Joe-1
USSR · 1949 · 22 kilotons · pure fission
Overview
First Soviet nuclear test.
With a yield of 22 kilotons[1, 2], the Joe-1 is comparable in yield to the Hiroshima bomb. As a pure fission weapon, it derives its energy from nuclear fission of uranium or plutonium. [3]
Joe-1 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[4, 5].
| Effect zone | Radius (air burst) |
|---|---|
| Fireball radius | 0.21 km |
| Severe blast (20 psi) | 0.62 km |
| Moderate blast (5 psi) | 1.75 km |
| Light blast (1 psi) | 4.85 km |
| 3rd-degree thermal burns | 2.60 km |
| 2nd-degree thermal burns | 3.32 km |
| 1st-degree thermal burns | 4.36 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 Joe-1 on a City
Use the interactive simulator to detonate the Joe-1 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 Joe-1Related Weapons
FAQ
How big is the Joe-1 blast radius?
In an air burst at optimum height, the Joe-1 produces a fireball roughly 0.21 km in radius and a 5 psi moderate-blast zone of about 1.75 km — the area in which most residential buildings would collapse. The 1 psi light-damage radius extends to roughly 4.85 km, where windows shatter.
What is the yield of the Joe-1?
The Joe-1 has a yield of 22 kilotons of TNT equivalent. That is comparable in yield to the Hiroshima bomb.
Is the Joe-1 bigger than the Hiroshima bomb?
The Hiroshima bomb (Little Boy) had a yield of approximately 15 kilotons. The Joe-1 at 22 kilotons is comparable in yield to the Hiroshima bomb.[6]
What thermal burn radius does the Joe-1 produce?
In an air burst at optimum height, thermal radiation from the Joe-1 can cause 3rd-degree burns out to roughly 2.60 km, 2nd-degree burns to 3.32 km, and 1st-degree burns to 4.36 km.
Sources
- 1.Source: Nuclear Weapon Archive (Carey Sublette), Soviet Atmospheric Tests (last updated 7 Oct 1997) — retrieved Oct 2026
- 2.Source: Atomic Archive, The Soviet Atomic Bomb — retrieved Oct 2026
- 3.Source: US DoD & ERDA (Glasstone & Dolan), via Atomic Archive, The Effects of Nuclear Weapons, 3rd ed. (1977), Chapter 1 — retrieved Oct 2026
- 4.Source: U.S. DoD / DOE (Glasstone & Dolan, via Atomic Archive), The Effects of Nuclear Weapons, 3rd ed. (1977) §2.127 — retrieved Oct 2026
- 5.Source: Wikipedia, Effects of nuclear explosions — scaling-law table — retrieved Oct 2026
- 6.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