W56

Missile warheadUnited StatesThermonuclear (staged)

No freely licensed photo of this device yet.

Yield · TNT equivalent1.2 Mt

Key specs

Country: United States
Design: Thermonuclear (staged)
Type: Missile warhead
Weight: 270 kg
Length: 1.2 m
Diameter: 440 mm
In service: 1963–1993
Number built: 1,000

Overview

A 1.2 Mt warhead for the Minuteman I and II intercontinental ballistic missiles, about 1,000 built. With a yield of nearly 4.4 Mt per tonne it was one of the most efficient US designs.

Effect radii: estimates

Calculated for 1.2 Mt

Fireball, maximum radius: ≈ 1 km
Initial radiation, 500 rem (5 Sv): ≈ 3.2 km
Blast 5 psi: most buildings collapse: ≈ 7.5 km
Thermal: third-degree burns: ≈ 12 km
Blast 1 psi: windows shatter: ≈ 23 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

Sources

Complete List of All U.S. Nuclear Weapons, Nuclear Weapon Archive (Carey Sublette)
W56, Wikipedia