Appendix D: Lilium-1 Extremities Simulation (Tze Yee)

This appendix showcases the simulation results that informs the hottest and coldest temperatures that the Lilium-1 CubeSat could be exposed to during its orbit due to other orbital orientations. In actual orbit, Lilium-1’s actual orientation is likely to not be as ideal as simulated, with different values for the hot and cold extremities depending on that particular orbit’s variance.

Fig D-1. Heating extremities of Lilium-1

The above simulation assumes maximum surface area pointing towards the sun at all times, causing the Lilium-1 CubeSat to receive much more thermal power than it does during its typical mission orbit where the payload camera is consistently pointed towards Earth. This causes it to reach a maximum temperature of 53°C, much higher than the mission mode maximum of 31°C. It explains why some orbits may reach a high temperature value of up to 44°C. Furthermore, these simulations do not take into account internal heating due to payload components (information not provided due to sensitivity). While the exact magnitude isn’t known, it is safe to assume that actual maximum temperatures could be even higher.

Fig D-2. Cooling extremities of Lilium-1

On the other hand, the +X and -X faces of Lilium-1 have very little surface area compared to the other 4 faces. Hence, should these faces be pointed towards the Sun or Earth for longer durations than expected, the radiative heat input of Lilium-1 will drop significantly, causing these cooling extremities of up to -41°C to be far below the minimum of -22°C obtained from on orbit telemetry.

While internal components’ temperatures are expected to remain much more constant relatively due to low emissivity coatings, external temperatures of the CubeSat, typically finished with high emissivity coatings such as black paint, can showcase drastic fluctuations due to orbital orientation.