Make your own free website on Tripod.com

RIFTS by Dustin M. 
Your Premiere Source for Quality RIFTS Supplements Since 1995


Site Navigation

 

Home
Advanced Rules
Answers & Erratas
Armour
Campaign Info
Equipment & Supplies
Humour
Magic
Miscellaneous Info
Monsters & Critters
Psionics
R.C.C.'s & O.C.C.'s
Reference Material
Skills
Vehicles
Weapons


Awards & Feedback
Guestbook
Links & Web Rings
Search
What's New

Advanced Nuclear Explosion Rules

By: Gary Gore

[Reprinted by special permission of the author]

[Please note that this information is intended for gaming purposes only; some figures and effects have been modified to better suit gaming scenarios]


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 u p 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 fro m 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 g round, 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 comedown to the ground.

EMP (Electromagnetic 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 super hot 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 minutes 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
Diameter

[1]

Fireball
Diameter

[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.

Damage Radius Modification Factors for Various Bursts Heights

Subsurface Explosion (-100 meters)

x0.80

x0.80

x0.80

x0.80

x0.80

Extra Low Air burst (600 meters)

x3.00

x3.00

x3.00

x3.00

x3.00

Low Air burst (2.5 kilometers)

x3.50

x3.50

x3.50

x3.50

x3.50

Medium Air burst (5.3 kilometers)

x4.00

x4.00

x4.00

x4.00

High Air burst (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 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.

TDR:

 Totally Destroyed

HDR:

 3d6 x 1,000 M.D.

MDR:

 2d6 x 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 x 1,000 M.D. to structures on/under the ground only

MDR:

 3d6 x 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"

    Dosage in RADS

    Incidence of Vomiting

    Convalescent 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 skin spots, nausea, vomiting, diarrhea, fevers, hemorrhages 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.

    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
    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 r ate 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 hour s, 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

    .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

    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 (Electromagnetic 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 i.e. 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 colored 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

    .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.

Home

Disclaimer

Site Index

webmaster@rifts-rpg.com

© 1995 - 1999 this page, contents, and accompanying pages, Dustin M. Ramsey, Dustinian Industries, and other authors as specified. Duplication of contents with permission only!

Click Here!