Accession Number : AD1051601


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


Descriptive Note : Technical Report,01 Sep 2015,31 Mar 2017


Corporate Author : Air Force Institute of Technology WPAFB United States


Personal Author(s) : Schwemmer,Joseph R


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/1051601.pdf


Report Date : 23 Mar 2017


Pagination or Media Count : 100


Abstract : 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. Its a novel approach; however, the vacuum presents challenges for the vehicles 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 the loading conditions. Finite-element analysis (FEA) and direct-search methods are employed, providing an optimal design under various regimes. Specically, ABAQUS Ris used as a FEA modeler, and mesh-adaptive direct search (MADS) is the optimization procedure. The goal of this research is to reduce the diameter of the vehicle using optimization techniques to a goal size of 31 inches (0.7874 meters). The smallest design to date has 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 a number of designs are presented and compared.


Descriptors :   mathematical models , operations research , carbon nanotubes , multiobjective optimization , linear programming , computational fluid dynamics , high performance computing , aircrafts , convex programming , algorithms , Vacuum


Subject Categories : Aircraft


Distribution Statement : APPROVED FOR PUBLIC RELEASE