Real data-based thermal environment definition for the ascent phase of Polar-Summer Long Duration Balloon missions from Esrange (Sweden)

Abstract

Long Duration Balloon missions are key platforms for scientific research and space technology development. Thermal analyses of this kind of systems are crucial for the success of the mission. Even though the science is usually performed at float altitude, the ascent phase, usually non-operational, is where the extreme cold conditions occur, due to the convective effects caused by relative wind speed together with the low temperatures found in the tropopause, making this scenario a dimensioning case. In this paper, a thorough study of the thermal environmental conditions during the ascent is carried out, in particular winds, temperature, and radiative thermal loads have been obtained as a function of the altitude. The study is based on real data obtained from different sources, including atmospheric soundings, radar and satellite, and a meticulous statistical treatment. The study is focussed on one of the main stratospheric balloon launch sites in Europe, Esrange (Sweden), a center of the Swedish Space Corporation, and the analyses are performed for the summer period. However, the methodology can be extended to any other location and epoch. As an example, the convective effect of the horizontal winds on a plate has been studied, and the heat transfer during the ascent phase has been quantified. A subcooling of around 7 °C was found in this case, which make worth the dedicated analysis.