A Computer Program for Calculating Tetroon Inflation-Factor Nomographs

Abstract

A slow but steady increase in the use of tetroons for tracing atmospheric air trajectories has prompted the development of an automatic method for calculating accurate tetroon inflation factors to float tetroons at desired elevations. The inflation factors are then used in nomograph form. Gross errors in tetroon flight altitude and premature loss of the tetroon package can result from use of inaccurate surface-free lift and surface superpressure, the required inflation factors. Therefore, a quick and easy method is described for obtaining these inflation factors by means of a computer program. The inflation-factor nomograph constructed from these factors allows rapid ?computation? of the specific factors required for inflating a tetroon to fly at a selected altitude for a given set of ambient atmospheric conditions. The only input arguments needed to use the nomograph are the existing inflation-shelter and existing or predicted flight-level temperatures. Use of the nomograph in the field obviates the need for a calculator, saves much time in determining inflation factors and greatly reduces errors since no arithmetic is used. With this program, the experimenter can design inflation-factor nomographs specifically for the location and season of the experiment, and for the size of tetroon being used, without needing to understand tetroon inflation theory. An illustrative example of the computation of a set of tetroon inflation factors and the construction of an inflation-factor nomograph is given. This system requires that the tetroon maintain superpressure at all times and elevations. The film stress versus volume relationship and the film stress at which volume creep begins are given for the nominal 1 m3 tetroon. Volume creep rates at specified high stress values also are shown.