The Roswell Report: Fact vs. Fiction in the New Mexico Desert

sufficiently to cause a short between the electrodes, firing the squib prematurely. If the distance is too large, however, there will be too great a height difference between the time of minimum pressure and the time the electrodes are shorted. For instance, a spacing of 10 mm. would delay the firing of the squib until the pressure reached 13.3 mb. above the minimum pressure. At an altitude of 50,000 feet, the equivalent height (standard atmosphere) would be about 2300 feet. It is obvious that for high level flights, a less dense and lower freezing electrolyte for the minimum pressure switch will be needed to obtain the desired sensitivity of 2000 feet.

By adding the pressure-activated automatic ballast valve to the manual ballast valve, the complete pattern of the solid curve in Figure 7 may be achieved ideally. At sunset the rapid cooling causes descent which cannot be compensated for by the manual ballast valve. As soon as the seal-off pressure of the automatic ballast valve is exceeded by the atmospheric pressure, ballast flow is begun, which restores the balloon to its ceiling.

The dashed curve in Figure 7 shows the action of a balloon when the automatic ballast valve alone is used for control purposes. In this case the balloon will sink slowly from its ceiling (where full buoyancy just equals the load) to the level where the automatic ballast valve drops ballast at a rate equal to the diffusion (the floor). It will be noted that a flight which is controlled in this manner is less wasteful of ballast and results in a correspondingly longer flight. The "floor" determined by this valve varies diurnally as the temperature (hence pressure) of the air entrapped in the diaphragm is affected by solar radiation. The amplitude of this diurnal oscillation may be as much as 6000 feet, the night level being higher than the day level.