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Research Papers

Stability Analysis of an Inflatable Vacuum Chamber

[+] Author and Article Information
Sean A. Barton

Department of Physics, Florida State University, Tallahassee, FL 32306

J. Appl. Mech 75(4), 041010 (May 14, 2008) (8 pages) doi:10.1115/1.2912742 History: Received February 16, 2007; Revised November 26, 2007; Published May 14, 2008

A lightweight “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 when the pressure in the wall is greater than a critical pressure. When membranes are nonelastic, the critical pressure is found to be greater than the pressure required for equilibrium by a factor of 43. When membranes have only finite stiffness, a first-order correction to the critical pressure is found. Preliminary experimental data show 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 such structures can be designed to have net positive buoyancy in air.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

General cross section of the proposed structure. The wall of the structure is composed of membranes under tension (solid lines) containing pressurized gas (heavily hatched area). The wall encloses the evacuated space at the center (unhatched area) isolating that space from the ambient pressure (lightly hatched area). Runit, R¯, and N are the inner radius, outer radius, and number of sections, respectively.

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Figure 2

Definition of the 4N degrees of freedom of the structure xni

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Figure 3

One “unit cell” of the idealized model of the system showing the pretension c, the spring constant γ, the effective pretensions a and b, the effective spring constants α and β, and pressures in bold type

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Figure 4

Subsystem for illustrating the meaning of effective tension

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Figure 5

Linear combination of k=2 mode and k=N−2 mode

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Figure 6

Experimental model of the inflatable vacuum chamber

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Figure 7

Three possible modifications of the structure of Fig. 1

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