Date of Award

3-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Aeronautics and Astronautics

First Advisor

Anthony N. Palazotto, PhD

Abstract

Lighter-than-air (LTA) systems have been developed for numerous applications and have taken several forms. Airships, aerostats, blimps, and balloons are all part of this family of systems, which uses Archimedes principle to achieve neutral and positive buoyancy in air by replacing an air volume with LTA gases. These lifting gases stiffen the otherwise compliant envelope structures, allowing them to sustain the pressure difference brought by the displaced air. The compliance of these structures is a byproduct of the weight requirement, materials and geometrical arrangement of which these structures are built from, typically resulting in dimensionalities that exhibit low or virtually non-existent in-plane bending stiffness. The former has constrained the development of LTA structures that utilize an internal partial vacuum, rather than a lifting gas, to achieve positive buoyancy, where the structure would be subjected to a pressure differential near atmospheric pressure. Given the above limitation, this research presents the development trajectory and structural characterization of air stiffened designs, which utilize air to shape and serve as the core of a set of enclosing envelopes. The development trajectory established a simulation framework that enables the structural characterization of air-stiffened designs under a variety of geometric and loading conditions. Such framework allowed for the development of finite element solutions that included geometric, fluid-structure and contact nonlinearities, with capacity for further generalization. Given the developed framework, the structural characterization of the Helical Sphere and Icoron air-stiffened designs demonstrated a reduction of material modulus and strength requirements compared to membrane-over-frame designs, and showed the capability of air-stiffened designs to be tailored for specific material strength limits.

AFIT Designator

AFIT-ENY-DS-21-M-285

DTIC Accession Number

AD1127564

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