• electric solar wind sail
• attitude control
• voltage modulation
• thrust vectoring

The Electric Solar Wind Sail is a propellantless propulsion system based on the extraction of momentum from the charged particles released from the Sun in order to create thrust. It consists of a number of thin centrifugally stretched tethers that are kept positively biased by an on board electron gun. The flight attitude control of the electric solar wind sail is a key challenge in its development, affecting the feasibility of the missions for which it is considered suitable. In this context, the aim of the present work is to design a control law capable of modifying the attitude of the sail by adequately changing the electric potential of each individual tether. Under the assumption of an axially-symmetric sail, an analytical expression is found for the control law. The attitude equations are then numerically integrated including the derived control law, in order to proof its validity. The results of this integration are discussed for two different electric sail configurations and attitude maneuvers. It is concluded that, within the discussed advantages and limitations of the model, the control law is valid for first approximation studies of future electric sail missions.