Project Manhigh
Project Manhigh was a pre–Space Age military project that took men in balloons to the middle layers of the stratosphere. It was conducted by the United States Air Force between 1955 and 1958.
The project started in December 1955 to study the effects of cosmic rays on humans. Three balloon flights to the stratosphere were made during the program:
With the pilot and the scientific payload, the Manhigh II gondola had a total mass of 748 kg (1,649 lb). At maximum altitude, the balloon expanded to a diameter of 60 m (200 ft) with a volume of over 85,000 m3 (111,000 cu yd).
A similar project in which a man in a gondola reached an altitude of 15,785 m (51,788 ft) was performed in 1931 by the Swiss physicist Auguste Piccard.
...
Wikipedia