Sheffield city centre sits 71.2 km from Menwith Hill, UK, the most plausible strategic target in the area (high targeting confidence). Modelled strike: 150 kt airburst.
Estimated survival chance at city centre: 99%
What a strike on Menwith Hill, UK would mean
A 150 kt detonation produces a fireball 490 m across in radius. Reinforced concrete fails out to 1.8 km (20 psi). Most residential buildings collapse within 3.7 km (5 psi), and windows shatter dangerously out to 8.2 km (1 psi). Anyone in line of sight within 5.2 km suffers third-degree burns from the thermal pulse.
An airburst maximises blast damage but produces minimal local fallout, so for Sheffield the dominant risks are blast and thermal effects rather than radiation.
Most plausible targets near Sheffield
| Target | Type | Distance | Assumed yield | Confidence |
|---|---|---|---|---|
| Menwith Hill, UK | communication | 71 km | 150 kt | high |
| RAF Lakenheath | military | 174 km | 300 kt | high |
| Whitehall, London | government | 228 km | 455 kt | high |
| Heathrow, London | airport | 223 km | 150 kt | medium |
| Faslane (HMNB Clyde, SSBN) | military | 368 km | 800 kt | high |
Key blast radii (150 kt airburst)
| Effect | Radius | What happens |
|---|---|---|
| Fireball | 490 m | Complete vaporisation |
| 20 psi blast | 1.8 km | Hardened structures destroyed, ~100% fatalities |
| 5 psi blast | 3.7 km | Most buildings collapse, widespread fatalities |
| 3rd-degree burns | 5.2 km | Full-thickness burns to exposed skin |
| 500 rem radiation | 2.1 km | Lethal dose without medical care |
| 1 psi blast | 8.2 km | Window breakage, light damage, glass injuries |
How Sheffield can prepare
With a population density of 3,900 people/km², Sheffield's outcome would hinge on the first hour. The guidance is identical everywhere: get inside, stay inside, stay tuned. A basement or the core of a large concrete building cuts fallout exposure by a factor of 10 or more, and radiation decays fast — dose rates fall ~90% within the first 7 hours and ~99% within two days.
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