Abstract:
High Altitude Platform (HAP) is an unmanned airship or airplane deployed at the altitude of 17- 20 km, in the stratosphere for the applications involving a very long-duration airborne presence. Lighter than air vehicles (LTA) like Airship, blimp or balloons are widely used for HAP related applications, however, research is also undergoing for utilizing heavier than air (HTA) vehicles like normal airplanes as a HAP. Long duration airborne presence requires continuous and uninterrupted power supply but the available power is limited as the only source of energy is solar radiation. This limits the performance capabilities of HAP. Low power consumption design which is achieved by low drag shaped hull offers extended hours of flight and higher payload capacity. In this study, a complete design approach for a lighter than air High Altitude Platform for providing wireless backhaul internet connectivity from conceptual and preliminary stage to finalized design has been presented along with the mathematical relations and various fabrication methodologies involved in prototype manufacturing. Initially, the total volume of the hull and accordingly the shape and dimensions have been calculated. Detailed CFD analysis for this initial shape has been performed along with geometries of different Length to Diameter ratios (L/D) obtained from the initial shape after shape manipulation to obtain low drag hull shape. The propeller blowing method has been employed on the obtained low drag hull geometry for optimal placement of propellers in an effort to further reduce the drag. A working prototype has been fabricated and successfully tested to demonstrate the capabilities of this design. Considering the mission requirements of the current application, HAP has been designed to be stationed at any specified fixed point relative to the earth at an altitude of 20 km. It is to be fabricated with lightweight nylon fabric and filled with helium gas. Propellers are to be used for holding the position of HAP relative to the earth within a radius of 2 km. Several modules of HAP have been designed and integrated to demonstrate a working prototype.
