nuclear bombs?

Question

What would happen in a city was hit by a thermonnuclear bomb? Death, damage and radiation wise?
thanks :)

Answer 1

It depends. How high above the city...any mountains, how big a bomb?

The energy released from a nuclear weapon comes in four primary categories:

Blast—40-60% of total energy
Thermal radiation—30-50% of total energy
Ionizing radiation—5% of total energy
Residual radiation—5-10% of total energy


A 1 megaton explosion would level and burn a mile around, 3 miles around building would be destroyed, moderate damage to buildings at 6 miles.
People would have 3rd degree burns for 8 miles and 2nd degree burns for 10
Lethal radiation for miles around, fallout would kill people for years and could be windborn for dozens of miles.

Answer 2

Dependin on size (measured in kilotons), A nuclear warhead
will first disrupt all electrical and radio frequencies. Then the initial blast upon first impact will instantly disinigrate everything in its path within a twenty mile radious. After this a
cloud of radiation (The infamous Mushroom in the sky) falls to
ground level and will melt the flesh off of everything it comes in contact with, and as it is dispersed and carried with the wind it poisins and contaminates the soil, all waters, and food sources. This can cover alot of territory, and virtually the largest cities cannot withstand any of the above and all inhabitants would parish. If you want to see this with your own eyes, I would strongly suggest the Movie called "The Day After". It is an accurate depiction of an actual event.

Answer 3

D: All of the above. Not only is dropping a nuke on a city the same as alot of any other explosive, it ads that extra cause of death: radiation. The city would be totlaly helpless basically. Not only will it lose all function, those surviving the inital blast will have a hard time contacting outsiders

Answer 4

Here is a frame of reference:

One Trident II missle from an Ohio class submarine can carry up to 12 warheads all with a yield of 200 kilotons each.

The bombs dropped on hiroshima and nagasaki had only a 12.5 kiloton yield.

Answer 5

Well I do know that today's nukes are about 1,000 times more powerful than the ones dropped on Japan so if you've ever seen what happened to those Japanese cities just think of it being a 1000x worse.

Answer 6

IT fall down go BOOOOM

Did you not learn about Hiroshima and Nagasaki in school?

Did you not hear about the people who died in agony for decades after and the upsurge in physically deformed children?

Answer 7

the world would colapse if not from extreme health hazards from panic and civil rebellion they should not exist

Answer 8

http://pro-resources.net/nuclear-power-plant-maps.html

Answer 9

Depends on the size of the device, is it air burst, surface or subsurface. Also the weather can influence distance of radiation/fallout travel and recovery.
NUCLEAR WEAPONS

EFFECTS OF NUCLEAR WEAPONS


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INTRODUCTION



The previous article explained the atomic structure and the principles that govern the design and operation of nuclear weapons. This article gives a brief overview of the nuclear weapon outputs and detailed explanation of thermal radiation and blast along with their respective effects on men and equipment.





GENERAL DATA



Development of Fireball

When a nuclear weapon is exploded, about 85% of the energy is released in the form of the kinetic energy of the fission products and the remaining 15% is emitted as nuclear radiation either immediately or later. The kinetic energy of fission products is quickly shared with the weapon debris producing several tens of million degrees of temperature and a pressure of many million atmospheres. The debris begins to radiate intense thermal energy but it is dwarfed by radiated soft X-rays with photon energy of several KeV. Most of these do not travel far to a great distance and are absorbed by air thus spreading the energy over an ever-increasing volume around the point of detonation. This constitutes the nuclear fireball, the size of which depends on the weapon yield. At the same time, the fireball starts to rise rapidly at the rate of about 100 meters per second initially and then slows down. As it moves up in the atmosphere, it radiates away its energy and cools down to an extent that it is no longer luminous. The debris, which was initially in the form of vapours now, condenses to create a visible cloud. The debris continues to rise under buoyancy and other forces until it finally stabilizes and spreads laterally at a height depending on the weapon yield (about 2.5 km for a 1 kT burst or 20 km for 1 MT). The Table-1 below shows the fireball radius for different yields:



YIELD (kT)
RADIUS (Meters)

1
67

20
222

1000
1062


Table-1





Thermal Radiation

One might expect that the temperature of the fireball should fall steadily with time. This certainly is not the case when measured from ground. There are definite variations in the temperature with passage of time as shown in Figure-1 below:





There are two factors which cause these variations: firstly the nuclear radiation creates absorbing compounds in the atmosphere and as a result, at 10-4 seconds after the explosion when the actual fireball temperature is close to 106 degrees, its temperature as measured from the ground is only 3000 degrees. As the absorbing compounds decay and the heat begins to radiate through to the ground, another effect then occurs. The kinetic energy of the fission products, which is steadily being transferred to other weapon debris generates a shock front or blast wave moving out through the fireball into the surrounding air. Its pressure is extremely high and the air behind it is heated by compression making it opaque to the thermal radiation from the fireball. This blanketing effect of the shock wave is at its maximum at about 10-2 seconds and the heat received on ground is entirely from air in the shock front. The time tmin corresponding to this stage is called “Thermal Minimum”.



The masking effect decreases as the shock front spreads and the thermal radiation from the fireball reaches the ground unhindered for the first time. For a 20 kT yield weapon, this occurs at about 0.16 seconds after the explosion and is called tmax with its actual temperature of around 8000 degrees as measured from the ground. Thus we see that the thermal radiation reaches the ground in two pulses but 99% of heat reaches the ground during the second pulse. The total length of the thermal pulse may be assumed to be the time in which 80% of the thermal radiation is received. This is less than half a second for 1 kT yield and over 8 seconds for 1000 kT. The interesting fact is that weapon yield hardly affects the observed temperatures, but a weapon of higher yield produces much larger fireball, which takes longer to cool. The time scale therefore depends on the yield. Except for Enhanced Radiation Weapons, the proportion of thermal energy out of the total energy released is about 35%.







Blast

After detonation close to the point of burst, the blast wave moves in all the directions and its very high pressure causes its velocity to greatly exceed the normal velocity of sound. At a distance of a kilometer, the velocity falls to around the speed of sound for low yields. The main features of the blast are shown in the Figure-2 below:



· Undisturbed air lies to the right of the Shock Front.

· A region of positive over-pressure called the “Positive Phase” lies to the left of Shock Front. The air density in this region is high which causes the overpressure.

· The region of under-pressure called the “Negative Phase” with below normal value of air density lies close to Ground Zero (GZ).



The non-uniformity of density indicates that there has been a mass movement of air molecules and thus during the positive phase, the wind blows outwards from GZ while the direction is reversed in the negative phase. The blast wind produces dynamic pressure, which has its own effects in addition to synergy given by the reflected waves from the ground.





Nuclear Radiation

Nuclear radiation comprises only 15% of the total energy released by a nuclear weapon except for the Neutron bomb. In contrast, blast and heat account for 50% and 35% respectively of the total energy. The sources of radiation from a nuclear weapon burst are as given below:



· Neutrons. These are emitted at high velocities of up to 1/30 of that of light and arrive at the ranges of interest within few tens of microseconds to few tens of milliseconds. A small number of neutrons are emitted after a delay of seconds or even few minutes after the explosion, which may cause fratricide if more than one weapon is exploded close together in time and space.



· Gamma Rays Emitted During Fission. They travel at the speed of light and cover a distance of one kilometer or so in around 3 microseconds.



· Gamma Rays Produced by Collision of Neutrons. When neutrons collide with or are captured by the atoms in the weapon debris and the atmosphere, gamma rays are produced which arrive with the fission gammas.



· Gamma Rays and Beta Particles from Decay of Radio-Active Fission Products. The Beta Particles have a limited range of a few meters in air as compared to neutrons and gamma rays, some of which travel thousands of meters up in the air.









Immediate Nuclear Radiation

All the radiation reaching the ground within one minute after a low airburst is normally described as “Immediate Nuclear Radiation”.



Residual Nuclear Radiation

Any radiation received after one minute of the explosion is called the “Residual Nuclear Radiation”. It is caused by the “Fallout” and “Neutron Induced Activity” (NIA), the former being not very significant for an air burst while the latter has detrimental effects. Neutrons, which reach the ground, are captured by nuclei in soil and equipment and the products of these reactions are usually radioactive and are a risk to personnel.





Burst Heights

Optimum Height. For a 1 kT weapon, the maximum blast damage radius against hard targets such as tanks etc is achieved when it is exploded 60 meters above the ground. For any other yield, the “Optimum Height of Burst” is given by the formula:



Opt Ht = 60 W 1/3 meters.



Surface Burst. A large crater is produced when the weapon explodes on the ground. The blast wave is not greatly affected but the dust and debris reduces the range of thermal radiation. The “Immediate Nuclear Radiation” is also affected particularly for very high and very low yields, which will be discussed separately.



On the other hand, the “Residual Nuclear Radiation” gets a boost from surface burst. While the Neutron Induced Activity increases due to a larger number of neutrons striking the ground, the major effect is on the fallout. If the height of the burst is optimum i.e. 60 W 1/3 meters, the fireball fails to touch the ground and the fallout is militarily not significant, but if the burst is at a lower height or on the surface, a large amount of soil is drawn up into the fireball providing ample supply of coarse particles on which the vapourized fission products condense. These fall from the radioactive cloud and cause intense local fallout mainly downwind from GZ.



Underground Burst. The greater the depth of the burst, the larger is the reduction in thermal and immediate nuclear radiation emerging into the atmosphere. If the explosion is so deep that it does not break through the ground, nearly all the energy goes into the ground effect and effects of other weapon output are negligible above the ground.



Underwater Burst. An explosion below the surface of water produces no thermal or EMP effects above or below the water but it does create intense underwater shock waves. The nuclear radiation received by the surface vessels would be from fission products and NIA in the water thrown up by the explosion.



Exo-Atmospheric Burst. When a nuclear burst occurs above the atmosphere, the low energy X-rays are not converted in to heat as in the case of explosion taking place within the atmosphere. The Gamma rays and neutrons spread out without much absorption and create a phenomenon called “System Generated Electromagnetic Pulse” (SGEMP), which may have serious effects on electronic equipment. In addition, a single short pulse of thermal radiation is produced when the X-rays hit the upper layer of atmosphere.





Enhanced Radiation Weapons

The neutron bomb obtains most of its energy from fusion and the Immediate Nuclear Radiation is the dominant effect for this weapon. The Table-2 below shows the comparison between ERWs and fission weapons for their relative energy outputs:





OUTPUT
PERCENTAGE OF ENERGY

FISSION WEAPON
ERW

THERMAL RADIATION
35
< 20

BLAST RADIATION
50
< 30

IMM NUCLEAR RADIATION
5
> 50

RESIDUAL NUCLEAR RADIATION (FALLOUT)
10
NEGLIGIBLE

RESIDUAL NUCLEAR RADIATION (NEUTRON INDUCED ACTIVITY)
SLIGHT
MORE


Table-2



The fallout from ERW is negligible because the product of the fusion reaction is stable helium. This perhaps is the best form of a tactical weapon since it produces more casualties per kiloton by virtue of its greater output of nuclear radiation than a fission weapon and at the same time has reduced collateral damage.





Time Histories of Weapon Outputs

The Figure-3 below shows the time history of each of the outputs received at a target 1km away from a 27 kT low air burst. A logarithmic time scale has been used to handle widely different velocities and durations of several outputs. The starting point is the instant at 10-9 secs after the burst when the first outputs (gamma rays and EMP) reach the target:



THERMAL RADIATION



Here, the thermal radiation will be covered in detail in respect of estimating the total heat energy at any range from a nuclear weapon and its effects on men and materials. The thermal threat is specified by the total thermal energy comprising ultraviolet, visible and infrared radiation striking a unit area at a given range. It is denoted by “Q” and expressed in either Joules per square meter (J/m2 ) or calories per square centimeter.



The total energy released in all forms by the explosion of a W kT weapon is 4.186 X 1012 W joules. As mentioned earlier, 35% of total energy appears in the form of heat from an airburst and therefore to find Q at a range R, the following formula is used:



0.35 X 4.186 X 1012 W

Q = joules/m2

4 II R2





However, this relation gives Q for an atmosphere that is perfectly transparent to all thermal radiation. Under normal conditions, the thermal energy will be scattered and absorbed due to the presence of water droplets, dust particles and smoke. While scattering increases the amount of energy arriving at a target, the absorption causes reduction, which is an important factor. In order to predict the effect of this reduction, the factor of transmissivity (T) is introduced to the above formula:



0.35 X 4.186 X 1012 W T





Q = joules/m2

4 II R2







If Q is wanted in calories/cm2 , the value in J/m2 should be multiplied by 2.4 X 10-5 .



Transmissivity depends on the visibility and its variation for an average to good visibility of 20 km is shown in the Figure-4 below:



When these values are used in relation to Q, we obtain the values of thermal energy for a 1 kT yield as shown in Figure-5:



This graph can be used to find “Q” for any other yield since for a given range and visibility, Q is simply proportional to the yield. For example if Q is required at 1000 meters from a 5 kT weapon, it will be five time the thermal energy from 1 kT at this range, which from the graph is 110 kJ/m2 . Therefore the energy from 5 kT is 550 kJ/m2 .



The graph may also be used to find the range at which Q has some particular value for a weapon of any yield. Suppose we want to know the range from a 10 kT weapon at which Q is 260 kJ/m2 when the visibility is 20 km. This will be the range at which 1 kT gives a thermal energy of 26 kJ/m2 , which is 2000 meters.



In case the visibility is poor, a correction must be made by multiplying the Q obtained from the graph by correction factor indicated in Table-3 below:





RANGE IN KILOMETERS
.5
1
2
4
8

CORRECTION FACTOR
.8
.5
.33
.25
.2


Table-3



Certain correction must also be made for enhancement of thermal radiation reaching the target due to reflection from clouds or snow or both. Neither of these have significant effect at ranges of 1 km and less, but at greater ranges the Q obtained from the graph and corrected for transmissivity must be multiplied by 1.5 if only clouds or snow are present individually. When both are present the correction factor is twice i.e 2.25. On the other hand, if the burst take place on ground, a large amount of dust thrown up and the thermal energy reaching the target is reduced to half of the value for an airburst. There is additional information that is required to correctly predict the thermal effects at a given range. This pertains to the shape and duration of thermal pulse. The Figure-6 below provides the data for all yields of a low air burst:



Here the time is expressed in terms of tmax, which is the time to second maximum of observed fireball temperature. The graph shows only the second pulse, which carries 90% of the total thermal energy. The time tmax , increases with yield and is given by the formula:



tmax = 0.0417 W 0.44 seconds





One curve indicates the build up of total thermal energy with time. The other shows how its rate of arrival (dQ/dt) varies during the pulse and is known as “Irradiance” (P) in kJ/m2 specified in terms of its peak value Pmax , which is simply related to Q and t :



Pmax = 0.38 Q/tmax kJ/ m2 per second





Thermal Effects on Man



Skin. The thermal energy needed to cause second-degree burns to bare skin is about 160 kJ/m2 from a 1 kT weapon which occurs at a range of about 800 meters. For a 1 MT weapon due to its longer pulse, the thermal energy required to produce the same effects rises to 270 kJ/m2 which occurs at about 20 km from GZ. However, adequate protection like wearing NBC suit over combat clothing, the thermal energy from a tactical weapon needed to cause extensive second-degree burns is about 1.3 MJ/m2 . Thus proper clothing greatly reduces the vulnerability of man to thermal radiation.



Eyes. The most important effects from thermal radiation (light & heat) are the dazzle and retinal burns. By day, the dazzle may last for about two minutes but this increases to around 10 minutes during night. The dazzle effect can be experienced at ranges of tens of kilometers even from quite a low yield weapon. Retinal burns are more severe but not widespread. It has been estimated that only 2-3 percent of those affected by dazzle will receive retinal burns, and very few of these will suffer permanent partial or complete blindness.





Effects on Material



The surface and nature of material will decide how it is affected by thermal radiation. Extremely high temperatures may be reached causing ignition. Some typical energies required for ignition are given in the Table-4 below:







MATERIAL
IGNITION ENERGY (kJ/m2 )

YIELD 1kT
YIELD 1MT

KHAKI DRILL FABRIC
210
460

DARK WOOL FLANNEL
250
550

COMBAT SUIT
630
1260

DRY GRASS & UNDERGROWTH
80-120
200-300

DRY CARDBOARD
250
550

PLASTICS
160-250
370-550




Table-4



While plastic has many advantages such as low cost and lightweight, it is vulnerable to thermal effects like melting distortion, charring etc. In case of metals, conduction of heat to the interior of the equipment can cause damage. Optical systems used in military equipment are particularly at the risk from thermal radiation, which can cause crazing of lenses, charring of non-reflective internal coating and damage to filters and photo-cathodes.



Military Significance



Thermal effects can be severe at large ranges but these can be reduced by light covers and as such these effects as casualty producers are not considered significant to be taken into account for target analysis. Enemy casualties occurring from thermal radiation are taken as bonus.





BLAST



Next we come to blast and see how it is influenced by factors such as weapon yields, height of burst and range and its interaction with the targets. Under the normal conditions, the velocity of sound is 330 meters per second (1100 ft/sec or 760 mph) regardless of its loudness. In a nuclear explosion, where the peak pressure is many times that of normal ambient pressure of 101.3 kPa (kilo Pascal) or14.7 psi (1 kPa= 0.145 psi and 1 psi = 6.895 kPa), the passage of shock wave causes transient heating of air due to compression. This results in marked increase in the velocity of the shock wave. The closer one is to the burst and higher the yield, the greater is the overpressure and hence greater the velocity. As a comparison, while the shock wave from a 1 kT weapon travels its first mile in 4.0 seconds, it takes just 1.25 seconds for the shock from 1 MT weapon to cover the same distance.





Static Overpressure

As mentioned earlier, the shock front marks the boundary between the undisturbed area in front and region of static overpressure behind (the positive phase). During this phase the highest value achieved for static overpressure is called “Peak Static Overpressure” (PSO). A 500 kg HE explosive would produce a PSO of 87 kPa (12.5 psi) at 30 meters range but the same pressure will be produced at 300 metrs by a 1 kT weapon; for a 1 MT, the range is 3000 meters.



The static overpressure steadily falls after the passage of shock front and after a time called the “Positive Phase Duration”, the pressure momentarily passes through the ambient pressure value. At a given range, the positive phase duration increases with yield and for a given yield the duration increases with range (see the Table-5 below):





YIELD
RANGE IN METERS


300
1000
3000
10,000


PEAK STATIC OVERPRESSURE




87 kPa




11.9 kPa




2.1 kPa




0.29 kPa




1 kT




12.5 psi


1.7 psi


0.30 psi


0.043 psi




1 MT


*


908 kPa


87 kPa


11.9 kPa




*


130 psi


12.5 psi


1.7 psi


POSITIVE PHASE DUARTION






0.22 sec






0.47 sec






0.75 sec






0.97 sec




1 kT






1 MT


*


0.73 sec


2.2 sec


4.7 sec



Table-5



* Blast wave not separated from the fireball.





The important point here is that damage to certain class of targets will depend on the product of overpressure and its duration.





Dynamic Pressure

As the shock front moves, it also creates intense gust of wind, which moves outwards from GZ during the positive phase and backwards towards GZ during negative phase. This wind exerts dynamic pressure on the targets along its path and its value will depend on the wind velocity. The outward blast wind is the strongest immediately behind the shock front with peak dynamic pressure.



In order to study a certain correlation between the different characteristics of blast, the Table-6 below may be of interest:



PEAK STATIC OVERPRESSURE


10


20


50


100


200


500

kPa

psi
1.45
2.90
7.25
14.5
29.0
72.5

PEAK DYNAMIC PRESSURE


0.35


1.37


8.26


31.0


110


516

kPa

psi
0.05
0.20
1.20
4.5
16.0
74.8

PEAK WIND VELOCITY


23


44


100


176


292


524

m/sec

mph
51
99
225
394
653
1172

SHOCK WAVE VELOCITY


354


367


405


462


545


777

m/sec

mph
792
821
906
1033
1219
1738

Table-6



This table is quite general – a PSO of 50 kPa for instance is always associated with a peak wind velocity of 100 m/sec, peak dynamic pressure of 1.2 kPa and shock velocity of 405 m/sec. However the data applies to burst at optimum height (60 W ) for hard targets. About 10 kPa tends to damage the aircraft, 20 kPa to ship and 50-200 to land based systems.






From an air burst, when the shock wave hit the ground, it is reflected and this wave travelling in a heated air at a higher velocity eventually catches up and merges with the incident wave to form the “Mach Stem”. Because of it, the target on ground experiences higher overpressures and winds than it would have if the ground were not there.





Blast Wave Data and Scaling Laws



The Figure-7 below show the Peak static Overpressures on the ground produced by 1 kT weapon at various heights:



It also explains the concept of Optimum Height of Burst. Suppose, some target requires a PSO of 105 kPa to damage it, the figure indicates that a 1 kT weapon, if detonated at a height of 200 meters produces 105 kPa out to a maximum range of 335 meters. A surface burst would produce the required pressure only out to 255 meters, and a burst at above 200 meters would likewise be effective out to a range less than 355 meters. Thus for a 1 kT yield and this particular target, 200 meters is the Optimum Height of Burst.



Blast overpressures for other yields can be found by using “Scaling Laws”. The first law states that if a weapon of yield W (usually 1 kT) produces at a range R some particular value of PSO ( or some other blast wave parameters such as peak dynamic pressure, shock wave velocity or blast wind peak velocity), then a weapon of yield W2 will produce the same value of that parameter out to a range R2 given by formula:



1/3

R2 / R1 = (W2 / W1 )





A similar law applies to the times such as those of arrival or positive phase durations at ranges where the overpressures are the same:



1/3

T2 / T1 = R2 / R1 = (W2 / W1 )





These scaling laws apply to mid-air burst where ground has no effect but for them to be valid for low air-bursts, the height of the burst has to be scaled in the same way.





Interaction with the Target



As the shock wave approaches the target, for the first few milliseconds, the static overpressure along with dynamic wind pressure tend to displace the target. However, in about 10-15 milliseconds, the static overpressure envelops the target and exerts crushing force on all the sides but now has no displacing effect. This short-lived displacing effect of the static overpressure is called the “Diffraction Loading” of the target.



The dynamic pressure continues to act on the front face of the target for the duration of the positive phase, which may be several hundred milliseconds. The actual force acting on the target at any moment is the product of the dynamic pressure, the area on which it acts, and the drag coefficient of the target. This force due to wind pressure is called “Drag Loading”. Most of the military targets are vulnerable to drag loading and are called “Drag Targets”. However, the dominant displacing force on a large building will be from diffraction loading and so it would be a “Diffraction Target”.







Blast Effects



Personnel. The direct effects of blast on men depend simply on the peak static overpressure. A PSO of 120 kPa would be extremely damaging to eardrums while lung damage can take place by 140 kPa, and 50% lethality is likely to result from exposure to 400 kPa (60 psi). On the other hand, a man lying on the ground may be literally blown away by the blast and suffer serious injury when he strikes a tree, a building or ground. One may expect 50% causalities from this cause at a range from 200-300 meters from a 1 kT weapon. This is called the indirect effect of the blast.





Vehicles and Equipment. The smaller military targets in the battlefield are expected to be affected by drag loading but some targets, which are weak against compression, may be at risk from crushing effects of overpressure. The Table-7 below shows the effects of PSO on targets at ranges where 50% of them would suffer enough damage requiring workshop repairs:





TARGET
1 kT
1 MT

RANGE (m)
PSO (kPa)
RANGE (m)
PSO (kPa)

TANKS
170
270
2700
150

FIELD ARTILLERY
200
200
3200
120

SOFT VEHICLE
300
125
4800
60

MAN (PRONE)
240
160
3800
100

BRICK HOUSES
750
27
7500
27

INDUSTRIAL BUILDINGS
350
110
5500
50

OVERHEAD TELEPHONE LINES
485
55
7900
30

NATUARAL CONIFER FOREST
760
35
12000
20


Table-7



Note that damage is produced by much lower values of PSO from 1 MT burst than from 1 kT due to much greater duration of blast.



Ships and Aircraft. Some elements of ship’s structure such as radar antennae and mast would be damaged by the blast wind. Static overpressure on the other hand would cause damage to hull and other machinery. Typically a PSO of 25 kPa marks the onset of significant damage and hull may be ruptured at 75 kPa. Aircraft are very vulnerable to air blast, particularly if it approaches from the side or the rear. Most effects are from static overpressure with destruction or damage beyond repair at 30 to 70 kPa.





SUMMARY



The major points of the article are enumerated below for easy reference:



Thermal Radiation



· Thermal radiation accounts for 35% of the total energy released by a nuclear weapon except the Enhanced Radiation Weapon (Neutron Bomb).



· Thermal radiation reaches the target in two distinct pulses separated by time. The second pulse, which carries around 99% of the total thermal energy, is more relevant to target damage than the first pulse.

· The duration of the thermal pulse depends on the weapon yield; higher the yield, the longer will be the pulse duration.



· With increased duration of the thermal pulse, the effects of the thermal radiation are evident at greater ranges from GZ.



· The amount of thermal energy reaching the target is reduced by the presence of dust, smoke, water droplets and bad visibility.



· Thermal radiation is enhanced when clouds and snow are present collectively or individually due to the phenomenon of reflection caused by them.



· Soldiers in the battlefield have a good chance of survival against the effects of thermal radiation provided they are suitably dressed.



· The effects on equipment will vary depending on the type of material with which they are manufactured.



Blast



· Detonation of a nuclear weapon produces Blast Wave also called shock wave, which travels at a very high velocity. Blast account for 50% of the total energy released by a nuclear explosion.



· The blast wave in turn produces a region of Peak Static Overpressure and underpressure, which results in high velocity wind.



· While the static overpressure exerts crushing force on targets, the wind is responsible for creating extremely high dynamic pressure causing overturning of military vehicles.

· The effects of Peak Static Overpressure will be more dominant if it lasts for greater duration. At a given range, the duration increases with yield, and for a given yield the duration increases with range (see Table – 5).



· The wind is strongest immediately behind the Shock Front with high dynamic pressure value, which causes maximum damage.



· There is a certain correlation between the values in respect of Peak Static Overpressure, Peak Dynamic Pressure, Peak Wind Velocity and Shock Wave Velocity regardless of the weapon yield (study Table – 6).



· Damage to military equipment and personnel is caused both by Peak Static Overpressure and Peak Dynamic Pressure. Damage to a particular target is associated with a certain specific value of Peak static Overpressure as given at Table – 7.



Of the two weapon outputs namely thermal radiation and blast covered above, the later is considered to be more effective in causing damage to the equipment and buildings and producing casualties. The effects of thermal radiation can be attenuated by wearing proper clothing and thus is not an important factor. However, it can cause severe disruption and damage if a nuclear weapon is dropped on concentrated areas like big cities and towns.



The next article will conclude the first stage of providing information on nuclear weapons by studying the remaining two outputs i.e. nuclear radiation and electromagnetic pulse and their effects.



The information in this article has been extracted from the book titled “Nuclear Weapons” by Charles S Grace.