Coupled orbit and attitude dynamics of a reconfigurable spacecraft with solar radiation pressure

This work investigates the orbital and attitude dynamics of future reconfigurable multi-panel solar sails able to change their shape during a mission. This can be enabled either by changing the relative position of the individual panels, or by using articulated mechanisms and deployable, retractable and/or inflatable structures. Such a model introduces the concept of modular spacecraft of variable morphology to large gossamer spacecraft. However, this joint concept is complex in nature and requires equations for coupled orbit/attitude dynamics. Therefore, as a starting point, the system is modelled as a rigid-body dumbbell consisting of two tip masses connected by a rigid, massless panel. The system is subjected to a central gravitational force field under consideration of solar radiation pressure forces. Therefore, we assign reflectivity coefficients to the tip masses and a high area-to-mass ratio. An analytical Hamiltonian approach is used to describe the planar motion of the system in Sun-centred Keplerian and non-Keplerian circular orbits. The stability and controllability of the system is enabled through changing the reflectivity coefficients, for example through the use of electro-chromic coating on its surface. The creation of artificial unstable equilibria of the system due to the presence of solar radiation pressure and heteroclinic connections between the equilibria are investigated. We further derive a constraint for the solar radiation pressure forces to maintain the system on a circular Sun-centred orbit. It is planned that the structure is eventually capable of reconfiguring between the equilibria by a minimum actuation effort.