How does a nuclear bomb kill you?

Answer 1

That depends upon how close you are to the explosion. You can be completely vaporized, or merely burned; the concussion can cause massive damage, and if all else fails, there is always radiation sickness.

As implied above, nuclear weapons can cause three categories of injuries: thermal (burns), radiation, and blast (physical trauma).

Thermal radiation (heat) released by the bomb will burn you in two ways: direct exposure to super-heated air, or absorption of high amounts of infrared radiation by your clothes. Which is more of a danger depends on your distance from the explosion, and what intervening structures there are.

Radiation is in the form of ionizing gamma rays and alpha particles, with secondary X-rays and other EM radiation also having some impact. In all cases, the threat is from radiation poisoning - the level of ionizing radiation that the human body can take before the cellular damage caused by such radiation causes organ failure.

Blast damage is via a force wave of pressure, which is the same as with ordinary explosives. Death can come from direct contact with the pressure wave, or, more likely, from debris the pressure wave causes.

Which one is the highest risk to you depends on the size of the particular weapon, the altitude above the ground it was detonated, and the distance from ground zero you are.

For large yield weapons ( > 100 kT), the primary danger is blast. The lethal range of radiation and thermal effects is well below that of the lethal blast radius.

In mid-size yields (15-100kT), the danger is a combination of blast and burns.

In small yield weapons ( < 5kT), the primary danger is radiation poisoning.

In addition, for the same yield of weapon, a ground burst will have a smaller lethal range than an air burst.