Learn
Understanding Nuclear Weapons
Core background on how nuclear weapons work, what their effects are, and why those effects scale the way they do.
Physics
Fission weapons split heavy atoms. Fusion weapons combine light isotopes. Thermonuclear systems use both to produce much larger yields.
Effects
A detonation produces blast pressure, thermal radiation, initial nuclear radiation, fallout, and in some cases EMP.
History
The history runs from the Manhattan Project to Hiroshima and Nagasaki, through the Cold War arms race and into non-proliferation and deterrence debates.
Blast Effects
The blast wave is a fast-moving front of compressed air moving outward from the detonation.
Two useful terms are overpressure and dynamic pressure. Together they determine how structures fail and how people are injured.
Damage varies with yield, distance, burst height, and the construction of the target area.
Typical Thresholds
0.5 psi: Window breakage
1-2 psi: Moderate house damage
3 psi: Residential collapse begins
5 psi: Most buildings collapse
10+ psi: Reinforced concrete heavily damaged
Thermal Radiation
Thermal radiation is the flash of heat and light from the fireball.
It causes burns, ignites materials, and can trigger large urban fires or firestorms under the right conditions.
Yield, atmospheric conditions, distance, and shielding all affect how far the thermal pulse reaches.
Burn Thresholds
1.4 cal/cm²: First-degree burns
3 cal/cm²: Second-degree burns
5 cal/cm²: Third-degree burns
8+ cal/cm²: Ignition risk rises sharply
Radiation and Fallout
Initial radiation is released immediately after detonation. Fallout is residual contamination returning to the surface later.
Fallout severity depends on yield, burst height, wind, weather, and terrain. Surface bursts generally generate more fallout than higher airbursts.
Dose is usually discussed in Gray or Sievert, with effects ranging from mild blood changes to acute radiation syndrome and death.
Dose Effects
0.05-0.1 Sv: Minor blood changes
0.5-1 Sv: Nausea, fatigue, reduced immunity
2-3 Sv: Severe radiation sickness
4-5 Sv: Death likely without major treatment
6+ Sv: Death highly likely