Experimental Methods for the Characterization of the Static and Dynamic Stability of a Spinning Body 2011-01-2735
Newly developed technologies are enabling the design of Unmanned Aerial Vehicles (UAVs) and Micro Air Vehicles (MAVs) with heretofore unrealized capabilities. A tube-launch MAV would allow the increased flexibility to launch an aircraft rapidly without need for a runway or complex launching system, either from a vehicle, installation, or as a man-portable device. The MAV would fill the diameter of the launch tube and deploy aerodynamic lifting and control surfaces after launch. In order to deploy the lifting surfaces the MAV must be capable of deploying control surfaces, negating any tube-imparted roll rate, and developing an optimal flight attitude automatically.
An experimental method was developed to characterize the aerodynamics and stability of a blunt body spinning under conditions of roll rate decay in the Clarkson University High Speed Wind tunnel. This method is to be used to evaluate the development of an active roll rate control system for spinning projectiles. The stability characteristics of an MAV during spin stabilized flight were examined and stability criteria developed. Several different methods to spin the wind tunnel model and to apply an initial roll rate to the model were designed and tested, in order to find a solution which minimized friction roll damping and vibration. Techniques to accurately measure the roll rate were developed. The model was operated in vacuum to compare the roll decay rates and separate out the aerodynamic contributions from friction contributions to roll damping. From the aerodynamic data and the associated roll and decay rates the performance of the experimental system was analyzed, and areas of improvement identified. From this data, the expected stability of a spin-stabilized blunt body was predicted. These predictions will enable us to design a roll control system which will actively cancel an initial roll rate without becoming unstable, allowing the vehicle to transition from spin stabilized to fin stabilized flight regimes.