An American nuclear test. Nuclear weapons tests are experiments carried out to determine the effectiveness yield and explosive capability of Nuclear weapons Throughout the twentieth century most nations

The energy released from a nuclear weapon detonated in the troposphere can be divided into four basic categories:

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

However, depending on the design of the weapon and the environment in which it is detonated the energy distributed to these categories can be increased or decreased to the point of nullification. The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75% of the atmosphere's mass and almost all of its Water vapor and An explosion is a sudden increase in Volume and release of Energy in an extreme manner usually with the generation of high Temperatures and the release Thermal radiation is Electromagnetic radiation emitted from the surface of an object which is due to the object's Temperature. Image talkNew_radiation_symbol_ISO_21482svg for details --> Ionizing radiation Fallout is the residual radiation hazard from a Nuclear explosion, so named because it "falls out" of the atmosphere into which it is spread during the explosion The blast effect is created by immense amounts of energy, spanning the electromagnetic spectrum, with the surroundings. The electromagnetic (EM spectrum is the range of all possible Electromagnetic radiation frequencies Locations such as submarine, surface, airburst, or exo-atmospheric determine how much energy is produced as blast and how much as radiation. In general, denser mediums around the bomb, like water, absorb more energy, and create more powerful shockwaves while at the same time limiting the area of its effect.

The dominant effects of a nuclear weapon where people are likely to be affected (blast and thermal radiation) are identical physical damage mechanisms to conventional explosives. An explosive material is a material that either is chemically or otherwise Energetically unstable or produces a sudden expansion of the material usually accompanied However the energy produced by a nuclear explosive is millions of times more powerful per gram and the temperatures reached are briefly in the tens of millions of degrees.

Energy from a nuclear explosive is initially released in several forms of penetrating radiation. When there is a surrounding material such as air, rock, or water, this radiation interacts with and rapidly heats it to an equilibrium temperature. This causes vaporization of surrounding material resulting in its rapid expansion. Kinetic energy created by this expansion contributes to the formation of a shockwave. The kinetic energy of an object is the extra Energy which it possesses due to its motion When a nuclear detonation occurs in air near sea level, much of the released energy interacts with the atmosphere and creates a shockwave which expands spherically from the hypocenter. Intense thermal radiation at the hypocenter forms a fireball and if the burst is low enough, its often associated mushroom cloud. A mushroom cloud is a distinctive Mushroom -shaped Cloud of condensed Water vapor or Debris resulting from a very large Explosion. In a burst at high altitudes, where the air density is low, more energy is released as ionizing gamma radiation and x-rays than an atmosphere displacing shockwave.

In 1945 there was some initial speculation among the scientists developing the first nuclear weapons that there might be a possibility of igniting the Earth's atmosphere with a large enough nuclear explosion. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five This would concern a nuclear reaction of two nitrogen atoms forming a carbon and an oxygen atom, with release of energy. This energy would heat up the remaining nitrogen enough to keep the reaction going until all nitrogen atoms were consumed. This was, however, quickly shown to be unlikely enough to be considered impossible [2]. Nevertheless, the notion has persisted as a rumour for many years.

Direct effects

Blast damage

Overpressure ranges from 1 to 50 psi of a 1 kiloton of TNT air burst as a function of burst height. The thin black curve indicates the optimum burst height for a given ground range.

An estimate of the size of the damage caused by the Atomic bombings of Hiroshima and Nagasaki. The atomic bombings of Hiroshima and Nagasaki were nuclear attacks near the end of World War II against the Empire of Japan by the United States at A modern hydrogen bomb would be tens[1] of times more powerful and cause similar levels of damage at 2-5 times the distance.

The high temperatures and pressures cause gas to move outward radially in a thin, dense shell called "the hydrodynamic front. " The front acts like a piston that pushes against and compresses the surrounding medium to make a spherically expanding shock wave. For the music album by Converter see Shock Front For the 1977 horror film see Shock Waves A shock wave (also called At first, this shock wave is inside the surface of the developing fireball, which is created in a volume of air by the X-rays. However, within a fraction of a second the dense shock front obscures the fireball, causing the characteristic double pulse of light seen from a nuclear detonation. For air bursts at or near sea-level between 50-60% of the explosion's energy goes into the blast wave, depending on the size and the yield-to-weight ratio of the bomb. As a general rule, the blast fraction is higher for low yield and/or high bomb mass. Furthermore, it decreases at high altitudes because there is less air mass to absorb radiation energy and convert it into blast. This effect is most important for altitudes above 30 km, corresponding to <1 per cent of sea-level air density.

Much of the destruction caused by a nuclear explosion is due to blast effects. Most buildings, except reinforced or blast-resistant structures, will suffer moderate to severe damage when subjected to overpressures of only 35. 5 kilopascals (kPa) (5. 15 pounds-force per square inch or 0. The pound per square inch or more accurately pound-force per square inch (symbol psi or lbf/in² or lbf/in²) is a unit of 35 atm).

The blast wind may exceed one thousand km/h. The range for blast effects increases with the explosive yield of the weapon and also depends on the burst altitude. Contrary to what one might expect from geometry the blast range is not maximal for surface or low altitude blasts but increases with altitude up to an "optimum burst altitude" and then decreases rapidly for higher altitudes. This is due to the nonlinear behaviour of shock waves. If the blast wave reaches the ground it is reflected. Below a certain reflection angle the reflected wave and the direct wave merge and form a reinforced horizontal wave, the so-called Mach stem (named after Ernst Mach). Ernst Mach (max ( February 18, 1838 &ndash February 19, 1916) was an Austrian Physicist and Philosopher and For each goal overpressure there is a certain optimum burst height at which the blast range is maximized. In a typical air burst, where the blast range is maximized for 5 to 20 psi (35 to 140 kPa), these values of overpressure and wind velocity noted above will prevail at a range of 0. 7 km for 1 kiloton (kt) of TNT yield; 3. Units of mass There are three similar units of Mass called the ton: Long ton (simply ton in countries such as the United 2 km for 100 kt; and 15. 0 km for 10 megatons (Mt) of TNT.

Two distinct, simultaneous phenomena are associated with the blast wave in air:

• Static overpressure, i. e. , the sharp increase in pressure exerted by the shock wave. The overpressure at any given point is directly proportional to the density of the air in the wave.
• Dynamic pressures, i. In Fluid dynamics dynamic pressure (indicated with q, or Q, and sometimes called velocity pressure) is the quantity defined by e. , drag exerted by the blast winds required to form the blast wave. These winds push, tumble and tear objects.

Most of the material damage caused by a nuclear air burst is caused by a combination of the high static overpressures and the blast winds. The long compression of the blast wave weakens structures, which are then torn apart by the blast winds. The compression, vacuum and drag phases together may last several seconds or longer, and exert forces many times greater than the strongest hurricane. A tropical cyclone is a storm system characterized by a low pressure center and numerous Thunderstorms that produce strong winds and Flooding

Acting on the human body, the shock waves cause pressure waves through the tissues. These waves mostly damage junctions between tissues of different densities (bone and muscle) or the interface between tissue and air. Bones are rigid organs that form part of the Endoskeleton of Vertebrates They function to move support and protect the various organs of the body produce Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the Lungs and the abdominal cavity, which contain air, are particularly injured. lung is the essential Respiration organ in air-breathing Animals including most Tetrapods a few Fish and a few Snails The most primitive The abdominal cavity is the Body cavity of the human body (and animal bodies that holds the bulk of the viscera and which is located below (or inferior The damage causes severe hemorrhaging or air embolisms, either of which can be rapidly fatal. The overpressure estimated to damage lungs is about 70 kPa. Some eardrums would probably rupture around 22 kPa (0. The tympanic membrane (also tympanum or myrinx is a thin membrane that separates the External ear from the Middle ear. 2 atm) and half would rupture between 90 and 130 kPa (0. 9 to 1. 2 atm).

Blast Winds: The drag energies of the blast winds are proportional to the cubes of their velocities multiplied by the durations. These winds may reach several hundred kilometers per hour.

Thermal radiation

Mushroom cloud height depending on yield for ground bursts.
0 = Approx altitude commercial aircraft operate
1 = Fat Man
2 = Castle Bravo. "Fat Man" is the codename for the Atomic bomb that was detonated over Nagasaki, Japan, by the United States on August 9 Castle Bravo was the Code name given to the first US test of a so-called dry fuel thermonuclear Hydrogen bomb device detonated on March 1,

Nuclear weapons emit large amounts of electromagnetic radiation as visible, infrared, and ultraviolet light. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. The chief hazards are burns and eye injuries. Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain On clear days, these injuries can occur well beyond blast ranges. The light is so powerful that it can start fires that spread rapidly in the debris left by a blast. The range of thermal effects increases markedly with weapon yield. Thermal radiation accounts for between 35-45% of the energy released in the explosion, depending on the yield of the device.

There are two types of eye injuries from the thermal radiation of a weapon:

Flash blindness is caused by the initial brilliant flash of light produced by the nuclear detonation. Flash blindness is visual impairment during and following exposure to a light flash of extremely high intensity More light energy is received on the retina than can be tolerated, but less than is required for irreversible injury. The retina is particularity susceptible to visible and short wavelength infrared light, since this part of the electromagnetic spectrum is focused by the lens on the retina. The electromagnetic (EM spectrum is the range of all possible Electromagnetic radiation frequencies The result is bleaching of the visual pigments and temporary blindness for up to 40 minutes. Blindness is the condition of lacking Visual perception due to Physiological or Neurological factors

Burns visible on a woman in Hiroshima during the blast, darker colors of her kimono at the time of detonation correspond to clearly visible burns on skin touching parts of the garment exposed to thermal radiation. The is the National costume of Japan. Originally the word "kimono" literally meant thing to wear ( ki wearing and mono thing but now has come Since kimonos are not form fitting attire, some parts were not directly touching her skin are visible as breaks in the pattern. As well as tighter fitting areas approaching the waistline where the pattern is much more defined.

A retinal burn resulting in permanent damage from scarring is also caused by the concentration of direct thermal energy on the retina by the lens. It will occur only when the fireball is actually in the individual's field of vision and would be a relatively uncommon injury. Retinal burns, however, may be sustained at considerable distances from the explosion. The apparent size of the fireball, a function of yield and range will determine the degree and extent of retinal scarring. A scar in the central visual field would be more debilitating. Generally, a limited visual field defect, which will be barely noticeable, is all that is likely to occur.

When thermal radiation strikes an object, part will be reflected, part transmitted, and the rest absorbed. The fraction that is absorbed depends on the nature and color of the material. A thin material may transmit a lot. A light colored object may reflect much of the incident radiation and thus escape damage. The absorbed thermal radiation raises the temperature of the surface and results in scorching, charring, and burning of wood, paper, fabrics, etc. If the material is a poor thermal conductor, the heat is confined to the surface of the material.

Actual ignition of materials depends on how long the thermal pulse lasts and the thickness and moisture content of the target. Near ground zero where the energy flux exceeds 125 J/cm², what can burn, will. The joule (written in lower case ˈdʒuːl or /ˈdʒaʊl/ (symbol J) is the SI unit of Energy measuring heat, Electricity M^2 redirects here For other uses see M². CM2 redirects here Farther away, only the most easily ignited materials will flame. Incendiary effects are compounded by secondary fires started by the blast wave effects such as from upset stoves and furnaces.

In Hiroshima, a tremendous fire storm developed within 20 minutes after detonation and destroyed many more buildings and homes. The Japanese city of ( is the capital of Hiroshima Prefecture, and the largest city in the Chūgoku region of western Honshū, the largest of Japan 's A firestorm is a Conflagration which attains such intensity that it creates and sustains its own wind system A fire storm has gale force winds blowing in towards the center of the fire from all points of the compass. It is not, however, a phenomenon peculiar to nuclear explosions, having been observed frequently in large forest fires and following incendiary raids during World War II. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including

Because thermal radiation travels more or less in a straight line from the fireball (unless scattered) any opaque object will produce a protective shadow. If fog or haze scatters the light, it will heat things from all directions and shielding will be less effective, but fog or haze would also diminish the range of these effects.

Indirect effects

The mushroom cloud from the first "true" Soviet hydrogen bomb test in 1955.

Electromagnetic pulse

Main article: Electromagnetic pulse

Gamma rays from a nuclear explosion produce high energy electrons through Compton scattering. The term electromagnetic pulse ( EMP) has the following meanings Electromagnetic radiation from an Explosion (especially a Nuclear The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J The Compton shift formula Klein-Nishina formulaCompton used a combination of three fundamental formulas representing the various aspects of classical and modern physics combining These electrons are captured in the earth's magnetic field, at altitudes between twenty and forty kilometers, where they resonate. The oscillating electric current produces a coherent electromagnetic pulse (EMP) which lasts about one millisecond. The term electromagnetic pulse ( EMP) has the following meanings Electromagnetic radiation from an Explosion (especially a Nuclear Secondary effects may last for more than a second.

The pulse is powerful enough to cause long metal objects (such as cables) to act as antennas and generate high voltages when the pulse passes. Electrical tension (or voltage after its SI unit, the Volt) is the difference of electrical potential between two points of an electrical These voltages, and the associated high currents, can destroy unshielded electronics and even many wires. Electric current is the flow (movement of Electric charge. The SI unit of electric current is the Ampere. There are no known biological effects of EMP. The ionized air also disrupts radio traffic that would normally bounce off the ionosphere. The ionosphere is the uppermost part of the atmosphere, distinguished because it is Ionized by solar radiation

One can shield electronics by wrapping them completely in conductive mesh, or any other form of Faraday cage. In Science and engineering, a conductor is a material which contains movable Electric charges. A Faraday cage or Faraday shield is an enclosure formed by conducting material, or by a mesh of such material Of course radios cannot operate when shielded, because broadcast radio waves can't reach them.

Ionizing radiation

About 5% of the energy released in a nuclear air burst is in the form of ionizing radiation: neutrons, gamma rays, alpha particles, and electrons moving at incredible speeds, but with different speeds that can be still far away from the speed of light (beta particles). Image talkNew_radiation_symbol_ISO_21482svg for details --> Ionizing radiation Neutron radiation is a kind of Ionizing radiation which consists of Free neutrons Sources Neutrons may be emitted during either spontaneous Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions Alpha particles (named after and denoted by the first letter in the Greek alphabet, α consist of two Protons and two Neutrons bound together into a The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J The neutrons result almost exclusively from the fission and fusion reactions, while the initial gamma radiation includes that arising from these reactions as well as that resulting from the decay of short-lived fission products. Nuclear fission is the splitting of the nucleus of an atom into parts (lighter nuclei) often producing Free neutrons and other smaller nuclei which may In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus

The intensity of initial nuclear radiation decreases rapidly with distance from the point of burst because the radiation spreads over a larger area as it travels away from the explosion. It is also reduced by atmospheric absorption and scattering.

The character of the radiation received at a given location also varies with distance from the explosion. Near the point of the explosion, the neutron intensity is greater than the gamma intensity, but with increasing distance the neutron-gamma ratio decreases. Ultimately, the neutron component of initial radiation becomes negligible in comparison with the gamma component. The range for significant levels of initial radiation does not increase markedly with weapon yield and, as a result, the initial radiation becomes less of a hazard with increasing yield. With larger weapons, above fifty kt (200 TJ), blast and thermal effects are so much greater in importance that prompt radiation effects can be ignored.

The neutron radiation serves to transmute the surrounding matter, often rendering it radioactive. When added to the dust of radioactive material released by the bomb itself, a large amount of radioactive material is released into the environment. This form of radioactive contamination is known as nuclear fallout and poses the primary risk of exposure to ionizing radiation for a large nuclear weapon. Radioactive contamination is the uncontrolled distribution of radioactive material in a given environment Fallout is the residual radiation hazard from a Nuclear explosion, so named because it "falls out" of the atmosphere into which it is spread during the explosion

Earthquake

The pressure wave from an underground explosion will propagate through the ground and cause a minor earthquake. An earthquake is the result of a sudden release of energy in the Earth 's crust that creates Seismic waves Earthquakes are recorded with a Seismometer [3] Theory suggests that a nuclear explosion could trigger fault rupture and cause a major quake at distances within a few tens of kilometers from the shot point. [4]

Summary of the effects

The following table summarizes the most important effects of nuclear explosions under certain conditions.

¹) For the direct radiation effects the slant range instead of the ground range is shown here, because some effects are not given even at ground zero for some burst heights. If the effect occurs at ground zero the ground range can simply be derived from slant range and burst altitude (Pythagorean theorem). In Mathematics, the Pythagorean theorem ( American English) or Pythagoras' theorem ( British English) is a relation in Euclidean geometry

²) "Acute radiation syndrome" corresponds here to a total dose of one gray, "lethal" to ten grays. The gray (symbol Gy is the SI unit of absorbed radiation dose. Note that this is only a rough estimate since biological conditions are neglected here.

Other phenomena

As the fireball rises through still air, it takes on the flow pattern of a vortex ring with incandescent material in the vortex core as seen in certain photographs. At the explosion of nuclear bombs sometimes lightning discharges occur. A vortex ring, also called a toroidal vortex, is a region of rotating Fluid moving through the same or different fluid where the flow pattern takes on a Not related to the explosion itself, often there are smoke trails seen in photographs of nuclear explosions. These are formed from rockets emitting smoke launched before detonation. The smoke trails are used to determine the position of the shockwave, which is invisible, in the milliseconds after detonation through the refraction of light, which causes an optical break in the smoke trails as the shockwave passes. Refraction is the change in direction of a Wave due to a change in its Speed. A fizzle occurs if the nuclear chain reaction is not sustained long enough to cause an explosion, or if the explosion is of much less energy than expected. A nuclear chain reaction occurs when one Nuclear reaction causes an average of one or more nuclear reactions thus leading to a self-propagating number of these reactions This can happen if, for example, the yield of the fissile material used is too low, the compression explosives around fissile material misfire or the neutron initiator fails. In Nuclear engineering, a fissile material is one that is capable of sustaining a Chain reaction of Nuclear fission. Nuclear weapon designs are physical chemical and engineering arrangements that cause the physics package of a nuclear weapon to detonate

Survivability

This is highly dependent on factors such as proximity to the blast and the direction of the wind carrying fallout. Death is highly likely, and radiation poisoning is almost certain if one is close enough within the radius of the blast, for example 3 to 4 miles for a 1 megaton atmospheric blast.

See also

• Cold War
• List of nuclear tests
• Nuclear testing
• Duck and Cover - a short educational film produced in 1951 to teach children what to do in case of nuclear explosion. Cold War is the state of conflict tension and competition that existed between the United States and the Soviet Union (USSR and their respective allies from the See also Nuclear testing The following is a list of nuclear test series designations organized first by Country and then by date Nuclear weapons tests are experiments carried out to determine the effectiveness yield and explosive capability of Nuclear weapons Throughout the twentieth century most nations Duck and Cover was a Social guidance film produced in 1951 (but first shown publicly in January 1952 by the United States federal government
• Nuclear weapon
• History of nuclear weapons
• Nuclear weapon design
• Nuclear warfare
• Peaceful nuclear explosions
• Rope trick effect
• Underwater explosion

References

External links

• Comprehensive video archive of Nuclear Weapon Testing Effects
• Underground Bomb Shelters
• The Federation of American Scientists provide solid information on weapons of mass destruction, including nuclear weapons and their effects
• The Nuclear War Survival Skills is a public domain text and is an excellent source on how to survive a nuclear attack. A nuclear weapon is an explosive device that derives its destructive force from Nuclear reactions either fission or a combination of fission and fusion. The history of nuclear weapons chronicles the development of Nuclear weapons. Nuclear weapon designs are physical chemical and engineering arrangements that cause the physics package of a nuclear weapon to detonate Peaceful nuclear explosions (PNEs are Nuclear explosions conducted for non-military purposes such as activities related to Economic development including the Rope trick is the term given by physicist John Malik to the curious lines and spikes which emanate from the fireball of certain nuclear explosions just after An underwater explosion, also known as an UNDEX, is an Explosion beneath the surface of water
• Ground Zero: A Javascript simulation of the effects of a nuclear explosion in a city
• Oklahoma Geological Survey Nuclear Explosion Catalog lists 2,199 explosions with their date, country, location, yield, etc.
• Australian Government database of all nuclear explosions
• Nuclear Weapon Archive from Carey Sublette (NWA) is a reliable source of information and has links to other sources.
• NWA repository of blast models mainly used for the effects table (especially DOS programs BLAST and WE)
• Nuclear Weapon Effects Calculator - Javascript form to calculate blast, heat, and radiation effects of a given explosive yield.
• Nuclear Weapons Frequently Asked Questions
• Atomic Forum
• Samuel Glasstone and Philip J. Dolan, The Effects of Nuclear Weapons, Third Edition, United States Department of Defense & Energy Research and Development Administration Available Online