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

the balloon can rise slowly until the balloon is again full and the equilibrium is again reached between the buoyancy and the load. In the General Mills 20-foot balloon, for example, diffusion losses equal about 300 grams per hour; the balloon at its ceiling of 50,000 feet, with a 30-pound payload, risea about 900 feet with each kilogram of ballast dropped. This means that a balloon, using the simple ballast-dropping technique, will float at a ceiling which rises at the rate of about 360 feet per hour. An idealized flight of this type is shown in the solid curve of Fig. 7., neglecting the oscillation shown at sunset.

The "manual ballast valve" which was developed for this simple control system is shown in Fig. 8. This valve can be adjusted prior to balloon release to allow any predetermined flow of compass fluid up to 2000 grams per hour. The filter housing and ballast reservoir used with this valve are shown in Figures 9 and 10. This method is good where 1) a slowly rising ceiling can be tolerated, and 2) the flight does not have to go through a sunset while at its ceiling.

For economy of ballast, hence longer flight duration, it is desirable to keep the constant flow as close as possible to the total loss of buoyancy resulting from diffusion and leakage. This means that whenever rapid loss of buoyancy occurs, due to changes in solar radiation, the manual ballast valve alone will not sustain the balloon. When the balloon is suddenly cooled, due to sunset or clouds cutting off insoilation (loss of superheat), the heavy loss will start the balloon downward and only a rapid expenditure of ballast will check its fall and restore its stability.

The second type of ballast dropping control has been devised to operate on a demand basis, when such a descent occurs. This control is called the automatic ballast valve. Figures 11, 12 and 13 show the appearance and design of this pressure-actuated needle valve.