Layout designment of an in-flight-deployable and fast self-stable small-UAV

An in-flight-deployable and fast self-stable small- UAV was developed to approaching carry out mission in dangerous and complex environments, which was fully utilizing the advantages of quick arrival for big-UAV and approaching reconnaissance for low-cost small-UAV to fast arrive to designed areas through throwing small-UAV by the big-UAV and execute the task. Because the small-UAV was enclosed in the pod before launching, folding tandem special-wings were designed to satisfy the demand of wing area in restricted space. In order to increase yawing stability, fixed and folded winglets were adopted on the rear wing. The small dimensions and low Reynolds number of wings was required to be considered in the airfoil design to prevent laminar separation which impacted controllability. Based on multi-objective optimization algorithm and wind tunnel test, the airfoil and aerodynamic configuration with largely available lift coefficient, high lift-drag ratio, appropriate yawing and rotating stability were obtained. After ejection, the UAV was free-fall and decelerated with a drag streamer. In this process, the rear wings were unfolded first to get the larger static stability marging, which guaranteed that the UAV for arbitrary launching posture could be fast self-stable in 2 seconds. Afterwards, the front wings began to deploy to gain the proper stability marging, that could make the UAV to lift, level and get into a stable flight to execute the task in 10 seconds. Model free-flight, ground running, wing deployment, and flight tests with hot air balloon and the large UAV launching were conducted to demonstrate the feasibility of the technique in this paper.