Superpressure Balloon and Precise Pressure Radio-sonde System for the Research of Vertical Air-m otion

Abstract

For the purpose of studyin g airflows over mountain regions, we have developed a superpressure balloon and a precise pressure radiosonde system.
First of all we examined the physical properties of the polyester film made in our country to know whether the material is available for use in a stable horizontal floating balloon. The modulus of elasticity in M-direction was found to be (3∼6) × 10⁸ kg/m² at 15°C,and the total creep to be 5% per 10,000 psi (Table 1).These values are almost similar to those of the mylar film which has been used sofar by U.S. research groups (see Table 1).
The balloon we designed is about 1.7 m in diameter, made of films 50 microns thick. The sphere consists of 12 segments. The size was determined to meet the purposes of measuring airflows at a hight of about 2∼5 kms above m.s.l., with a payload of about 1 kg.
The changes of volume in the balloon thus constructed du e to the superpressure were measured and the results are shown in Fig. 2 on three samples of the balloon. We find that the rate of the volume change (ΔV/V₀ in %) is about 2% for a superpressure of 50 mb.
The rate of the volume change can also be estimated analytic a lly by eq. (7) and as for the balloon we made, which has a radius of 0.82 m, thickness of 50 microns and modulus of elasticity of (3∼6) × 10⁸ kg/m², we can get ΔV/V₀=0.02∼0.04 for a superpressure of 50 mb. Thus the observed and the calculated values of the rate of volume change may be said to coincide well. The solid lines in Fig. 2 show the calculated values.