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Nagasaki nuclear blast radius

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This page loads Fat Man over the Nagasaki hypocenter. The city sits in a valley; this model still draws circular rings and ignores terrain, so the 3D view matters more here than the disk does.

Open Nagasaki in the 3D simulator

Educational estimate only. Blast and heat rings use simplified yield scaling. They ignore terrain, weather, shielding, and weapon design. Casualty counts use WorldPop 2020 residents on an approximately 1 km grid and ignore time of day, commuting, shelter, and evacuation. This is not a targeting or civil-defense tool. About the model.

Aim point: 1945 hypocenter (Urakami basin) · Weapon: Fat Man (21 kt, 607 m (1,991 ft) optimum airburst)

Ground ranges for Fat Man (21 kt, 607 m (1,991 ft) optimum airburst) in this simulator.
Effect Ground range What the model means
Fireball 304 m (998 ft) Maximum luminous radius
20 psi 938 m (3,078 ft) Heavy destruction
5 psi 2.0 km (1.3 mi) Most buildings collapse
Thermal 2.3 km (1.4 mi) 3rd-degree burns
1 psi 4.7 km (2.9 mi) Windows shatter
Rings scaled to 1 psi. Yellow fireball, red 20 psi, orange 5 psi, gold thermal, blue 1 psi. Not a map of buildings.

Casualty estimate at this pin

People on the WorldPop 2020 grid inside this scenario’s 1 psi ring. Rounded educational estimate, not a forecast.
Estimated deaths 39,416
Estimated injuries 53,741
Residents inside 1 psi 188,627

What the rings cover

Inner rings sit in the Urakami basin around the hypocenter. 5 psi fills much of the inner valley in the model. 1 psi reaches toward neighbouring ridges on the map even though real hills would have changed that in 1945.

Fat Man was a plutonium implosion bomb detonated over Nagasaki on 9 August 1945, with a yield around 21 kt. The tool uses that named preset, not a custom wartime height of burst.

Hills shielded parts of Nagasaki in 1945. This simulator does not. The rings will look more symmetric than the historic damage pattern. That limitation is stated on the about page for a reason.

WorldPop 2020 counts people who live there now. It is not the 1945 death toll. Use this page to understand yield and geography, not to adjudicate history.

Related pages

Hiroshima · Fat Man · Trinity Site · Tokyo

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City index · Historic sites · Weapon yields

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