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

in high altitudes, since it freezes below -80 $ ^{\circ} \mathrm{C} $ and will flow readily at low temperatures. Also, this fluid will absorb only a very slight amount of water which might freeze aloft.

Basically three different principles have been used in the control of ballast flow. The first of these is calculated constant flow; the second is displacement-switch control; and the third is rate-of-ascent switch control.

## (1) Constant Flow

In the simplest of the control systems, liquid ballast is allowed to flow continuously through an orifice (Figure 8) at a predetermined rate. This rate is set to slightly exceed the expected loss of lift of the balloon due to leakage and diffusion. If this method is successfully used, the balloon stays full because the gas remaining in it has less load to support. Therefore, the balloon will rise slowly as ballast is dropped, maintaining equilibrium between the buoyancy and the load. In the General Mills 20-foot balloon, for example, diffusion losses are about 200 grams per hour at altitudes near 40,000 feet. The balloon at its ceiling of 40,000 feet with a 26-kilogram payload rises about 700 feet with each kilogram of ballast dropped. This means that such a balloon using this constant-flow type control will float at a "ceiling" which rises at the rate of about 140 feet per hour. Constant flow was first obtained by use of the manual ballast valve shown in Figure 9. Due to excessive clogging of this valve, caused by its annular ring opening, gate-type valves were tested, and finally the use of

Figure 8. Orifice for fixed-rate ballast flow.