Fleixble and compact preliminary thermal analysis tool for cubesats

Abstract

Thermal behaviour estimation is crucial for any space system. Temperature of the components needs to stay within their operating range. Thus, an analysis should be done and the design should consider the results of the analysis. Obtaining the exact temperature results requires a fully developed design, commercial software and time-consuming analysis runs. Therefore, affordable approximate temperature estimation is important for CubeSats in preliminary design stages or low-budget projects. In this study, a thermal analysis tool is developed using MATLAB that can execute a thermal analysis in much less time. Evaluating the temperature change in the orbit can be done by considering the thermal environment and internal heat exchanges. Thermal environment for Earth's orbits includes solar radiation, albedo radiation and Earth's infrared radiation. Internal heat exchange for a CubeSat considers only radiation and conduction between components and parts. External heat loads and internal heat exchanges are put together in the thermal network equation by using the conservation of energy rule. Thermal network equation is an initial value problem that is an ordinary differential equation with an initial condition and in this study, it is solved numerically using the fourth-order Runge-Kutta method. Also, transient solutions are studied in this thesis because boundary conditions in the space environment vary over time and the results will be more meaningful to compare. Steady-state solution can also be solved using average values of boundary heat fluxes. Components and parts are labelled as nodes and these nodes create the thermal network model. MATLAB code requires inputs to work. Inputs such as the surface coordinates of each node, material and coating selections for nodes and thermal coupling matrices for conduction and radiation. Radiation matrix should indicate if any radiative heat transfer is occurring between each node. Conduction matrix contains the contact conduction values between each node. Orbital parameters and the orientation of the satellite also need to be entered. These inputs provide flexibility for analysis. In this study, thermal analysis for the simplified model of the UBAKUSAT is performed using the developed MATLAB tool and Siemens NX software. Both analyses and run times are compared to each other for different scenarios. Similar results are found for each scenario and the code takes much less time to analyse.