Improved Aerodynamic Calculations for High Altitude Scientific Research Balloons

Abstract

A high altitude scientific balloon is a flexible structure where the shape and stress are dependent on the pressure differential across the envelope. When a balloon is floating at a constant altitude, the pressure distribution over the envelope is given by the hydrostatic equation. However, when a balloon is climbing to its float altitude, the pressure distribution is also affected by the airflow over the balloon. Usual simple aerodynamic estimation methods are not applicable because the balloon is not a slender body. In previous studies, the balloon was represented by a distribution of sources located on the axis of symmetry. In this paper, improvements to this potential flow solution are introduced, and limitations of the method are examined. With results from the improved potential flow solution, a boundary-layer calculation has been programmed to provide separation point and skin friction estimates.