Abstract
In recent years, there has been an increasing interest in the research and development of high-altitude airships. These systems provide a suspended platform using buoyancy at 17–25 km altitude. They have an enormous yet untapped potential for telecommunication, broadcasting relays, regional navigation, scientific exploration, and many other potential applications in an affordable fashion. Consequently, a large volume of literature has emerged covering the various aspects of design and development. This paper presents a state-of-the-art review of research and development in high-altitude airships. It covers the critical area, e.g., worldwide involvement, shape optimization, thermal analysis, design studies, etc. Realistic prediction of thermal behavior is essential to determine its effect on energy generation and altitude control. The paper discusses the various thermal investigations and numerical modeling approaches to study thermal performance. The envelope is the largest entity and directly contributes to the drag, hence energy demand. The energy generated also depends on the layout of the solar array. Therefore, aerodynamic shape optimization and solar array layout optimization are also studied. The efficiency of the solar array degrades as the temperature rises. The thermal model must be coupled to the design technique to compensate for the power loss. Therefore, various design optimization methods are critically analyzed with and without thermal consideration. Thermal behavior has been captured well in the existing literature through analytic, numerical, and machine-learning techniques. However, more experimental investigations are needed to validate these studies under generic conditions. The developed design techniques can design and optimize the airships conceptually only. Therefore, a comprehensive method must be developed based on a robust MDO framework. The paper highlights the challenges in designing and developing these systems and research gaps for future investigations.