Multidisciplinary design optimization of a satellite structure by Additive Manufacturing

Fraunhofer EMI is currently designing a 12U nanosatellite. The mission is called ERNST (Experimental Spacecraft based on Nanosatellite Technology) and its main goal is to evaluate the utility of a nanosatellite mission for scientific and military purposes. As spacecraft developments demand the adaption of different subsystems for every mission, Fraunhofer EMI decided to use Additive Manufacturing (AM) in the construction of secondary satellite structures in order to achieve a highly adjusted structure which serves the exact required purpose of the mission. The significant advantage of using AM lies in the design freedom, with almost no design restrictions as compared to conventional manufacturing methods. On this basis, the design freedom can be used to implement a numerical optimization process, using Topology Optimization algorithms. During the optimization process, material is only placed at necessary areas. A Multidisciplinary Design Optimization for the optical mounting structure (optical bank) of the satellite was established, considering vibrational boundary conditions during the launch period and thermal boundary conditions during the operational phase. Based on this, the optimized design was additively manufactured by using Selective Laser Melting (SLM). The presented work correlates the simulated results concerning the vibration response with experiments carried out on a shaker. More precisely, the calculated eigenfrequencies and random-response will be evaluated using simulated and experimentally determined data

Dynamic compression of 3D printed metallic mesostructures with in-situ X-ray imaging

Additive manufacturing (AM) is an attractive approach for the design and production of complex structures not possible to realize with conventional methods. While the dynamic mechanical response of bulk material is object of extensive investigation, the dynamic behavior of mesostructured material is lacking attention. In this study, a series of different mesostructures, such as lattice and auxetic structures, was designed and additively manufactured in Ti-6Al-4V by laser beam melting (LBM). Dynamic compression tests at velocities around 150 – 360 m/s were conducted at selected samples using a gas-gun. In-situ X-ray imaging provided image data showing an influence of the design of the mesostructure on its failure behavior. Numerical simulations of the impact were compared to the experiments demonstrating a promising accordance. The results enable improved numerical simulation models enhancing their prognostic capacity. Moreover, the findings support the development of design approaches considering the structure-dependent failure behavior

Generation and transfer of internal variability in a regional climate model

There is a strong need for tools allowing the comparison between the performance of a regional climate model (RCM) and the corresponding model providing lateral boundary conditions (LBC) for the RCM, which is a global general circulation model (GCM) in most cases. A method is presented to investigate the temporal scales on which a RCM is able to generate internal variability on its own and on which variability is copied from the driving model. This is implemented by a cross-spectral analysis between the RCM output and a bi-linearly interpolated version of the driving model, leading to an estimate of the coherence spectrum. Applying the aforementioned technique to surface temperature and temperature and specific humidity at 850 hPa from the RCM COSMO-CLM East Asia with a horizontal resolution of 50 km and its driving model ECHAM5, it was found that features in the spatial distribution of coherence are related to atmospheric dynamics in East Asia, e.g. monsoons and inter-tropical convergence zone (ITCZ). A further application to a double-nesting approach, where COSMO-CLM East Asia is the driving model for two domains – namely the Haihe catchment and the Poyang catchment – each with a horizontal resolution of 7 km, shows that the frequencies on which internal variability is generated by the driven model are much higher compared to the first nesting step. Concluding RCMs can produce a considerable variability on the respective temporal scales. This implies that a dynamical downscaling with a re-analysis as LBC is conceptually different to a regional re-analysis, i.e. data assimilation on the regional scale