Multi-objective multidisciplinary design analyses and optimization of high altitude airships

High Altitude Airships (HAAs) offer tremendous potential as long-endurance relocatable aerial platforms for several strategic and commercial applications. Design, analyses, and optimization of HAAs involves a complex interplay of various disciplines, and hence a multidisciplinary approach is essential. This paper describes a methodology to obtain the optimal design of an HAA meeting the requirements of onboard payload and power. The methodology couples six mutually interacting disciplines, viz., Environment, Geometry, Energy, Structure, Aerodynamics, and Thermal. The design problem is posed in a multidisciplinary optimization framework involving eleven design variables drawn from these six disciplines, and optimal solutions are obtained using Genetic Algorithm. The methodology obtains the optimal envelope shape, layout of the solar array, and altitude of operation, and determines the most critical day of operation. To demonstrate the efficacy of methodology, the optimal solutions are obtained for five different geographical locations of deployment, and compared with those for a standard envelope shape. A comparative study of these solutions is carried out to highlight the importance of thermal considerations in design optimization. Since the problem involves mutually conflicting disciplines; a multi-objective optimization involving Aerodynamics and Structures are also carried out. It is noticed that operating parameters and thermal behavior have a significant effect on design.