VLEO CubeSat attitude dynamics during and after flexible panels deployment using torsion springs

Abstract

This paper deals with the attitude motion of VLEO CubeSats during and after the deployment of flexible stabilizing panels driven by torsion springs. Unlike in higher orbits, in VLEO, the attitude motion of the satellite is primarily influenced by the interaction with the atmosphere. Therefore, in order to study the evolution of the satellite attitude during the panels deployment, we considered not only the torques from the torsion springs and the elastic oscillations of the flexible panels, but also the restoring and damping aerodynamic torques, which depend on the satellite shape and thus change substantially during the panels deployment process. Numerical simulations show that if the satellite has intermediate stable equilibrium positions, the combined effect of all above-mentioned torques may result in qualitatively different regimes of oscillations in the angle of attack after the deployment. These oscillations have low-frequency harmonics, related to the aerodynamic torque, and a high-frequency one, induced by the elastic oscillations of the panels after the collisions in the system caused by panels latching. The amplitude of the high-frequency oscillations depends on the post-collision state of the system, which is found analytically using the Appell algorithm. The post-collision state, in its turn, depends on the inevitable inaccuracies of the deployment process, causing the panels to start their rotation at slightly different moments in time. As a result of the study, recommendations for the torsion spring-driven panels deployment in VLEO are formulated. Their focus is to maintain the attitude stability of the satellite and reduce the vibrations of its body in presence of disturbances, such as elastic oscillations of the panels themselves or uneven panels deployment.