The Mesicopter : A MesoScale Flight Vehicle NIAC Phase I Final Report 1

1. Abstract The following report summarizes the findings of a six month research investigation of the ' mesicopter' concept, a flying vehicle with dimensions of about two and a half centimeters. Research focused on low Reynolds number aerodynamics, motor and power system design, and meso scale fabrication methods. Our work resulted in the design, component fabrication, and assembly of two mesicopter prototypes. The first version, a 4-motor design with 1.5 cm rotor diameters, externally powered, and mounted on a constrained arm, was used to demonstrate lift off. Each motor was able to lift over 700mg, more than enough to support the weight of the 325mg motor-rotor assembly and leaving sufficient room to carry airframe and battery. A second design shows batteries and airframe integrated into a single structure, free flight tests of this vehicle are envisioned in the near future. The present work established a methodology for the fabrication of fully 3D shaped propeller blades less than 100 micron thin and with surface roughness of less than one micron. Simulations and measuments indicate the critical importance of blade shape details for aerodynamic performance. Finally, studies of currently available battery technology revealed that a free flight mesicopter with missions times of tens of minutes is feasible. The prospect of fabricating large number of mesicopters has implications for several future NASA missions. The science of flight of millimeter and centimeter size vehicles is largely unexplored. The Reynolds number of such devices lies in the range of less than 10,000 where aerodynamics are dominated by viscous considerations and few analysis or design tools are available. This is one of the areas in which scaling laws are unfavorable, with lower lift-to-drag ratios and limited rotor lift capabilities. Some of the aerodynamic features are poorly understood in this size regime and means by which improved performance may be realized have been little explored. In an effort to shed further light on insect scale aerodynamics, faculty and students from the Aero/Astro Department and the Mechanical Engineering Department at Stanford University with support from NASA embarked on a half year study towards assessing the feasibility of creating a centimeter sized flying vehicle called the ' mesicopter'. Vehicles in this size range may be used on earth for atmospheric science, permitting in-situ measurements of meteorological phenomena such as downbursts and wind shear, and on planets like Mars where atmospheric flight permits unique opportunities for exploration. Swarms of mesicopters …