The principle was to make the air stored in the volume surrounded by the hull, not to store the air in between the hull cases. One of the major costs in storin

The principle was to make the air stored in the volume surrounded by the hull, not to store the air in between the hull cases. One of the major costs in storing air at high pressures is the impact shell. This can be merged with a thick hull, which are already designed with this purpose in mind. True, there are other alternatives. One can have a heavy fuel and a much larger hull. But if the fuel and tank and hull combo are buoyant you minimize the required material, lowering cost.