RDS-1

50°26′15″N 77°48′51″E / 50.43750°N 77.81417°E / 50.43750; 77.81417

RDS-1
The first Soviet atomic bomb, "RDS-1", was an implosion-type, like the U.S. "Fat Man" bomb, even in appearance; the front "eyes" are radar fuzes.
Type	Nuclear weapon
Place of origin	Soviet Union
Specifications
Mass	4.6 tons
Blast yield	21 kt (88 TJ)

The RDS-1 (Russian: РДС-1), also known as Izdeliye 501 (device 501) and First Lightning (Russian: Пе́рвая мо́лния, tr. Pyérvaya mólniya, IPA: [ˈpʲervəjə ˈmolnʲɪjə]),^[1] was the nuclear bomb used in the Soviet Union's first nuclear weapon test. The United States assigned it the code-name Joe-1, in reference to Joseph Stalin. It was detonated on 29 August 1949 at 7:00 a.m.,^[2] at the Semipalatinsk Test Site, Kazakh SSR,^[3] after top-secret research and development as part of the Soviet atomic bomb project.^{[citation needed]}