column. The base surge billows upward to a height of
several hundred feet and expands rapidly outward to a
distance of several thousand yards. Then it gradually
rises from the surface and merges with the cloud formed
by the escaping fireball.
EFFECTS OF NUCLEAR WEAPONS
Detonation of the nuclear bomb creates a blast wave
that travels outward in all directions at an initial speed
much greater than the speed of sound. When the wave
strikes the earth’s surface, another wave is formed by
reflection. At some distance from ground zero
(depending on the height of the blast), the primary and
reflected waves combine to form a reinforced blast
wave. Pressure at the wave front, called overpressure, is
many times that of normal atmospheric pressure and is
what causes most of the physical damage. Additionally,
underwater bursts create large water waves, some of
which reach heights of over 90 feet within a few
hundred feet from the blast. The water waves travel
outward at high speed for a distance of several miles,
gradually diminishing in size. The overpressure
decreases as the distance from the blast increases, but it
can cause damage many miles from the blast.
Nuclear weapons produce explosions of great force
and heat and release nuclear radiation. Their primary
purpose is the mass destruction of property and
personnel. Their effects are divided into three
categories—blast waves or shock waves, incendiary,
and radiation.
Blast Waves or Shock Waves
Injuries caused by blast waves can be divided into
primary (direct) injuries and secondary (indirect)
injuries.
PRIMARY BLAST INJURIES.—Primary blast
injuries result from the direct action of the air shock
wave on the human body. The greater the weapon’s size,
the greater the blast wave’s effective range, with a
subsequent increase in casualties.
SECONDARY BLAST INJURIES.—Secondary
blast injuries are caused by strong blast winds reaching
hundreds of miles per hour collapsing buildings and
timber and flinging debris about. Personnel may also be
hurled against stationary objects or thrown to the
ground by high winds accompanying the explosion.
At sea, the shock wave accompanying an
underwater burst produces various secondary injuries.
Causalities resemble those caused by more
conventional underwater weapons, such as mines and
depth charges. Instead of being localized, the casualties
extend over the entire ship. Also, injuries result from
personnel being thrown against fixed objects or
structures. Unsecured objects can act as missiles and
cause many injuries.
Incendiary
There are two general ways fires can originate in a
nuclear explosion.
1. First, kindling fuels can be ignited as a direct
result of the absorption of thermal radiation.
2. Second, fires can be started from electrical short
circuits, broken gas lines, or other interrupted
heat sources as an indirect effect of the blast
wave.
13-10
Student Notes:
Figure 13-4.—A subsurface burst.
