<p style="text-align: center;"><img src="/ueditor/php/upload/image/20260118/1768712626606532.png" title="1768712626606532.png" alt="2.png"/></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 12px;">To define the steady-state heat transfer analysis, several parameters need to be set. The thermal conductivity of all materials must be specified. In our project, the casing was made of aluminum while all other parts were made of steel. Thermal contacts between all solid parts must also be defined, as thermal interfaces are never perfect and depend on factors such as surface finish or roughness. We referred to the Spacecraft Thermal Control Handbook (Ref. 2) to determine the thermal contact resistance or interface thermal coefficient. The heat generated by each bearing was defined based on data provided by SKF (Ref. 3), the bearing manufacturer. This data covered 97 load cases for when the first gear is engaged and 43 load cases for the second gear, each representing a specific input gear rotation speed and torque. From these combinations, we selected three worst-case scenarios that generated the most power loss. Next, the heat transfer coefficients (HTC or film coefficient) at each node were imported to define film conditions that characterize the convective heat exchange, along with an estimated fixed lubricant temperature. Figure 10 illustrates the mapping of the film coefficients on the gears around the narrow region. Given the highly turbulent nature of lubrication inside the casing, assuming a constant temperature throughout is acceptable. The lubricant temperature can be easily adjusted to run multiple scenarios, allowing for the study of its sensitivity on the predicted solid temperatures.</span></p>