RDS-4 (also known as Tatyana) was a Soviet nuclear bomb that was first tested at Semipalatinsk Test Site, on August 23, 1953. The device weighed approximately 1200 kg (2646 lb). The device was approximately one-third the size of the RDS-3. The bomb was dropped from an IL-28 aircraft at an altitude of 11 km and exploded at 600 m, with a yield of 28 kt.
|Test site||Semipalatinsk Test Site, Kazakh SSR|
|Number of tests||1|
|Test type||Atmospheric Test|
|Max. yield||Total yield 28 kilotons of TNT (120 TJ)|
The Soviet Union's first mass-produced tactical nuclear weapon was based on the RDS-4 and remained in service until 1966. It used a composite core of 4.2kg Pu-239 and 6.8kg 90% enriched U-235  and had a nominal yield of 30 kilotons. The bomb was delivered from a Tu-4 and Tu-16 aircraft. A tactical weapon based on the RDS-4 was also used on September 14, 1954 during Snowball military exercise near Totskoye (similar to Western Desert Rock exercises), when the bomb was dropped by the Tu-4 bomber (the reverse-engineered Boeing B-29). The purpose of this exercise was not to test the bomb itself, but the ability of using it while breaking through enemy defenses (presumably in West Germany). After the explosion Soviet jet fighters were sent to fly through the mushroom cloud while tanks and infantry were forced to move through ground zero.
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