maintenance of the purity of the lifting gas, this balloon floated in a region of very low pressure, thus reducing the loss of buoyancy by diffusion.
Figure 30: Aluminum battens for balloon appendix
A third factor contributing to the long flight was the heat gained by adiabatic compression of the helium during descent. In the temperature in- version of the stratosphere this adiabatic heating would add to the buoyancy by superheating the lifting gas.
From this flight it becomes apparent that the control required to maintain buoyancy at high levels is much smaller than that at low levels. On the next day, before Flight 75 had ended, a second 70-foot balloon was flown with standard automatic ballast controls, and this flight was never recovered. Presumably the marked easterly flow then observed above 60,000 feet carried this second flight into the Pacific Ocean.
Radar, RDF and theodolite were used to track the balloon.