please don't piss people off or you'll be nuked until you glow
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who should be applauded
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xavier frank tom laura
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peggy: maybe
alice
?
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distances. Third, the nuclear explosion is accompanied by highlypenetrating
and harmful invisible rays, called the "initial nuclear
radiation." Finally, the substances remaining after a nuclear explosion
are radioactive, emitting similar radiations over an extended
period of time. This is known as the "residual nuclear radiation"
or "residual radioactivity" (Fig. 1.02).
1.03 It is because of these fundamental differences between a
nuclear and a conventional explosion, including the tremendously
greater power of the former, that the effects of nuclear weapons
require special consideration. In this connection, a knowledge and
understanding of the mechanical and the various radiation phenomena
associated with a nuclear explosion are of vital importance.
1.04 The purpose of this book is to describe the different forms
in which the enei'gy of a nuclear explosion are released, to explain
how they are propagated, and to show how they may affect men and
materials. Where numerical values are given for specific observed
effects, it should be kept in mind that there are inevitable uncertainties
associated with the data, for at least two reasons. In the first place,
there are inherent difficulties in making exact measurements of
weapons effects. The results are often dependent on circumstances
which are difficult, if not impossible, to control, even in a test and
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1.29 Almost immediately after a nuclear explosion, the weapon
residues incorporate material from the surrounding medium and form
an intensely hot and luminous mass, roughly spherical in shape, called
the "fireball." An "air burst" is defined as one in which the weapon
is exploded in the air at an altitude below 100,000 feet, but at such a
height that the fireball (at roughly maximum brilliance in its later
stages) does not touch the surface of the earth. For example, in the
explosion of a 1-megaton weapon the fireball may grow until it is
nearly 5,800 feet (1.1 mile) across at maximum brilliance. This
means that, in this particular case, the explosion must occur at least
2,900 feet above the earth's surface if it is to be called an air burst.
1.30 The quantitative aspects of an air burst will be dependent
upon the actual height of the explosion, as well as upon its energy
yield, but the general phenomena are much the same in all cases.
Nearly all of the shock energy appears as air blast, although some is
generally also transmitted into the ground. The thermal radiation
will travel large distances through the air and will be of sufficient
intensity to cause moderately severe burns of exposed skin as far away
as 12 miles from a 1-megaton explosion, on a fairly clear day. The
warmth may be felt at a distance of 75 miles. For air bursts of higher
energy yields, the corresponding distances will, of course, be greater.
Since the thermal radiation is largely stopped by ordinary opaque
materials, buildings and clothing can provide protection.
1.31 The initial nuclear radiations from an air burst will also penetrate
a long way in air, although the intensity falls off fairly rapidly
at increasing distances from the explosion. The nuclear radiations
are not easily absorbed, and fairly thick layers of materials, preferably
of high density, are needed to reduce their intensity to harmless proportions.
For example, at a distance of 1 mile from the air burst of a
1-megaton nuclear weapon, an individual would probably need the
protection of about 1 foot of steel or 4 feet of concrete to be relatively
safe from the efl'ects of the initial nuclear radiations. However, at
this distance the blast effect would be so great that only specially
designed blast-resistant structures would survive.
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4.01 The phenomena associated with a blast wave in air have
been treated in the preceding chapter. On the basis of the information
developed, consideration will now be given to the interaction
of the air blast with a target and the factors affecting the response
of the target. Criteria of damage to targets of different types will
be discussed and relationships given between the damage and the
distances over which such damage may be expected from nuclear
weapons of various yields. In addition, quantitative methods of
computing structural loads and their duration will be outlined.
4.02 The general conclusions concerning the expected effects of
nuclear explosions on various targets are summarized in the form of
nomographs (Figs. 4.58 a and b). These are based on a combination
of theoretical analysis with data obtained from actual nuclear explosions,
both in Japan and at various tests, as well as from laboratory
studies. However, the nature of any target complex, especially a
city, is such that no exact prediction of the eft'ect of blast on structures
can be made. Nor is it possible to indicate the reliability of the
prediction for any particular situation. Nevertheless, by the application
of proper judgment to the available information, it is believed
that results of practical value can be obtained. The conclusions
given here are considered to be the most representative for the average
situations that might be encountered in actual target complexes.
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4.04 Direct damage to structures attributable to air blast can
take various forms. For example, the blast may deflect structural
steel frames, collapse roofs, dish-in walls, shatter panels, and break
windows. In general, the damage results from some type of displacement
(or distortion) and the manner in which such displacement
can arise as the result of a nuclear explosion will be examined below.
4.06 For an air burst, the direction of propagation of the incident
blast wave will be towards the ground at ground zero. In the regular
reflection region, where the direction of propagation of the blast
wave is not parallel to the horizontal axis of the structure, the forces
exerted upon structures will also have a considerable downward
component (prior to passage of the reflected wave) due to the reflected
pressure build-up on the horizontal surfaces. Consequently,
in addition to the horizontal loading, as in the Mach region (§ 3.24),
there will also be initially an appreciable downward force. This
tends to cause crushing toward the ground, e.g., dished-in roofs,
in addition to distortion due to translational motion.
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