In this type a subcritical mass, which is in the shape of a ball, is placed in the center of the weapon. This subcritical mass is surrounded in a spherical arrangement of conventional explosives. When the fuse is triggered all of the conventional explosives explode at the same time. This causes the subcritical mass to be compressed into a smaller volume, thus creating a supercritical mass to be formed. After this supercritical mass is obtained, a self-sustained chain reaction takes place and causes the atomic explosion (World Book, 1990). This type of stomic bomb was used on Nagasaki, and given the nickname “Fat Man” after Winston Churchill (Outlaw Labs).

The blast from an atomic bomb’s explosion will last for only one-half to one second, but in this amount of time a great deal of damage is done (Physicians and Scientists on Nuclear War, 1981). A fireball is created by the blast, which consists mainly of dust and gasses. The dust produced in this fireball has no substantial effect on humans or their environment. However, as the gasses expand a blast wave is produced. As this blast wave moves, it creates static overpressure. This static overpressure then in turn creates dynamic pressure. The static overpressure has the power to crush buildings. The dynamic pressure creates winds, which have the power to blow down trees (International Physicians for the Prevention of Nuclear War, 1982). The blast pressure and fireball together only last for approximately eleven seconds, but because it contaitns fifty percent of the atomic bomb’s latent energy a great deal of destruction occures (The Committee for the Compilation of Materials on Damage Caused by the Atomic Bombs in Hiroshima and Nagasaki, 1981).

In Hiroshima the blast from the atomic bomb was measured to be about four and a half to six and seven tenths tons of pressure per square mere, while in Nagasaki the blast was measured to be about six to eight tons of pressure per square meter (International Physicians for the Prevention of Nuclear War, 1982). Because of thsidramatic change in the pressure most of the cities were destroyed. The static overpressure in Hiroshima caused ninety-one and nine tenths percent of all the buildings to be destroyed, while in Nagasaki it casued thirty-six and one tenth of all of the buildings to be destroyed. The static overpressure created a dynamic pressure that had winds up to four hundred miles per hour (The Committee for the Compilation of Materials on Damage Caused by the Atomic Bombs in Hiroshima and Nagasaki, 1981).