Multi-Disciplinary Design Optimization of Unconventional Airship Configurations with Heuristic Algorithms

This paper describes the Multi Disciplinary Optimization of an airship with unconventional configuration. The shape of the airship is based upon two semi-ellipsoids, whose axis ratios can be altered for optimization purpose. The parameters to optimize are: volume, ratio between longitudinal and lateral semi-axis, ratio between vertical and lateral semi-axis, percentage of the top surface covered by photovoltaic films, dimension of the tail. The goals of the optimization are: equilibrium between buoyancy and weight, reaching of the design speed, static longitudinal stability of the vehicle. The mathematical model developed to evaluate airship features includes the computation of the ballonet volume, a weight breakdown, the energy storage for night operations, the power system evaluation and stability considerations. Six heuristic optimization strategies have been applied in order to achieve the best solution; some case studies have been developed and the final optimal configurations found by algorithms have been analyzed in order to validate the optimization framework. The approach demonstrate that the heuristic optimization strategies used are good tool for the conceptual design of unconventional airship since this problem requires a multi-disciplinary approach and several parameters including aerodynamics, propulsion, mass breakdown, aerostatics and stability, which are strongly dependent each other, must be jointly considered and addressed at the same time to obtain an optimum and balanced design.