were to be freed at 40,000, 42,000 and 45,000 feet. The use of sand ballast, to be dropped in increments upon descent to altitudes below 31,000 feet, was supplemented by an early model of the automatic ballast valve set to expend liquid ballast at 34,000 feet.
From the height-time curve of the flight (Figure 2), it will be seen that the maximum altitude reached was much above the predicted 35,000 feet. Also
Figure 2
the rate of rise was greater than expected. Both of these evidences of excess buoyancy are attributed to superheating of the balloon by sunshine. The real height is somewhat in doubt because the conventional radiosonde baro switch (Army type ML-310/) was used, and the pressure signal which was transmitted was ambiguous at some points.
On this flight theodolite readings were taken until the balloon was 90 miles away from release point after 260 minutes of flight. In addition, visual observations were taken from a B-17 aircraft which circled the balloon for most of the flight.