Abstract:
Three-Dimensional (3D) aeromechanical analysis is carried out on the rotor blades of a 20 kg Mars Hexacopter. The objectives are to understand the aeroelastic behavior of its unique and ultra-thin low-Reynolds number and high-Mach number blades and study the interactions of structures, aerodynamics, and control moments in the Martian atmosphere. Beginning with structural analysis in vacuum, comprehensive analysis is carried out in hover and forward flight using 3D FEM, 2D airfoil tables, and free-wake. Natural frequencies of the rotor, elastic response of the blade, control momentoftheroot, airloads, wake, and 3D stresses are studied. Two types of designs are considered: a baseline design with pitch axis at the quarter chord and an unconventional design with the pitch axis moved to the mid-chord. Unusual nose-up elastic twist is observed on the rotor blades that appears to stem from the trapeze effect that counteracts the f lattening effect of the propeller moment. By moving the pitch axis to mid-chord, the control moment is reduced by 30%-40% without any noticeable adverse effect on stability due to the low Lock number. Both designs have maximum stresses well below the material limits but the mid-chord design has a more uniform distribution of stress in general and lower levels of shear stress in particular. These, and many other unconventional phenomena make Martian aeromechanics unique and ripe with possibilities of innovations tailored to its atmosphere.