Determination of parafoil lift and drag coefficients using both three-dimensional modeling and experimental methods
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The High Altitude Balloon Experiments in Technology (HABET) program started at Iowa State University to carry payloads into the upper atmosphere and to simulate the activities involved with satellite programs. As HABET has evolved through the years, the payloads for HABET have become increasingly more sophisticated and expensive. The current recovery system employs a circular parachute that does not provide any means of control. This allows the payload to land in inconvenient locations such as roads or train tracks. The parachute can also land in places where the payload is not recoverable such as lakes or rivers, even causing injury to people, property or animals. The Recovery Guidance System (RGS) is a solution to these problems. The goal of the Recovery Guidance System project is to develop a fully autonomous landing system that will select its landing sites from a list of preprogrammed sites based on where the system is and where it can go. This research is designed to give the RGS project a better understanding of the aerodynamic properties of the parafoil. This research has three parts. First, a two-dimensional lifting line equation is used to determine the lift coefficient and the drag coefficient. Next, a three-dimensional model of the parafoil used in the RGS program was put into a program called PMARC to obtain the coefficients of lift and drag. Finally, the parafoil was hooked up to a dummy payload of the same size and weight as the RGS electronic package so that the coefficient of lift and drag were experimentally obtained. All of these results were then compared to each other for accuracy. The lift coefficient values were close to the predicted values ([Plus or minus]16 percent) but the drag coefficient values differed from the experimental results by a factor of three.