Hardy Köke

Flight test results of investigation of acceleration effects on a gun launched rocket engine

Nowadays, much research has been done in the field of electromagnetic-driven Lorentz rail accelerators (LRA). To apply this technology to launch a sophisticated payload carrying vehicle, mechanical loads due to high acceleration have to be taken into account. The German Aerospace Center (DLR) is doing research in the field of a hybrid rocket propelled payload carrier which shall be launched from an LRA. The structure of the hybrid rocket engine (HRE) is the most critical component, regarding mechanical stress. To investigate the effects of high acceleration during the launch from an LRA, an experimental setup is created. An 80% scale model of an HRE is mounted on a 155-mm howitzer shell. The experimental setup is then launched from the Panzerhaubitze 2000 with an acceleration of 3300 g. The model is equipped with strain gauge sensors to determine deformation during the acceleration phase. An acceleration sensor is integrated to measure the acceleration during launch. Data of the strain gauge bridges and the accelerometer are sampled by an electronic device mounted on the projectile, and buffered in the internal RAM. The data are transmitted to a ground station during free flight by a telemetry device, which is mounted on the howitzer shell instead of a fuse. The flight path of the projectile is tracked by different radar stations to determine the impact point, so that the experiment can be recovered. The test shows that the HRE structure can withstand the mechanical loads that are caused by high acceleration that would occur during a launch from an LRA. Therefore, an HRE is suitable for high-acceleration launch. The sampled data are compared with finite element method calculations. Differences in simulation and measurement are observed.

BESO with strain controlled material assignment

The Bi-directional Evolutionary Structural Optimization scheme (BESO) is a well tested method for a wide range of topology optimization problems. In this paper a heuristic selection scheme for orthotropic materials is implemented in a 2D BESO algorithm. A method is presented to achieve convergence of both, the material orientation and material distribution. This allows a detailed evaluation of the suitability of fiber reinforced materials for the considered structure.

Structural optimisation of a composite aircraft frame applying a particle swarm algorithm

In this paper a heuristic optimisation technique for the maximisation of weight specific elastic deformation energy of CFRP z-frames used in aerospace applications is investigated. Therein, the focus was on the simultaneous consideration of mixed discrete and continuous variables. For that purpose a parametric finite element model was established. In that discrete laminate stacks and continuous geometry parameters were used for structural optimisation. In order to solve the non-linear unconstrained optimisation task, a particle swarm optimiser was selected and applied. Convergence was achieved after a reasonable number of function evaluations. within the solution space, a structural layout of the z-frame was identified being the best solution with respect to the optimisation objective. While the deformation energy appeared to be flange width dependent, the corresponding frame weight showed a strong relation to the applied laminate stacks. The majority of the suggested solutions exhibited similar response with respect to the overall deformation. Prior to structural failure, flexural-torsional buckling was the governing deformation mode.

Holistic design and implementation of pressure-actuated cellular structures

Providing the possibility to develop energy-efficient, lightweight adaptive components, Pressure-Actuated Cellular Structures (PACS) are primarily conceived for aeronautics applications. The realization of shape-variable flaps and even airfoils provides the potential to safe weight, increase aerodynamic efficiency and enhance agility. The herein presented holistic design process points out and describes the necessary steps for designing a real-life PACS structure, from the computation of truss geometry to the manufacturing and assembly. The already published methods for the form finding of PACS are adjusted and extended for the exemplary application of a variable-camber wing. The transfer of the form-finding truss model to a cross-sectional design is discussed. The end cap and sealing concept is described together with the implementation of the integral fluid flow. Conceptual limitations due to the manufacturing and assembly processes are discussed. The method’s efficiency is evaluated by Finite Element Method (FEM). In order to verify the underlying methods and summarize the presented work a modular real-life demonstrator is experimentally characterized and validates the numerical investigations.