Nuclear Weapons

"The splitting of the atom has changed everything save our mode of thinking and thus we drift toward unparalleled catastrophe"
- Albert Einstein

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 lifted 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)




Yield



Crater
Dia

[1]

Fireball
Dia.

[2]
Total
Destruction
Radius

[3]
Heavy
Damage
Radius

[4]
Moderate
Damage
Radius

[5]
Light
Damage
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 lb.)
Mt = megaton (1 Mt = 1000 kilotons = 2 billion lb.)
Note: All measurements are in kilometers.



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 Air bursts

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 Detonation goes out in all directions - up as well as along the ground.

Surface and Air Burst
TDR - Totally Destroyed
HDR - 3d6*1,000 M.D.
MDR - 2d6*100 M.D.
LDR - Only S.D.C. Inflicted

Note: For aerial targets roll the following percentage additions against the particular skill used to fly the aerial vehicle only if the vehicle survives the initial blast wave. Roll again for the second return blast wave with the same modifications.

HDR: -90%
MDR: -70%
LDR: -40%

If the roll fails, the pilot loses control of the aircraft/mecha, which results in the aircraft tumbling out of the sky and should be role-played to it's fullest.

Sub-Surface Explosion
TDR - Totally Destroyed
HDR - 4d6*1,000 M.D. to structures on/under the ground only
MDR - 3d6*100 M.D. to structures on/under the ground only
LDR - Only S.D.C. Inflicted to structures on/under the ground only

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 added 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< RADS <=70

Should avoid further exposure

RC-2

70< RADS <=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"

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.

Gaming Penalization for Radiation Levels

RAD Level

Penalty

0-25

None

26-100

P.S. -1, P.P. -1, P.E. -1

101-200

P.S. -2, P.P. -2, P.E. -2, P.B. -2, P.P.E. -10

201-400

P.S. -3, P.P. -3, P.E. -3, P.B. -3, P.P.E. -20

401-600

P.S. -5, P.P. -5, P.E. -5, P.B. -5, P.P.E. -40

601-800

P.S. -7, P.P. -7, P.E. -7, P.B. -7, P.P.E. -50

801-5000+

P.S. -15, P.P. -15, P.E. -15, P.B. -15, P.P.E. -100

The above effects are permanent and cannot be modified by normal means.

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 Burst

Surface Burst

Air Burst

High Air Burst

Zone 1

8000 RADS/Hr

6000

4000

2000

Zone 2

4000 RADS/Hr

3000

N/A

N/A

Dose Rates

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 at 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. following are examples of various nuclear levels after Y hours percentage population dead exposure to 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.

Distance (km)

Surface Burst (kph)

Optimum Air Burst (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.

Back to Revised and Expanded Missile & Bomb Tables.

The original author of this article has requested not to be named.
The article is edited by Chris Curtis (curtis@thepentagon.com) and
Mad Dog (maddog1@Alaska.NET).
Copyright © 1997, 1998 Original Author and Chris Curtis. All rights reserved.

Robotech® is a registered trademark owned and licensed by Harmony Gold USA, Inc. Characters for Robotech are copyright 1985 Harmony Gold USA, Inc./Tatsunoko Production Co., Ltd. All Rights Reserved.

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