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Encyclopedia > Thermonuclear explosion
A 23 kiloton tower shot called BADGER, fired on April 18, 1953 at the Nevada Test Site, as part of the Operation Upshot-Knothole nuclear test.

A nuclear explosion (nuclear detonation) has occurred: Download high resolution version (1151x953, 205 KB)Nuclear fireball from a US nuclear test. ... Download high resolution version (1151x953, 205 KB)Nuclear fireball from a US nuclear test. ... The Nevada Test Site is a United States Department of Energy reservation located in Nye County, Nevada, about 65 miles (105 km) northwest of the City of Las Vegas. ... Operation Upshot-Knothole was a series of eleven nuclear test shots conducted in 1953 at the Nevada Test Site. ... A nuclear test explosion is an experiment involving the detonation of a nuclear weapon. ...

Potential other applications (not yet applied, or the idea was considered but abandoned): The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 km (11 mi) above the epicenter. ... Citizens of Hiroshima walk by the A-Bomb Dome, the closest building to have survived the citys atomic bombing. ... A nuclear test explosion is an experiment involving the detonation of a nuclear weapon. ... The 1962 Sedan plowshares shot displaced 12 million tons of earth and created a crater 320 feet deep and 1,280 feet wide. ...

Nuclear explosions are associated with "mushroom clouds" although mushroom clouds can occur with ground based chemical explosions and it is possible to have an air burst nuclear explosion without these clouds. Nuclear explosions produce large amounts of radiation and radioactive materials. An artists conception of a spacecraft powered by nuclear pulse propulsion Nuclear pulse propulsion (or External Pulsed Plasma Propulsion, as it is termed in one recent NASA document) is a proposed method of spacecraft propulsion that uses nuclear explosions for thrust. ... Since 1994 when Comet Shoemaker-Levy 9 collided with Jupiter, scientists have been researching if it may be possible to deflect incoming asteroids. ... The sun is a natural fusion reactor Fusion power is the extraction of energy in some useful form, generally expected to be electricity, from a nuclear fusion reaction, that is, by combining two light atomic nuclei into a heavier one with the release of energy. ... Pacer could refer to: A type of British train, see Pacer (train). ... The atomic bombing of Nagasaki on August 9, 1945 A picture of the mushroom clouds of the nuclear attack on the robot city of Zero One in the Animatrixs The Second Renaissance. ... Radiation generally means the transmission of waves, objects or information from a source into a surrounding medium or destination. ... Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles. ...

In the case of a fizzle the effects of the first part of the nuclear chain reaction prevent it to be continued, by blowing the material apart too soon. A nuclear chain reaction occurs when on average more than one nuclear reaction is caused by another nuclear reaction, thus leading to an exponential increase in the number of nuclear reactions. ...


Effects of a nuclear explosion

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 (fallout)—5-10% of total energy

However, the above values vary depending on the design of the weapon, and the environment in which it is detonated. The interaction of the X-rays and debris with the surroundings determines how much energy is produced as blast and how much as light. In general, the denser the medium around the bomb, the more it will absorb, and the more powerful the shockwave will be. Thermal radiation drops off the slowest with distance, so the larger the weapon the more important this effect becomes. Ionizing radiation is strongly absorbed by air, so it is only dangerous by itself for smaller weapons. Blast damage falls off more quickly than thermal radiation but more slowly than ionizing radiation.

The dominant effects of a nuclear weapon (the blast and thermal radiation) are the same physical damage mechanisms as conventional explosives, but the the energy produced by a nuclear explosive is millions of times more per gram and the temperatures reached are in the tens of millions of degrees. This article is concerned solely with chemical explosives. ...

The energy of a nuclear explosive is initially released in the form of gamma rays and neutrons. When there is a surrounding material such as air, rock, or water, this radiation interacts with the material, rapidly heating it to an equilibrium temperature in about a microsecond. The hot material emits thermal radiation, mostly soft X-rays, which accounts for 75% of the energy of the explosion. In addition, the heating and vaporization of the surrounding material causes it to rapidly expand and the kinetic energy of this expansion accounts for almost all of the remaining energy. This article is about electromagnetic radiation. ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939. ... A microsecond is an SI unit of time equal to one millionth (10-6) of a second. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... Kinetic energy (also called vis viva, or living force) is energy possessed by a body by virtue of its motion. ...

An American nuclear test.

When a nuclear detonation occurs in air near sea level, most of the soft X-rays in the primary thermal radiation are absorbed within a few feet. Some energy is reradiated in the ultraviolet, visible light and infrared, but most of the energy heats a spherical volume of air. This forms a fireball and its associated effects. Download high resolution version (559x700, 396 KB) 14 kiloton atomic explosion, from a 1951 US nuclear test at the Nevada Test Site. ... Download high resolution version (559x700, 396 KB) 14 kiloton atomic explosion, from a 1951 US nuclear test at the Nevada Test Site. ... A nuclear test explosion is an experiment involving the detonation of a nuclear weapon. ... Ultraviolet (UV) radiation is electromagnetic radiation of a wavelength shorter than that of the visible region, but longer than that of soft X-rays. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ... The term fireball is often used in reference to any large explosion or burst of fire. ... Nuclear explosion photographed less than 1/1000 of a second after detonation. ...

In a burst at high altitudes, where the air density is low, the soft X-rays travel long distances before they are absorbed. The energy is so diluted that the blast wave may be half as strong or less. The rest of the energy is dissipated as a more powerful thermal pulse.

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. 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 were finished. This was, however, quickly shown to be unlikely enough to be considered impossible [1] (http://www.fas.org/sgp/othergov/doe/lanl/docs1/00329010.pdf). Nevertheless, the notion has persisted as a rumor for many years. Atmosphere may refer to: a celestial body atmosphere, e. ...

Direct effects

Blast damage

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

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. 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, making the characteristic double pulse of light seen from a nuclear detonation. Download high resolution version (1902x1300, 103 KB) Wikipedia does not have an article with this exact name. ... Download high resolution version (1902x1300, 103 KB) Wikipedia does not have an article with this exact name. ... In fluid dynamics, a shock wave is a nonlinear pressure wave. ...

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 pounds/square inch or 0.35 Atm). The pascal (symbol Pa) is the SI unit of pressure. ...

The blast wind may exceed several hundred 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). 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, these values of overpressure and wind velocity noted above will prevail at a range of 0.7 km for 1 kiloton (kt) yield; 3.2 km for 100 kt; and 15.0 km for 10 Megatons (Mt). Ernst Mach (February 18, 1838 - February 19, 1916) was an Austrian physicist and philosopher. ... A megaton or megatonne is a unit of mass equal to 1,000,000 metric tons, i. ... A megaton or megatonne is a unit of mass equal to 1,000,000 metric tons, i. ...

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.e., drag exerted by the blast winds required to form the blast wave. These winds push, tumble and tear objects.
Positive and negative blast pressures.

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. OK, who removed the image description page? - Ta bu shi da yu 05:24, 19 Oct 2004 (UTC) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... OK, who removed the image description page? - Ta bu shi da yu 05:24, 19 Oct 2004 (UTC) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...

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. Lungs and the gut, which contain air, are particularly injured. The damage causes severe hemorrhaging or air embolisms, either of which can be rapidly fatal. The overpressure estimated to damage lungs is about 68.9 kPa. Some eardrums would probably rupture around 22 kPa (0.2 atm) and half would rupture between 90 and 130 kPa (0.9 to 1.2 atm). Grays illustration of a human femur, a typically recognized bone. ... A top-down view of skeletal muscle Muscle is a contractile form of tissue. ... The heart in relation to the lungs (from an older edition of Grays Anatomy) This x-ray of the human chest shows the lungs as dark regions The lung is an organ belonging to the respiratory system and interfacing to the circulatory system of air-breathing vertebrates. ... The tympanum or tympanic membrane, colloquially known as eardrum, is a thin membrane that separates the outer ear from the middle ear. ...

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

Nuclear weapons emit large amounts of electromagnetic radiation as visible, infrared, and ultraviolet light. The chief hazards are burns and eye injuries. 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. Electromagnetic radiation or EM radiation is a combination (cross product) of oscillating electric and magnetic fields perpendicular to each other, moving through space as a wave, effectively transporting energy and momentum. ... An eye is an organ that detects light. ...

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. 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 result is bleaching of the visual pigments and temporary blindness for up to 40 minutes. The electromagnetic spectrum encompasses all possible wavelengths of electromagnetic radiation. ... Blindness can be defined physiologically as the condition of lacking sight. ...

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.

Since thermal radiation travels in straight lines 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.

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 the how long the thermal pulse lasts and the thickness and moisture content of the target. Near ground zero where the light exceeds 125 joules/cm2, what can burn, will. 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. The joule (symbol J, also called newton meter, watt second, or coulomb volt) is the SI unit of energy and work. ... cm redirects here, alternate uses: cm (disambiguation) A centimetre (symbol cm; American spelling: centimeter) is an SI unit of length. ...

In Hiroshima, a tremendous fire storm developed within 20 minutes after detonation. 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. Main keep of Hiroshima Castle The city of Hiroshima (広島市; -shi) is the capital of Hiroshima Prefecture, and the largest city in the Chugoku region of western Japan. ... For the comic book superhero, see Firestorm (comics). ... Mushroom cloud from the nuclear explosion over Nagasaki rising 18 km into the air. ...

Indirect effects

Electromagnetic pulse

Gamma rays from a nuclear explosion produce high energy electrons through Compton scattering. 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 1 millisecond. Secondary effects may last for more than a second. Properties The electron (sometimes called negatron; commonly represented as e−) is a subatomic particle. ... The Compton effect, observed by Arthur Compton in 1923, is the increase in wavelength which occurs when photons with energies of around 0. ... In telecommunications and warfare, the term electromagnetic pulse (EMP) has the following meanings: The electromagnetic radiation from an explosion (especially nuclear explosions) or an intensely fluctuating magnetic field caused by Compton-recoil electrons and photoelectrons from photons scattered in the materials of the electronic or explosive device or in a...

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. These voltages, and the associated high currents, can destroy unshielded electronics and even many wires. There are no known biological effects of EMP. The ionized air also disrupts radio traffic that would normally bounce off the ionosphere. In the physical sciences, potential difference is the difference in potential between two points in a conservative vector field. ... In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ... The ionosphere is the part of the atmosphere that is ionized by solar radiation. ...

One can shield electronics by wrapping them completely in conductive mesh, or any other form of Faraday cage. Of course radios cannot operate when shielded, because broadcast radio waves can't reach them. En [ [ ciencia ] ] y [ [ ingeniería ] ], los conductores son los materiales de los cuales contenga las cargas movibles [ [ electricidad ] ]. Cuando una diferencia potencial eléctrica se impresiona a través de puntos separados en un conductor, las cargas móviles dentro del conductor se fuerzan para moverse, y una corriente eléctrica entre esos puntos aparece... The Faraday cage is an electrical apparatus designed to prevent the passage of electromagnetic waves, either containing them in or excluding them from its interior space. ...

The largest-yield nuclear devices are designed for this use. An air burst at the right altitude could produce continent-wide effects.

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 (alpha particles). 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. Ionizing radiation is radiation in which an individual particle (for example, a photon, electron, or helium nucleus) carries enough energy to ionize an atom or molecule (that is, to completely remove an electron from its orbit). ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939. ... This article is about electromagnetic radiation. ... An alpha particle is deflected by a magnetic field Alpha particles or alpha rays are a form of particle radiation which are highly ionizing and have low penetration. ... Properties The electron (sometimes called negatron; commonly represented as e−) is a subatomic particle. ... In general fission is a splitting or breaking up into parts. ... Fusion may refer to: the merging of two or more entities into a single one For the combining of two atomic nuclei into a single nucleus (with possible emission of radioactivity), see nuclear fusion cold fusion refers to a controversial form of nuclear fusion which has recently (April/May 2005...

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 50 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. The radiation warning symbol (trefoil). ... Fallout is the residual radiation hazard from a nuclear explosion and is named from the fact that it falls out of the atmosphere in to which it is spread during the explosion. ...

Summary of the effects

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

  • relatively flat terrain,
  • clear weather, visibility 20 kilometres,
  • height of burst optimized for 15 PSI (103 kPa),
  • "average" bombs, i.e. no neutron bombs or other devices with extremely enhanced or reduced radiation.

Due to the applied cubic root scaling the peak overpressure in ground zero is approximately 42 PSI (290 kPa) in all cases.

Effective range GR / km

Explosive yield / Height of Burst

1 kT / 200 m

20 kT / 540 m

1 MT / 2.0 km

20 MT / 5.4 km

Blast effects

Urban areas almost completely levelled (20 PSI)





Destruction of most civil buildings (5 PSI)





Moderate damage to civil buildings (1 PSI)





Thermal radiation effects






Third degree burns





Second degree burns





First degree burns





Effects of instant nuclear radiation (at slant range1 SR / km)

Lethal2 total dose (neutrons and gamma rays)





Total dose for acute radiation syndrome2





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. There are thousands of proofs of the Pythagorean theorem. ...

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

See also

The Cold War was the open yet restricted rivalry that developed after World War II between the United States and its allies (roughly speaking, NATO members) and the Soviet Union and its allied (roughly speaking, Warsaw Pact members), until the collapse of the Soviet Union in 1991. ... A nuclear test explosion is an experiment involving the detonation of a nuclear weapon. ... Duck and cover was a method of personal protection against the effects of a nuclear detonation which the United States government taught to the generations of United States school children from the late 1940s in to the 1980s. ... Film refers to the celluloid media on which movies are printed Film is a term that encompasses motion pictures as individual projects, as well as the field in general. ... 1951 was a common year starting on Monday; see its calendar. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 km (11 mi) above the epicenter. ... A nuclear fireball lights up the night in a United States nuclear test. ... The first nuclear weapons, though large and cumbersome, provided the basic design building blocks of all future weapons. ... Nuclear war, or atomic war, is war in which nuclear weapons are used. ... Nuclear explosion photographed less than 1/1000 of a second after detonation. ...


The Smyth Report was the common name given to an administrative history written by physicist Henry DeWolf Smyth about the Allied World War II effort to develop the atomic bomb, the Manhattan Project. ...

External links

  Results from FactBites:
Effects of nuclear explosions - Wikipedia, the free encyclopedia (3046 words)
A nuclear explosion occurs as a result of the rapid release of energy from an uncontrolled nuclear reaction.
Atmospheric nuclear explosions are associated with "mushroom clouds" although mushroom clouds can occur with large chemical explosions and it is possible to have an air burst nuclear explosion without these clouds.
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.
Supernova - Wikipedia, the free encyclopedia (3833 words)
Months after the explosion, when the outer layers have expanded to the point of transparency, the spectrum is dominated by light emitted by material near the core of the star, heavy elements synthesized during the explosion, most prominently iron-group elements.
Heavier elements than iron are formed during this explosion by neutron capture, and from the pressure of the neutrinos pressing into the boundary of the "neutrinosphere", seeding the surrounding space with a cloud of gas and dust which is richer in heavy elements than the one the star originally formed from.
By ignoring the first second of the explosion, and assuming that an explosion is started, astrophysicists have been able to make detailed predictions about the elements produced by the supernova and of the expected light curve from the supernova.
  More results at FactBites »



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