Stability Analysis of an Inflatable Vacuum Chamber.pdf

Stability Analysis of an Inflatable Vacuum Chamber Stability Analysis of an Inflatable Vacuum Chamber Sean A. Barton 5 Department of Physics, Florida State University, Tallahassee, FL 32306 Abstract 10 A light-weight inflatable tensioned-membrane-structure vacuum container is proposed and its stability is analyzed. The proposed structure consists of a pressurized lobed cylindrical wall surrounding a central evacuated space. Stability is analyzed by discretizing the system and diagonalizing the second derivative of the potential energy. The structure is found to be stable 15 when the pressure in the wall is greater than a critical pressure. When membranes are non- elastic, the critical pressure is found to be greater than the pressure required for equilibrium by a factor of 4/3. When membranes have only finite stiffness, a first order correction to the critical pressure is found. Preliminary experimental data shows that a stable structure can be made in this way, and that the observed critical pressure is consistent with theory. It is also found that 20 such structures can be designed to have net positive buoyancy in air. Introduction A structurally stable vacuum container that is of minimal total mass for a given evacuated 25 volume might have applications in airship design (buoyancy control) [1], aerospace (low aerodynamic drag magnetic levitation launch systems) [2], industry (large industrial vacuum chambers), transportation (supersonic maglev trains) [2], and solar energy production (solar chimney technology) [3]. Unfortunately, issues of structural stability are often overwhelming in the design of such a structure. 30 The history of lightweight vacuum containers is somewhat disconnected. Von