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The utilisation of the Very Low Earth Orbit (VLEO) region offers significantapplication specific, technological, operational, and cost benefits. However,attaining sustained and economically viable VLEO flight is challenging,primarily due to the significant, barely predictable and dynamically changingdrag caused by the residual atmosphere, which leads to a rapid deterioration ofany spacecraft's orbit unless mitigated by a combination of active and passivetechniques. This article addresses one passive method by optimising satelliteshapes in order to achieve a minimisation of the atmospheric drag force andthus extension of operational lifetime. Contrary to previous investigations inthe field, a constant internal volume is maintained to account for theplacement of satellite instruments and payload inside the structure. Moreover,the satellite geometry is not varied heuristically but optimised via anumerical 2D profile optimisation specifically developed for this purpose. Fromthe resulting optimal satellite profiles, 3D satellite bodies are derived,which are then verified via the Direct Simulation Monte Carlo method within theopen-source particle code PICLas. In addition, rather unconventional designs,i.e. ring geometries, which are based on the assumption of fully specularparticle reflections, are proposed and assessed. The optimised satellitegeometries offer pure passive lifetime extensions of up to 46 $\%$ compared toa GOCE like reference body, while the above-mentioned ring geometries achievepassive lifetime extensions of more than 3000 $\%$. Finally, the articlepresents design recommendations for VLEO satellites in dependence of differentsurface properties.

Optimisation of VLEO Satellite Geometries for Drag Minimisation and Lifetime Extension