5 ;
While
the
official
handbook
deals with what may be called the
“Model T” bomb of 1945 vintage,
it gives scaling laws to extrapolate
on the effects of larger bombs.
Here it clears up a general misconception that a bomb twice the
power will do twice the damage,
which is far from true.
Different Sealing Laws
There are different scaling laws
that apply to the different effects
the fission products to be raised to
a temperature of more than 1,000,0G0 degrees centigrade. The maximum temperature in a convention-
al high explosive bomb is about
5,000 degrees.
Since this material at the instant of the explosion is restricted
to the region occupied by the original constituents of the bomb, the
pressure is of the order of hun-
dreds of thousands of atmospheres.
Because of the extremely high
the 1945 model, one equal to 160,-
temperature, there is an emission
of energy by electromagnetic radiations, covering a wide range of
wave-lengths, from infra red (heat
rays) through the visible to the
This means that a bomb releasing 160,000 tons of TNT would pro-
air immediately surrounding the
bomb, with the result that the air
itself becomes heated to incande-
of an atomic explosion. The blast
effect, for example, increases with
the cube root of the power, so that
a bomb eight times the power of
000 tons of TNT, would increase
its radius of destruction by the
cube root of eight.
duce
damage
and
casualties
to
about twice the distance from the
center of the explosion as would be
caused by a 20,000-ton bomb.
Even the hydrogen bomb, which
may reach an explosive power as
high as 20,000,000 tons of TNT,
1,000 times the 1945 model, would
Produce
damage
and
casualties
over a radius ten times greater,
the cube root of a 1,000.
Whenit comes to the incendiary
effect, the increase in the radius
of destructiveness goes by the
square root of the power, so that
you would need to increase the
power of a bomb four, instead of
eight, times to produce the incendiary effect over a radius twice
as great as that of 20,000-ton mod.
els.
The official handbook provides
the most detailed description yet
to appear anywhere of the imme-
diate visible effects of an atomic
detonation, in the air and under
water. These effects take place at
such an incredibly rapid rate that
actually no complete observations
of all the phenomena have been
made, some eluding even the highest speed cameras.
First come the phenomena of an
air burst, an explosion at a distance of about 2,000 feet above the
earth’s surface.
The liberation of
such a large amount of energy in
a very short period within a limit-
ed space results in an extremely
high energy density, which causes
ultraviolet and beyond. Much of
this radiation is absorbed by the
scence.
In this condition the detonated
bomb begins to appear, after a few
millionths of a second, as a luminous sphere called the Ball of
Fire.
As the energy is radiated into
a greater region, raising the temperature of the air through which
it passes, the Ball of Fire increases in size, but the temperature, pressure and himinosity decrease correspondingly.
After about one ten-thousandth
of a second has elapsed, the radius
of the Bali of Fire is some fortyfive feet, and the temperature is
then in the vicinity of 300,000 degrees centigrade.
At this instant, the luminosity,
as observed at a distance of 10,000
yards
(5.7 miles), is about
100
times that of the sun as seen at
the earth’s surface.
The Ball of Fire continues to
grow rapidly in size for about fifteen milliseconds (thousandths of a
second), by which time its radius
has increased to about 300 feet.
The surface temperature
has by
then dropped to around 5.000 degrees centigrade, although the interior is very much hotter.
As the Ball of Fire grows
2
shock wave develops in the air.
At first the shock front coincides
with the surface of the Ball of
Fire, but as the temperature drops
below 300,000 degrees the shock
wave advances more rapidty. In
other words, transfer of energy by
the shock wave is faster than by
radiation.
The Shock Front
Although the rate of advance of
the shock front, which reaches the
vicinity of 15,000 feet per second,
decreases with time, it continues to
move forward more rapidiy than
the Ball of Fire. After the lapse
of one second the Ball of Fire has
essentially attained ifs maximum
radius of 450 feet, and the shock
front is then some 600 feet further
ahead. After ten seconds the Ball
of Fire has risen about 1,500 feet,
the shock wave has traveled about
12,000 feet and nas passed the
region of maximum damage.
If the bomb is detonated at a
height of less than 450 feet, the
Ball of Fire can actually touch the
earth’s surface, as it did in the
historic “Trinity” test at Alamo-
gordo, N. M. Because of its low
density the Ball of Fire rises, like
a gas balloon, starting at rest and
accelerating within a few seconds
to its maximum rate of ascent of
300 feet per second.
After
about
ten
seconds
from
detonation. when the luminosity of
the Ball of Fire has almost died
and the excess pressure of the
shock wave has decreased to vir-
tually harmless proportions, the
immediate effects of the bomb may
be regarded as over. The emission
of gamma rays and neutrons ac-
companying fission, the most dead-
ly forms of radiations, will aiso
have ceased py this time.
Soon after the detonation a
violet-colored glow is observed,
particularly at night or in dim day-
light, at some distance from the
Ball of Fire. This glow may per-
sist for a considerable length of
time, distinctly visible in the column of cloud that forms after the
Ball of Fire has disappeared. It is
believed to be the ultimate result
of a complex series of processes
initiated by the action of gamma
radiation on the nitrogen and oxygen in the air.