| In 2004, The Atmospheric and Space Threshold Research Oklahoma (ASTRO) program was launched to provide access to the near space environment for both educational and research purposes. Mainly, this ASTRO vehicle consisted of four parts: Sounding weather balloon to produce buoy force during the ascent phase, circular parachute to produce drag force during the descent phase, tracking gear with GPS (Global Positioning System) to check the position from the ground, and experimental payloads.;The descent phase utilizes a circular parachute, and as such, there are no means of controlling the landing location of the vehicle and payloads. Without control, the direction the parachute takes is dependent upon the winds aloft which can allow payloads to land in undesirable locations, such as rivers, lakes, or the middle of vast forests. At times, the flight must be cancelled before it even begins if the risks of a long or difficult recovery are predicted. As the ASTRO project has evolved, the necessity of control of the payloads over the descent phase has also become obvious. In order to address this need, a study of a Return-to-Point Vehicle (RPV) has been started.;Parafoil vehicles which are used for RPVs have proven to be useful in many situations from the previous research. Once the RPV has reached the desired altitude, generally around 100,000 ft, it is released from the balloon. When the RPV has been released, it will follow a trajectory which is programmed on Autopilot to direct it a desired landing zone. Some researchers tried to analyze and test the parafoil, but there are no reported uses of the parafoil for dropping the payload from high altitudes; in addition, there are not commercial products to be matched with the ASTRO research as well. Therefore, the purpose of this research is to design the RPV and to develop the optimal trajectory to satisfy the requirements of the ASTRO project.;In this research, the most important objective is to develop a cost-effective, simple, and reliable autopilot system which can be applied to the payload used in the ASTRO project. |
