MSc Project: Aerodynamic Drag Modelling for LEO Mega-Constellations

This research project formed the basis of a master’s thesis on the impact of higher-fidelity aerodynamic drag modeling in the orbit propagation of spacecraft in low Earth orbit. The study involved developing a custom 3D aerodynamic drag model and comparing it to the widely-used SGP4 propagation. The research was conducted using a subset of the OneWeb and Starlink mega-constellations, covering around 40% of the total satellites.

The study found that there are significant differences in the ephemerides generated by propagation containing the 3D and 1D models. The 3D model corrects a secular effect that could impact the orbit propagation process on the order of tens of meters within a few hours, even at altitudes above which these effects are typically neglected. For Space Situational Awareness providers, this kind of mismodelling will impact their ability to deliver meaningful conjunction warnings to spacecraft operators in LEO. For mega-constellation operators, such effects will impact the evolution of constellation geometry which will influence their station-keeping regime. Making the required corrections has implications for the constellation lifetime and service provision as it directly impacts constellation geometry and fuel consumption.

The study highlights the benefits of using higher-fidelity aerodynamic drag models within orbit propagators and the high computational cost associated with modeling atmospheric density in the orbit propagation process. The size of uncertainties in the atmospheric density modeling problem outweighs many other aspects of the orbit propagation process.

The research concludes that current drag modeling methods used in operational systems are too coarse and contribute to the high false-positive rate of conjunction warnings. For mega-constellation operators, using higher-fidelity drag models will predict the spacecraft network geometry more accurately, impacting the scheduling of maneuvers and station-keeping.

Overall, this study contributes to improving our understanding of the impacts of higher-fidelity aerodynamic drag modeling in the orbit propagation process for spacecraft in low Earth orbit. The results show that higher physical fidelity aerodynamic drag modeling significantly impacts the accuracy of orbit propagation, emphasizing the need for continued research and development in this area to improve space traffic management and the longevity of mega-constellations. The findings of this study have important implications for the wider space community, including operators, regulators, and researchers.