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.

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.