Air loads on solar panels during launch

The dynamical behaviour of solar panels during launch is significantly affected by the thin layers of air trapped between the panels. For narrow gaps the air manifests itself not only as a considerable added mass, but its viscosity can result in a substantial amount of damping. A model has been developed which describes the pressure distribution in the gap. The model includes the effects of inertia, viscosity, compressibility and thermal conductivity. The model is written in terms of dimensionless parameters which govern the motion of the air in the gap For rigid panels, suspended in springs, located parallel to a fixed surface and performing translational or rotational oscillations, analytical solutions are presented. The results from specially designed experiments show good agreement with the analytical results. A large shift in eigenfrequency is observed and an increase in damping to almost critical values for narrow gaps. On the basis of the theory, a new acoustic finite element has been developed for the calculation of acousto-elastic interaction. Numerical results are shown for a flexible panel located parallel to a fixed surface.