(4) One percent as EMP.
b. Larger weapons are more destructive than smaller weapons, but the destructive effect is not linear. [Table A-1] presents a comparison of three aspects of nuclear weapons effects with yield.
Figure A-1. Distribution of energy.
c. The altitude at which the weapon is detonated determines the blast, thermal, and nuclear radiation effects. Nuclear blasts are classified as air, surface, or subsurface bursts.
(1) An airburst is a detonation in air at an altitude below 30,000 meters, but high enough that the fireball does not touch the land or water surface. The altitude is varied to obtain the desired tactical effects. Initial radiation will be a significant hazard, but there is essentially no local fallout. However, the ground immediately below the airburst may have a small area of neutron-induced radioactivity. This may pose a hazard to troops passing through the area.
(2) A surface burst is a detonation in which the fireball actually touches and vaporizes the land or water surface. In this case, the area affected by blast, thermal radiation, and initial nuclear radiation will be smaller than for an airburst of comparable yield. However, in the region around ground zero, the destruction will be much greater and a crater is often produced. Additionally, all the material that was within the fireball becomes fallout and will be a hazard downwind. A surface burst is the most likely type of terrorist detonation.
(3) A subsurface burst is an explosion in which the detonation is below the surface of land or water. Cratering usually results. If the burst does not penetrate the surface, the only hazard is from the ground or water shock. If the burst penetrates the surface, blast, thermal, and initial nuclear radiation will be present, though less than for a surface burst of comparable yield. Local fallout will be heavy over a small area.
(4) A high altitude burst occurs above 30,000 meters. Radiation and physical effects do not reach the ground and there is no local fallout. This is the only detonation where the effects of the EMP are significant. Nonhardened electronic equipment including many medical devices may become inoperative. The EMP damage is a moot point with other types of detonations, as its range is primarily limited to the area of intense physical destruction.