Dynamic Performance of High-altitude Balloons during Ascent and Descent

The high-altitude balloon proposed in this study is a long-life balloon that suspends a pod through a cable and flies from the ground to an altitude of 20 km and back to the ground. The balloon can rise by natural expansion at zero pressure, but it needs to be inflated and maintain its shape to stay at any altitude or return to the ground. A pressure difference-based altitude control is achieved to realize transitions between different altitudes. The process of dynamic modeling and controller design is presented. The dynamic performance of the system, including the dynamics of the hanging pod coupled with the thermodynamics of the buoyancy body, is discussed. The internal thermodynamic model provides information on the pressure differential and volume variations of the balloon during the entire process. The hanging model calculates the maximum pull force that the cable can withstand. The attitude of the pod during the ascending and descending processes is depicted, which provides the basis for equipment loading. Simulation results show that controlling altitude through air mass exchange by blower flow control is feasible, and the overall system dynamics are stable. This research also provides basic knowledge for the design of pod suspension systems.