Optimal Design of a Hexakis Icosahedron Vacuum-Based Lighter-Than-Air Vehicle

摘要

Because of the rising cost and scarcity of helium, new methods to ensure buoyancy for lighter-than-air vehicles are being sought. One alternative under study uses an internal vacuum to reduce the weight-to-buoyancy ratio. It is a novel approach, but the vacuum presents challenges for the vehicle's structure. The structure must have minimum mass while preventing buckling and excess stress throughout the frame and membrane. The structure under analysis is a hexakis icosahedron with a membrane covering. Achieving minimum mass involves optimizing the structure under loading conditions. Finite element analysis and direct-search methods are employed, providing an optimal design under various regimes. Specifically, ABAQUS is used as the finite element analysis modeler, and mesh-adaptive direct search is the optimization scheme. Overall size is a concern, and so one objective is to reduce the diameter of the vehicle as much as possible, using materials available at this time. To date, the smallest design analyzed had a diameter of 20 ft (6.096 m). This research demonstrates the feasibility of two designs, one at 15 ft (4.572 m) and another at 4 ft (1.2192 m). The problem formulation includes multiple black-box objectives and constraints. Results for various designs investigated are presented and compared.