Attitude Dynamics of an Electric Sail Model with a Realistic Shape

The Electric Solar Wind Sail (E-sail) is an innovative propulsion system that gains thrust from the interaction with solar wind particles. The incoming ions interact with an artificial electric field produced by means of long charged tethers, which are deployed and maintained stretched by spin. Many studies analyze the behaviour of an E-sail in the interplanetary environment, and in most cases it is described in a simplified way assuming an ideally flat shape. The actual shape, however, is more involved, as it is the result of the complex coupling between the effect of the solar wind dynamic pressure and the centrifugal force due to the spacecraft rotation. This problem has been addressed in recent papers, which deal with the analytical expressions of thrust and torque vectors of a spinning and axiallysymmetric E-sail-based spacecraft. The torque acting on the E-sail induces a perturbation on the orientation of the thrust vector, which is studied in this paper by analyzing the spacecraft attitude dynamics. A numerical integration of the Euler’s equations shows that the spacecraft motion is characterized by a combined undamped precession with a nutation motion. A simple control law, capable of removing the perturbative torque, is discussed in the last part of the paper.