Auswertung einer formbasierten Strahlungsoptimierung von Niedrigschub-Transfertrajektorien

Abstract

Radiation exposure poses a danger to spacecraft with low-thrust propulsion systems for near-earth transfers. Due to the relatively long transfertime and the high number of revolutions the radiation belts are passed more frequently. For this, a quick estimation of the radiation accumulation and optimization of the trajectories for the early stages of planning is of interest. The aim of this Master's thesis is to extend a shape-based low-thrust optimization software with a radiation model in order to enable an optimization according to the accumulated radiation quantity for orbit transfer in the near-earth region. The software will be adapted and a radiation model implemented. Subsequently, the effects of the number of trajectory calculation steps and optimization parameters for the LEO to GEO transfer are examined. In addition, LEO to GEO and LEO to MEO transfer optimizations are performed and examined using a small and large transfer window. The optimized solutions using a simple and complex radiation model are compared with those for minimum ∆v budget. It turns out that an increasing ratio of the calculation steps of the trajectories to the number of revolutions increases the accuracy of the calculation of the radiation quantity. By reducing the amount of solution through a smaller transfer window or a smaller difference in orbital heights, a clear solution can be found for all except the LEO to GEO transfer with a large transfer window. For the transfer from LEO to GEO with a large transfer window, an overflight over the target orbit is performed to accumulate less radiation. For the other transfers, a direct transfer with less transfertime is the best solution. The optimized transfers are mainly distinguished by the amount and course of the acceleration. In addition, it can be seen that different amounts of radiation result using a simple and a complex radiation model. On the other hand, the trajectories differ only slightly.