W79
Encyclopedia
The W79 was an American nuclear artillery
shell, fired from any standard 8 inch (203 mm) howitzer
e.g. the M115.
The W79 was produced in two models, the "W79 Mod 0" and "W79 Mod 1". Both were a plutonium
-based linear-implosion, nuclear weapon
.
The "Mod 0" was a variable yield
device with three yields, ranging from 100 tons up to 1.1 kiloton and an enhanced-radiation
(popularly known as Neutron bomb
) mode which could be turned on or off.
The "Mod 1" was fission
only, without the enhanced-radiation option, and had a fixed 0.8 kiloton yield (800 tons of TNT). This probably corresponds with the maximum pure-fission yield of the "Mod 0".
Both models were 8 inches (203 mm) in diameter, 44 inches (112 cm) long and weighed 200 pounds (90 kg).
The W79 was produced starting in 1981 and continuing into 1986. All units were retired from active service by the end of 1992.
of nuclear material
which is more than one critical mass
at normal pressure
and in a spherical configuration. The mass, known as pit, is configured in a lower density
non-spherical configuration prior to firing the weapon and then, small to moderate amounts of explosive collapse and slightly reshape the nuclear-material into a supercritical-mass which then undergoes chain-reaction
and explodes. Three methods are known to compress and reshape the nuclear-material; collapsing hollow spaces inside the nuclear material, using plutonium-gallium alloy
, which is stabilized in the low-density delta-phase at a density of 16.4 (and which collapses to denser alpha-phase under moderate explosive-compression), and shaping an explosive and nuclear material so that the explosive pressure changes a stretched-out, elliptical or football shape to collapse towards a spherical or more spherical end-shape.
A bare critical mass of plutonium at normal density and without additional neutron reflector
material is roughly 10 kilograms. To achieve a large explosive-yield, a linear-implosion weapon needs somewhat more material, on the order of 13 kilograms. 13 kilograms of alpha-phase (highest density) plutonium at a density of 19.8 g/cm^3 is 657 cubic centimeters
, a sphere of radius
5.4 cm (diameter
10.8 cm / 4.25 inches).
Linear-implosion weapons could use tampers or reflectors, but the overall diameter of the fissile
-material plus tamper/reflector increases compared to the volume required for an untamped, unreflected pit. To fit weapons into small artillery-shells (155 mm and 152 mm are known; 105 mm has been alleged to be possible by nuclear-weapon designer Ted Taylor), bare pits may be required.
Linear-implosion weapons have much lower efficiency due to low pressure, and require two to three times more nuclear-material than conventional implosion weapons. They are also considerably heavier, and much smaller than conventional implosion weapons. The W54
nuclear warhead used for special purposes and the Davy Crockett
nuclear-artillery unit was about 11 inches diameter and weighs 51 pounds. The 155 mm W48
is 6 inches in diameter and weighs over twice as much, and probably requires twice as much plutonium
. Independent researchers have determined that one model of US Army conventional implosion fission-weapon cost $1.25 million per-unit produced, of which $0.25 million was the total cost for all non-nuclear components and $1 million the cost of the plutonium. Linear-implosion weapons, requiring two to three times more plutonium, are considerably more expensive.
Nuclear artillery
Nuclear artillery is a subset of limited-yield tactical nuclear weapons, in particular those weapons that are launched from the ground at battlefield targets...
shell, fired from any standard 8 inch (203 mm) howitzer
Howitzer
A howitzer is a type of artillery piece characterized by a relatively short barrel and the use of comparatively small propellant charges to propel projectiles at relatively high trajectories, with a steep angle of descent...
e.g. the M115.
The W79 was produced in two models, the "W79 Mod 0" and "W79 Mod 1". Both were a plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...
-based linear-implosion, nuclear weapon
Nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission bomb test released the same amount...
.
The "Mod 0" was a variable yield
Variable yield
Variable yield — or dial-a-yield — is an option available on most modern nuclear weapons. It allows the operator to specify a weapon's yield, or explosive power, allowing a single design to be used in different situations...
device with three yields, ranging from 100 tons up to 1.1 kiloton and an enhanced-radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
(popularly known as Neutron bomb
Neutron bomb
A neutron bomb or enhanced radiation weapon or weapon of reinforced radiation is a type of thermonuclear weapon designed specifically to release a large portion of its energy as energetic neutron radiation rather than explosive energy...
) mode which could be turned on or off.
The "Mod 1" was fission
Nuclear fission
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...
only, without the enhanced-radiation option, and had a fixed 0.8 kiloton yield (800 tons of TNT). This probably corresponds with the maximum pure-fission yield of the "Mod 0".
Both models were 8 inches (203 mm) in diameter, 44 inches (112 cm) long and weighed 200 pounds (90 kg).
The W79 was produced starting in 1981 and continuing into 1986. All units were retired from active service by the end of 1992.
Linear implosion
Linear-implosion uses a massMass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
of nuclear material
Nuclear material
Nuclear material refers to the metals uranium, plutonium, and thorium, in any form, according to the IAEA. This is differentiated further into "source material", consisting of natural and depleted uranium, and "special fissionable material", consisting of enriched uranium , uranium-233, and...
which is more than one critical mass
Critical mass
A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The...
at normal pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
and in a spherical configuration. The mass, known as pit, is configured in a lower density
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
non-spherical configuration prior to firing the weapon and then, small to moderate amounts of explosive collapse and slightly reshape the nuclear-material into a supercritical-mass which then undergoes chain-reaction
Nuclear chain reaction
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. The specific nuclear reaction may be the fission of heavy isotopes or the fusion of light isotopes...
and explodes. Three methods are known to compress and reshape the nuclear-material; collapsing hollow spaces inside the nuclear material, using plutonium-gallium alloy
Plutonium-gallium alloy
Plutonium-gallium alloy is an alloy of plutonium and gallium, used in nuclear weapon pits – the component of a nuclear weapon where the fission chain reaction is started....
, which is stabilized in the low-density delta-phase at a density of 16.4 (and which collapses to denser alpha-phase under moderate explosive-compression), and shaping an explosive and nuclear material so that the explosive pressure changes a stretched-out, elliptical or football shape to collapse towards a spherical or more spherical end-shape.
A bare critical mass of plutonium at normal density and without additional neutron reflector
Neutron reflector
A neutron reflector is any material that reflects neutrons. This refers to elastic scattering rather than to a specular reflection. The material may be graphite, beryllium, steel, and tungsten carbide, or other materials...
material is roughly 10 kilograms. To achieve a large explosive-yield, a linear-implosion weapon needs somewhat more material, on the order of 13 kilograms. 13 kilograms of alpha-phase (highest density) plutonium at a density of 19.8 g/cm^3 is 657 cubic centimeters
Cubic centimetre
A cubic centimetre is a commonly used unit of volume extending the derived SI-unit cubic metre, and corresponds to the volume of a cube measuring 1 cm × 1 cm × 1 cm...
, a sphere of radius
Radius
In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...
5.4 cm (diameter
Diameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...
10.8 cm / 4.25 inches).
Linear-implosion weapons could use tampers or reflectors, but the overall diameter of the fissile
Fissile
In nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission. By definition, fissile materials can sustain a chain reaction with neutrons of any energy. The predominant neutron energy may be typified by either slow neutrons or fast neutrons...
-material plus tamper/reflector increases compared to the volume required for an untamped, unreflected pit. To fit weapons into small artillery-shells (155 mm and 152 mm are known; 105 mm has been alleged to be possible by nuclear-weapon designer Ted Taylor), bare pits may be required.
Linear-implosion weapons have much lower efficiency due to low pressure, and require two to three times more nuclear-material than conventional implosion weapons. They are also considerably heavier, and much smaller than conventional implosion weapons. The W54
W54
The W54 was the smallest nuclear warhead deployed by the United States. It was a very compact implosion-type nuclear weapon design, designed for tactical use and had a very low yield for a nuclear weapon.- Development :...
nuclear warhead used for special purposes and the Davy Crockett
Davy Crockett (nuclear device)
The M-28 or M-29 Davy Crockett Weapon System was a tactical nuclear recoilless gun for firing the M388 nuclear projectile that was deployed by the United States during the Cold War...
nuclear-artillery unit was about 11 inches diameter and weighs 51 pounds. The 155 mm W48
W48
The W48 was an American nuclear artillery shell, fired from a standard 155 mm howitzer e.g. the M114 or M198. It was manufactured starting in 1963, and all units were retired in 1992....
is 6 inches in diameter and weighs over twice as much, and probably requires twice as much plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...
. Independent researchers have determined that one model of US Army conventional implosion fission-weapon cost $1.25 million per-unit produced, of which $0.25 million was the total cost for all non-nuclear components and $1 million the cost of the plutonium. Linear-implosion weapons, requiring two to three times more plutonium, are considerably more expensive.
See also
- Nuclear weapon designNuclear weapon designNuclear weapon designs are physical, chemical, and engineering arrangements that cause the physics package of a nuclear weapon to detonate. There are three basic design types...
- List of nuclear weapons
- W48W48The W48 was an American nuclear artillery shell, fired from a standard 155 mm howitzer e.g. the M114 or M198. It was manufactured starting in 1963, and all units were retired in 1992....
- W74W74The W74 was an experimental American nuclear artillery shell.Responding to a 1969 United States Army request for a replacement for the W48 155 mm artillery shell, the Los Alamos National Laboratory started development of the W74. However, by mid 1973 the program was discontinued without...
- W75
- W82W82The W82 was a low yield tactical nuclear warhead developed by the United States and designed to be used in a 155mm artillery shell . It was conceived as a more flexible replacement for the W48, the previous generation of 155mm nuclear artillery shell...