When designing a spacecraft, engineers face some challenges in developing an effective thermal control subsystem. A spacecraft is subjected to internal thermal loads caused by the heat dissipated from electrical and mechanical equipment, as well as external thermal loads, which vary depending on the type of orbit throughout the mission. To ensure that all the avionic systems maintain their allowable temperature ranges throughout the spacecraft’s operational life, the thermal control system must be carefully designed and optimized. Today, the exploration and utilization of space are becoming increasingly common. With the expected rise in long-duration missions, such as the Lunar Gateway, thermal control systems are becoming even more essential and critical, not only to manage the temperature of avionics boxes but also to ensure crew comfort.