Flight 92: Released from Alamogordo, New Mexico, 0911 MST, August 31, 1948
Recovered at Ft. Stockton, Texas
On this flight an automatic ballast valve (with ballast meter) was used to support a 20-foot, .001" polyethylene balloon. The automatic ballast valve operated properly for about six hours, and 3000 grams of ballast was exhausted soon after sunset. In this case (Figure 41) the floating level of the
[figure]
Figure 41
balloon was not seriously affected by sunset as was the case in Flight 90, since the balloon had already descended to the activation level of the automatic ballast valve. This descent followed about three hours of relatively stable flight during which time no ballast was released. The 5000-foot descent represents the delay in operation caused by the activation of the aneroid capsule by a minimum-pressure switch, added to the lag of the aneroid itself. Following the initial activation at about 38,500 feet, small oscillations were introduced into the flight pattern by the action of the automatic ballast valve.
Flight 92 provides a good example of the control of a balloon's altitude by the use of a pressure-set automatic ballast valve. In such a flight there is no tendency to rise to higher and higher levels. The adulteration of the lifting gas with air reduces the buoyancy of the balloon, and through the ballast-valve control, the load is diminished to the same extent so that equilibrium is maintained at the activation pressure of the automatic ballast valve's aneroid. In this flight the altitude constancy achieved was the best of all flights made to date. For seven hours and 35 minutes this balloon was held within 1000 feet at 38,000 feet MSL. (At this altitude 1000 feet corresponds to a pressure difference of 10 millibars.)
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