The design and use of plastic balloons for stratospheric research in India

Abstract

Plastic balloon flying has been developed at the Tata Institute of Fundamental Research as a research technique which has a number of important applications in India: (a) cosmic ray studies; (b) air sampling in the stratosphere for fall-out measurements; (c) meteorological investigations; (d) astronomical observations; (e) defence research. Comparatively little work has been done till now in these fields at equatorial latitudes, particularly at stratospheric altitudes. Large plastic balloons with volumes of the order of half a million cubic feet, and more, have been constructed by heat welding polyethylene sheeting 0.0015 thick. With these balloons, successful level flights at altitudes of 110,000 ft. have been achieved; in some cases, individual loads weighing a hundred pounds have been carried up. The most serious problem encountered is the extremely low temperature(about-85DegreeC), of the tropopause at the equatorial latitudes; all known plastics for balloon manufacture become brittle at these low temperatures. To overcome this, dark fabrics have been employed so that the material is heated by solar radiation. The plastic sheeting employed is extruded in India to balloon specifications from chosen polymers. The low temperatures and the turbulent conditions that prevail in the atmosphere at low latitudes present problems in balloon flying which are different from those encountered at high latitudes present in balloon flying which are different from those encountered at high latitudes. The techniques employed, the design of the balloons, and their performance under these conditions are discussed.