On the Fabrication of Ultra-Thin Composite Rotors for Martian Flight

This paper describes the fabrication and frequency testing of 4.72-foot diameter composite rotor blades of radical geometry and 1% thickness-to-chord designed by the University of Maryland and NASA Ames Research Center for future Mars helicopters. The ultra-thin nature of the blade, along with its twist, chord, and material variations, pose several fabrication challenges. These challenges and the steps needed to overcome them are the subject of this paper. The principal challenges were the control of resin flow during curing and the construction of the root geometry. These obstacles were overcome by implementing an innovative foam core and a layer-wise construction with stencils, respectively. Two sets of blades were fabricated: a baseline blade that followed the geometry as designed, and a parametric variation with a simpler internal construction. Once successfully fabricated, the non-rotating frequencies were measured. The measured frequencies matched remarkably well with predictions, verifying the effectiveness of the fabrication process.