z
+8
3
5
ings, thus greatly increasing the
of twelve square miles subject
designed to be earthquake-resist-
5. Light damage, which is mostly
additional destruction by fire.
Certain structures in Japan were
Extent and Degree of Nuclear
stronger than their counterparts
in the United States, while other
plaster damage and window
breakage, may extend to a radius
of eight miles or more, giving a
Desolation Are Depicted
Hghter than that in this country.
However, contrary to popular
miles. Actually these distances,
at which window and light plas-
ant,
which
the
most
al bomb, most structural failures
occur during a small part of the
positive phase while the pressure
is essentially constant.
An examination of the areas in
Japan affected by atomic bombing
shows that small masonry buildings were engulfed by the oncoming pressure wave and collapsed
of damage by a bomb that is burst
completely. Light buildings and
residences were totally demolished
in the air.
There are, of course, other applications, such as the possible use
of an atomic weapon as an instrument of radiological warfare by
exploding it in a conveniently
buildings of steel construction were
day), or in restricting the escape
concrete
stroyed.
smoke stacks, was deSome buildings leaned
to ground level, carrying the wires
down with them, and gas containers ruptured and collapsed.
Heat, Fire and Blast
Many buildings that at a distance appeared sound were found
on close inspection to be damaged
and ruined by fire. Telephone poles
were charred and granite surfaces
were etched by heat and by sand
blasting from the high winds carrying abrasive material.
There were many evidences of
The Mass Distortion
The great power of the former
results in a destruction feature
called mass distortion of buildings. An ordinary explosion usually will damage only part of a
large structure, but the atomic
blast can engulf and flatten whole
buildings.
Further, because the shock wave
that provide a temperature inversion in the lower atmosphere.
would not be markedly different
from those in Hiroshima and
In the Report of the British
Mission to Japan on ‘‘The Effects
American
in
general
Some Conclusions
of the Atomic Bombs at Hiroshima
and Nagasaki,” it was estimated
Japan it is possible to draw some
conclusions about the blast dam-
have (1) caused complete collapse
were damaged
by
blast and burned out. Most im-
portant, water pressure was lost
by the breaking of pipes, mainly as
a result of the collapse of build-
that in a British city such as Lon-
From the observations made in
don
age and the radii within which
they may be expected to occur, will
be as follows:
1. Virtually complete destruction
roof material, which consisted of
corrugated sheet metal or asbestos
cement.
Since this did not occur
instantaneously, a large impulsive
force was applied to the frame.
Severe damage occurred up to a
distance of 6,000 feet.
There were several types of
failure of such structures.
Close
to the explosion the buildings were
pushed over, and at greater dis-
severe to destructive.
. Moderate damage short of major
tances
to render the structure unusable
the lateral] force.
Sometimes columns failed by a
combination of lateral force, causing flexure, at the same time that
to
radius of about 15, miles, giving an area of eight square miles
in which the damage ranges
from moderate to destructive.
. Partial damage will be inflicted
to a radius of about two miles,
an increased downward load came
from the vertical component of
blast on the roof,
This caused
buckling and collapse. Roof trusses
were buckled by compression re-
adding four square miles of damand making
they were in many cases
left leaning away from the source
of the blast. The long and slender
columns offered little resistance to
structural damage but sufficient
age area,
Construction was generally
comparable to that in the United
States. The first effect of blast
was to strip off the siding and
one-half mile from ground zero,
corresponding to an area of destruction of about three-quarters
of a square mile.
. Severe damage, defined as major
structura] damage that would
result in collapse or liability to
collapse of the building, will
occur to a radial distance slightly in excess of one mile from
ground zero, This corresponds to
an area of four square miles in
which the damage ranges from
occur
would
steel buildings used for manufac-
turing.
will occur te a radius of about
will
bomb
feet: (3) rendered uninhabitable
without extensive repair out to
7,920 feet, and (4) rendered uninhabitable without minor repairs
out too 13,200 feet.
In Nagasaki there were many
damage, the various types of dam-
repaired,
Nagasaki
3,000 feet from ground zero; (2)
damaged beyond repair out to 5,280
assumption that the height of the
until
the
of normal houses to a distance of
age to be expected at various distances from ground zero for an air
burst of a ‘nominal atomic bomb,”
ing out materials that were not
highly combustible. All vehicles at
18
residences
Nagasaki.
ing fires and in scorching and dryrange
ical conditions at the time of the
detonation and may be considerably greater under conditions
veyed the atomic bomb damage
that the resistance to blast of
the effect of radiant heat in start-
close
ter damage will be inflicted, vary
appreciably with the meteorolog-
of a group of highly qualified
architects and engineers who sur-
burst is such as to inflict maximum
of damage, as if struck by a hurricane of stupendous proportions.
Telephone poles were snapped off
bomb blast and those of a conventional high-explosive bomb.
light damage area of 200 square
resi-
equal to 20,000 tons of TNT. On the
away from ground zero, the center
might also be employed to produce
earth or water shock through a
subsurface explosion.
Such
uses,
although
potent,
must. because of the restrictive
conditions placed on the delivery
problem and the target location
and configuration, be regarded as
special applications of the varied
destructive characteristics of the
bomb,
There is an important difference
between the effects of an atomic
the Japanese
Manufacturing
Nearly everything above ground
at close range, except reinforced-
of fission products by means of a
subterranean explosion. The bomb
of
denuded of roofing and siding, and
only the twisted frames remained.
by blast and fire.
located body of water, te produce
a base surge (described yester-
was
te
effect,
undoubtedly
dence, it is the considered opinion
ad
disruptive
important agent in producing destruction.
This implies that the other
characteristics of an atomic bomb
that can be employed in warfare,
such as heat and visible radiations,
neutrons, gamma rays, and fission
products, are at present not serious competitors in the production
them
conceptions about the flimsy char-
of an atomic explosion is of relatively long duration, of the order
of a second as compared with a
few milliseconds for a convention-
point of view of weapon delivery
made
Ca
The shock wave produced by an
air-burst atomic bomb is, from the
probably
construction
acteristics
and
to some degree of damage and
window destruction.
a total
19