Buoyancy and high altitude ballooning: the Red Bull Stratos mission
A detailed analysis of buoyancy in the context of Felix Baumgartner's historic jump from 39 km altitude as the culminating event of the Red Bull Stratos mission. Buoyancy was provided by a helium-filled balloon that made the equipment less dense overall from the surrounding air.
This article takes readers through the calculation of the density of the relevant gases (air and helium) and the net density of the ascent equipment. An error analysis shows that helium and air must have counter-diffused through the balloon wall and estimates the composition in the balloon. Also discussed are possible reasons for why the ascent equipment achieved a greater altitude than expected.