Dynamic Modelling of Thermal Shock

When a spacecraft's orbit passes through the earth's shadow, known as an eclipse, temperature changes arise in the vehicle. These thermal gradients can cause components to deform from their nominal position. For satellites with appendages that are sensitive to thermal changes, the deformations can be very rapid. As a result, angular momentum is transferred between the spacecraft body and the moving appendages. Thus, pointing errors occur. Several spacecraft have experienced this while in orbit and, depending upon their requirements and geometry, the errors range from being tolerable to unacceptable. The phenomena is called thermal shock and an alternative dynamic modelling strategy for the physical disturbance is presented herein. The model varies in complexity and integrity from conventional modelling techniques. However, the alternative model yields similar results, despite the differences in fidelity, compared to the more complex models. The strengths and weaknesses of the models are discussed. In particular, those factors which influence the choice of a model for a specific analysis or design problem are discussed.