RDS-4 was a Soviet nuclear bomb that was first tested at Semipalatinsk Test Site, on August 23, 1953. The device weighed approximately 1,200 kilograms (2,646 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 kilometres (7 mi) and exploded at 600 metres (1,969 ft), with a yield of 28 kt.