USSR-1

USSR-1
USSR-1 over Moscow Kremlin on a 1933 postage stamp (Scott C37).
Here the balloon is shown in low altitude configuration; in stratosphere the envelope expanded into a nearly perfect sphere. The balloon did not pass over the Kremlin directly, but it was clearly in sight for the first few hours of the flight.
Role Stratospheric research Helium balloon
National origin Soviet Union
Manufacturer First Airship Division
Number built 1
Developed from Osoaviakhim-1

USSR-1 (Russian: СССР-1) was a record-setting, hydrogen-filled Soviet Air Forces high-altitude balloon designed to seat a crew of three and perform scientific studies of the Earth's stratosphere. On September 30, 1933, USSR-1 under Georgy Prokofiev's command set an unofficial world altitude record of 18,501 m (60,699 ft).

After the crash of Osoaviakhim-1 in January 1934 USSR-1 was retrofitted with a gondola parachute and a new gas envelope. June 26, 1935 it flew again as USSR-1 Bis. The balloon reached 16,000 meters where an accidental release of hydrogen, probably caused by a faulty valve, forced it into an unexpected descent. After expending all available ballast, two crew members bailed out on personal parachutes at low altitudes; the flight commander stayed on board and managed to perform a soft landing.