Modelling aerodynamic drag of a very low earth orbit 1U CubeSat utilising a Boltzmann-BGK approach

The aerodynamic drag of a 1U CubeSat at various Very Low Earth Orbit (VLEO) altitudes and conditions have been investigated utilising an in-house Boltzmann-BGK solver. This region of space has numerous benefits, however significant drag can lead to short satellite lifespans. The analyses focus on determining drag coefficients, as well as absolute drag values. Flow fields are illustrated. Monoatomic oxygen number density ratios on exposed surfaces were presented to help guide corrosion analysis. Material properties for satellite surface coatings have been analysed, including drag reduction performance. All atmospheric parameters were sourced from NASA’s NRLMSIS 2.0 atmospheric model. Altitudes investigated range from 50 km to 500 km. Periods of solar minima and maxima, seasonal variances and local day/night cases were investigated. Drag coefficients were evaluated and compared with corresponding Knudsen numbers. Although there are significant variations of the drag coefficient (C D ) at very low altitudes, higher altitudes produced consistent values. Two CubeSat geometric orientations were studied, one settled to a consistent C D of around 1.24 for higher altitudes, while the other case settled to a C D of 1.60. The material property of specularlity was found to have a considerable impact on drag coefficients – altering this parameter could lead to significantly higher drag coefficients, in some cases exceeding values of 2.0. The drag coefficients computed can be coupled with other existing models to determine satellite lifespan, as well as to estimate expected drag at various orbital altitudes. This will be insightful for determining thrust values of drag compensation systems, serving to extend the lifespan of VLEO operating satellites.