Mk 18 “Super Oralloy Bomb”

Aircraft bombUnited StatesImplosion fission

No freely licensed photo of this device yet.

Yield · TNT equivalent500 kt

Key specs

Country: United States
Design: Implosion fission
Type: Aircraft bomb
Weight: 3.9 t
Length: 3.25 m
Diameter: 1.52 m
In service: 1953–1956
Number built: 90

Overview

The most powerful pure-fission bomb the United States ever built, using about 60 kg of highly enriched uranium. Its design was proved by the 500 kt Ivy King test in 1952, an interim weapon until hydrogen bombs arrived.

Effect radii: estimates

Calculated for 500 kt

Fireball, maximum radius: ≈ 730 m
Initial radiation, 500 rem (5 Sv): ≈ 2.7 km
Blast 5 psi: most buildings collapse: ≈ 5.6 km
Thermal: third-degree burns: ≈ 8.6 km
Blast 1 psi: windows shatter: ≈ 17 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
Nov 16, 1952	Ivy King	Enewetak Atoll, Marshall Islands	500 kt

Sources

Complete List of All U.S. Nuclear Weapons, Nuclear Weapon Archive (Carey Sublette)
Mark 18 nuclear bomb, Wikipedia