Description of the payload

The objective of the experiment was to transport to the stratosphere during 24 hours each two similar gondolas containing emulsion plates to track the path of particles nuclei created by the collision of cosmic rays with them.

The emulsion plates in each gondola was composed by a stack of 500 special photographic emulsions made by a London (England) firm, measuring 18 x 24 inches, conforming a block weighting near 400 kg. When cosmic rays strike the fine-grain emulsions, they leave microscopic trails, or marks as fingerprints of known or new particles. The collisions can also indicate much about the cosmic ray which created the explosion.

The block was contained in a sealed cilindrical shape gondola made of aluminum, measuring 7 ft long and 3 ft of diameter with a total -full loaded- weight of 800 kgs. At right can be seen one of the gondolas after being recovered from the sea (click to enlarge).

The cost of the entire project was $ 625.000 of which near $ 100.000 was of the emulsions cost alone.

The best place to launch the huge balloons needed for the task was the deck of the USS Valley Forge an aircraft carrier, which sailing with the prevailing winds in open sea, generated an artificial "no wind" condition to allow the vertical inflation and launch of the balloons. Also, during the previous months the Navy made several rehearsals to train their personnel on the recovery efforts, using a full scale mockup of the gondola which was released by a helicopter over Lake Michigan and recovered from the lake surface.

The place choosen for the launches was the Caribeean sea in central America near the Lesser Antilles at the end of January 1960. The timing of the launchings was of especial significance, because France had announced plans to conduct a nuclear test in the Sahara Desert in the same month. Radiation from such an event would have fogged the emulsion sheets to be sent aloft.

Once recovered, one of the emulsion blocks was meant to be analyzed entirely in the University of Chicago, and the other would be divided among US Universities like Minnesota, Winsconsin, Rochester, Washington, California and Tenessee and research groups from Canada, England, France, Italy, Switzerland, Brasil, India and Japan. Nevertheless, the failure of one of the flights of the campaign left one block unexposed. Apparently it was flown during a later campaign carried out the same year at the Glynco Naval Air Station, in Georgia. This later fact will be confirmed in the near future.

As a side product of the scientific campaign, as the information available about the high altitude wind behaviour in the region was poor, the United States Weather Bureau developed in paralel a balloon sounding campaign using several stations in different nations of the region to send weather-balloons and Skyhook-type balloons to obtain this data.

Details of the balloon flight and scientific outcome

Launch site: USS Valley Forge (CV-45)  
Balloon launched by: Winzen
Balloon manufacturer/size/composition: Zero Pressure Balloon Winzen - 280.000 m3
Balloon serial number: 290.75-100x100-V-3
Flight identification number: WRI 859
Payload weight: 800 kgs
Gondola weight: 800 kgs

The balloon, nicknamed "Skyhook Bravo" was launched on 26 january 1960, from the deck of the USS Valley Forge by vertical method.

It rose without mishap to 116,000 feet but unexpectedly strong winds in the upper stratosphere drove the balloon southwestward too fast. To avoid the risk of losing the gondola in the Venezuelan jungle, it was cut down over the sea about 400 miles off the South American coast, where it was retrieved by a destroyer the next day.

This was the first flight of the ICEF effort. The payload in this flight achieved 5 hours of exposure so it was reflown four days later.

External references and bibliographical sources

Images of the mission