to activate the ballast valve. A fixed ballast leak of about 400 grams per hour was caused by a defective valve fitting and this was sufficient to maintain the balloon at nearly constant level until all the ballast was exhausted. Following this experience, the use of a preset fixed leak was employed on many flights.
The very unstable "floating" seen on Flight 10, when the automatic ballast valve controlled the flight, is not found on this flight where the vehicle used only a fixed-leak control. This eliminates both the overcompensation and the serious effects of temperature changes on the aneroid capsule, which are found when the automatic ballast valve is used.
The trajectory of this balloon (Figure 8) shows a very interesting deformation at the transit of the Sacramento Mountains. The anti-cyclonic
Figure 8
curvature over the eastern slope suggests that the air stream at the floating level was distributed by the terrain, and the deformation predicted by dynamic theory may thus be given a physical illustration. The trajectory was determined by aircraft and theodolite observation.
Another striking feature of the flight is the disagreement between the actual flight path and the trajectory which might have been estimated from routine upper-wind reports. Reports from El Paso, Roswell, Albuquerque and White Sands were used for comparison with the observed trajectory. Except for White Sands, none of these stations reported any wind from the WSW at or near the floating level during the 12-hour period covered by the flight. At White Sands a very shallow current was detected moving in the direction indicated by the balloon flight. This clearly demonstrates the non-representiveness of the ordinary pilot balloon observation.