Tactics for Heliogyro Solar Sail Attitude Control via Blade Pitching

Heliogyros generate attitude control moments by pitching their sail membrane blades collectively or cyclically, similar to a helicopter. Past work has focused on simple blade pitch profiles with the heliogyro normal to the sun; however, most solar sail missions will require sun angles of at least 35deg. Furthermore, combination pitch profiles (e.g., cyclic plus collective) are needed for attitude control during all mission segments. The control moments for such situations vary in an unintuitive, nonlinear fashion. This paper explores heliogyro control moment authority with varying sun angles and combinations of pitch profiles, providing critical insight for future development of heliogyro attitude control schemes. Three tactics for generating control moments using various profile combinations are introduced for three-axis attitude control during a variety of practical mission scenarios. These tactics indicate that the heliogyro can generate control moments from any orientation, including edge-on to the sun. A restricted, nonlinear, constrained optimization is used to determine the blade pitch profile combination required to generate the desired attitude control torques. This approach could be employed for analyzing mission performance and for designing closed-loop attitude control.