We are always fascinated by a rising balloon into the atmosphere. Analysis of a rising balloon can be very complicated, due to wind drag forces, decreasing air pressure and density, changing air temperature, decreasing gravity, gas used in the balloon, balloon’s structural integrity, and so on. For every engineering problem we want to solve, we have to make reasonable simplifying assumptions and obtain approximate answers. In this analysis, let us assume that there are no wind drag forces on the balloon and a constant gravity all the way through the upper stratosphere, 50 km from the Earth’s surface. Let us also assume that the ideal gas law applies all the way through the upper stratosphere.