Contents I. Introduction
The electric sail (E-sail) concept was proposed in 2004 as an alternative propulsion technology to rockets for solar system exploration [1]. The common E-sail design includes a central spinning spacecraft with positively charged tethers (namely the main tethers) in radial direction in a hub-and-spoke configuration [2], [3]. Each main tether connects to a remote unit at its end and rotate stably in a plane (namely the spin plane) at a given rate. The spin plane generates an electric field that deflects protons in the solar wind, leading to a propulsive force acting on the main tethers [4]. Different from the similar heliogyro solar sail [5], [6] and the hub-spoke tethered satellite formation [7], the adjacent main tethers are connected by nonconductive tethers (namely the auxiliary tethers) at the remote units to prevent them from colliding each other [8]–[10]. The propulsive force is proportional to (1/), where is the distance between the Sun and the E-sail, and decays slower than the solar sail [8], [11], [12]. This advantage makes the E-sail an attractive alternative to the solar sail for solar system missions, such as outer solar system exploration [13], [14], artificial equilibrium point maintenance [15], and heliocentric transfer mission [16]–[19].
