Showing papers by "Dale Lawrence published in 2014"

Heliogyro Solar Sail Research at NASA

Abstract: The recent successful flight of the JAXA IKAROS solar sail has renewed interest within NASA in spinning solar sail concepts for high-performance solar sailing. The heliogyro solar sail, in particular, is being re-examined as a potential game-changing architecture for future solar sailing missions. In this paper, we present an overview of ongoing heliogyro technology development and feasibility assessment activities within NASA. In particular, a small-scale heliogyro solar sail technology demonstration concept will be described. We will also discuss ongoing analytical and experimental heliogyro structural dynamics and controls investigations and provide an outline of future heliogyro development work directed toward enabling a low-cost heliogyro technology demonstration mission ca. 2020.

Heliogyro Attitude Control Moment Authority via Blade Pitch Maneuvers

Abstract: 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 35°. 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 angle and combinations of pitch profiles, providing critical insight for future development of heliogyro attitude control schemes. Three strategies for generating control moments using various profile combinations are investigated for three-axis attitude control. These strategies indicate that the heliogyro can generate control moments while edge-on to the sun, allowing for recovery from any orientation. A control algorithm is presented that determines the required blade pitch profile combination to generate the desired attitude control torques. This algorithm could be employed for closed-loop control in attitude dynamics simulations.