Development of the Mars Helicopter Rotor System

The Mars Helicopter is a 1.8 kg coaxial rotorcraft designed to demonstrate aerial mobility at the surface of Mars after deployment from the Mars 2020 rover. In this paper, the authors present the development of the Mars Helicopter rotor system from preliminary design through fabrication and testing of the flight hardware. The vehicle has a 1.21 m counter-rotating coaxial rotor system which is driven by electric motors and which features collective and cyclic controls on both the upper and lower rotor sets. The rotor blade design is characterized by the low Reynolds number (∼104), high Mach number (∼0.7), high stiffness (first flap frequency ∼1.9/rev), and minimum mass. Airfoil design focused on minimizing drag at the low operating Reynolds number while maintaining sufficient spar depth for structural requirements, and the blade planform was based on a minimum induced loss profile with modifications to reduce mass of the outboard blade sections for increased flap frequency. The swashplate and servos were designed to provide actuation of the rotor at up to 12Hz bandwidth while minimizing system mass and volume, and the primary structure of the rotor blades and hubs relies heavily on molded carbon fiber composites and ceramic ball bearings.