Optimal Design of a Hexakis Icosahedron Vacuum Based Lighter than Air Vehicle

摘要

Due to the rising cost and scarcity of helium, new methods to ensure buoyancy for lighter-than-air vehicles (LTAVs) are being sought. One alternative under study uses an internal vacuum to reduce the weight-to-buoyancy ratio. 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 (FEA) and direct-search methods are employed, providing an optimal design under various regimes. Specifically, ABAQUS ® is used as the FEA modeler, and mesh-adaptive direct search (MADS) is the optimization scheme. Overall size is a concern, 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 feet (6.096 meters). This research demonstrates the feasibility of two designs, one at 15 feet (4.572 meters) and another at 4 feet (1.2192 meters). The problem formulation includes multiple black-box objectives and constraints. Results for various designs investigated are presented and compared.