Nonlinear dynamics of flexible heliogyro subject to sinusoidal root pitch command

A heliogyro is a particular solar sail configuration whose reflective surface is divided into a number of long and slender blades, which are stiffened by a suitable spin-induced centrifugal force. The reflective blades can rotate around their longitudinal axes to change (either collectively or cyclically) the pitch angles and allow the spacecraft attitude (and so the thrust vector) to be effectively controlled. The aim of this paper is to perform implicit nonlinear finite element analyses of a heliogyro solar sail in order to investigate the dynamic response of the structure subject to a sinusoidal pitch command, while centrifugal stiffening and solar radiation pressure are acting on it. Using a parametric modeling approach, sensitivity studies relative to a set of design parameters are conducted for identifying possible solutions that improve the heliogyro maneuverability. In particular, by adopting the design of the proposed HELIOS spacecraft as a reference configuration, the influence of some geometric parameters and the effect of a number of structural arrangements are investigated. The performed analyses demonstrate that, compared to the reference configuration, the arrangement with a lower blade aspect ratio, same tip mass, and one traversal reinforcement at the tip is the only configuration without irreversible torsional instability of the blades when the pitch command has an amplitude of 25 deg.