A Nuclear Explosion
When a nuclear weapon explodes, in about a millionth of a second a
temperature of up to eighteen million degrees Fahrenheit, comparable
to that inside the sun, is produced. About half of this is immediately
lost in the close vicinity of the explosion as a luminous white
fireball appears, expands and begins to rise.
For up to a minute, energy in the forms of radiation, EMP
(electromagnetic pulse), light, heat, sound, and blast is released in
all directions. The fireball then ceases to be luminous and begins to
cool as its cloud rises many thousands of meters at up to 480
kilometers per hour. As the cloud billows out into its eventual
mushroom shape it sucks up after it a column of dust from the earth's
surface. This dust mixes with residue of the weapon and becomes
radioactive fallout.
Components of the Nuclear Explosion
----------------------------------------------------------------------
Light
This is largely ultraviolet and infrared, more intense than it appears
to be, and liable to cause blindness, even though sight may return
within a few days.
Heat
One third of the energy of a nuclear weapon is emitted in this form.
It radiates in straight lines at the velocity of light, but has little
penetrating power and is weakened by haze or mist. Its range, however,
is greater than that of blast or of initial radiation, and it may
cause injury or death to those exposed and damage to property by
starting fires.
Blast
A wave of compressed air moves away from the site of a nuclear
explosion at about the speed of sound. Lasting several seconds, it
maintains pressure upon objects in its path in a manner more usually
associated with a very high wind than the shock wave of an explosion.
It is the main cause of damage to buildings, and a hazard to those
outside or within. A wave of air rushes back in to fill the void
seconds after the initial blast wave passes. This wave is not as
strong, maybe several hundred kilometers per hour.
Side Affects of the Nuclear Explosion
----------------------------------------------------------------------
Radiation
The electromagnetic spectrum consists of cosmic rays, gamma rays,
x-rays, ultraviolet rays, visible light rays, infrared rays, and radio
rays. Of these, gamma rays are of chief concern to us. Gamma rays,
alpha and beta particles, and neutrons result from decay of
radioactive substances, and all four are emitted following a nuclear
explosion. Their effects are all referred to below as radiation.
When ionizing radiation enters the body, some of it is absorbed. This
ionizes molecules in some of the body's cells, producing chemical
changes so they cease to function. What is called "radiation sickness"
may then occur.
Fallout
With surface explosions, or at altitudes low enough for the fireball
to touch the ground, huge quantities of earth and debris, together
with the fission products, are sucked into the fireball. As the
fireball cools, the radioactivity condenses on the particles that were
liften from the ground; many of these are large particles and they
come down by the force of gravity within a day, or, at distances not
too far from the burst, some hundreds of kilometers. This constitutes
the "local" or "early" fallout. The extent and location of the early
fallout depends primarily on the meteorological conditions, e.g. the
velocity and direction of the wind. They also depend on precipitation
conditions; the particles may come down to earth with the rain or
snow, which is referred to as "rainout" or "snowout".
In addition to surface bursts and air bursts, underwater bursts occur
at times. Radioactive fission products would mainly be absorbed by the
water. However, some would escape to produce radioactive materials
carried in a cloud of fog/spray which could drift in over land, adding
to the exposure.
It should be noted that all nuclear weapons detonated in the air give
rise to fallout, but where and when it occurs depends primarily on the
altitude of the explosion. With explosions in the air at altitudes
such that the fireball does not touch the ground, the fission
products, which are initially in gaseous form, rise with the fireball
to great heights into the troposphere or stratosphere. When the
temperature of the fireball becomes sufficiently low, the radioactive
materials form particles, through condensation and coagulation. These
particles are very small, and as a result their descent is very slow;
it may take many months before they come down to the ground.
EMP (Electro-magnetic Pulse)
This is a byproduct of the immediate energy release from a detonated
nuclear device which, as well as the other effects mentioned above,
also has the effect of altering the electrical properties of electrons
in the nearby atmosphere. This can produce intense electrical and
magnetic fields that can extend for considerable distances from the
point of detonation. The resultant electrical current eddies which
pass through these disturbed electrical fields give rise to the EMPs
that can, by themselves produce so much energy that they can severely
affect electronic-based equipment and electrical and radar
transmissions to the point of destroying equipment circuits,
components and communications. The effects of EMP diminish sharply
with distance from the point of detonation but can still cause damage
at ranges greater than those for the other 3 major effects (under
certain circumstances). Their main significance will be to
communications; the communications networks will probably be rendered
inoperative for considerable periods of time by interference from
EMPs, and the results of such breakdowns can well be imagined. At the
very moment when radio and other links (including land lines) between
various command levels are at their most important the EMPs will
render them virtually useless over large areas. Even when a nuclear
explosion has passed, the reverberations produced by the EMP in the
atmosphere may well linger to cause continued interruptions. Heavy
concentrations of fallout will produce radiation to create further
interference across radio and other communication frequencies.
Mass Fires
There are two types of mass fires - the conflagration and the
firestorm. Both are created from the hundreds of individual fires that
are started as a result of the nuclear blast.
Conflagration Fire
The conflagration is a large-area fire which is moved by a strong
wind, devouring everything in its path. The wind causes a literal wall
of flame to form and to move before it. This type of mass fire can be
expected to occur in many forests and in dry grassy areas. If you
consider the damage done over the last few years by brush and forest
fires in California, you can begin to understand the destruction that
would be caused by hundreds of such fires massing together.
Firestorm
The firestorm is a mass fire that burns intensely in one area. As the
many smaller fires burn, they cause air to be pulled into the area,
and smoke and superhot gases then escape upward. Once this airflow
pattern begins, it feeds on itself, creating a sort of a chimney
effect. Once the phenomenon is fully developed the air flows into the
area at between 80 and 115 kilometers per hour. Temperatures reach as
high as 1000 to 2000 degrees Fahrenheit, so even things that aren't
actually touched by flames are consumed and destroyed. Unlike the
conflagration, a firestorm doesn't travel; it moves little, if at all,
due the strong winds blowing in from all sides.
A firestorm can form in an area of many smaller fires in about 15 to
20 minuets and may last anywhere from 3 to 8 hours. Many parts of the
area may remain too hot to enter for a couple of days after the fires
have burned themselves out.
Nuclear Weapon Explosion Data (Surface Burst)
[1] [2] [3] [4] [5]
Total Heavy Moderate Light
Crater Fireball Destruction Damage Damage Damage
Yield Dia. Dia. Radius Radius Radius Radius
5 Kt 0.068 0.084 0.469 0.678 1.042 1.303
10 Kt 0.085 0.111 0.591 0.919 1.313 1.642
20 Kt 0.108 0.146 0.745 1.158 1.655 2.608
50 Kt 0.146 0.211 1.011 1.572 2.246 2.807
100 Kt 0.184 0.278 1.273 1.981 2.830 3.537
200 Kt 0.232 0.368 1.604 2.495 3.565 4.456
300 Kt 0.265 0.433 1.836 2.857 4.081 5.101
500 Kt 0.315 0.531 2.177 3.387 4.838 6.048
1 Mt 0.396 0.700 2.743 4.267 6.096 7.620
2 Mt 0.499 0.924 3.456 5.376 7.680 9.601
3 Mt 0.572 1.087 3.956 6.154 8.792 10.980
4 Mt 0.629 1.219 4.355 6.774 9.677 12.096
5 Mt 0.678 1.333 4.691 7.297 10.424 13.030
8 Mt 0.792 1.609 5.486 8.534 12.192 15.240
10 Mt 0.854 1.759 5.910 9.193 13.133 16.417
20 Mt 1.076 2.322 7.466 11.583 16.547 20.684
25 Mt 1.159 2.538 8.021 12.477 17.825 22.281
30 Mt 1.231 2.730 8.524 13.259 18.942 23.677
40 Mt 1.355 3.063 9.382 14.594 20.848 26.060
50 Mt 1.460 3.349 10.106 15.720 22.458 28.072
100 Mt 1.839 4.420 12.733 19.807 28.295 35.369
150 Mt 2.105 5.198 14.575 22.673 32.390 40.487
Kt = kiloton (1 Kt = 1000 tons = 2 million lbs.)
Mt = megaton (1 Mt = 1000 kilotons = 2 billion lbs.)
NOTE: All measurements are in kilometers
Damage Radius Modification Factors for Various Bursts Heights
Subsurface Explosion (-100 meters)
x0.80 x0.80 x0.80 x0.80 x0.80
Extra Low Airburst (600 meters)
x3.00 x3.00 x3.00 x3.00 x3.00
Low Airburst (2.5 kilometers)
x3.50 x3.50 x3.50 x3.50 x3.50
Medium Airburst (5.3 kilometers)
x4.00 x4.00 x4.00 x4.00
High Airburst (10 kilometers)
x4.50 x4.50 x4.50 x4.50
Extra High Air Burst (25 - 30 kilometers)
x0.75 x1.00 x3.00 x6.00
Outer Atmosphere Burst (Above 30 kilometers)
No significant damage done, EMP is the most destructive effect of this
type of detonation.
Crater Depths
Crater formation will occur when the height of the burst is less than
1/10th of the maximum radius of the fireball.
Surface Explosions and Low Airbursts
1 Mt 36.576 meters
10 Mt 60.960 meters
100 Mt 100.584 meters
Subsurface Explosions
1 Mt 88.392 meters
10 Mt 131.064 meters
100 Mt 192.024 meters
All values can be extrapolated for values in between.
Radius M.D. Factors for Ground and Aerial Targets The following damage factors
take Heat and Blast effect in account.
Note: A nuclear Detotion goes out in all directions - up as well as along the
ground.
Breakdown of the Blast Zones
.
. .
. . .
. .
[5] [4] [5]
.
. . . .
. . . .
. [3] _ [3] .
. . [2] . .
. _._ .
. .~ ~. .
. . [4] . .[2]. [1] .[2]. . [4] . .
. . . .
. ~-.-~ .
. . [2] . .
. [3] - [3] .
. . . .
. . . .
.
[5] . [4] . [5]
.
. .
. .
.
Diagram Outline
===============
[1] Vaporization Point (Crater)
---------------------------
Everything is vaporized by the blast.
[2] Total Destruction
-----------------
All structures above ground are destroyed.
[3] Severe Blast Damage
-------------------
Factories and other large-scale buildings collapse. Severe
damage to highway bridges. Rivers sometimes flow counter-
current.
[4] Severe Heat Damage
------------------
Everything flammable burns. People in the area suffocate due
to the fact that most available oxygen is consumed by the
fires.
[5] Severe Fire & Wind Damage
-------------------------
Residency structures are severely damaged. People are blown
around. 2nd and 3rd-degree burns suffered by most survivors.
Radiation Damage
Radiation damage is permanent and any further exposure is cumulative
and is added to the character's total. The following list is the classes of
radiation exposure a character is placed in according to their cumulative
total. The classes are to be used to determine which character should allow
themselves to be exposed to radiation if they are given the choice.
New stat addd for game play: Radiation Exposure Class (RC). All starting
characters start out with RC-0.
Exposure Classes
Class Exposure (in RADS) Risk
======= ================== ====
RC-0 0 Exposure May take normal risks
RC-1 > 0, <= 70 Should avoid further
exposure
RC-2 > 70, <= 150 Should not risk any further
exposure
RC-3 > 150 Only in absolute emergency
should any further exposure
be risked
Whole Body Radiation Damage from Craters and Fallout
The following table lists the effects of different whole body
radiation dosages on humans. The damage resulting from radiation is listed
with the convalescent period being the time required to recover from the
damage.
Note: Though the damage resulting from radiation can be healed the
radiation absorbed is permanent and cannot be "healed"
Dosage Incidence Convalescent
in RADS of Vomiting Period Effects
======= =========== ============ =======
0-25 0% N/A Practically no "short-term"
effects. May be some blood
cell damage.
26-100 5% 7 Days A small amount of nausea and
sickness for highest dose
level. Blood changes
noticeable.
101-200 100% Up to 40 Days Definite identifiable changes
in blood cells. Highest dose
causes hair loss, livid shin
spots, nausea, vomiting,
diarrhea, fevers, haemorrhages
and great fatigue. Heart
failure in some.
201-400 100% Several weeks Symptoms as above but more
to months severe. Fatal to 25% in low
range, 50% in high range.
401-600 100% Death Symptoms as above but now very
and occurring soon after
exposure. Death will occur
within 1d6 days.
601-800 100% Death Symptoms as above but
circulatory system and parts
of the central nervous system
malfunction rapidly. Death
will occur in 1d6 hours.
801-5000+ 100% Death Outcome very rapid.
Vomiting, falling blood
count, diarrhea, great
fatigue, internal bleeding,
organ failure, nervous system
collapse heart failure, coma,
and then death.
These doses are immediate or one hour doses, these are strictly
worse case possible results. The same dosage acquired over a longer time
span would have significantly less drastic effects.
Radioactive Contamination Zones in Crater
The most radioactive area would be the bomb crater itself. This
area is referred to as Zone 1, and the radioactive level of this zone varies
according to the type of burst (see following table). The size of this is
equal to the size of the bomb crater itself. Zone 2 is a secondary area of
radiation surrounding the bomb crater. The radiation in this zone is only
found in craters resulting from surface and subsurface bursts. The size of
Zone 2 is equal to the diameter of the bombs fireball. The contamination
levels will be very high for several decades after a ground/subsurface
burst.
The residual radiation for Zones 1 and 2 are shown below;
Subsurface Surface Air High Air
Burst Burst Burst Burst
========== ======= ===== ========
Zone 1 8000 RADS/Hr 6000 4000 2000
Zone 2 4000 RADS/Hr 3000 N/A N/A
Dose Rates
**********
The following table lists RADs per melee.
RADS/Hr RADS/ Melee
======= ===========
10000 42
9000 37
8000 33
7000 29
6000 25
5000 21
4000 17
3000 12.5
2000 8
1000 4
500 2
100 0.4
50 0.2
25 0.1
To find any value in between these just divide RADS/Hr by 240 (4
melees per minute x 60 minutes in one hour).
Fallout/Snowout
Fallout follows the t-1.2 law which states that for every sevenfold
increase in time after detonation there is a tenfold drop in radiation
output.
Example 1. A reading of X level of radioactivity
at Y hours after detonation would indicate a level of
radioactivity of .1X at 7Y hours after detonation. This
is accurate for 2500 hours (14 weeks) following the explosion,
thereafter the dose rate is lower than t-1.2 would predict.
Example 2. If a dose rate of 100 RADS/Hr was found at
1 hour after detonation (this assumes all significant fallout
from the bomb has fallen, therefore starting with the seven hour
point is probably more realistic) would be 10 RADS/Hr a 7 hours,
1 RAD/Hr at 48 hours (2 days), .1 RAD/Hr at 343 hours (2 weeks),
.01 RAD/Hr at 2401 hours (14 weeks).
Fallout blows downwind, and will fall out at some distance from the
explosion. The following are some examples of various nuclear fallout
levels after Y hours and the percentage of population dead after exposure to
the levels of fall out.
Time RADS/Hr Death Percentage in population
An area 16 Km wide by 48 Km downwind from a single 1 MT ground burst
1 Hr. 1,000 100% dead at 1 hour of exposure
7 Hours 100 50% dead within 7-8 hours of continuous
exposure
2 Days 10 50% dead for 5 days of continuous exposure
2 Week 1 50% dead for 1 month continuous exposure
14 Weeks 0.1 0% dead from radiation hereafter
An area 19 Km by 152 Km downwind for a single 1 MT ground burst
1 Hr. 0 Radiation has not arrived yet
7 Hrs. 50 50% dead for 18 hours of continuous
exposure
2 Days 5 5% dead for 2 weeks of continuous exposure
2 Weeks 0.5 0% dead from radiation hereafter
14 Weeks 0.05 0% dead from radiation hereafter
The above examples indicate conditions and exposures that would only be
acceptable in wartime. In the examples the wind is continuous in
direction and velocity. A real wind would not make such nice neat
patterns.
Examples of levels of fallout from a single 1 Mt ground burst with a 24
kph wind.
As a very general rule of thumb, you can expect fallout to move
approximately 48 kph. The fallout from a medium-size bomb will extend for
several 100's of with the heaviest concentrations within about 325 km of
the blast. Areas farther downwind may not receive any fallout for several
hours; those closer may get it within fifteen minutes.
The following table shows approximately how long it will take, under
normal atmospheric conditions, for fallout to reach the ground at
specified distances downwind from a 5 Mt burst.
Distance from Blast Fallout Will Begin After
=================== ========================
8 Km 20 Minutes
40 km 1 Hour
160 Km 3-5 Hours
Fallout usually drifts down over a period of time; it doesn't just
plop down all at once. In areas receiving immediate fallout, the particles
may continue to fall for a much as 24 hours. Outside the immediate burst
area most of the fallout - about 80% of it - will come down within the first
48 hours. Any rain or snow will bring it down even faster and in greater
concentrations. Many of the smaller particles may stay in the atmosphere
for months or even years.
The following table lists estimated levels of radiation one hour after
the detonation of a 20 Mt bomb.
Distance from Blast Radiation Level
=================== ===============
8-24 km 10000-1000
24-120 Km 1000-100
120-193 km 100-0
For all practical purposes, radiation levels in excess of a few
thousand rads can be ignored. The areas that receive such heavy fallout
also will be hit hard by the initial blast and heat.
The following table shows how a starting radiation level of 2000
rads will decay and the total accumulation one can expect as it does so. An
area receiving this amount of fallout is likely to be relatively close to a
blast site. Figures such as these are not exact. The actual dosages and
rates of decay will be altered by local factors such as weather and terrain,
but this table does provide a good example.
Time Interval Interval Dose Cumulative Dose
============= ============= ===============
1st-2nd hour 2000 2000
2nd-3rd hour 1000 3000
3rd-4th hour 640 3640
4th-5th hour 440 4080
5th-10th hour 1200 5280
10th-24th hour 1200 6480
2nd day 760 7240
3rd day 400 7640
4th day 240 7880
5th day 180 8060
6th day 140 8200
7th day 96 8296
2nd week 430 8726
3rd week 230 8956
4th week 110 9066
2nd month 175 9241
3rd month 80 9321
4th month 50 9371
5th month 30 9401
6th month 20 9421
6th-12th month 50 9471
2nd year 16 9487
3rd year 5 9492
4th year 3 9495
Areas covered by a given accumulated doses from fallout
Upper Limit of
Accumulated Dose Area (Km2)
**************** **********
RADs 1 Mt 10 Mt
==== ==== =====
1000 900 11000
800 1200 14000
600 1700 18000
400 2600 27000
200 5500 52000
100 10500 89000
50 18600 148000
25 32700 234000
10 56000 414000
These figures are just rough estimations of the actual areas covered.
EMP (Electro-magnetic Pulse)
EMP damage goes out in all directions, to distances greater than
that of the effects of the blast itself.
As a general rule of thumb, the distance an EMP will travel is
directly related to the height of the burst, the strength of the blast and
any natural features in its path.
Rough rule of thumb for the EMP distance covered.
=================================================
(Height of burst in km x 1000) x (Megatonnage of bomb / 10) = radius of
EMP in km
Example:
A 10 Mt bomb detonated at a height of 50 Km.
(50 x 500) x (10/10) = 25000 Km radius
Damage from Pulse
=================
The damage inflicted from the pulse will be to electrical equipment
only ie computers, radios, telephones, mecha, aircraft, power distribution
networks and any other device not hardened from an EMP. The manifestation
of this damage will be burnt out electronic components, circuits fried
beyond repair etc.
Miscellaneous Notes on Nuclear Explosions
Visibility Distances
====================
The tables shows the distances at which an exposed person would
suffer second-degree burns, or at which exposed dark coloured clothing or
paint would catch fire. It further shows how these distances are affected
by varying visibilities. Distances are in kilometers.
Visibility (km) Size of bomb (Mt)
=============== =================
1 5 10 20 50 100
---------------------------------------------------------------------
16 10 18 21 24 26 28
48 11 22.5 26.5 29 35 42
80 14 27 33 42 52 61
---------------------------------------------------------------------
The next table looks at the same effects from weapons detonated at an
altitude to maximize blast effects.
Visibility (km) Size of bomb (Mt)
=============== =================
1 5 10 20 50 100
----------------------------------------------------------------------
19 14 29 40 51 76 98
4 10.5 22.5 29 39 61 80
1.9 4.5 10 13 19 26 30.5
0.96 0.5 3 4 6.5 11 18
----------------------------------------------------------------------
19 km visibility is considered an average clear day.
4 km visibility is considered a medium-hazy day.
1.9 km visibility is considered a day of heavy cloudiness.
0.96 km visibility is considered a day of dense cloudiness.
Wind Speeds
***********
The following table gives examples of wind speeds that could be
expected at various distances from a 20 Mt explosion.
Surface Optimum
Distance Burst Air Burst
(km) (kph) (kph)
======== ======= =========
3.2 2333 3138
4.8 1046 2253
8 483 684
16 177 321
24 88.5 185
32 56 121
48 30.5 72.5
80 14.5 32
These figures are approximation, since variables such as terrain and
obstructions affect the speeds. The winds will be highest in areas where
the land is flat and smooth; hilly terrain or many large buildings will
lower velocity. When I say that the winds will be lowered so much that they
are no longer be any danger. Rather, the area of danger will simply be
decreased somewhat.
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