d. Methods of Attack
(1) After a survey of available literature in aerostatics and after conferences with various balloon manufacturers and authorities it is believed that the basic problem of maintaining the 15 lbs. of payload at constant altitude can best be solved by using a non-extensible balloon and a device operated by pressure which drops ballast whenever the balloon descends below a preset altitude.
The specifications for the equipment are as follows:
The balloon should be of large known volume, light in weight, non-extensible, either transparent or highly reflective to solar radiation. Rigging should be used to distribute the load evenly about the balloon.
A safety valve should be used to hold the inflation appendix of the balloon normally closed (as any hydrogen lost decreases the time possible at nominal constant altitude). The valve would act as a safety vent if the balloon should rise appreciably above the altitude where it is fully inflated, as there is danger of rupturing the envelope unless the excess pressure is relieved. The safety valve should be set to release pressure before the limit of the working stress of the balloon fabric is reached.
If the exact volume of the balloon is known and the air density vs. altitude relationship is determined on the day of flight, it is possible to compute the total lift of the gas in the balloon at any altitude. By adjusting the gross load to be supported by the gas to equal the total lift at the desired altitude of flight, the balloon will level off at the desired
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