Quasi-static numerical simulation of the dynamic launching process for high-altitude balloon

Abstract In this paper, by establishing a set of mathematical models and computing methods, the numerical simulation of the ground dynamic launching process under the quasi-static assumption for a high-altitude balloon system is conducted to reveal the rich mechanical and geometric behaviors involved in it. The mathematical model includes the solution of the bubble shapes and the kinematic analysis, as well as the static model of the “membrane bundle system”. Considering the middle and lower region of the bubble still meet the zero circumferential stress condition under the hydrostatic pressure gradient, the upper fully expanded shape generatrix is the same as the balloon generatrix of the ceiling height. The multiple shooting method combined with Sequential Quadratic Programming (SQP) is used to solve the lower partially expanded bubble generatrix. Based on the force balance equations of the microelement in “membrane bundle system”, and considering the friction force in contact with the horizontal ground and the characteristics that the membrane bundle is a variable mass system along the arc length direction, the “multiple shooting method + SQP” method is still used to solve the shape and internal force of the “membrane bundle system” under two end geometric boundary conditions. In co-simulation, taking the dynamic launching process of the zero-pressure balloon system with the ceiling flight height of 30 km and hanging a load of 300 kg as the object, under the conditions of 1.5 m/s and 4.5 m/s wind speeds, the initial layout and the rising process of dynamic launching is calculated. Through the analyses of the simulation results, four stages of the rising process are concluded, namely, the stage of the “membrane bundle system” relaxation and falling to the ground, the longitudinal rising stage, the main rising stage, and the straightening stage. The geometry and force characteristics of the bubble and the “membrane bundle system” are discussed to provide a reference for the simulation of the actual high-altitude balloon ground dynamic launching testing.