncertainties for the AErodynamic Data Base (AEDB) of the vehicle with focus on the backward oriented configuration. First data was obtained in the Trisonic Wind Tunnel (TMK) at the DLR Department of Supersonic- and Hypersonic Flow Technologies in Cologne for a 1:35 model in a Mach number range from 0.5 up to 2.0. The second dataset was generated in the transonic wind tunnel (HST) of the DNW in Amsterdam for a 1:10 model in a Mach number range of 0.2 up to 1.3. Within this paper, the data from the two aforementioned facilities is compared with wind tunnel data of a simplified CALLISTO model [3,4,5] and the data [2] generated from numerical simulations. The results showed good agreement between the different facilities and datasets and was used to verify and improve the AEDB, especially in terms of uncertainties.

There are renewed interest in the development of propellers due to the increased and extensive applications of unmanned air vehicles (UAVs) or commonly known as drones for aerial photography, parcel delivery, aerial surveillance, inspection, marketing and many other applications. These UAVs or drones are usually powered by fixed pitch propellers of small diameters driven by electrical motors. The required operating conditions for achieving the designed tasks in terms of lifts and speeds are typically in contrast with the need for having quieter or even silent UAVs or drones. The desire for light weight UAVs or drones has resulted in the use of carbon fibre composite propellers and such carbon fibre composite propellers have become common parts for the design and assembly of UAVs or drones. The present research would explore the use of natural fibre composites, for example, flax fibres composites and also hybrid fibre composites in mitigating the propeller noise with the increased damping characteristics due to the introduction of natural fibres. Typical natural fibre and hybrid fibre propellers for drones were fabricated for benchmarking with commercially available carbon fibre composite propellers as well as composite propellers produced by 3d printing. The noise characteristics at various rotating speeds for propellers made of both the natural fibre and hybrid composites as well as commercially available carbon composites were measured in an anechoic chamber by attaching the propellers to a motor on a stationary platform. The natural fibre and hybrid fibre composite propellers were also fixed onto standard quadrotor drones for assessing the flight performance besides the noise characteristics.

Determining the flight dynamic characteristics of a space transportation vehicle in its preliminary design phase is a complex task since a large variety of vehicle parameters need to be estimated. For the SpaceLiner vehicle, a concept of a hypersonic suborbital space plane, such an analysis has now been established. In this study a 6 DOF trajectory simulation has been developed to assess the general feasibility of fulfilling the mission requirements during nominal and off-nominal flight conditions.

The latest architecture of the SpaceLiner 7 configuration is described including major geometrical and mass data. Some elements of the next iteration step, the SpaceLiner 8, are highlighted, having its focus on most recent analyses, partially not previously published. A passenger rescue capsule is intended to be used in case of extreme emergencies. The design of the cabin and the ejection system is refined in a systems engineering approach to obtain a feasible and viable solution. Multibody simulations of the emergency capsule separation are performed in a wide range of flight conditions and technical challenges are identified. The adaptation of the large unmanned booster stage, currently under way might include a new wing lay-out capable of swiveling-out in the lower speed regime. Advantages and technical challenges of this approach are addressed in the paper. Simulated 6DOF ascent trajectories analyze behavior of the Thrust Vector Control system in case of wind and gusts interacting with the winged configuration in nominal and off-nominal conditions.

Since a couple of years the DLR launcher systems analysis division is investigating a visionary and extremely fast passenger transportation concept based on rocket propulsion. The fully reusa-ble concept consists of two vertically launched winged stages in parallel arrangement. In a second role the SpaceLiner concept serves as a reusable TSTO space transportation launcher for which technical details are now available. The SpaceLiner configuration serves as a catalyst for applied research on advanced hypersonic systems and reusable launchers. The paper presents the latest status of the SpaceLiner concept and its key mission and system requirements. At the same time the paper functions as the intro-duction to other papers addressing more detailed SpaceLiner design and research questions.

Reusability applied to launchers is expected to reduce costs for access to space and to increase the operational flexibility. DLR, CNES and JAXA are jointly developing a vertical take-off and landing (VTVL) reusable subscaled first stage demonstrator with the objective to improve knowledge in this field. With this vehicle, called CALLISTO (Cooperative Action Leading to Launcher Innovation in Stage Toss back Operations), DLR, CNES and JAXA want to acquire and demonstrate the capability to launch, land and relaunch a vehicle under conditions representative for the first stage of an operational launch vehicle. Furthermore, during CALLISTO demonstration flights, data will be gathered to improve knowledge on the operation of a reusable vehicle which will help to optimize the reusability capabilities of future launch systems [1-2]. The entire CALLISTO reference mission is complex and includes many flight phases: ascent, tilt-over manoeuvre, descent and landing during which the aerodynamic shape and the thrust level are changing radically. For instance, the simulation of the retro-propulsion plume is of particular importance, as it has a major impact on the base pressure distribution and aerothermal loads. In order to refine the requirements in preparation for the product preliminary design review (Product PDR), extensive aerodynamic analyses and tests have been performed [3]. The key challenge is to create an extensive aerodynamic data base covering all the flight configurations and conditions which than can be used for 6-DoF flight dynamics simulation, considering the complex aerodynamic shape of the demonstrator with limited computing resources. Indeed, the aerodynamic performance plays a central role in the global performance of CALLISTO. The use of classic engineering aero prediction methods cannot provide the precision and reliability necessary for the estimation of the aerodynamic coefficients. It is necessary to use a combination of models and CFD methods of different complexity. Another important aspect is the estimation of the uncertainties, based on the comparison of results calculated by different CFD methods as well as experimental results obtained in wind tunnels [4-6]. This paper will describe the concept and structure of the aerodynamic data base as well as the methods used for the calculation. The main findings of the aerodynamic analysis and the progress made during the CALLISTO project will be presented.