Orange Herald
UK · 1957 · 720 kilotons · boosted fission
Overview
Largest single-stage device ever tested (largest UK test: Grapple Y, about 3 Mt, 1958).
With a yield of 720 kilotons[1], the Orange Herald is 48× more powerful than the Hiroshima bomb. As a boosted fission weapon, it derives its energy from nuclear fission of uranium or plutonium. [2]
Orange Herald 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 | 0.85 km |
| Severe blast (20 psi) | 2.14 km |
| Moderate blast (5 psi) | 5.56 km |
| Light blast (1 psi) | 15.3 km |
| 3rd-degree thermal burns | 10.5 km |
| 2nd-degree thermal burns | 13.2 km |
| 1st-degree thermal burns | 16.7 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 Orange Herald on a City
Use the interactive simulator to detonate the Orange Herald 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 Orange HeraldRelated Weapons
FAQ
How big is the Orange Herald blast radius?
In an air burst at optimum height, the Orange Herald produces a fireball roughly 0.85 km in radius and a 5 psi moderate-blast zone of about 5.56 km — the area in which most residential buildings would collapse. The 1 psi light-damage radius extends to roughly 15.3 km, where windows shatter.
What is the yield of the Orange Herald?
The Orange Herald has a yield of 720 kilotons of TNT equivalent. That is 48× more powerful than the Hiroshima bomb.
Is the Orange Herald bigger than the Hiroshima bomb?
The Hiroshima bomb (Little Boy) had a yield of approximately 15 kilotons. The Orange Herald at 720 kilotons is 48× more powerful than the Hiroshima bomb.[5]
What thermal burn radius does the Orange Herald produce?
In an air burst at optimum height, thermal radiation from the Orange Herald can cause 3rd-degree burns out to roughly 10.5 km, 2nd-degree burns to 13.2 km, and 1st-degree burns to 16.7 km.
Sources
- 1.Source: Wikipedia, Operation Grapple — 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
- 5.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