## 6 Thermal System Design
### Thermal Load Case Testing (SolidWorks)
Identical thermal loading was then applied to the 100 \(\times\) 100 mm end faces of the CubeSat, as it is assumed these faces only interact with the background space temperature to dissipate heat from the CubeSat body (Figure 53). The view factor for the radiation to background space is assumed equal to 1 [9]. Figure 53: Heat Dissipation to Background Space using Surface to Surface Modelling. Figure 52: Applied Albedo and Earths Infra-Red Fluxes. The CubeSat geometry was then designated an Aluminum 6061-T6 material in SolidWorks. The material selection for the steady-state analysis has no impact upon the results, only the surface area impacts upon the results. The initial results presented a temperature gradient across the CubeSat which would be expected according to theory. The panel's incident with the incoming solar flux is at the highest temperature, a value of 547.6 K. The panels enduring no incoming solar flux are at the lowest temperature which also matches established theory. Temperatures on the \"cold\" faces drop as low as 427.7 K shown in Figure 54.  
Although the temperature gradient throughout the CubeSat matches that of theory, the magnitude of the steady-state temperature is much higher than that stated in literature [9]. Steady-state analysis upon the 1U Compass-1, also orbiting at 600 km polar orbit, calculated a steady-state temperature range of 318.3 K to 326.516 K [9]. The average internal temperature of compass-1's orbit in the Sun phase is 322.408 K whereas the author's analysis produced an average value of 510.15 K. This represents a 1.5823 magnitude difference between the values illustrated by Figure 55.  
Figure 54: Initial Steady-state Simulation Results end of the Heating Phase. Figure 55: Compass-1 Temperature at the end of the Heating Phase [10]. It is, therefore, necessary to reconsider the loading scenario to produce a steady-state temperature range matching that presented in validated theory. The loading case has been significantly altered from the initial testing and may have a significant impact upon the proposed design. The preliminary design had solar flux incident upon two faces, this assumption has been altered to have solar flux incident on the singular top face. This would significantly impact the power system, as the theoretical power generation would be halved to 5.39 W. It was previously assumed heat was only radiated from the 3 cold faces; however, heat would be radiated from the top face as the Sun is an extreme distance away, and the side face incident has no solar flux as this faces background space. Heat would not be dissipated from the bottom face assumed perpendicular to Earth, as the expected temperature range of this body would be extremely similar to that of Earth, approximately 20 \({}^{\circ}\)C.  
The alteration in the thermal load case has provided a temperature range much closer to that stated in literature. The temperature range for this thermal load scenario has been reduced to a minimum of 313 K (40 \({}^{\circ}\)C) and a maximum of 338.9 K (65.9 \({}^{\circ}\)C) illustrated by Figure 51.0 This gives an average steady-state heating phase temperature of 325.95 K (52.95 \({}^{\circ}\)C). This is an extremely similar value to the average steady-state heating phase value of compass-1, which is 322.408 K (49.408 \({}^{\circ}\)C) [10]. Assuming theory to be the correct value, the percentage error between the values is 1.09% which is an acceptable error as an error below 5% is deemed negligible [59]. The significant difference in upper temperature limit on the face incident with solar flux is due to the difference in area exposed to the incoming solar flux between the two models. As compass-1 is a 1U CubeSat, the area of one face exposed to incoming solar flux is 100 mm \(\times\) 100 mm (0.01 m\({}^{2}\)) [1] whereas the 3U has a total exposed surface of 100 mm \(\times\) 300 mm (0.3 m\({}^{2}\)). As the solar flux is assumed perpendicular to this face, triple the amount of radiation is incident.