Very Low Earth Orbit from a Thermal Perspective: Thermal Analysis of a 16U CubeSat

Kurzfassung

Very Low Earth Orbit (VLEO) improves the geometric performance of optical payloads and increases communication link margins relative to conventional Low Earth Orbit (LEO), but exposes spacecraft to aerothermal heating, aerodynamic disturbances, and large environmental uncertainty. These effects are particularly challenging for CubeSat-class platforms, where mass, volume, and available thermal-control hardware are limited. This thesis assesses the thermal feasibility of a predominantly commercial-off-the-shelf 16U CubeSat platform operating down to a minimum perigee altitude of 130 km. A simulation-based thermal-analysis framework is developed to construct conservative VLEO thermal cases and propagate them into spacecraft temperatures. Atmospheric, aerothermal, aerodynamic, and Earth-radiation inputs are defined for bounding hot and cold conditions. Analytical free-molecular aerothermal and aerodynamic models are benchmarked against DSMC reference data and used for rapid altitude- and attitude-dependent load evaluation. Earth albedo and infrared radiation are represented with a CERES-derived zonal-harmonics model after comparison with constant and ECSS-based alternatives. The resulting cases are analysed with a reduced-order LTspice thermal network and a spatially resolved COMSOL finite-element model. Morris screening, deterministic design sweeps, and surrogate-based uncertainty propagation are then used to size and verify the passive thermal configuration. The baseline configuration is non-compliant in the hot case even without internal dissipation, identifying insufficient bus heat rejection as the limiting mechanism. A passive design combining a ram-facing heat shield, high-emissivity side panels, and thermally controlled external interfaces permits a deterministic payload duty cycle of 20 % at 130 km. The propagated maximum structure temperature is centred at 39.7 °C with a standard deviation of 0.85 °C and remains more than 7 °C below the 50 °C structure-to-payload interface requirement. No requirement exceedance is observed within the propagated uncertainty set. The results indicate that passive thermal control of a 16U COTS-based CubeSat is feasible for short-duration operation down to 130 km perigee, provided that interface conductances and subsystem-level thermal behaviour are verified by further modelling and test correlation.