Manhigh II gondola.
Project Manhigh was an experimental program begun in December 1955 to study the behavior of a balloon in an environment above 99% of Earth's atmosphere and to investigate cosmic rays and their effects on human beings. Three balloon flights to the edge of space were made during the program:
Manhigh 1 to 29,500 meters, by Captain Joseph Kittinger on June 2, 1957
Manhigh 2 to 30,900 meters, by Major David Simons on August 19-20, 1957
Manhigh 3 to 29,900 meters by Lieutenant Clifton McClure on October 8, 1958.
Including pilot and scientific equipment, the total mass of the Manhigh 2 gondola was 748 kilograms. At maximum altitude, the balloon expanded to a diameter of 60 meters with a volume of over 85,000 cubic meters.