Back to main

Methodology: How the Simulator Calculates Nuclear Effects

Everything the simulator draws on the map is calculated from openly published, declassified models of nuclear weapons effects. This page explains where the numbers come from and what assumptions they rely on.

Primary sources

The core reference is The Effects of Nuclear Weapons by Samuel Glasstone and Philip J. Dolan (3rd edition, 1977) — the standard, formerly official U.S. government compendium of nuclear effects data, long since declassified and freely available. Supplementary relationships come from E. Royce Fletcher's scaling work, the U.S. Office of Technology Assessment's The Effects of Nuclear War (1979) and the openly documented equations popularised by Alex Wellerstein's NUKEMAP project.

Blast overpressure

Blast damage is expressed in psi (pounds per square inch) of overpressure. Distances scale with the cube root of yield (Hopkinson–Cranz scaling): a bomb 8× more powerful pushes each pressure ring only 2× farther. The simulator's default rings correspond to well-established damage benchmarks: 20 psi — reinforced concrete buildings destroyed, fatalities approach 100%; 5 psi — most residential buildings collapse; 1 psi — window glass breaks, causing injuries. For airbursts, the model can optimise the height of burst to maximise the radius of any chosen overpressure.

Thermal radiation

The thermal rings show the slant-range distance at which the heat pulse delivers enough energy (in cal/cm²) to cause first-, second- or third-degree burns with a given probability, or to ignite dry wood. The required energy grows slowly with yield because larger explosions emit their pulse over a longer time. The model assumes reasonably clear atmospheric visibility; haze, clouds and shadows change real-world results significantly.

Ionizing radiation

The radiation rings show the distance at which a prompt dose (in rem) is delivered by the initial burst of neutrons and gamma rays. Doses of 500–600 rem are usually fatal without intensive medical care. For large-yield weapons the lethal blast and thermal radii extend far beyond the prompt radiation radius, which is why this effect matters most for small, Hiroshima-class weapons.

Fallout

The fallout plume is modelled for surface bursts (an airburst whose fireball never touches the ground produces little local fallout). Inputs are yield, fission fraction, wind speed and direction; the output is a set of dose-rate contours in rads per hour, referenced to one hour after detonation («H+1»), following the simplified SIMFIC-style approach described in openly published literature. Real fallout patterns are far messier — they depend on winds at every altitude, rain and terrain.

Known limits

  • The models are calibrated for yields between roughly 1 kiloton and 20 megatons; values outside this range are extrapolated and less reliable. The hard cap is 100 megatons.
  • Casualty and damage figures assume uniform conditions — no terrain shielding, no weather, average construction.
  • Results are estimates for education, not civil-defence planning. See effects of a nuclear explosion for what each mechanism does, or try the simulator to see the numbers for any city and yield.