Semester

Summer

Date of Graduation

2010

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Wade W Huebsch

Abstract

This study presents both feasibility and preliminary design studies of a ruggedized, stowable, ballistically launched Micro Air Vehicle (MAV). A vehicle capable of being stored within a 40 mm diameter, 133 mm long cylinder and able to withstand a significantly rough environment when stowed was desired. Minimum performance specifications were a 20% range increase from a 450 m range, 45° launch angle ballistic trajectory and a gliding time of 30 s from the apex of said trajectory. To this end, a study of comparable MAV systems, available control and communication electronics, low Reynolds number flight, ballistic flight, and advanced projectiles was conducted. It was found that the concept was possible using current electronics, however, these would require a large majority of the available volume necessitating the novel, compact, wing stowage systems discussed within. While aerodynamically feasible the transition between ballistic and aircraft flight will necessitate significant sensor and control logic design. The small scales of this project necessitated consideration of the vagaries of low Reynolds number flight. Despite the final design proposals maintaining chordwise Reynolds numbers greater than 100,000 several key trends were found to be significantly different than those encountered in classical aerodynamic theory; particularly the existence of an optimum aspect ratio for maximum lift to drag ratio of the wing alone. For a fixed wing area and velocity increasing the aspect ratio, thereby reducing induced drag, also reduced the chordwise Reynolds number which reduced the efficiency of the airfoil. At the optimum benefits from reducing induced drag balanced with the penalties of reduced airfoil performance. The feasibility study focused primarily on volumetric concerns; minimizing stowed wing volume was the main goal. Several design iterations were constructed in SolidWorks prior to the development of two concepts ready for prototyping and testing. Design optimization was performed with both classical semi-empirical methods using Missile DATCOM and a custom in-house Matlab code as well as the Fluent CFD package. Significant work was done to find a suite of solver settings and mesh generation parameters capable of predicting 2D and 3D low Reynolds number airfoil performance with sufficient quality for preliminary design work. Optimization studies found that achieving both initial performance goals with a single aircraft would be highly inefficient. This effort concluded with a pair of designs, one high-speed cruise-to-target version capable of 700 m range and 9 s gliding time optimized for rapid-response, and a long-endurance glider with a flight time greater than 60 s optimized for surveillance purposes.

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