Date of Award


Document Type


Degree Name

Master of Science


Department of Aeronautics and Astronautics

First Advisor

Anthony N. Palazotto, PhD.


Three designs for a Lighter Than Air (LTA) structure that achieve positive buoyancy using a vacuum in place of a lifting gas were proposed and evaluated. The ratio of structure weight to the weight of displaced air was termed Weight/Buoyant Force (W/B) where a W/B1 corresponds to positive buoyancy. Two methods of geometrically stiffening a sphere were investigated and their W/B evaluated. A thin shelled sphere of beryllium stiffened with an isogrid of blade type stiffeners using Ultra High Modulus (UHM) carbon epoxy was predicted to give a W/B= 0.79. A geodesic sphere composed of a frame of cylindrical, UHM, carbon epoxy, pultruded rods with a thin external membrane was evaluated using Finite Element Analysis. A W/B=0.57 was calculated for the frame. The skin was predicted to add 0.37 to the W/B if Zylon was used to reinforce a Mylar membrane, which resulted in a predicted structure W/B=0.94. These structures were optimized using a non-linear programming optimization routine in MATLAB. A unique LTA vehicle concept composed of twin counter-rotating cylinders that made use of a virtual elliptical body to reduce drag and maintain structural integrity with a vacuum was also investigated and found to be infeasible.

AFIT Designator


DTIC Accession Number