Stability of Gossamer Propellers for High-Altitude Ballooning

High-altitude balloon sensor platforms could benefit greatly from lift augmentation, for example, to control altitude and ascent/descent rate, that does not depend on expendable lifting gas or ballast. Electric lift augmentation using solar power and a novel gossamer propeller concept is studied here, where extremely lightweight membrane propeller blades derive their stiffness from centripetal forces rather than rigid members. Although bearing a close resemblance to heliogyro solar sails, the application of gossamer propellers in an atmosphere differs significantly due to destabilizing aerodynamic moments. A method for producing static stability of propeller blade pitch using a particular rigging geometry for the leading- and trailing-edge membrane tensile members is introduced and analyzed, and lift and drag measurements are made using optical measurement techniques on a scaled prototype.