Castle Yankee
USA · 1954 · 13.5 megatons · thermonuclear (hydrogen bomb)
Overview
Second-largest US nuclear test.
With a yield of 13.5 megatons[1], the Castle Yankee is 900× more powerful than the Hiroshima bomb. As a thermonuclear (hydrogen bomb) weapon, it derives its energy from a fission explosion that ignites fusion fuel, releasing on average roughly equal energy from fission and fusion. [2]
Castle Yankee Blast Effects
The table below shows the calculated radius of each effect zone for an air burst at optimum height. Values are scaling laws from The Effects of Nuclear Weapons (Glasstone & Dolan, 1977) and the published effects scaling table[3, 4].
| Effect zone | Radius (air burst) |
|---|---|
| Fireball radius | 2.74 km |
| Severe blast (20 psi) | 5.63 km |
| Moderate blast (5 psi) | 14.9 km |
| Light blast (1 psi) | 41.1 km |
| 3rd-degree thermal burns | 32.7 km |
| 2nd-degree thermal burns | 38.2 km |
| 1st-degree thermal burns | 46.3 km |
All radii assume an air burst at optimum height and are 1-D ground-distance estimates from the detonation point. Real-world effects depend on terrain, weather, and building construction. Casualty and fallout estimates are not shown pending a verified population and fallout model.
Run the Castle Yankee on a City
Use the interactive simulator to detonate the Castle Yankee on any city worldwide. Click any location on the map to see the fireball, blast, and thermal radii (air burst at optimum height) overlaid on real geography.
🎯 Simulate Castle YankeeRelated Weapons
FAQ
How big is the Castle Yankee blast radius?
In an air burst at optimum height, the Castle Yankee produces a fireball roughly 2.74 km in radius and a 5 psi moderate-blast zone of about 14.9 km — the area in which most residential buildings would collapse. The 1 psi light-damage radius extends to roughly 41.1 km, where windows shatter.
What is the yield of the Castle Yankee?
The Castle Yankee has a yield of 13.5 megatons of TNT equivalent. That is 900× more powerful than the Hiroshima bomb.
Is the Castle Yankee bigger than the Hiroshima bomb?
The Hiroshima bomb (Little Boy) had a yield of approximately 15 kilotons. The Castle Yankee at 13.5 megatons is 900× more powerful than the Hiroshima bomb.[1]
What thermal burn radius does the Castle Yankee produce?
In an air burst at optimum height, thermal radiation from the Castle Yankee can cause 3rd-degree burns out to roughly 32.7 km, 2nd-degree burns to 38.2 km, and 1st-degree burns to 46.3 km.
Sources
- 1.Source: US DOE / NNSA Nevada Field Office, United States Nuclear Tests, July 1945 through September 1992 (DOE/NV-209 Rev. 16, Sep 2015), NNSS publication library — retrieved Oct 2026
- 2.Source: US DoD & ERDA (Glasstone & Dolan), via Atomic Archive, The Effects of Nuclear Weapons, 3rd ed. (1977), Chapter 1 — retrieved Oct 2026
- 3.Source: U.S. DoD / DOE (Glasstone & Dolan, via Atomic Archive), The Effects of Nuclear Weapons, 3rd ed. (1977) §2.127 — retrieved Oct 2026
- 4.Source: Wikipedia, Effects of nuclear explosions — scaling-law table — retrieved Oct 2026