Hover Performance of a Small-Scale Helicopter Rotor for Flying on Mars

The present study is in response to increased interest towards assessing the feasibility of a small-scale autonomous helicopter (gross weight less than 1 kg) for Martian exploration. An autonomous rotorcraft may be ideally suited for such an application because of its unique advantages, which include the ability to take off/land vertically on harsh terrain, and greater speed, range, and field of view, when compared to a traditional surface rover. The atmospheric conditions on Mars present a unique set of design challenges. Even though the Martian gravity is only about 38% of Earth’s gravity, the Martian average atmospheric density is about 70 times lower than Earth’s atmospheric density. Therefore, the rotors would be operating at extremely low Reynolds numbers, even lower than 5000 for a small-scale helicopter. However, the Mach number will be significantly higher (M>0.4) because of the higher tip speed required (due to lower density) and because of the fact that the speed of sound on Mars is only about ...