'RDS-37' on 22 November 1955 - the Soviet Union's first thermonuclear test

22 November 1955 - RDS-37

Andrei Dmitrievich Sakharov invented the Soviet thermonuclear bomb.

On 22 November 1955, the Soviet Union conducted its first hydrogen bomb test, code-named RDS-37, at the Semipalatinsk  Test Site in modern day Kazakhstan. RDS-37 was the first Soviet two-stage thermonuclear weapon test. The Soviet Union had already proclaimed a previous test as thermonuclear, the RDS-6 test on 12 August 1953, which was actually an enhanced fission bomb.

The RDS-37 design was commonly known as Sakharov’s “Third Idea” named after the Soviet nuclear physicist Andrei Dmitrievich Sakharov. The U.S. equivalent is the Teller-Ulam design.

RDS-37 was the first bomb of its kind to be air-dropped, detonating at an altitude of 1,550 metres. The Soviet Union thus held the monopoly for deployable thermonuclear weapons for half a year until the United States drew level with the Cherokee nuclear test on 20 May 1956. In the 1950s, both countries conducted more large-yield atmospheric tests than ever before or afterwards, leading to a significant rise in global radiation levels and increased political tension.

The weapon's nominal yield of 3 megatons was scaled down to 1.45 megatons for the live test.

The yield of RDS-37 had been downscaled from 3 to 1.45 megatons for the purpose of the test. The actual yield was reported to be 1.6 megatons. The bomb, however, exploded underneath a thermal inversion layer (a layer of warm air on top of colder air), which unexpectedly focused much of the shock wave’s energy back towards the ground. This caused a building in a nearby village to collapse, killing one child. Forty-two people were injured by glass fragments. A trench collapsed onto soldiers observing the detonation at 36 km from ground zero, killing one and injuring five others.

The bomb was air-dropped from a Tupolev-16 bomber.

The Soviet Union conducted a total of 456 tests at Semipalatinsk in modern day Kazakhstan, the main Soviet testing site from 1949 to 1989. The area affected by these explosions was 300,000 square kilometres wide and inhabited by about 1.5 million people. It was only after the dissolution of the Soviet Union that the harmful effects of radiation on the people and the environment became publicly known. Above-average cancer rates and birth defects continue to affect the local population even in the third generation.

The Semipalatinsk Test Site was closed on 29 August 1991 by the newly founded Republic of Kazakhstan. The date was a symbolic choice as the Soviet Union had conducted its first nuclear test there on 29 August 1949. This date was also declared the International Day against Nuclear Tests by the UN General Assembly at the initiative of Kazakhstan, which hosted the International Forum for a Nuclear-Weapon-Free World in commemoration of the 20th anniversary of the closure of the Semipalatinsk Test Site in October 2011.