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.

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.

Civilian projects by Osoaviakhim and the national Meteorology Committee were delayed by lack of finance, and in the first half 1933 the military stratospheric program had a solid lead in time.

[1] Gas envelope of USSR-1 was of conventional design, differing from low-altitude balloons only in its size (24,500 cubic meters at stratospheric altitudes).

It employed around five thousand meters[ambiguous] of thin fabric made in Noginsk that what impregnated with 25 layers of latex-based sealant[1] and sewn into the desired shape at a rubber factory in Khamovniki.

The landing basket, like the crumple zones of modern automobiles, was designed and tested to collapse at impact speeds exceeding 5 meters per second.

Life support consisted of pressurized oxygen tanks and chemical carbon dioxide absorption packages; all crew members carried personal parachutes.

[1] At 16:36 (8,000 meters) Prokofiev stopped recording flight data and concentrated on airspeed control; around 17:00 the aircraft softly landed on a field near the town of Kolomna, around 110 kilometers from the launch site.

[10] Fully half the 80,000 population of Kolomna, carefully primed by Dictator Stalin's propagandists to witness a great scientific conquest by their nation, poured across the Moscow River to greet the aeronauts.

Pilot George Prokofiev mounted the gondola, harangued the crowd with a lecture in which he credited the flight's success entirely to the Proletarian Revolution and the Communist Party.

While the USSR-1 gondola was deliberately designed for safety, in case of the catastrophic failure of the balloon the crew had to bail out on personal parachutes.

[4] The USSR-1 Bis with military pilots Christian Zille (flight commander), Yury Prilutsky (co-pilot) and professor Alexander Verigo as an on-board researcher lifted off from Kuntsevo at 05:25, June 26, 1935.

A brief stay at this level was terminated by an unexpected descent, probably caused by losing hydrogen through a faulty valve; soon, under 15,000 meters, vertical speed passed the safety limits, threatening to destroy the USSR-1 Bis in an Osoaviakhim-1-like crash dive.