The BOK-1 (''Byuro Osobykh Konstrooktsiy'' - bureau of special design), (a.k.a. SS (''Stratosfernii Samolyet'' – stratospheric aircraft)), was an experimental high-altitude aircraft designed and built in the

USSR The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen nation ...

from 1934.

Development

The BOK was formed as part of

TsAGI The Central Aerohydrodynamic Institute (also (Zhukovsky) Central Institute of Aerodynamics, russian: Центра́льный аэрогидродинами́ческий институ́т, ЦАГИ, Tsentral'nyy Aerogidrodinamicheskiy Institut, ...

(''Tsentrahl'nyy Aerodinamicheskiy i Ghidrodinamicheskiy Institoot''- central aerodynamics and hydrodynamics institute) on the orders of the Soviet Revolutionary Military Council in Dec 1930. One of the first tasks of BOK was to design and build the hermetically sealed gondola of the SSSR-1 high-altitude balloon. BOK engineers were sent to the

Junkers Junkers Flugzeug- und Motorenwerke AG (JFM, earlier JCO or JKO in World War I, English: Junkers Aircraft and Motor Works) more commonly Junkers , was a major German aircraft and aircraft engine manufacturer. It was founded there in Dessau, ...

factory at

Dessau Dessau is a town and former municipality in Germany at the confluence of the rivers Mulde and Elbe, in the '' Bundesland'' (Federal State) of Saxony-Anhalt. Since 1 July 2007, it has been part of the newly created municipality of Dessau-Ro� ...

to study the

Junkers Ju 49 The Junkers Ju 49 was a German aircraft designed to investigate high-altitude flight and the techniques of cabin pressurization. It was the world's second working pressurized aircraft, following the Engineering Division USD-9A which first flew ...

which was the first aircraft fitted with a sealed cabin for high-altitude flight. The gondola for the SSSR-1 was designed, built and flown successfully to an altitude of 18,000m in 1933. The BOK was then assigned the task of applying the 'hermetic' cabin to an aircraft with the

Tupolev RD The Tupolev ANT-25 was a Soviet long-range experimental aircraft which was also tried as a bomber. First constructed in 1933, it was used by the Soviet Union for a number of record-breaking flights. Development The ANT-25 was designed as the r ...

chosen as the basis of the BOK-1. A sealed 1.8 m³ cylindrical cabin constructed from D1 light alloy was fitted to a modified RD airframe. The cabin had convex bulkheads front and rear with the main entry hatch in the roof and emergency exit through a porthole at the re