An electric sail is a new propulsion system uses the solar wind dynamic pressure as a thrust force. We analyzed the probability of the orbital control not changing sail plane angle but switching an electron gun connected with tethers. First, locally optimal switching laws are derived from Lagrange variational equations analytically. By theoretical calculations and numerical simulations, these switching laws are effective for changing some orbital elements. Moreover, mission applicability is studied. Assuming minimum time transfer problem between circular and coplanar orbits, optimal control laws are studied with direct approach. We conclude that the switching orbital control method is effective for exploration of other planets.

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A Coulomb force attractor is studied for orbital deflection of potentially hazardous asteroids. The concept of a Coulomb force attractor is based on towing an asteroid by utilizing the mutual gravitational force and Coulomb force, induced by artificial charging, between a spacecraft and the asteroid. Particular attention is placed on evaluating the resulting change in the asteroid orbit. The electric potential distribution around the spacecraft is studied, and an analytic expression of the mutual Coulomb force is derived. The equations of motion are derived for a rotating reference frame, and the performance of the Coulomb force attractor is investigated through numerical simulation. The differences between a Coulomb force attractor and a traditional gravity tractor are also examined, and the concept of asteroid towing using several spacecraft is proposed.

A method for controlling a Coulomb force attractor spacecraft in the vicinity of an asteroid is presented. A Coulomb force attractor tows and deflects an asteroid through a combination of mutual gravitational and Coulomb forces. We show asteroid deflection distances with time before impact and the required fuel consumption for efficient mission design with limited resources. By considering the asteroid and the spacecraft as a single body, motion is represented with the separation distance between the spacecraft and the asteroid and two Eulerian angles. We also investigate linearized dynamics and identify the stability requirements using the Routh-Hurwiz stability criterion. Numerical simulations are also performed and the feedback law to stabilize the position of the spacecraft is investigated. By investigating the interaction between the separation distance and Eulerian angles, we propose and evaluate a method for independently controlling each motion.