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W71

W71
Missile warheadUnited StatesThermonuclear (staged)
No freely licensed photo of this device yet.
Yield · TNT equivalent5 Mt

Key specs

Design
Thermonuclear (staged)
Type
Missile warhead
Weight
1.29 t
Length
2.57 m
Diameter
1.07 m
In service
1975
Number built
30

Overview

The 5 Mt warhead of the Spartan anti-ballistic missile, meant to destroy incoming warheads above the atmosphere mainly with X-rays. Its Cannikin test of 1971 on Amchitka was the largest US underground explosion; only 30 were built and the Safeguard system served just a few months in 1975.

Effect radii: estimates

Calculated for 5 Mt

Fireball, maximum radius
≈ 1.8 km
Initial radiation, 500 rem (5 Sv)
≈ 4.2 km
Blast 5 psi: most buildings collapse
≈ 12 km
Thermal: third-degree burns
≈ 22 km
Blast 1 psi: windows shatter
≈ 38 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

DateEventSiteYield
Nov 6, 1971CannikinAmchitka Island, Alaska, USA5 Mt

Sources

  1. Complete List of All U.S. Nuclear Weapons, Nuclear Weapon Archive (Carey Sublette)
  2. W71, Wikipedia