cell with very low diffusion through the walls and one capable of maintaining super-pressure in excess of that lost with reductions of gas temperature. Such a balloon could be sealed off completely or a pressure-activated valve could be used to permit efflux of the gas when the bursting pressure is approached. The neoprene-coated nylon balloon built by Seyfang Laboratories (Figure 7) has been used with a valve set to prevent rupturing.
[figure]
Figure 7. Neoprene-coated nylon balloon, two-thirds inflated.
The fabric has been coated with a metallic paint to minimize the effects of radiation. However, the values of superheat obtained by the gas when the balloon is in the sun have been of the order of 30°C. The amount of buoyancy lost when circulation
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