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A thermonuclear weapon, fusion weapon or hydrogen bomb (H bomb) is a second-generation
nuclear weapon design Nuclear weapon designs are physical, chemical, and engineering arrangements that cause the physics package of a nuclear weapon to detonate. There are three existing basic design types: * pure fission weapons, the simplest and least technically ...
. Its greater sophistication affords it vastly greater destructive power than first-generation
nuclear bomb A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions (thermonuclear bomb), producing a nuclear explosion. Both bomb ...
s, a more compact size, a lower mass, or a combination of these benefits. Characteristics of
nuclear fusion Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles ( neutrons or protons). The difference in mass between the reactants and products is manifest ...
reactions make possible the use of non-fissile
depleted uranium Depleted uranium (DU; also referred to in the past as Q-metal, depletalloy or D-38) is uranium with a lower content of the fissile isotope than natural uranium.: "Depleted uranium possesses only 60% of the radioactivity of natural uranium, hav ...
as the weapon's main fuel, thus allowing more efficient use of scarce fissile material such as
uranium-235 Uranium-235 (235U or U-235) is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear chain reaction. It is the only fissile isotope that exis ...
() or
plutonium-239 Plutonium-239 (239Pu or Pu-239) is an isotope of plutonium. Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 is also used for that purpose. Plutonium-239 is also one of the three main ...
(). The first full-scale thermonuclear test was carried out by the United States in 1952; the concept has since been employed by most of the world's
nuclear powers Eight sovereign states have publicly announced successful detonation of nuclear weapons. Five are considered to be nuclear-weapon states (NWS) under the terms of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). In order of acquisit ...
in the design of their weapons. Modern fusion weapons consist essentially of two main components: a
nuclear fission Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radio ...
primary stage (fueled by or ) and a separate nuclear fusion secondary stage containing thermonuclear fuel: the heavy hydrogen isotopes
deuterium Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two Stable isotope ratio, stable isotopes of hydrogen (the other being Hydrogen atom, protium, or hydrogen-1). The atomic nucleus, nucleus of a deuterium ato ...
and
tritium Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with half-life about 12 years. The nucleus of tritium (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus o ...
, or in modern weapons
lithium deuteride Lithium hydride is an inorganic compound with the formula Li H. This alkali metal hydride is a colorless solid, although commercial samples are grey. Characteristic of a salt-like (ionic) hydride, it has a high melting point, and it is not solub ...
. For this reason, thermonuclear weapons are often colloquially called hydrogen bombs or H-bombs.The misleading term "hydrogen bomb" was already in wide public use before fission product
fallout Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and the shock wave has passed. It commonly refers to the radioac ...
from the
Castle Bravo Castle Bravo was the first in a series of high-yield thermonuclear weapon design tests conducted by the United States at Bikini Atoll, Marshall Islands, as part of ''Operation Castle''. Detonated on March 1, 1954, the device was the most powerful ...
test in 1954 revealed the extent to which the design relies on fission as well.
A fusion explosion begins with the detonation of the fission primary stage. Its temperature soars past approximately 100 million
kelvin The kelvin, symbol K, is the primary unit of temperature in the International System of Units (SI), used alongside its prefixed forms and the degree Celsius. It is named after the Belfast-born and University of Glasgow-based engineer and phys ...
, causing it to glow intensely with thermal X-rays. These X-rays flood the void (the "radiation channel" often filled with
polystyrene foam Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a ...
) between the primary and secondary assemblies placed within an enclosure called a radiation case, which confines the X-ray energy and resists its outward pressure. The distance separating the two assemblies ensures that debris fragments from the fission primary (which move much more slowly than X-ray photons) cannot disassemble the secondary before the fusion explosion runs to completion. The secondary fusion stage—consisting of outer pusher/tamper, fusion fuel filler and central
plutonium Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibi ...
spark plug—is imploded by the X-ray energy impinging on its pusher/tamper. This compresses the entire secondary stage and drives up the density of the plutonium spark plug. The density of the plutonium fuel rises to such an extent that the spark plug is driven into a supercritical state, and it begins a nuclear fission chain reaction. The fission products of this chain reaction heat the highly compressed, and thus super dense, thermonuclear fuel surrounding the spark plug to around 300 million kelvin, igniting fusion reactions between fusion fuel nuclei. In modern weapons fueled by lithium deuteride, the fissioning plutonium spark plug also emits free neutrons which collide with lithium nuclei and supply the tritium component of the thermonuclear fuel. The secondary's relatively massive tamper (which resists outward expansion as the explosion proceeds) also serves as a thermal barrier to keep the fusion fuel filler from becoming too hot, which would spoil the compression. If made of
uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...
,
enriched uranium Enriched uranium is a type of uranium in which the percent composition of uranium-235 (written 235U) has been increased through the process of isotope separation. Naturally occurring uranium is composed of three major isotopes: uranium-238 (238 ...
or plutonium, the tamper captures fast
fusion neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behave ...
s and undergoes fission itself, increasing the overall explosive yield. Additionally, in most designs the radiation case is also constructed of a
fissile material In nuclear engineering, fissile material is material capable of sustaining a nuclear fission chain reaction. By definition, fissile material can sustain a chain reaction with neutrons of thermal energy. The predominant neutron energy may be ty ...
that undergoes fission driven by fast thermonuclear neutrons. Such bombs are classified as two stage weapons, and most current Teller–Ulam designs are such fission-fusion-fission weapons. Fast fission of the tamper and radiation case is the main contribution to the total yield and is the dominant process that produces
radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...
fission product Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons, the release ...
fallout Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and the shock wave has passed. It commonly refers to the radioac ...
. Before Ivy Mike,
Operation Greenhouse Operation Greenhouse was the fifth American nuclear test series, the second conducted in 1951 and the first to test principles that would lead to developing thermonuclear weapons (''hydrogen bombs''). Conducted at the new Pacific Proving Grou ...
of 1951 was the first American nuclear test series to test principles that led to the development of thermonuclear weapons. Sufficient fission was achieved to boost the associated fusion device, and enough was learned to achieve a full-scale device within a year. The design of all modern thermonuclear weapons in the United States is known as the ''Teller–Ulam configuration'' for its two chief contributors,
Edward Teller Edward Teller ( hu, Teller Ede; January 15, 1908 – September 9, 2003) was a Hungarian-American theoretical physicist who is known colloquially as "the father of the hydrogen bomb" (see the Teller–Ulam design), although he did not care fo ...
and
Stanislaw Ulam Stanisław Marcin Ulam (; 13 April 1909 – 13 May 1984) was a Polish-American scientist in the fields of mathematics and nuclear physics. He participated in the Manhattan Project, originated the Teller–Ulam design of thermonuclear weapon ...
, who developed it in 1951 for the United States, with certain concepts developed with the contribution of physicist
John von Neumann John von Neumann (; hu, Neumann János Lajos, ; December 28, 1903 – February 8, 1957) was a Hungarian-American mathematician, physicist, computer scientist, engineer and polymath. He was regarded as having perhaps the widest cove ...
. Similar devices were developed by the Soviet Union, United Kingdom, France, and China. The thermonuclear
Tsar Bomba The Tsar Bomba () ( code name: ''Ivan'' or ''Vanya''), also known by the alphanumerical designation "AN602", was a thermonuclear aerial bomb, and the most powerful nuclear weapon ever created and tested. Overall, the Soviet physicist Andrei Sa ...
was the most powerful bomb ever tested. As thermonuclear weapons represent the most efficient design for weapon energy yield in weapons with yields above , virtually all the nuclear weapons of this size deployed by the five nuclear-weapon states under the Non-Proliferation Treaty today are thermonuclear weapons using the Teller–Ulam design.


Public knowledge concerning nuclear weapon design

Detailed knowledge of fission and fusion weapons is classified to some degree in virtually every industrialized nation. In the United States, such knowledge can by default be classified as "
Restricted Data Restricted Data (RD) is a category of proscribed information, per National Industrial Security Program Operating Manual (NISPOM). Specifically, it is defined by the Atomic Energy Act of 1954 as: :''all data concerning (1) design, manufacture, or u ...
", even if it is created by persons who are not government employees or associated with weapons programs, in a legal doctrine known as " born secret" (though the constitutional standing of the doctrine has been at times called into question; see '' United States v. Progressive, Inc.''). Born secret is rarely invoked for cases of private speculation. The official policy of the
United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and manages the research and development of nuclear power and nuclear weapons in the United Stat ...
has been not to acknowledge the leaking of design information, as such acknowledgment would potentially validate the information as accurate. In a small number of prior cases, the U.S. government has attempted to censor weapons information in the public press, with limited success. According to the ''New York Times'', physicist
Kenneth W. Ford Kenneth William Ford (born May 1, 1926) is an American theoretical physicist, teacher, and writer, currently residing near Philadelphia, Pennsylvania. He was the first chair of the physics department at the University of California, Irvine, and l ...
defied government orders to remove
classified information Classified information is material that a government body deems to be sensitive information that must be protected. Access is restricted by law or regulation to particular groups of people with the necessary security clearance and need to know, ...
from his book, ''Building the H Bomb: A Personal History''. Ford claims he used only pre-existing information and even submitted a manuscript to the government, which wanted to remove entire sections of the book for concern that foreign nations could use the information. Though large quantities of vague data have been officially released, and larger quantities of vague data have been unofficially leaked by former bomb designers, most public descriptions of nuclear weapon design details rely to some degree on speculation,
reverse engineering Reverse engineering (also known as backwards engineering or back engineering) is a process or method through which one attempts to understand through deductive reasoning how a previously made device, process, system, or piece of software accompli ...
from known information, or comparison with similar fields of
physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...
(
inertial confinement fusion Inertial confinement fusion (ICF) is a fusion energy process that initiates nuclear fusion reactions by compressing and heating targets filled with thermonuclear fuel. In modern machines, the targets are small spherical pellets about the size of ...
is the primary example). Such processes have resulted in a body of unclassified knowledge about nuclear bombs that is generally consistent with official unclassified information releases, related physics, and is thought to be internally consistent, though there are some points of interpretation that are still considered open. The state of public knowledge about the Teller–Ulam design has been mostly shaped from a few specific incidents outlined in a section below.


Basic principle

The basic principle of the Teller–Ulam configuration is the idea that different parts of a thermonuclear weapon can be chained together in "stages", with the detonation of each stage providing the energy to ignite the next stage. At a bare minimum, this implies a ''primary'' section that consists of an implosion-type fission bomb (a "trigger"), and a ''secondary'' section that consists of fusion fuel. The energy released by the ''primary'' compresses the ''secondary'' through a process called "
radiation implosion Radiation implosion is the compression of a target by the use of high levels of electromagnetic radiation. The major use for this technology is in fusion bombs and inertial confinement fusion research. History Radiation implosion was first deve ...
", at which point it is heated and undergoes
nuclear fusion Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles ( neutrons or protons). The difference in mass between the reactants and products is manifest ...
. This process could be continued, with energy from the secondary igniting a third fusion stage; Russia's AN602 "
Tsar Bomba The Tsar Bomba () ( code name: ''Ivan'' or ''Vanya''), also known by the alphanumerical designation "AN602", was a thermonuclear aerial bomb, and the most powerful nuclear weapon ever created and tested. Overall, the Soviet physicist Andrei Sa ...
" is thought to have been a three-stage fission-fusion-fusion device. Theoretically by continuing this process thermonuclear weapons with arbitrarily high yield could be constructed. This contrasts with
fission weapon Nuclear weapon designs are physical, chemical, and engineering arrangements that cause the physics package of a nuclear weapon to detonate. There are three existing basic design types: * pure fission weapons, the simplest and least technically ...
s which are limited in yield because only so much fission fuel can be amassed in one place before the danger of its accidentally becoming supercritical becomes too great. Surrounding the other components is a
hohlraum In radiation thermodynamics, a hohlraum (a non-specific German word for a "hollow space" or "cavity") is a cavity whose walls are in radiative equilibrium with the radiant energy within the cavity. This idealized cavity can be approximated in pra ...
or ''radiation case'', a container that traps the first stage or primary's energy inside temporarily. The outside of this radiation case, which is also normally the outside casing of the bomb, is the only direct visual evidence publicly available of any thermonuclear bomb component's configuration. Numerous photographs of various thermonuclear bomb exteriors have been declassified. The primary is thought to be a standard implosion method fission bomb, though likely with a
core Core or cores may refer to: Science and technology * Core (anatomy), everything except the appendages * Core (manufacturing), used in casting and molding * Core (optical fiber), the signal-carrying portion of an optical fiber * Core, the centra ...
boosted by small amounts of fusion fuel (usually 50/50%
deuterium Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two Stable isotope ratio, stable isotopes of hydrogen (the other being Hydrogen atom, protium, or hydrogen-1). The atomic nucleus, nucleus of a deuterium ato ...
/
tritium Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with half-life about 12 years. The nucleus of tritium (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus o ...
gas) for extra efficiency; the fusion fuel releases excess
neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...
s when heated and compressed, inducing additional fission. When fired, the or core would be compressed to a smaller sphere by special layers of conventional
high explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An exp ...
s arranged around it in an
explosive lens An explosive lens—as used, for example, in nuclear weapons—is a highly specialized shaped charge. In general, it is a device composed of several explosive charges. These charges are arranged and formed with the intent to control the shape ...
pattern, initiating the
nuclear chain reaction In nuclear physics, a nuclear chain reaction occurs when one single nuclear reaction causes an average of one or more subsequent nuclear reactions, thus leading to the possibility of a self-propagating series of these reactions. The specific nu ...
that powers the conventional "atomic bomb". The secondary is usually shown as a
column A column or pillar in architecture and structural engineering is a structural element that transmits, through compression, the weight of the structure above to other structural elements below. In other words, a column is a compression member. ...
of fusion fuel and other components wrapped in many layers. Around the column is first a "pusher-tamper", a heavy layer of
uranium-238 Uranium-238 (238U or U-238) is the most common isotope of uranium found in nature, with a relative abundance of 99%. Unlike uranium-235, it is non-fissile, which means it cannot sustain a chain reaction in a thermal-neutron reactor. However, it ...
() or
lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
that helps compress the fusion fuel (and, in the case of uranium, may eventually undergo fission itself). Inside this is the fusion fuel itself, usually a form of
lithium deuteride Lithium hydride is an inorganic compound with the formula Li H. This alkali metal hydride is a colorless solid, although commercial samples are grey. Characteristic of a salt-like (ionic) hydride, it has a high melting point, and it is not solub ...
, which is used because it is easier to weaponize than liquefied tritium/deuterium gas. This dry fuel, when bombarded by
neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...
s, produces
tritium Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with half-life about 12 years. The nucleus of tritium (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus o ...
, a heavy
isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...
of
hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
which can undergo
nuclear fusion Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles ( neutrons or protons). The difference in mass between the reactants and products is manifest ...
, along with the
deuterium Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two Stable isotope ratio, stable isotopes of hydrogen (the other being Hydrogen atom, protium, or hydrogen-1). The atomic nucleus, nucleus of a deuterium ato ...
present in the mixture. (See the article on
nuclear fusion Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles ( neutrons or protons). The difference in mass between the reactants and products is manifest ...
for a more detailed technical discussion of fusion reactions.) Inside the layer of fuel is the "
spark plug A spark plug (sometimes, in British English, a sparking plug, and, colloquially, a plug) is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air ...
", a hollow column of fissile material ( or ) often boosted by deuterium gas. The spark plug, when compressed, can itself undergo nuclear fission (because of the shape, it is not a
critical mass In nuclear engineering, 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 (specifically, its nuclear fissi ...
without compression). The tertiary, if one is present, would be set below the secondary and probably be made of the same materials. Separating the secondary from the primary is the
interstage In rocketry, an adapter is a hollow Cylinder (geometry), cylindrical or conical segment which provides a sound aerodynamics, aerodynamic and structural connection, either between multistage rocket, rocket stages (referred to as an interstage adapter ...
. The fissioning primary produces four types of energy: 1) expanding hot gases from high explosive charges that implode the primary; 2) superheated
plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral), a green translucent silica mineral * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood pla ...
that was originally the bomb's fissile material and its tamper; 3) the
electromagnetic radiation In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic field, electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, inf ...
; and 4) the
neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...
s from the primary's nuclear detonation. The interstage is responsible for accurately modulating the transfer of energy from the primary to the secondary. It must direct the hot gases, plasma, electromagnetic radiation and neutrons toward the right place at the right time. Less than optimal interstage designs have resulted in the secondary failing to work entirely on multiple shots, known as a "fissile fizzle". The Castle Koon shot of
Operation Castle Operation Castle was a United States series of high-yield (high-energy) nuclear tests by Joint Task Force 7 (JTF-7) at Bikini Atoll beginning in March 1954. It followed ''Operation Upshot–Knothole'' and preceded ''Operation Teapot''. Condu ...
is a good example; a small flaw allowed the neutron flux from the primary to prematurely begin heating the secondary, weakening the compression enough to prevent any fusion. There is very little detailed information in the open literature about the mechanism of the interstage. One of the best sources is a simplified diagram of a British thermonuclear weapon similar to the American W80 warhead. It was released by
Greenpeace Greenpeace is an independent global campaigning network, founded in Canada in 1971 by Irving Stowe and Dorothy Stowe, immigrant environmental activists from the United States. Greenpeace states its goal is to "ensure the ability of the Earth t ...
in a report titled ''"Dual Use Nuclear Technology"''. The major components and their arrangement are in the diagram, though details are almost absent; what scattered details it does include likely have intentional omissions or inaccuracies. They are labeled "End-cap and Neutron Focus Lens" and "Reflector Wrap"; the former channels neutrons to the / Spark Plug while the latter refers to an
X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10  picometers to 10  nanometers, corresponding to frequencies in the range 30&nb ...
reflector; typically a cylinder made of an X-ray opaque material such as uranium with the primary and secondary at either end. It does not reflect like a
mirror A mirror or looking glass is an object that Reflection (physics), reflects an image. Light that bounces off a mirror will show an image of whatever is in front of it, when focused through the lens of the eye or a camera. Mirrors reverse the ...
; instead, it gets heated to a high temperature by the X-ray flux from the primary, then it emits more evenly spread X-rays that travel to the secondary, causing what is known as
radiation implosion Radiation implosion is the compression of a target by the use of high levels of electromagnetic radiation. The major use for this technology is in fusion bombs and inertial confinement fusion research. History Radiation implosion was first deve ...
. In Ivy Mike, gold was used as a coating over the uranium to enhance the
blackbody A black body or blackbody is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. The name "black body" is given because it absorbs all colors of light. A black body ...
effect. Next comes the "Reflector/Neutron Gun Carriage". The reflector seals the gap between the Neutron Focus Lens (in the center) and the outer casing near the primary. It separates the primary from the secondary and performs the same function as the previous reflector. There are about six neutron guns (seen here from
Sandia National Laboratories Sandia National Laboratories (SNL), also known as Sandia, is one of three research and development laboratories of the United States Department of Energy's National Nuclear Security Administration (NNSA). Headquartered in Kirtland Air Force Ba ...
) each protruding through the outer edge of the reflector with one end in each section; all are clamped to the carriage and arranged more or less evenly around the casing's circumference. The neutron guns are tilted so the neutron emitting end of each gun end is pointed towards the central axis of the bomb. Neutrons from each neutron gun pass through and are focused by the neutron focus lens towards the centre of primary in order to boost the initial fissioning of the plutonium. A "
polystyrene Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a ...
Polarizer/Plasma Source" is also shown (see below). The first U.S. government document to mention the interstage was only recently released to the public promoting the 2004 initiation of the
Reliable Replacement Warhead The Reliable Replacement Warhead (RRW) was a proposed new American nuclear warhead design and bomb family that was intended to be simple, reliable and to provide a long-lasting, low-maintenance future nuclear force for the United States. Initiated ...
Program. A graphic includes blurbs describing the potential advantage of a RRW on a part by part level, with the interstage blurb saying a new design would replace "toxic, brittle material" and "expensive 'special' material...
hich require Ij ( fa, ايج, also Romanized as Īj; also known as Hich and Īch) is a village in Golabar Rural District, in the Central District of Ijrud County, Zanjan Province, Iran Iran, officially the Islamic Republic of Iran, and also ...
unique facilities". The "toxic, brittle material" is widely assumed to be
beryllium Beryllium is a chemical element with the symbol Be and atomic number 4. It is a steel-gray, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with other elements to form mi ...
which fits that description and would also moderate the
neutron flux The neutron flux, φ, is a scalar quantity used in nuclear physics and nuclear reactor physics. It is the total length travelled by all free neutrons per unit time and volume. Equivalently, it can be defined as the number of neutrons travelling ...
from the primary. Some material to absorb and re-radiate the X-rays in a particular manner may also be used. Candidates for the "special material" are
polystyrene Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a ...
and a substance called "
Fogbank Fogbank is a code name given to a material used in the W76, W78 and W88 nuclear warheads that are part of the United States nuclear arsenal. Fogbank's precise nature is classified; in the words of former Oak Ridge general manager Dennis Ruddy, ...
", an unclassified codename. Fogbank's composition is classified, though
aerogel Aerogels are a class of synthetic porous ultralight material derived from a gel, in which the liquid component for the gel has been replaced with a gas, without significant collapse of the gel structure. The result is a solid with extremely low ...
has been suggested as a possibility. It was first used in thermonuclear weapons with the
W76 The W76 is an American thermonuclear warhead, designed for use on the UGM-96 Trident I submarine-launched ballistic missiles (SLBMs) and subsequently moved to the UGM-133 Trident II as Trident I was phased out of service. The first variant, the ...
thermonuclear warhead, and produced at a plant in the Y-12 Complex at Oak Ridge, Tennessee, for use in the W76. Production of Fogbank lapsed after the W76 production run ended. The W76 Life Extension Program required more Fogbank to be made. This was complicated by the fact that the original Fogbank's properties were not fully documented, so a massive effort was mounted to re-invent the process. An impurity crucial to the properties of the old Fogbank was omitted during the new process. Only close analysis of new and old batches revealed the nature of that impurity. The manufacturing process used
acetonitrile Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not clas ...
as a
solvent A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...
, which led to at least three evacuations of the Fogbank plant in 2006. Widely used in the petroleum and pharmaceutical industries, acetonitrile is flammable and toxic. Y-12 is the sole producer of Fogbank.


Summary

A simplified summary of the above explanation is: # A (relatively) small fission bomb known as the "primary" explodes. # Energy released in the primary is transferred to the secondary (or fusion) stage. This energy compresses the fusion fuel and sparkplug; the compressed sparkplug becomes supercritical and undergoes a fission chain reaction, further heating the compressed fusion fuel to a high enough temperature to induce fusion. # Energy released by the fusion events continues heating the fuel, keeping the reaction going. # The fusion fuel of the secondary stage may be surrounded by a layer of additional fuel that undergoes fission when hit by the neutrons from the reactions within. These fission events account for about half of the total energy released in typical designs.


Compression of the secondary

The basic idea of the Teller–Ulam configuration is that each "stage" would undergo fission or fusion (or both) and release energy, much of which would be transferred to another stage to trigger it. How exactly the energy is "transported" from the ''primary'' to the ''secondary'' has been the subject of some disagreement in the open press, but is thought to be transmitted through the
X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10  picometers to 10  nanometers, corresponding to frequencies in the range 30&nb ...
s and
Gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
s that are emitted from the fissioning ''primary''. This energy is then used to compress the ''secondary''. The crucial detail of ''how'' the X-rays create the pressure is the main remaining disputed point in the unclassified press. There are three proposed theories: *
Radiation pressure Radiation pressure is the mechanical pressure exerted upon any surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of any wavelength that is a ...
exerted by the X-rays. This was the first idea put forth by
Howard Morland Howard Morland (born September 14, 1942) is an American journalist and activist against nuclear weapons who, in 1979, became famous for apparently discovering the "secret" of the hydrogen bomb (the Teller–Ulam design) and publishing it after a ...
in the article in ''
The Progressive ''The Progressive'' is a left-leaning American magazine and website covering politics and culture. Founded in 1909 by U.S. senator Robert M. La Follette Sr. and co-edited with his wife Belle Case La Follette, it was originally called ''La Follett ...
''. * X-rays creating a
plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral), a green translucent silica mineral * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood pla ...
in the radiation channel's filler (a
polystyrene Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a ...
or "
Fogbank Fogbank is a code name given to a material used in the W76, W78 and W88 nuclear warheads that are part of the United States nuclear arsenal. Fogbank's precise nature is classified; in the words of former Oak Ridge general manager Dennis Ruddy, ...
" plastic foam). This was a second idea put forward by
Chuck Hansen Chuck Hansen (May 13, 1947 - March 26, 2003) was the compiler, over a period of 30 years, of the world's largest private collection of unclassified documents on how America developed atomic and thermonuclear weapons. Research Hansen's documents ...
and later by Howard Morland. * Tamper/Pusher
ablation Ablation ( la, ablatio – removal) is removal or destruction of something from an object by vaporization, chipping, erosion, erosive processes or by other means. Examples of ablative materials are described below, and include spacecraft materi ...
. This is the concept best supported by physical analysis.


Radiation pressure

The
radiation pressure Radiation pressure is the mechanical pressure exerted upon any surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of any wavelength that is a ...
exerted by the large quantity of X-ray
photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they always ...
s inside the closed casing might be enough to compress the secondary. Electromagnetic radiation such as X-rays or light carries
momentum In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass an ...
and exerts a force on any surface it strikes. The pressure of radiation at the intensities seen in everyday life, such as sunlight striking a surface, is usually imperceptible, but at the extreme intensities found in a thermonuclear bomb the pressure is enormous. For two thermonuclear bombs for which the general size and primary characteristics are well understood, the Ivy Mike test bomb and the modern W-80 cruise missile warhead variant of the W-61 design, the radiation pressure was calculated to be for the Ivy Mike design and for the W-80.


Foam plasma pressure

Foam Foams are materials formed by trapping pockets of gas in a liquid or solid. A bath sponge and the head on a glass of beer are examples of foams. In most foams, the volume of gas is large, with thin films of liquid or solid separating the reg ...
plasma pressure is the concept that Chuck Hansen introduced during the Progressive case, based on research that located declassified documents listing special foams as liner components within the radiation case of thermonuclear weapons. The sequence of firing the weapon (with the foam) would be as follows: # The high explosives surrounding the core of the primary fire, compressing the fissile material into a supercritical state and beginning the fission
chain reaction A chain reaction is a sequence of reactions where a reactive product or by-product causes additional reactions to take place. In a chain reaction, positive feedback leads to a self-amplifying chain of events. Chain reactions are one way that syst ...
. # The fissioning primary emits thermal
X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10  picometers to 10  nanometers, corresponding to frequencies in the range 30&nb ...
s, which "reflect" along the inside of the casing, irradiating the polystyrene foam. # The irradiated foam becomes a hot
plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral), a green translucent silica mineral * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood pla ...
, pushing against the tamper of the secondary, compressing it tightly, and beginning the fission chain reaction in the spark plug. # Pushed from both sides (from the primary and the spark plug), the lithium deuteride fuel is highly compressed and heated to thermonuclear temperatures. Also, by being bombarded with neutrons, each
lithium-6 Naturally occurring lithium (3Li) is composed of two stable isotopes, lithium-6 and lithium-7, with the latter being far more abundant on Earth. Both of the natural isotopes have an unexpectedly low nuclear binding energy per nucleon ( for ...
(6Li) atom splits into one
tritium Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with half-life about 12 years. The nucleus of tritium (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus o ...
atom and one
alpha particle Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay, but may also be produce ...
. Then begins a fusion reaction between the tritium and the deuterium, releasing even more neutrons, and a huge amount of energy. # The fuel undergoing the fusion reaction emits a large
flux Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport ph ...
of high energy neutrons (), which irradiates the tamper (or the bomb casing), causing it to undergo a fast fission reaction, providing about half of the total energy. This would complete the fission-fusion-fission sequence. Fusion, unlike fission, is relatively "clean"—it releases energy but no harmful radioactive products or large amounts of
nuclear fallout Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and the shock wave has passed. It commonly refers to the radioac ...
. The fission reactions though, especially the last fission reactions, release a tremendous amount of fission products and fallout. If the last fission stage is omitted, by replacing the uranium tamper with one made of
lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
, for example, the overall explosive force is reduced by approximately half but the amount of fallout is relatively low. The
neutron bomb A neutron bomb, officially defined as a type of enhanced radiation weapon (ERW), is a low-yield thermonuclear weapon designed to maximize lethal neutron radiation in the immediate vicinity of the blast while minimizing the physical power of the b ...
is a hydrogen bomb with an intentionally thin tamper, allowing as many of the fast fusion neutrons as possible to escape. Current technical criticisms of the idea of "foam plasma pressure" focus on unclassified analysis from similar high energy physics fields that indicate that the pressure produced by such a plasma would only be a ''small multiplier'' of the basic photon pressure within the radiation case, and also that the known foam materials intrinsically have a very low absorption efficiency of the
gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
and
X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10  picometers to 10  nanometers, corresponding to frequencies in the range 30&nb ...
radiation from the primary. Most of the energy produced would be absorbed by either the walls of the radiation case or the tamper around the secondary. Analyzing the effects of that absorbed energy led to the third mechanism:
ablation Ablation ( la, ablatio – removal) is removal or destruction of something from an object by vaporization, chipping, erosion, erosive processes or by other means. Examples of ablative materials are described below, and include spacecraft materi ...
.


Tamper-pusher ablation

The outer casing of the secondary assembly is called the "tamper-pusher". The purpose of a tamper in an implosion bomb is to delay the expansion of the reacting fuel supply (which is very hot dense plasma) until the fuel is fully consumed and the explosion runs to completion. The same tamper material serves also as a pusher in that it is the medium by which the outside pressure (force acting on the surface area of the secondary) is transferred to the mass of fusion fuel. The proposed tamper-pusher ablation mechanism posits that the outer layers of the thermonuclear secondary's tamper-pusher are heated so extremely by the primary's X-ray flux that they expand violently and ablate away (fly off). Because total momentum is conserved, this mass of high velocity ejecta impels the rest of the tamper-pusher to recoil inwards with tremendous force, crushing the fusion fuel and the spark plug. The tamper-pusher is built robustly enough to insulate the fusion fuel from the extreme heat outside; otherwise the compression would be spoiled. Rough calculations for the basic ablation effect are relatively simple: the energy from the primary is distributed evenly onto all of the surfaces within the outer radiation case, with the components coming to a
thermal equilibrium Two physical systems are in thermal equilibrium if there is no net flow of thermal energy between them when they are connected by a path permeable to heat. Thermal equilibrium obeys the zeroth law of thermodynamics. A system is said to be in ...
, and the effects of that thermal energy are then analyzed. The energy is mostly deposited within about one X-ray
optical thickness In physics, optical depth or optical thickness is the natural logarithm of the ratio of incident to ''transmitted'' radiant power through a material. Thus, the larger the optical depth, the smaller the amount of transmitted radiant power through ...
of the tamper/pusher outer surface, and the temperature of that layer can then be calculated. The velocity at which the surface then expands outwards is calculated and, from a basic Newtonian
momentum In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass an ...
balance, the velocity at which the rest of the tamper implodes inwards. Applying the more detailed form of those calculations to the
Ivy Mike Ivy Mike was the codename given to the first full-scale test of a thermonuclear device, in which part of the explosive yield comes from nuclear fusion. Ivy Mike was detonated on November 1, 1952, by the United States on the island of Elugelab in ...
device yields vaporized pusher gas expansion velocity of and an implosion velocity of perhaps if of the total tamper/pusher mass is ablated off, the most energy efficient proportion. For the W-80 the gas expansion velocity is roughly and the implosion velocity . The pressure due to the ablating material is calculated to be in the Ivy Mike device and in the W-80 device.


Comparing implosion mechanisms

Comparing the three mechanisms proposed, it can be seen that: The calculated ablation pressure is one order of magnitude greater than the higher proposed plasma pressures and nearly two orders of magnitude greater than calculated radiation pressure. No mechanism to avoid the absorption of energy into the radiation case wall and the secondary tamper has been suggested, making ablation apparently unavoidable. The other mechanisms appear to be unneeded.
United States Department of Defense The United States Department of Defense (DoD, USDOD or DOD) is an executive branch department of the federal government charged with coordinating and supervising all agencies and functions of the government directly related to national secu ...
official declassification reports indicate that foamed plastic materials are or may be used in radiation case liners, and despite the low direct plasma pressure they may be of use in delaying the
ablation Ablation ( la, ablatio – removal) is removal or destruction of something from an object by vaporization, chipping, erosion, erosive processes or by other means. Examples of ablative materials are described below, and include spacecraft materi ...
until energy has distributed evenly and a sufficient fraction has reached the secondary's tamper/pusher.
Richard Rhodes Richard Lee Rhodes (born July 4, 1937) is an American historian, journalist, and author of both fiction and non-fiction, including the Pulitzer Prize-winning ''The Making of the Atomic Bomb'' (1986), and most recently, ''Energy: A Human Histor ...
' book ''Dark Sun'' stated that a layer of plastic foam was fixed to the lead liner of the inside of the
Ivy Mike Ivy Mike was the codename given to the first full-scale test of a thermonuclear device, in which part of the explosive yield comes from nuclear fusion. Ivy Mike was detonated on November 1, 1952, by the United States on the island of Elugelab in ...
steel casing using copper nails. Rhodes quotes several designers of that bomb explaining that the plastic foam layer inside the outer case is to delay ablation and thus recoil of the outer case: if the foam were not there, metal would ablate from the inside of the outer case with a large impulse, causing the casing to recoil outwards rapidly. The purpose of the casing is to contain the explosion for as long as possible, allowing as much X-ray ablation of the metallic surface of the secondary stage as possible, so it compresses the secondary efficiently, maximizing the fusion yield. Plastic foam has a low density, so causes a smaller impulse when it ablates than metal does.


Design variations

A number of possible variations to the weapon design have been proposed: * Either the tamper or the casing have been proposed to be made of (
highly enriched uranium Enriched uranium is a type of uranium in which the percent composition of uranium-235 (written 235U) has been increased through the process of isotope separation. Naturally occurring uranium is composed of three major isotopes: uranium-238 (238U ...
) in the final fission jacket. The far more expensive is also fissionable with fast neutrons like the in depleted or
natural uranium Natural uranium (NU or Unat) refers to uranium with the same isotopic ratio as found in nature. It contains 0.711% uranium-235, 99.284% uranium-238, and a trace of uranium-234 by weight (0.0055%). Approximately 2.2% of its radioactivity comes fr ...
, but its fission-efficiency is higher. This is because nuclei also undergo fission by slow neutrons ( nuclei require a minimum energy of about ), and because these slower neutrons are produced by other fissioning nuclei in the jacket (in other words, supports the nuclear chain reaction whereas does not). Furthermore, a jacket fosters neutron multiplication, whereas nuclei consume fusion neutrons in the fast-fission process. Using a final fissionable/fissile jacket of would thus increase the yield of a Teller–Ulam bomb above a depleted uranium or natural uranium jacket. This has been proposed specifically for the
W87 The W87 is an American thermonuclear missile warhead formerly deployed on the LGM-118A Peacekeeper ("MX") ICBM. 50 MX missiles were built, each carrying up to 10 W87 warheads in multiple independently targetable reentry vehicles (MIRV), and were ...
warheads retrofitted to currently deployed
LGM-30 Minuteman The LGM-30 Minuteman is an American land-based intercontinental ballistic missile (ICBM) in service with the Air Force Global Strike Command. , the LGM-30G Minuteman III version is the only land-based ICBM in service in the United States and r ...
III ICBMs. * In some descriptions, additional internal structures exist to protect the secondary from receiving excessive neutrons from the primary. * The inside of the casing may or may not be specially machined to "reflect" the X-rays. X-ray "reflection" is not like light reflecting off of a
mirror A mirror or looking glass is an object that Reflection (physics), reflects an image. Light that bounces off a mirror will show an image of whatever is in front of it, when focused through the lens of the eye or a camera. Mirrors reverse the ...
, but rather the reflector material is heated by the X-rays, causing the material itself to emit X-rays, which then travel to the secondary. Two special variations exist that will be discussed in a subsequent section: the
cryogenically In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cr ...
cooled liquid deuterium device used for the
Ivy Mike Ivy Mike was the codename given to the first full-scale test of a thermonuclear device, in which part of the explosive yield comes from nuclear fusion. Ivy Mike was detonated on November 1, 1952, by the United States on the island of Elugelab in ...
test, and the putative design of the
W88 The W88 is an American thermonuclear warhead, with an estimated yield of , and is small enough to fit on MIRVed missiles. The W88 was designed at the Los Alamos National Laboratory in the 1970s. In 1999, the director of Los Alamos who had pres ...
nuclear warhead—a small, MIRVed version of the Teller–Ulam configuration with a
prolate A spheroid, also known as an ellipsoid of revolution or rotational ellipsoid, is a quadric surface obtained by rotating an ellipse about one of its principal axes; in other words, an ellipsoid with two equal semi-diameters. A spheroid has circ ...
(
egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
or
watermelon Watermelon (''Citrullus lanatus'') is a flowering plant species of the Cucurbitaceae family and the name of its edible fruit. A scrambling and trailing vine-like plant, it is a highly cultivated fruit worldwide, with more than 1,000 varieti ...
shaped) primary and an elliptical secondary. Most bombs do not apparently have tertiary "stages"—that is, third compression stage(s), which are additional fusion stages compressed by a previous fusion stage. (The fissioning of the last blanket of uranium, which provides about half the yield in large bombs, does not count as a "stage" in this terminology.) The U.S. tested three-stage bombs in several explosions (see
Operation Redwing Operation Redwing was a United States series of 17 nuclear test detonations from May to July 1956. They were conducted at Bikini and Enewetak atolls by Joint Task Force 7 (JTF7).Blumenson, Martin and Hugh D. Hexamer (1956). ''A History of ...
) but is thought to have fielded only one such tertiary model, i.e., a bomb in which a fission stage, followed by a fusion stage, finally compresses yet another fusion stage. This U.S. design was the heavy but highly efficient (i.e.,
nuclear weapon yield The explosive yield of a nuclear weapon is the amount of energy released when that particular nuclear weapon is detonated, usually expressed as a TNT equivalent (the standardized equivalent mass of trinitrotoluene which, if detonated, would produ ...
per unit bomb weight)
B41 nuclear bomb The B-41 (also known as Mk-41) was a thermonuclear weapon deployed by the United States Strategic Air Command in the early 1960s. It was the most powerful nuclear bomb ever developed by the United States, with a maximum yield of . The B-41 was ...
. The Soviet Union is thought to have used multiple stages (including more than one tertiary fusion stage) in their ( in intended use)
Tsar Bomba The Tsar Bomba () ( code name: ''Ivan'' or ''Vanya''), also known by the alphanumerical designation "AN602", was a thermonuclear aerial bomb, and the most powerful nuclear weapon ever created and tested. Overall, the Soviet physicist Andrei Sa ...
(however, as with other bombs, the fissionable jacket could be replaced with lead in such a bomb, and in this one, for demonstration, it was). If any hydrogen bombs have been made from configurations other than those based on the Teller–Ulam design, the fact of it is not publicly known. (A possible exception to this is the Soviet early ''
Sloika Joe 4 was an American nickname for the first Soviet test of a thermonuclear weapon on August 12, 1953, that detonated with a force equivalent to 400 kilotons of TNT. The proper Soviet terminology for the warhead was RDS-6s, , . RDS-6 utilized a ...
'' design.) In essence, the Teller–Ulam configuration relies on at least two instances of implosion occurring: first, the conventional (chemical) explosives in the primary would compress the fissile core, resulting in a fission explosion many times more powerful than that which chemical explosives could achieve alone (first stage). Second, the radiation from the fissioning of the primary would be used to compress and ignite the secondary fusion stage, resulting in a fusion explosion many times more powerful than the fission explosion alone. This chain of compression could conceivably be continued with an arbitrary number of tertiary fusion stages, each igniting more fusion fuel in the next stage although this is debated (see more: Arbitrarily large yield debate). Finally, efficient bombs (but not so-called
neutron bomb A neutron bomb, officially defined as a type of enhanced radiation weapon (ERW), is a low-yield thermonuclear weapon designed to maximize lethal neutron radiation in the immediate vicinity of the blast while minimizing the physical power of the b ...
s) end with the fissioning of the final natural uranium tamper, something that could not normally be achieved without the
neutron flux The neutron flux, φ, is a scalar quantity used in nuclear physics and nuclear reactor physics. It is the total length travelled by all free neutrons per unit time and volume. Equivalently, it can be defined as the number of neutrons travelling ...
provided by the fusion reactions in secondary or tertiary stages. Such designs are suggested to be capable of being scaled up to an arbitrary large yield (with apparently as many fusion stages as desired), potentially to the level of a "
doomsday device A doomsday device is a hypothetical construction — usually a weapon or weapons system — which could destroy all life on a planet, particularly Earth, or destroy the planet itself, bringing "doomsday", a term used for the end of planet Earth. ...
." However, usually such weapons were not more than a dozen megatons, which was generally considered enough to destroy even the most hardened practical targets (for example, a control facility such as the
Cheyenne Mountain Complex The Cheyenne Mountain Complex is a Space Force installation and defensive bunker located in unincorporated El Paso County, Colorado, next to the city of Colorado Springs, at the Cheyenne Mountain Space Force Station, which hosts the activities o ...
). Even such large bombs have been replaced by smaller-yield
bunker buster A bunker buster is a type of munition that is designed to penetrate hardened targets or targets buried deep underground, such as military bunkers. Armor piercing shells Germany Röchling shells were bunker-busting artillery shells, developed by ...
type nuclear bombs (see more:
nuclear bunker buster A nuclear bunker buster, also known as an earth-penetrating weapon (EPW), is the nuclear equivalent of the conventional bunker buster. The non-nuclear component of the weapon is designed to penetrate soil, rock, or concrete to deliver a nuclear ...
). As discussed above, for destruction of cities and non-hardened targets, breaking the mass of a single missile payload down into smaller MIRV bombs, in order to spread the energy of the explosions into a "pancake" area, is far more efficient in terms of area-destruction per unit of bomb energy. This also applies to single bombs deliverable by cruise missile or other system, such as a bomber, resulting in most operational warheads in the U.S. program having yields of less than .


History


United States

The idea of a thermonuclear fusion bomb ignited by a smaller fission bomb was first proposed by
Enrico Fermi Enrico Fermi (; 29 September 1901 – 28 November 1954) was an Italian (later naturalized American) physicist and the creator of the world's first nuclear reactor, the Chicago Pile-1. He has been called the "architect of the nuclear age" and ...
to his colleague
Edward Teller Edward Teller ( hu, Teller Ede; January 15, 1908 – September 9, 2003) was a Hungarian-American theoretical physicist who is known colloquially as "the father of the hydrogen bomb" (see the Teller–Ulam design), although he did not care fo ...
when they were talking at
Columbia University Columbia University (also known as Columbia, and officially as Columbia University in the City of New York) is a private research university in New York City. Established in 1754 as King's College on the grounds of Trinity Church in Manhatt ...
in September 1941, at the start of what would become the
Manhattan Project The Manhattan Project was a research and development undertaking during World War II that produced the first nuclear weapons. It was led by the United States with the support of the United Kingdom and Canada. From 1942 to 1946, the project w ...
. Teller spent much of the Manhattan Project attempting to figure out how to make the design work, preferring it to work on the atomic bomb, and over the last year of the project was assigned exclusively to the task. However once World War II ended, there was little impetus to devote many resources to the ''
Super Super may refer to: Computing * SUPER (computer program), or Simplified Universal Player Encoder & Renderer, a video converter / player * Super (computer science), a keyword in object-oriented programming languages * Super key (keyboard butt ...
'', as it was then known. The first atomic bomb test by the Soviet Union in August 1949 came earlier than expected by Americans, and over the next several months there was an intense debate within the U.S. government, military, and scientific communities regarding whether to proceed with development of the far more powerful Super. The debate covered matters that were alternatively strategic, pragmatic, and moral. In their ''Report of the General Advisory Committee,''
Robert Oppenheimer J. Robert Oppenheimer (; April 22, 1904 – February 18, 1967) was an American theoretical physicist. A professor of physics at the University of California, Berkeley, Oppenheimer was the wartime head of the Los Alamos Laboratory and is often ...
and colleagues concluded that " e extreme danger to mankind inherent in the proposal o develop thermonuclear weaponswholly outweighs any military advantage." Despite the objections raised, on 31 January 1950, President
Harry S. Truman Harry S. Truman (May 8, 1884December 26, 1972) was the 33rd president of the United States, serving from 1945 to 1953. A leader of the Democratic Party, he previously served as the 34th vice president from January to April 1945 under Franklin ...
made the decision to go forward with the development of the new weapon. But deciding to do it did not make it a reality, and Teller and other U.S. physicists struggled to find a workable design.
Stanislaw Ulam Stanisław Marcin Ulam (; 13 April 1909 – 13 May 1984) was a Polish-American scientist in the fields of mathematics and nuclear physics. He participated in the Manhattan Project, originated the Teller–Ulam design of thermonuclear weapon ...
, a co-worker of Teller, made the first key conceptual leaps towards a workable fusion design. Ulam's two innovations that rendered the fusion bomb practical were that compression of the thermonuclear fuel before extreme heating was a practical path towards the conditions needed for fusion, and the idea of staging or placing a separate thermonuclear component outside a fission primary component, and somehow using the primary to compress the secondary. Teller then realized that the gamma and X-ray radiation produced in the primary could transfer enough energy into the secondary to create a successful implosion and fusion burn, if the whole assembly was wrapped in a ''
hohlraum In radiation thermodynamics, a hohlraum (a non-specific German word for a "hollow space" or "cavity") is a cavity whose walls are in radiative equilibrium with the radiant energy within the cavity. This idealized cavity can be approximated in pra ...
'' or radiation case. Teller and his various proponents and detractors later disputed the degree to which Ulam had contributed to the theories underlying this mechanism. Indeed, shortly before his death, and in a last-ditch effort to discredit Ulam's contributions, Teller claimed that one of his own "graduate students" had proposed the mechanism. The "George" shot of
Operation Greenhouse Operation Greenhouse was the fifth American nuclear test series, the second conducted in 1951 and the first to test principles that would lead to developing thermonuclear weapons (''hydrogen bombs''). Conducted at the new Pacific Proving Grou ...
of 9 May 1951 tested the basic concept for the first time on a very small scale. As the first successful (uncontrolled) release of nuclear fusion energy, which made up a small fraction of the total yield, it raised expectations to a near certainty that the concept would work. On 1 November 1952, the Teller–Ulam configuration was tested at full scale in the "
Ivy Mike Ivy Mike was the codename given to the first full-scale test of a thermonuclear device, in which part of the explosive yield comes from nuclear fusion. Ivy Mike was detonated on November 1, 1952, by the United States on the island of Elugelab in ...
" shot at an island in the
Enewetak Atoll Enewetak Atoll (; also spelled Eniwetok Atoll or sometimes Eniewetok; mh, Ānewetak, , or , ; known to the Japanese as Brown Atoll or Brown Island; ja, ブラウン環礁) is a large coral atoll of 40 islands in the Pacific Ocean and with it ...
, with a yield of (over 450 times more powerful than the bomb dropped on Nagasaki during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
). The device, dubbed the ''Sausage'', used an extra-large fission bomb as a "trigger" and liquid
deuterium Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two Stable isotope ratio, stable isotopes of hydrogen (the other being Hydrogen atom, protium, or hydrogen-1). The atomic nucleus, nucleus of a deuterium ato ...
—kept in its liquid state by of
cryogenic In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cr ...
equipment—as its fusion fuel, and weighed around altogether. The liquid deuterium fuel of Ivy Mike was impractical for a deployable weapon, and the next advance was to use a solid
lithium deuteride Lithium hydride is an inorganic compound with the formula Li H. This alkali metal hydride is a colorless solid, although commercial samples are grey. Characteristic of a salt-like (ionic) hydride, it has a high melting point, and it is not solub ...
fusion fuel instead. In 1954 this was tested in the "
Castle Bravo Castle Bravo was the first in a series of high-yield thermonuclear weapon design tests conducted by the United States at Bikini Atoll, Marshall Islands, as part of ''Operation Castle''. Detonated on March 1, 1954, the device was the most powerful ...
" shot (the device was code-named ''Shrimp''), which had a yield of (2.5 times expected) and is the largest U.S. bomb ever tested. Efforts in the United States soon shifted towards developing miniaturized Teller–Ulam weapons that could fit into
intercontinental ballistic missile An intercontinental ballistic missile (ICBM) is a ballistic missile with a range greater than , primarily designed for nuclear weapons delivery (delivering one or more thermonuclear warheads). Conventional, chemical, and biological weapons c ...
s and
submarine-launched ballistic missile A submarine-launched ballistic missile (SLBM) is a ballistic missile capable of being launched from submarines. Modern variants usually deliver multiple independently targetable reentry vehicles (MIRVs), each of which carries a nuclear warhead ...
s. By 1960, with the
W47 The W47 was an American thermonuclear warhead used on the Polaris A-1 sub-launched ballistic missile system. Various models were in service from 1960 through the end of 1974. The warhead was developed by the Lawrence Radiation Laboratory between 1 ...
warhead deployed on
Polaris Polaris is a star in the northern circumpolar constellation of Ursa Minor. It is designated α Ursae Minoris ( Latinized to ''Alpha Ursae Minoris'') and is commonly called the North Star or Pole Star. With an apparent magnitude that ...
ballistic missile submarine A ballistic missile submarine is a submarine capable of deploying submarine-launched ballistic missiles (SLBMs) with nuclear warheads. The United States Navy's hull classification symbols for ballistic missile submarines are SSB and SSBN – t ...
s, megaton-class warheads were as small as in diameter and in weight. Further innovation in miniaturizing warheads was accomplished by the mid-1970s, when versions of the Teller–Ulam design were created that could fit ten or more warheads on the end of a small MIRVed missile (see the section on the W88 below).


Soviet Union

The first Soviet fusion design, developed by
Andrei Sakharov Andrei Dmitrievich Sakharov ( rus, Андрей Дмитриевич Сахаров, p=ɐnˈdrʲej ˈdmʲitrʲɪjevʲɪtɕ ˈsaxərəf; 21 May 192114 December 1989) was a Soviet nuclear physicist, dissident, nobel laureate and activist for nu ...
and
Vitaly Ginzburg Vitaly Lazarevich Ginzburg, ForMemRS (russian: Вита́лий Ла́заревич Ги́нзбург, link=no; 4 October 1916 – 8 November 2009) was a Russian physicist who was honored with the Nobel Prize in Physics in 2003, together with ...
in 1949 (before the Soviets had a working fission bomb), was dubbed the ''Sloika'', after a Russian
layer cake A layer cake (US English) or sandwich cake (UK English) is a cake consisting of multiple stacked sheets of cake, held together by frosting or another type of filling, such as jam or other preserves. Most cake recipes can be adapted for lay ...
, and was not of the Teller–Ulam configuration. It used alternating layers of fissile material and lithium deuteride fusion fuel spiked with
tritium Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with half-life about 12 years. The nucleus of tritium (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus o ...
(this was later dubbed Sakharov's "First Idea"). Though nuclear fusion might have been technically achievable, it did not have the scaling property of a "staged" weapon. Thus, such a design could not produce thermonuclear weapons whose explosive yields could be made arbitrarily large (unlike U.S. designs at that time). The fusion layer wrapped around the fission core could only moderately multiply the fission energy (modern Teller–Ulam designs can multiply it 30-fold). Additionally, the whole fusion stage had to be imploded by conventional explosives, along with the fission core, substantially multiplying the amount of chemical explosives needed. The first Sloika design test,
RDS-6s Joe 4 was an American nickname for the first Soviet test of a thermonuclear weapon on August 12, 1953, that detonated with a force equivalent to 400 kilotons of TNT. The proper Soviet terminology for the warhead was RDS-6s, , . RDS-6 utilized a ...
, was detonated in 1953 with a yield equivalent to ( from fusion). Attempts to use a ''Sloika'' design to achieve megaton-range results proved unfeasible. After the United States tested the "
Ivy Mike Ivy Mike was the codename given to the first full-scale test of a thermonuclear device, in which part of the explosive yield comes from nuclear fusion. Ivy Mike was detonated on November 1, 1952, by the United States on the island of Elugelab in ...
" thermonuclear device in November 1952, proving that a multimegaton bomb could be created, the Soviets searched for an alternative design. The "Second Idea", as Sakharov referred to it in his memoirs, was a previous proposal by Ginzburg in November 1948 to use lithium deuteride in the bomb, which would, in the course of being bombarded by neutrons, produce
tritium Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with half-life about 12 years. The nucleus of tritium (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus o ...
and free deuterium. In late 1953 physicist
Viktor Davidenko Viktor Aleksandrovich Davidenko (russian: Виктор Александрович Давиденко; 26 February 1914 – 15 February 1983) was a Soviet military engineer and mathematical physicist, whose research significantly enhanced the deve ...
achieved the first breakthrough, that of keeping the ''primary'' and ''secondary'' parts of the bombs in separate pieces ("staging"). The next breakthrough was discovered and developed by Sakharov and Yakov Zel'dovich, that of using the
X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10  picometers to 10  nanometers, corresponding to frequencies in the range 30&nb ...
s from the fission bomb to compress the ''secondary'' before fusion ("radiation implosion"), in early 1954. Sakharov's "Third Idea", as the Teller–Ulam design was known in the USSR, was tested in the shot "
RDS-37 RDS-37 was the Soviet Union's first two-stage hydrogen bomb, first tested on 22 November 1955. The weapon had a nominal yield of approximately 3 megatons. It was scaled down to 1.6 megatons for the live test. Leading to the RDS-37 The RDS-3 ...
" in November 1955 with a yield of . The Soviets demonstrated the power of the "staging" concept in October 1961, when they detonated the massive and unwieldy ''
Tsar Bomba The Tsar Bomba () ( code name: ''Ivan'' or ''Vanya''), also known by the alphanumerical designation "AN602", was a thermonuclear aerial bomb, and the most powerful nuclear weapon ever created and tested. Overall, the Soviet physicist Andrei Sa ...
'', a hydrogen bomb that derived almost of its energy from fusion. It was the largest nuclear weapon developed and tested by any country.


United Kingdom

In 1954 work began at
Aldermaston Aldermaston is a village and civil parish in Berkshire, England. In the 2011 Census, the parish had a population of 1015. The village is in the Kennet Valley and bounds Hampshire to the south. It is approximately from Newbury, Basingstoke ...
to develop the British fusion bomb, with Sir William Penney in charge of the project. British knowledge on how to make a thermonuclear fusion bomb was rudimentary, and at the time the United States was not exchanging any nuclear knowledge because of the
Atomic Energy Act of 1946 The Atomic Energy Act of 1946 (McMahon Act) determined how the United States would control and manage the nuclear technology it had jointly developed with its World War II allies, the United Kingdom and Canada. Most significantly, the Act rule ...
. However, the British were allowed to observe the U.S. Castle tests and used sampling aircraft in the
mushroom cloud A mushroom cloud is a distinctive mushroom-shaped flammagenitus cloud of debris, smoke and usually condensed water vapor resulting from a large explosion. The effect is most commonly associated with a nuclear explosion, but any sufficiently ener ...
s, providing them with clear, direct evidence of the compression produced in the secondary stages by radiation implosion. Because of these difficulties, in 1955 British prime minister
Anthony Eden Robert Anthony Eden, 1st Earl of Avon, (12 June 1897 – 14 January 1977) was a British Conservative Party politician who served as Prime Minister of the United Kingdom from 1955 until his resignation in 1957. Achieving rapid promo ...
agreed to a secret plan, whereby if the Aldermaston scientists failed or were greatly delayed in developing the fusion bomb, it would be replaced by an extremely large fission bomb. In 1957 the
Operation Grapple Operation Grapple was a set of four series of British nuclear weapons tests of early atomic bombs and hydrogen bombs carried out in 1957 and 1958 at Malden Island and Kiritimati (Christmas Island) in the Gilbert and Ellice Islands in the P ...
tests were carried out. The first test, Green Granite, was a prototype fusion bomb, but failed to produce equivalent yields compared to the U.S. and Soviets, achieving only approximately . The second test
Orange Herald Orange Herald was a British nuclear weapon, tested on 31 May 1957. At the time it was reported as an H-bomb, although in fact it was a large boosted fission weapon and remains to date, the largest fission device ever detonated. Technical Oran ...
was the modified fission bomb and produced —making it the largest fission explosion ever. At the time almost everyone (including the pilots of the plane that dropped it) thought that this was a fusion bomb. This bomb was put into service in 1958. A second prototype fusion bomb,
Purple Granite Purple is any of a variety of colors with hue between red and blue. In the RGB color model used in computer and television screens, purples are produced by mixing red and blue light. In the RYB color model historically used by painters, pu ...
, was used in the third test, but only produced approximately . A second set of tests was scheduled, with testing recommencing in September 1957. The first test was based on a "… new simpler design. A two stage thermonuclear bomb that had a much more powerful trigger". This test Grapple X Round C was exploded on 8 November and yielded approximately . On 28 April 1958 a bomb was dropped that yielded —Britain's most powerful test. Two final air burst tests on 2 September – 11 September 1958, dropped smaller bombs that yielded around each. American observers had been invited to these kinds of tests. After Britain's successful detonation of a megaton-range device (and thus demonstrating a practical understanding of the Teller–Ulam design "secret"), the United States agreed to exchange some of its nuclear designs with the United Kingdom, leading to the 1958 US–UK Mutual Defence Agreement. Instead of continuing with its own design, the British were given access to the design of the smaller American Mk 28 warhead and were able to manufacture copies. The United Kingdom had worked closely with the Americans on the Manhattan Project. British access to nuclear weapons information was cut off by the United States at one point due to concerns about Soviet espionage. Full cooperation was not reestablished until an agreement governing the handling of secret information and other issues was signed.


China

Mao Zedong Mao Zedong pronounced ; also romanised traditionally as Mao Tse-tung. (26 December 1893 – 9 September 1976), also known as Chairman Mao, was a Chinese communist revolutionary who was the founder of the People's Republic of China (PRC) ...
decided to begin a Chinese nuclear-weapons program during the
First Taiwan Strait Crisis The First Taiwan Strait Crisis (also the Formosa Crisis, the 1954–1955 Taiwan Strait Crisis, the Offshore Islands Crisis, the Quemoy-Matsu Crisis, and the 1955 Taiwan Strait Crisis) was a brief armed conflict between the Communist People's ...
of 1954–1955. The People's Republic of China detonated its first hydrogen (thermonuclear) bomb on 17 June 1967, 32 months after detonating its first fission weapon, with a yield of 3.31 Mt. It took place in the Lop Nor Test Site, in northwest China. China had received extensive technical help from the Soviet Union to jump-start their nuclear program, but by 1960, the rift between the Soviet Union and China had become so great that the Soviet Union ceased all assistance to China. A story in ''
The New York Times ''The New York Times'' (''the Times'', ''NYT'', or the Gray Lady) is a daily newspaper based in New York City with a worldwide readership reported in 2020 to comprise a declining 840,000 paid print subscribers, and a growing 6 million paid ...
'' by
William Broad William J. Broad (born March 7, 1951) is an American science journalist, author and a Senior Writer at ''The New York Times''. Education Broad earned a master's degree from the University of Wisconsin in 1977.double agent In the field of counterintelligence, a double agent is an employee of a secret intelligence service for one country, whose primary purpose is to spy on a target organization of another country, but who is now spying on their own country's organi ...
delivered information indicating that China knew secret details of the U.S.
W88 The W88 is an American thermonuclear warhead, with an estimated yield of , and is small enough to fit on MIRVed missiles. The W88 was designed at the Los Alamos National Laboratory in the 1970s. In 1999, the director of Los Alamos who had pres ...
warhead, supposedly through espionage. (This line of investigation eventually resulted in the abortive trial of
Wen Ho Lee Wen Ho Lee or Li Wenho (; born December 21, 1939) is a Taiwanese-American scientist who worked for the University of California at the Los Alamos National Laboratory in New Mexico. He created simulations of nuclear explosions for the purposes of ...
.)


France

The French nuclear testing site was moved to the unpopulated French atolls in the Pacific Ocean. The first test conducted at these new sites was the "Canopus" test in the
Fangataufa Fangataufa (or Fangatafoa) is an uninhabited coral atoll in the eastern part of the Tuamotu Archipelago in French Polynesia. The atoll has been fully-owned by the French state since 1964. From 1966 to 1996 it was used as a nuclear test site by th ...
atoll in
French Polynesia )Territorial motto: ( en, "Great Tahiti of the Golden Haze") , anthem = , song_type = Regional anthem , song = " Ia Ora 'O Tahiti Nui" , image_map = French Polynesia on the globe (French Polynesia centered).svg , map_alt = Location of Frenc ...
on 24 August 1968, the country's first multistage thermonuclear weapon test. The bomb was detonated from a balloon at a height of . The result of this test was significant atmospheric contamination. Very little is known about France's development of the
Teller–Ulam design A thermonuclear weapon, fusion weapon or hydrogen bomb (H bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs, a more compact size, a low ...
, beyond the fact that France detonated a device in the "Canopus" test. France reportedly had great difficulty with its initial development of the Teller-Ulam design, but it later overcame these, and is believed to have nuclear weapons equal in sophistication to the other major nuclear powers. France and China did not sign or ratify the
Partial Nuclear Test Ban Treaty The Partial Test Ban Treaty (PTBT) is the abbreviated name of the 1963 Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer Space and Under Water, which prohibited all test detonations of nuclear weapons except for those conducted ...
of 1963, which banned nuclear test explosions in the atmosphere, underwater, or in
outer space Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, pred ...
. Between 1966 and 1996 France carried out more than 190 nuclear tests. France's final nuclear test took place on 27 January 1996, and then the country dismantled its Polynesian test sites. France signed the
Comprehensive Nuclear-Test-Ban Treaty The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is a multilateral treaty to ban nuclear weapons test explosions and any other nuclear explosions, for both civilian and military purposes, in all environments. It was adopted by the United Nations ...
that same year, and then ratified the Treaty within two years. France confirmed that its nuclear arsenal contains about 300 warheads, carried by
submarine-launched ballistic missile A submarine-launched ballistic missile (SLBM) is a ballistic missile capable of being launched from submarines. Modern variants usually deliver multiple independently targetable reentry vehicles (MIRVs), each of which carries a nuclear warhead ...
s (SLBMs) and
fighter-bombers A fighter-bomber is a fighter aircraft that has been modified, or used primarily, as a light bomber or attack aircraft. It differs from bomber and attack aircraft primarily in its origins, as a fighter that has been adapted into other roles, ...
in 2015. France has four Triomphant-class ballistic missile submarines. One ballistic missile submarine is deployed in the deep ocean, but a total of three must be in operational use at all times. The three older submarines are armed with 16 M45 missiles. The newest submarine, "Le Terrible", was commissioned in 2010, and it has
M51 M51 or M-51 may refer to: * M-51 (Michigan highway), a state highway in Michigan * M51 highway (Russia) * M51 (Cape Town), a Metropolitan Route in Cape Town, South Africa * M51 Skysweeper, an anti-aircraft gun * M51 MACI mine * M51 SLBM, a Fre ...
missiles capable of carrying
TN 75 The TN 75 is a French-built 150kt thermonuclear warhead used on France's M45 and M51 submarine-launched ballistic missiles, carried by the last of the ''Redoutable'' class submarines, S616 '' Inflexible'', and by the ''Triomphant'' class sub ...
thermonuclear warheads. The air fleet is four squadrons at four different bases. In total, there are 23
Mirage 2000N The Dassault Mirage 2000N is a variant of the Dassault Mirage 2000, Mirage 2000 designed for nuclear strike. It formed the core of the French air-based Strategic nuclear weapon, strategic nuclear Deterrence theory, deterrent. The Mirage 2000D ...
aircraft and 20 Rafales capable of carrying nuclear warheads. The M51.1 missiles are intended to be replaced with the new M51.2 warhead beginning in 2016, which has a greater range than the M51.1. France also has about 60 air-launched missiles tipped with
TN 80 TN 80 was deployed between 1985 and 1991 as the warhead of the ASMP air-to-surface missile carried by the Dassault Dassault Group (; also GIM Dassault or Groupe Industriel Marcel Dassault SAS) is a French group of companies established in 1929 ...
/
TN 81 The French ''airborne nuclear warheads (TN81)'' is a thermonuclear warhead carried by the Air-Sol Moyenne Portée (ASMP) medium-range air-to-surface missile, a component of the Force de frappe French nuclear deterrent. The warhead was introduced ...
warheads with a yield of about each. France's nuclear program has been carefully designed to ensure that these weapons remain usable decades into the future. Currently, France is no longer deliberately producing critical mass materials such as plutonium and enriched uranium, but it still relies on nuclear energy for electricity, with as a byproduct.


India

On 11 May 1998, India announced that it had detonated a thermonuclear bomb in its
Operation Shakti The Pokhran-II tests were a series of five nuclear bomb test explosions conducted by India at the Indian Army's Pokhran Test Range in May 1998. It was the second instance of nuclear testing conducted by India; the first test, code-named ''Sm ...
tests ("Shakti-I", specifically, in Hindi the word 'Shakti' means power). Dr.
Samar Mubarakmand Dr. Samar Mubarakmand (Urdu: ; b. 17 September 1942; ), is a Pakistani nuclear physicist known for his research in gamma spectroscopy and experimental development of the linear accelerator. He came to public attention as the director of the t ...
, a Pakistani nuclear physicist, asserted that if Shakti-I had been a thermonuclear test, the device had failed to fire. However, Dr.
Harold M. Agnew Harold Melvin Agnew (March 28, 1921 – September 29, 2013) was an American physicist, best known for having flown as a scientific observer on the Hiroshima bombing mission and, later, as the third director of the Los Alamos National Laboratory ...
, former director of the
Los Alamos National Laboratory Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development laboratories of the United States Department of Energy (DOE), located a short distance northwest of Santa Fe, New Mexico, ...
, said that India's assertion of having detonated a staged thermonuclear bomb was believable. India says that their thermonuclear device was tested at a controlled yield of because of the close proximity of the Khetolai village at about , to ensure that the houses in that village do not suffer significant damage. Another cited reason was that radioactivity released from yields significantly more than 45
Kilotons TNT equivalent is a convention for expressing energy, typically used to describe the energy released in an explosion. The is a unit of energy defined by that convention to be , which is the approximate energy released in the detonation of a m ...
might not have been contained fully. After the
Pokhran-II The Pokhran-II tests were a series of five nuclear bomb test explosions conducted by India at the Indian Army's Pokhran Test Range in May 1998. It was the second instance of nuclear testing conducted by India; the first test, code-named ''Smil ...
tests, Dr. Rajagopal Chidambaram, former chairman of the
Atomic Energy Commission of India The Atomic Energy Commission of India is the governing body of the Department of Atomic Energy (DAE), Government of India. The DAE is under the direct charge of the Prime Minister. The Indian Atomic Energy Commission was set up on 3 August 1948 ...
said that India has the capability to build thermonuclear bombs of any yield at will. The yield of India's hydrogen bomb test remains highly debatable among the Indian science community and the international scholars. The question of politicisation and disputes between Indian scientists further complicated the matter. In an interview in August 2009, the director for the 1998 test site preparations, Dr. K. Santhanam claimed that the yield of the thermonuclear explosion was lower than expected and that India should therefore not rush into signing the
CTBT The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is a multilateral treaty to ban nuclear weapons test explosions and any other nuclear explosions, for both civilian and military purposes, in all environments. It was adopted by the United Nation ...
. Other Indian scientists involved in the test have disputed Dr. K. Santhanam's claim, arguing that Santhanam's claims are unscientific. British seismologist Roger Clarke argued that the magnitudes suggested a combined yield of up to , consistent with the Indian announced total yield of . U.S. seismologist Jack Evernden has argued that for correct estimation of yields, one should ‘account properly for geological and seismological differences between test sites’. India officially maintains that it can build thermonuclear weapons of various yields up to around on the basis of the Shakti-1 thermonuclear test.


Israel

Israel is alleged to possess thermonuclear weapons of the Teller–Ulam design, but it is not known to have tested any nuclear devices, although it is widely speculated that the
Vela incident The Vela incident was an unidentified double flash of light detected by an American Vela Hotel satellite on 22 September 1979 near the South African territory of Prince Edward Islands in the Indian Ocean, roughly midway between Africa and Antar ...
of 1979 may have been a joint Israeli–South African nuclear test. It is well established that
Edward Teller Edward Teller ( hu, Teller Ede; January 15, 1908 – September 9, 2003) was a Hungarian-American theoretical physicist who is known colloquially as "the father of the hydrogen bomb" (see the Teller–Ulam design), although he did not care fo ...
advised and guided the Israeli establishment on general nuclear matters for some twenty years. Between 1964 and 1967, Teller made six visits to Israel where he lectured at the
Tel Aviv University Tel Aviv University (TAU) ( he, אוּנִיבֶרְסִיטַת תֵּל אָבִיב, ''Universitat Tel Aviv'') is a public research university in Tel Aviv, Israel. With over 30,000 students, it is the largest university in the country. Locate ...
on general topics in theoretical physics. It took him a year to convince the
CIA The Central Intelligence Agency (CIA ), known informally as the Agency and historically as the Company, is a civilian intelligence agency, foreign intelligence service of the federal government of the United States, officially tasked with gat ...
about Israel's capability and finally in 1976, Carl Duckett of the CIA testified to the
U.S. Congress The United States Congress is the legislature of the federal government of the United States. It is Bicameralism, bicameral, composed of a lower body, the United States House of Representatives, House of Representatives, and an upper body, ...
, after receiving credible information from an "American scientist" (Teller), on Israel's nuclear capability. During the 1990s, Teller eventually confirmed speculations in the media that it was during his visits in the 1960s that he concluded that Israel was in possession of nuclear weapons. After he conveyed the matter to the higher level of the U.S. government, Teller reportedly said: "They sraelhave it, and they were clever enough to trust their research and not to test, they know that to test would get them into trouble."


Pakistan

According to the
scientific data In the pursuit of knowledge, data (; ) is a collection of discrete Value_(semiotics), values that convey information, describing quantity, qualitative property, quality, fact, statistics, other basic units of meaning, or simply sequences of sy ...
received and published by PAEC, the Corps of Engineers, and
Kahuta Research Laboratories The Dr. A. Q. Khan Research Laboratories, ( ur, ) or KRL for short, is a federally funded, multi-program national research institute and national laboratory site primarily dedicated to uranium enrichment, supercomputing and fluid mechanics. It ...
(KRL), in May 1998, Pakistan carried out six
underground Underground most commonly refers to: * Subterranea (geography), the regions beneath the surface of the Earth Underground may also refer to: Places * The Underground (Boston), a music club in the Allston neighborhood of Boston * The Underground ...
nuclear tests Nuclear weapons tests are experiments carried out to determine nuclear weapons' effectiveness, yield, and explosive capability. Testing nuclear weapons offers practical information about how the weapons function, how detonations are affected by ...
in
Chagai Hills The Chagai Hills is a range of granite hills in the Chagai District in Pakistan's Balochistan province. Location The Chagai Hills lie between 28' 46" to 29' 34" N and 63' 18" to 64' 50" in a desert area in the northernmost part of Chagai Dist ...
and
Kharan Desert The Kharan Desert ( ur, صحرائے خاران) is a sandy and mountainous desert situated in Balochistan province in south-western Pakistan.The desert covers an area of about 36,000 square kilometers, making it one of the largest deserts in ...
in
Balochistan Province Balochistan (; bal, بلۏچستان; ) is one of the four provinces of Pakistan. Located in the southwestern region of the country, Balochistan is the largest province of Pakistan by land area but is the least populated one. It shares land ...
(see the code-names of the tests, ''
Chagai-I Chagai-I is the code name of five simultaneous underground nuclear tests conducted by Pakistan at 15:15 hrs PKT on 28 May 1998. The tests were performed at Ras Koh Hills in the Chagai District of Balochistan Province. Chagai-I was Pakistan' ...
'' and ''
Chagai-II Chagai-II is the codename assigned to the second atomic test conducted by Pakistan, carried out on 30 May 1998 in the Kharan Desert in Balochistan Province of Pakistan. ''Chagai-II'' took place two days after Pakistan's first successful test, ...
''). None of these boosted fission devices was the thermonuclear weapon design, according to KRL and PAEC.


North Korea

North Korea claimed to have tested its miniaturised thermonuclear bomb on 6 January 2016. North Korea's first three nuclear tests (2006, 2009 and 2013) were relatively low yield and do not appear to have been of a thermonuclear weapon design. In 2013, the South Korean Defense Ministry speculated that North Korea may be trying to develop a "hydrogen bomb" and such a device may be North Korea's next weapons test. In January 2016, North Korea claimed to have successfully tested a hydrogen bomb, although only a magnitude 5.1 seismic event was detected at the time of the test, a similar magnitude to the 2013 test of a atomic bomb. These seismic recordings cast doubt upon North Korea's claim that a hydrogen bomb was tested and suggest it was a non-fusion nuclear test. On 3 September 2017, the country's state media reported that a hydrogen bomb test was conducted which resulted in "perfect success". According to the U.S. Geological Survey (USGS), the blast resulted in an earthquake with a magnitude of 6.3, 10 times more powerful than previous nuclear tests conducted by North Korea.
U.S. Intelligence The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
released an early assessment that the yield estimate was , with an uncertainty range of . On 12 September,
NORSAR NORSAR or Norwegian Seismic Array was established in 1968 as part of the Norwegian- US agreement for the detection of earthquakes and nuclear explosions. Description Located at Kjeller, north of Oslo, NORSAR runs and maintains seismic arrays i ...
revised its estimate of the earthquake magnitude upward to 6.1, matching that of the
CTBTO The Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization, or CTBTO Preparatory Commission, is an international organization based in Vienna, Austria, that is tasked with building up the verification regime of the Co ...
, but less powerful than the
USGS The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, a ...
estimate of 6.3. Its yield estimate was revised to , while noting the estimate had some uncertainty and an undisclosed margin of error. On 13 September, an analysis of before and after
synthetic-aperture radar Synthetic-aperture radar (SAR) is a form of radar that is used to create two-dimensional images or three-dimensional reconstructions of objects, such as landscapes. SAR uses the motion of the radar antenna over a target region to provide fine ...
satellite imagery of the test site was published suggesting the test occurred under of rock and the yield "could have been in excess of 300 kilotons".


Public knowledge

The Teller–Ulam design was for many years considered one of the top nuclear secrets, and even today it is not discussed in any detail by official publications with origins "behind the fence" of
classification Classification is a process related to categorization, the process in which ideas and objects are recognized, differentiated and understood. Classification is the grouping of related facts into classes. It may also refer to: Business, organizat ...
.
United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and manages the research and development of nuclear power and nuclear weapons in the United Stat ...
(DOE) policy has been, and continues to be, that they do not acknowledge when "leaks" occur, because doing so would acknowledge the accuracy of the supposed leaked information. Aside from images of the warhead casing, most information in the public domain about this design is relegated to a few terse statements by the DOE and the work of a few individual investigators.


DOE statements

In 1972 the United States government declassified a document stating " thermonuclear (TN) weapons, a fission 'primary' is used to trigger a TN reaction in thermonuclear fuel referred to as a 'secondary'", and in 1979 added, " thermonuclear weapons, radiation from a fission explosive can be contained and used to transfer energy to compress and ignite a physically separate component containing thermonuclear fuel." To this latter sentence the US government specified that "''Any elaboration of this statement will be classified''."emphasis in original The only information that may pertain to the ''spark plug'' was declassified in 1991: "Fact that fissile or fissionable materials are present in some secondaries, material unidentified, location unspecified, use unspecified, and weapons undesignated." In 1998 the DOE declassified the statement that "The fact that materials may be present in channels and the term 'channel filler,' with no elaboration", which may refer to the polystyrene foam (or an analogous substance). Whether these statements vindicate some or all of the models presented above is up for interpretation, and official U.S. government releases about the technical details of nuclear weapons have been purposely equivocating in the past (see, e.g.,
Smyth Report The Smyth Report (officially ''Atomic Energy for Military Purposes'') is the common name of an administrative history written by American physicist Henry DeWolf Smyth about the Manhattan Project, the Allied effort to develop atomic bombs du ...
). Other information, such as the types of fuel used in some of the early weapons, has been declassified, though precise technical information has not been.


''The Progressive'' case

Most of the current ideas on the workings of the Teller–Ulam design came into public awareness after the
Department of Energy A Ministry of Energy or Department of Energy is a government department in some countries that typically oversees the production of fuel and electricity; in the United States, however, it manages nuclear weapons development and conducts energy-rel ...
(DOE) attempted to censor a magazine article by U.S. antiweapons activist
Howard Morland Howard Morland (born September 14, 1942) is an American journalist and activist against nuclear weapons who, in 1979, became famous for apparently discovering the "secret" of the hydrogen bomb (the Teller–Ulam design) and publishing it after a ...
in 1979 on the "secret of the hydrogen bomb". In 1978, Morland had decided that discovering and exposing this "last remaining secret" would focus attention onto the
arms race An arms race occurs when two or more groups compete in military superiority. It consists of a competition between two or more states to have superior armed forces; a competition concerning production of weapons, the growth of a military, and t ...
and allow citizens to feel empowered to question official statements on the importance of nuclear weapons and nuclear secrecy. Most of Morland's ideas about how the weapon worked were compiled from highly accessible sources—the drawings that most inspired his approach came from none other than the ''
Encyclopedia Americana ''Encyclopedia Americana'' is a general encyclopedia written in American English. It was the first major multivolume encyclopedia that was published in the United States. With ''Collier's Encyclopedia'' and ''Encyclopædia Britannica, Encyclo ...
''. Morland also interviewed (often informally) many former Los Alamos scientists (including Teller and Ulam, though neither gave him any useful information), and used a variety of interpersonal strategies to encourage informative responses from them (i.e., asking questions such as "Do they still use spark plugs?" even if he was not aware what the latter term specifically referred to). Morland eventually concluded that the "secret" was that the ''primary'' and ''secondary'' were kept separate and that
radiation pressure Radiation pressure is the mechanical pressure exerted upon any surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of any wavelength that is a ...
from the ''primary'' compressed the ''secondary'' before igniting it. When an early draft of the article, to be published in ''
The Progressive ''The Progressive'' is a left-leaning American magazine and website covering politics and culture. Founded in 1909 by U.S. senator Robert M. La Follette Sr. and co-edited with his wife Belle Case La Follette, it was originally called ''La Follett ...
'' magazine, was sent to the DOE after falling into the hands of a professor who was opposed to Morland's goal, the DOE requested that the article not be published, and pressed for a temporary injunction. The DOE argued that Morland's information was (1) likely derived from classified sources, (2) if not derived from classified sources, itself counted as "secret" information under the " born secret" clause of the 1954 Atomic Energy Act, and (3) was dangerous and would encourage
nuclear proliferation Nuclear proliferation is the spread of nuclear weapons, fissionable material, and weapons-applicable nuclear technology and information to nations not recognized as " Nuclear Weapon States" by the Treaty on the Non-Proliferation of Nuclear Wea ...
. Morland and his lawyers disagreed on all points, but the injunction was granted, as the judge in the case felt that it was safer to grant the injunction and allow Morland, et al., to appeal, which they did in '' United States v. The Progressive'' (1979). Through a variety of more complicated circumstances, the DOE case began to wane as it became clear that some of the data they were attempting to claim as "secret" had been published in a students' encyclopedia a few years earlier. After another H-bomb speculator,
Chuck Hansen Chuck Hansen (May 13, 1947 - March 26, 2003) was the compiler, over a period of 30 years, of the world's largest private collection of unclassified documents on how America developed atomic and thermonuclear weapons. Research Hansen's documents ...
, had his own ideas about the "secret" (quite different from Morland's) published in a Wisconsin newspaper, the DOE claimed that ''The Progressive'' case was moot, dropped its suit, and allowed the magazine to publish its article, which it did in November 1979. Morland had by then, however, changed his opinion of how the bomb worked, suggesting that a foam medium (the polystyrene) rather than radiation pressure was used to compress the ''secondary'', and that in the ''secondary'' there was a ''spark plug'' of fissile material as well. He published these changes, based in part on the proceedings of the appeals trial, as a short erratum in ''The Progressive'' a month later. In 1981, Morland published a book about his experience, describing in detail the train of thought that led him to his conclusions about the "secret". Morland's work is interpreted as being at least partially correct because the DOE had sought to censor it, one of the few times they violated their usual approach of not acknowledging "secret" material that had been released; however, to what degree it lacks information, or has incorrect information, is not known with any confidence. The difficulty that a number of nations had in developing the Teller–Ulam design (even when they apparently understood the design, such as with the United Kingdom), makes it somewhat unlikely that this simple information alone is what provides the ability to manufacture thermonuclear weapons. Nevertheless, the ideas put forward by Morland in 1979 have been the basis for all the current speculation on the Teller–Ulam design.


Nuclear reduction

In January 1986, Soviet leader
Mikhail Gorbachev Mikhail Sergeyevich Gorbachev (2 March 1931 – 30 August 2022) was a Soviet politician who served as the 8th and final leader of the Soviet Union from 1985 to dissolution of the Soviet Union, the country's dissolution in 1991. He served a ...
publicly proposed a three-stage program for abolishing the world's nuclear weapons by the end of the 20th century. Two years before his death in 1989, Andrei Sakharov's comments at a scientists’ forum helped begin the process for the elimination of thousands of nuclear ballistic missiles from the US and Soviet arsenals. Sakharov (1921–89) was recruited into the Soviet Union's nuclear weapons program in 1948, a year after he completed his doctorate. In 1949 the US detected the first Soviet test of a fission bomb, and the two countries embarked on a desperate race to design a thermonuclear hydrogen bomb that was a thousand times more powerful. Like his US counterparts, Sakharov justified his H-bomb work by pointing to the danger of the other country's achieving a monopoly. But also like some of the US scientists who had worked on the Manhattan Project, he felt a responsibility to inform his nation's leadership and then the world about the dangers from nuclear weapons.A. Sakharov, Memoirs, R. Lourie, trans., Knopf (1990), and Moscow and Beyond, 1986–1989, A. Bouis, trans., Knopf (1991); for Elena Bonner's account of their time in Gorky, see E. Bonner, Alone Together, A. Cook, trans., Knopf (1986). Sakharov's first attempt to influence policy was brought about by his concern about possible genetic damage from long-lived radioactive carbon-14 created in the atmosphere from nitrogen-14 by the enormous fluxes of neutrons released in H-bomb tests. In 1968, a friend suggested that Sakharov write an essay about the role of the intelligentsia in world affairs. Self-publishing was the method at the time for spreading unapproved manuscripts in the Soviet Union. Many readers would create multiple copies by typing with multiple sheets of paper interleaved with carbon paper. One copy of Sakharov's essay, "Reflections on Progress, Peaceful Coexistence, and Intellectual Freedom", was smuggled out of the Soviet Union and published by the New York Times. More than 18 million reprints were produced during 1968–69. After the essay was published, Sakharov was barred from returning to work in the nuclear weapons program and took a research position in Moscow. In 1980, after an interview with the New York Times in which he denounced the Soviet invasion of Afghanistan, the government put him beyond the reach of Western media by exiling him and his wife to Gorky. In March 1985, Gorbachev became general secretary of the Soviet Communist Party. More than a year and a half later, he persuaded the Politburo, the party's executive committee, to allow Sakharov and Bonner to return to Moscow. Sakharov was elected as an opposition member to the Soviet Congress of People's Deputies in 1989. Later that year he had a
cardiac arrhythmia Arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adults ...
and died in his apartment. He left behind a draft of a new Soviet constitution that emphasized democracy and human rights.


Notable accidents

On 5 February 1958, during a training mission flown by a
B-47 The Boeing B-47 Stratojet (Boeing company designation Model 450) is a retired American long- range, six-engined, turbojet-powered strategic bomber designed to fly at high subsonic speed and at high altitude to avoid enemy interceptor aircr ...
, a
Mark 15 nuclear bomb The Mark 15 nuclear bomb, or Mk-15, was a 1950s American thermonuclear bomb, the first relatively lightweight () thermonuclear bomb created by the United States. A total of 1,200 Mark 15 bombs were produced from 1955 to 1957. There were thre ...
, also known as the
Tybee Bomb The Tybee Island mid-air collision was an incident on February 5, 1958, in which the United States Air Force lost a Mark 15 nuclear bomb in the waters off Tybee Island near Savannah, Georgia, United States. During a practice exercise, an F-86 ...
, was lost off the coast of
Tybee Island Tybee Island is a city and a barrier island located in Chatham County, Georgia, 18 miles (29 km) east of Savannah, United States. Though the name "Tybee Island" is used for both the island and the city, geographically they are not identica ...
near
Savannah, Georgia Savannah ( ) is the oldest city in the U.S. state of Georgia (U.S. state), Georgia and is the county seat of Chatham County, Georgia, Chatham County. Established in 1733 on the Savannah River, the city of Savannah became the Kingdom of Great Br ...
. The bomb was thought by the Department of Energy to lie buried under several feet of silt at the bottom of
Wassaw Sound Wassaw Sound is a bay of the Atlantic Ocean on the coast of Georgia, United States near Savannah at the mouth of the Wilmington River. American Civil War naval battle It was the location of an American Civil War naval battle between the CSS Atlan ...
. On 17 January 1966, a fatal collision occurred between a B-52G and a KC-135 Stratotanker over Palomares, Spain. The conventional explosives in two of the Mk28-type
hydrogen bombs A thermonuclear weapon, fusion weapon or hydrogen bomb (H bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs, a more compact size, a lowe ...
detonated upon impact with the ground, dispersing plutonium over nearby farms. A third bomb landed intact near Palomares while the fourth fell 12 miles (19 km) off the coast into the Mediterranean sea. On 21 January 1968, a B-52G, with four B28FI thermonuclear bombs aboard as part of
Operation Chrome Dome Operation Chrome Dome was a United States Air Force Cold War-era mission from 1960 to 1968 in which B-52 strategic bomber aircraft armed with thermonuclear weapons remained on continuous airborne alert and flew routes to points on the Soviet ...
, crashed on the ice of the
North Star Bay North Star Bay ( da, North Star Bugt), also known as Thule Harbor and Wolstenholme Bay, is a bay off the mouth of Wolstenholme Fjord, Greenland. The bay is named after HMS ''North Star''. Thule Air Base is located at the edge of the bay. There ...
while attempting an emergency landing at
Thule Air Base Thule Air Base (pronounced or , kl, Qaanaaq Mitarfik, da, Thule Lufthavn), or Thule Air Base/Pituffik Airport , is the United States Space Force's northernmost base, and the northernmost installation of the U.S. Armed Forces, located north o ...
in Greenland. The resulting fire caused extensive radioactive contamination. Personnel involved in the cleanup failed to recover all the debris from three of the bombs, and one bomb was not recovered.


Variations


Ivy Mike

In his 1995 book ''Dark Sun: The Making of the Hydrogen Bomb'', author
Richard Rhodes Richard Lee Rhodes (born July 4, 1937) is an American historian, journalist, and author of both fiction and non-fiction, including the Pulitzer Prize-winning ''The Making of the Atomic Bomb'' (1986), and most recently, ''Energy: A Human Histor ...
describes in detail the internal components of the "
Ivy Mike Ivy Mike was the codename given to the first full-scale test of a thermonuclear device, in which part of the explosive yield comes from nuclear fusion. Ivy Mike was detonated on November 1, 1952, by the United States on the island of Elugelab in ...
" ''Sausage'' device, based on information obtained from extensive interviews with the scientists and engineers who assembled it. According to Rhodes, the actual mechanism for the compression of the secondary was a combination of the radiation pressure, foam plasma pressure, and tamper-pusher ablation theories described above; the radiation from the primary heated the polyethylene foam lining of the casing to a plasma, which then re-radiated radiation into the secondary's pusher, causing its surface to ablate and driving it inwards, compressing the secondary, igniting the sparkplug, and causing the fusion reaction. The general applicability of this principle is unclear.


W88

In 1999 a reporter for the ''
San Jose Mercury News ''The Mercury News'' (formerly ''San Jose Mercury News'', often locally known as ''The Merc'') is a morning daily newspaper published in San Jose, California, in the San Francisco Bay Area. It is published by the Bay Area News Group, a subsidiar ...
'' reported that the U.S.
W88 The W88 is an American thermonuclear warhead, with an estimated yield of , and is small enough to fit on MIRVed missiles. The W88 was designed at the Los Alamos National Laboratory in the 1970s. In 1999, the director of Los Alamos who had pres ...
nuclear warhead, a small MIRVed warhead used on the
Trident II A trident is a three- pronged spear. It is used for spear fishing and historically as a polearm. The trident is the weapon of Poseidon, or Neptune, the God of the Sea in classical mythology. The trident may occasionally be held by other marine ...
SLBM A submarine-launched ballistic missile (SLBM) is a ballistic missile capable of being launched from Ballistic missile submarine, submarines. Modern variants usually deliver multiple independently targetable reentry vehicles (MIRVs), each of whic ...
, had a
prolate A spheroid, also known as an ellipsoid of revolution or rotational ellipsoid, is a quadric surface obtained by rotating an ellipse about one of its principal axes; in other words, an ellipsoid with two equal semi-diameters. A spheroid has circ ...
(
egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
or
watermelon Watermelon (''Citrullus lanatus'') is a flowering plant species of the Cucurbitaceae family and the name of its edible fruit. A scrambling and trailing vine-like plant, it is a highly cultivated fruit worldwide, with more than 1,000 varieti ...
shaped) ''primary'' (code-named ''Komodo'') and a spherical ''secondary'' (code-named ''Cursa'') inside a specially shaped radiation case (known as the "peanut" for its shape). The value of an egg-shaped primary lies apparently in the fact that a MIRV warhead is limited by the diameter of the primary—if an egg-shaped primary can be made to work properly, then the MIRV warhead can be made considerably smaller yet still deliver a high-yield explosion—a W88 warhead manages to yield up to with a
physics package Nuclear weapon designs are physical, chemical, and engineering arrangements that cause the physics package of a nuclear weapon to detonate. There are three existing basic design types: * pure fission weapons, the simplest and least technically ...
long, with a maximum diameter of , and by different estimates weighing in a range from . The smaller warhead allows more of them to fit onto a single missile and improves basic flight properties such as speed and range.


See also

*
COLEX process (isotopic separation) The COLEX process (or COLEX separation) is a chemical method of isotopic separation of lithium-6 and lithium-7, based on the use of mercury. COLEX stands for column exchange. Since the beginning of the atomic era, a variety of lithium enrichments m ...
*
History of the Teller–Ulam design This article chronicles the history and origins of the Teller–Ulam design, the technical concept behind modern thermonuclear weapons, also known as Nuclear weapon design#Hydrogen bombs, hydrogen bombs. The design, the details of which are mili ...
* NUKEMAP *
Pure fusion weapon A pure fusion weapon is a hypothetical hydrogen bomb design that does not need a fission "primary" explosive to ignite the fusion of deuterium and tritium, two heavy isotopes of hydrogen used in fission-fusion thermonuclear weapons. Such a weapon ...


Notes


References


Further reading


Basic principles

* * * 2,600 pages. *


History

* * * * * * * * * *


Analyzing fallout

* *


External links


Principles


"Hydrogen bomb / Fusion weapons"
at GlobalSecurity.org (see also links on right)

from Carey Sublette's NuclearWeaponArchive.org.

from Carey Sublette's Nuclear Weapons FAQ.

from Carey Sublette's Nuclear Weapons FAQ.

from Carey Sublette's Nuclear Weapons FAQ.
Annotated bibliography for nuclear weapons design from the Alsos Digital Library for Nuclear Issues


History



(with U.S. and USSR bomb designers as well as historians).

(includes many slides).
''The Progressive'' November 1979 issue
– "The H-Bomb Secret: How we got it, why we're telling" (entire issue online).
Annotated bibliography on the hydrogen bomb from the Alsos Digital Library

University of Southampton, Mountbatten Centre for International Studies, Nuclear History Working Paper No5.


– documentary film on the history of nuclear weapon testing.
YouTube Playlist of declassified nuclear explosion tests obtained by converting film scans to digital at Lawrence Livermore Laboratory
{{Authority control Nuclear weapon design Nuclear secrecy ur:ہائیڈروجن بم