RDS-6s (Joe-4)

RDS-6s

Aircraft bombSoviet UnionLayered fission–fusion

No freely licensed photo of this device yet.

Yield · TNT equivalent400 kt

Key specs

Country: Soviet Union
Design: Layered fission–fusion
Type: Aircraft bomb

Overview

The first Soviet weapon to draw part of its energy from fusion, tested on 12 August 1953 at Semipalatinsk with a yield of 400 kt. Its "Sloika" (layer cake) design alternated layers of uranium-238 and lithium-6 deuteride around a fission core.

The layered scheme came from Andrei Sakharov and the use of lithium deuteride from Vitaly Ginzburg. Fusion supplied only about 15–20% of the yield and the design could not be scaled up to megatons, so it proved a dead end; two years later it was overtaken by the two-stage RDS-37. Unlike Ivy Mike, it was compact enough to be an aircraft bomb.

Effect radii: estimates

Calculated for 400 kt

Fireball, maximum radius: ≈ 670 m
Initial radiation, 500 rem (5 Sv): ≈ 2.6 km
Blast 5 psi: most buildings collapse: ≈ 5.2 km
Thermal: third-degree burns: ≈ 7.8 km
Blast 1 psi: windows shatter: ≈ 16 km

Estimated ground ranges for an air burst at the optimum height over flat, open ground, computed from the yield with standard scaling laws. These are not measurements: real effects depend on the height of burst, terrain, buildings and weather.

Formulas from: Glasstone & Dolan, The Effects of Nuclear Weapons (1977), chapter II; Carey Sublette, Nuclear Weapons FAQ, section 5

Tests and use

Date	Event	Site	Yield
Aug 12, 1953	Joe-4Tower shot of the first Soviet weapon with a fusion component.	Semipalatinsk Test Site, Kazakh SSR	400 kt

Sources

Soviet Nuclear Test Summary, Nuclear Weapon Archive (Carey Sublette)
Joe 4, Wikipedia