Purpose of the flight and payload description
Project COLDTROP was a series of balloon test flights performed by the National Center for Atmospheric Research (NCAR) in the Panama Canal Zone, as part of the preparations for the 1965 IQSY-EQEX (International Quiet Sun Year - Equator Expedition) balloon campaign in India.
The IQSY-EQEX program required balloons of approximately 3 million cubic feet in volume to lift 325-lb payloads to altitudes of 120,000 ft or higher for periods up to 12 hr. Experience in flying balloons of this size range in the United States showed at the time that the majority of balloon failures occured during ascent in the region of 40,000 to 60,000 ft, the region of very low temperatures. The chances of ascent failure appeared to increase as the temperature decreased.
Since the tropopause temperatures encountered near the equator are considerably lower than those found over middle latitudes, and in view of the continuing difficulties experienced with ascent failures, the NCAR Scientific Balloon Facility decided to test balloons of standard polyethylene and a then new film trade named "StratoFilm" manufactured by Winzen Research, Inc., under meteorological conditions similar to those in India. The manufacturer claimed that StratoFilm was considerably less brittle at low temperatures than the standard polyethylene being used in balloons at that time.
With the assistance of the Office of Naval Research, arrangements were made with the U.S. Army Tropic Test Center, at Fort Clayton, in the Panama Canal Zone, for operational support of a test program there. A series of eight flights were conducted by NCAR during August 1964. Four flights were made with 3 million cubic feet tailored, tapeless, polyethylene balloons which then was one of the most consistently successful balloon designs. Another four flights were made with 2.94 million cubic feet natural shape tailored, taped balloons constructed of Winzen's StratoFilm.
Flight tests conducted with the standard balloons were poor. Only one of four balloons of this type successfully penetrated the tropopause, and this flight occurred at a time when the tropopause temperature was the warmest of the nine-day period of the campaign. On the other hand, the StratoFilm balloons had two successful flights and two ground failures. Both failures were caused by manufacturing deficiences. As a result of the Project Coldtrop test findings, NCAR contracted with Winzen Research, Inc. for construction of 2.94 million cubic feet balloons made from StratoFilm for use in the IQSY-EQEX expedition. The contract called for 100 per cent factory inspection and about 20 changes in specifications of the balloons flown during Project Coldtrop. These changes were aimed at increased balloon reliability.
Details of the balloon flight
Balloon launched on: 8/13/1964
Launch site: Fort Clayton, Channel Zone, Panama
Balloon launched by: National Center for Atmospheric Research (NCAR)
Balloon manufacturer/size/composition: Zero Pressure Balloon Raven 3.000.000 cuft (Polyethilene 0.75 mil)
Flight identification number: N-16
End of flight (L for landing time, W for last contact, otherwise termination time): 8/13/1964
Payload weight: 325 lbs
Balloon burst at 14.9 km