Editing Nuclear weapon (section)

== Types ==
{{Main|Nuclear weapon design}}
[[File:Trinity shot color.jpg|thumb|left|The [[Trinity (nuclear test)|Trinity test]] of the [[Manhattan Project]] was the first detonation of a nuclear weapon, which led [[J. Robert Oppenheimer]] to recall verses from the [[Hindu]] scripture ''[[Bhagavad Gita]]'': "If the radiance of a thousand suns were to burst at once into the sky, that would be like the splendor of the mighty one&nbsp;"... "I am become Death, the destroyer of worlds".{{sfn|Jungk|1958|p=201}}]]

[[File:Oppenheimer (cropped).jpg|thumb|right|[[J. Robert Oppenheimer]], principal leader of the [[Manhattan Project]], often referred to as the "father of the atomic bomb".]]

There are two basic types of nuclear weapons: those that derive the majority of their energy from [[nuclear fission]] reactions alone, and those that use fission reactions to begin [[nuclear fusion]] reactions that produce a large amount of the total energy output.<ref name="Inc.1954">{{cite journal|author=Educational Foundation for Nuclear Science, Inc.|title=Bulletin of the Atomic Scientists|journal=Bulletin of the Atomic Scientists: Science and Public Affairs |url=https://books.google.com/books?id=rw0AAAAAMBAJ&pg=PA61|date=February 1954|publisher=Educational Foundation for Nuclear Science, Inc.|pages=61–|issn=0096-3402 |url-status=live |archive-url=https://web.archive.org/web/20170331041028/https://books.google.com/books?id=rw0AAAAAMBAJ&pg=PA61|archive-date=March 31, 2017}}</ref>

=== Fission weapons ===
[[File:Fission bomb assembly methods.svg|upright=1.4|thumb|The two basic [[Nuclear fission|fission]] weapon designs]]
All existing nuclear weapons derive some of their explosive energy from nuclear fission reactions. Weapons whose explosive output is exclusively from fission reactions are commonly referred to as '''atomic bombs''' or '''atom bombs''' (abbreviated as '''A-bombs'''). This has long been noted as something of a [[misnomer]], as their energy comes from the [[Atomic nucleus|nucleus]] of the atom, just as it does with fusion weapons.

In fission weapons, a mass of [[fissile material]] ([[enriched uranium]] or [[plutonium]]) is forced into [[critical mass|supercriticality]]—allowing an [[exponential growth]] of [[nuclear chain reaction]]s—either by shooting one piece of sub-critical material into another (the "gun" method) or by compression of a sub-critical sphere or cylinder of fissile material using chemically fueled [[explosive lens]]es. The latter approach, the "implosion" method, is more sophisticated and more efficient (smaller, less massive, and requiring less of the expensive fissile fuel) than the former.

A major challenge in all nuclear weapon designs is to ensure that a significant fraction of the fuel is consumed before the weapon destroys itself. The amount of energy released by fission bombs can range from the equivalent of just under a ton to upwards of 500,000 tons (500 [[kiloton]]s) of [[trinitrotoluene|TNT]] ({{convert|1|to|5E5|tTNT|sigfig=2|disp=out}}).<ref name="Hansen">Hansen, Chuck. ''U.S. Nuclear Weapons: The Secret History.'' San Antonio, TX: Aerofax, 1988; and the more-updated Hansen, Chuck, "[http://www.uscoldwar.com/ Swords of Armageddon: U.S. Nuclear Weapons Development since 1945] {{webarchive |url=https://web.archive.org/web/20161230020259/http://www.uscoldwar.com/ |date=December 30, 2016}}" (CD-ROM & download available). PDF. 2,600 pages, Sunnyvale, California, Chuklea Publications, 1995, 2007. {{ISBN|978-0-9791915-0-3}} (2nd Ed.)</ref>

All fission reactions generate [[Nuclear fission product|fission products]], the remains of the split atomic nuclei. Many fission products are either highly [[Radioactive decay|radioactive]] (but short-lived) or moderately radioactive (but long-lived), and as such, they are a serious form of [[radioactive contamination]]. Fission products are the principal radioactive component of [[nuclear fallout]]. Another source of radioactivity is the burst of free neutrons produced by the weapon. When they collide with other nuclei in the surrounding material, the neutrons transmute those nuclei into other isotopes, altering their stability and making them radioactive.

The most commonly used fissile materials for nuclear weapons applications have been [[uranium-235]] and [[plutonium-239]]. Less commonly used has been [[uranium-233]]. [[Neptunium-237]] and some isotopes of [[americium]] may be usable for nuclear explosives as well, but it is not clear that this has ever been implemented, and their plausible use in nuclear weapons is a matter of dispute.<ref>{{cite web |last1=Albright |first1=David |author-link=David Albright |last2=Kramer |first2=Kimberly |date=August 22, 2005 |title=Neptunium 237 and Americium: World Inventories and Proliferation Concerns |url=http://isis-online.org/uploads/isis-reports/documents/np_237_and_americium.pdf |publisher=[[Institute for Science and International Security]] |access-date=October 13, 2011 |url-status=live |archive-url=https://web.archive.org/web/20120103234833/http://isis-online.org/uploads/isis-reports/documents/np_237_and_americium.pdf |archive-date=January 3, 2012}}</ref>

=== Fusion weapons ===
{{Main|Thermonuclear weapon}}
[[File:Teller-Ulam device 3D.svg|thumb|The basics of the [[Teller–Ulam design]] for a hydrogen bomb: a fission bomb uses radiation to compress and heat a separate section of fusion fuel.]]

The other basic type of nuclear weapon produces a large proportion of its energy in nuclear fusion reactions. Such fusion weapons are generally referred to as '''[[thermonuclear weapon]]s''' or more colloquially as '''hydrogen bombs''' (abbreviated as '''H-bombs'''), as they rely on fusion reactions between isotopes of [[hydrogen]] ([[deuterium]] and [[tritium]]). All such weapons derive a significant portion of their energy from fission reactions used to "trigger" fusion reactions, and fusion reactions can themselves trigger additional fission reactions.<ref>Carey Sublette, [http://nuclearweaponarchive.org/Nwfaq/Nfaq4-5.html#Nfaq4.5.2 Nuclear Weapons Frequently Asked Questions: 4.5.2 "Dirty" and "Clean" Weapons] {{webarchive |url=https://web.archive.org/web/20160303170957/http://nuclearweaponarchive.org/Nwfaq/Nfaq4-5.html |date=March 3, 2016}}, accessed May 10, 2011.</ref>

Only six countries—the [[United States]], [[Russia]], the [[United Kingdom]], [[China]], [[France]], and [[India]]—have conducted thermonuclear weapon tests. Whether India has detonated a "true" multi-staged [[thermonuclear weapon]] is controversial.<ref>On India's alleged hydrogen bomb test, see Carey Sublette, [http://nuclearweaponarchive.org/India/IndiaRealYields.html What Are the Real Yields of India's Test?] {{webarchive |url=https://web.archive.org/web/20110927013551/http://nuclearweaponarchive.org/India/IndiaRealYields.html |date=September 27, 2011}}.</ref> [[North Korea]] claims to have tested a fusion weapon {{as of|2016|January|lc=y}}, though this claim is disputed.<ref>{{cite web|last1=McKirdy|first1=Euan|title=North Korea announces it conducted nuclear test |url=http://www.cnn.com/2016/01/05/asia/north-korea-seismic-event/|website=CNN|date=January 6, 2016|access-date=January 7, 2016 |url-status=live |archive-url=https://web.archive.org/web/20160107193043/http://www.cnn.com/2016/01/05/asia/north-korea-seismic-event/|archive-date=January 7, 2016}}</ref> Thermonuclear weapons are considered much more difficult to successfully design and execute than primitive fission weapons. Almost all of the nuclear weapons deployed today use the thermonuclear design because it results in an explosion hundreds of times stronger than that of a fission bomb of similar weight.<ref>{{Cite web |url=https://www.armscontrol.org/factsheets/Nuclear-Testing-and-Comprehensive-Test-Ban-Treaty-CTBT-Timeline|title=Nuclear Testing and Comprehensive Test Ban Treaty (CTBT) Timeline |website=Arms control association |url-status=dead |archive-url=https://web.archive.org/web/20200421174531/https://www.armscontrol.org/factsheets/Nuclear-Testing-and-Comprehensive-Test-Ban-Treaty-CTBT-Timeline|archive-date=April 21, 2020}}</ref>

Thermonuclear bombs work by using the energy of a fission bomb to compress and heat fusion fuel. In the [[Teller-Ulam design]], which accounts for all multi-megaton yield hydrogen bombs, this is accomplished by placing a fission bomb and fusion fuel ([[tritium]], [[deuterium]], or [[lithium deuteride]]) in proximity within a special, radiation-reflecting container. When the fission bomb is detonated, [[gamma ray]]s and [[X-ray]]s emitted first compress the fusion fuel, then heat it to thermonuclear temperatures. The ensuing fusion reaction creates enormous numbers of high-speed [[neutron]]s, which can then induce fission in materials not normally prone to it, such as [[depleted uranium]]. Each of these components is known as a "stage", with the fission bomb as the "primary" and the fusion capsule as the "secondary". In large, megaton-range hydrogen bombs, about half of the yield comes from the final fissioning of depleted uranium.<ref name="Hansen" />

Virtually all thermonuclear weapons deployed today use the "two-stage" design described to the right, but it is possible to add additional fusion stages—each stage igniting a larger amount of fusion fuel in the next stage. This technique can be used to construct thermonuclear weapons of arbitrarily large yield. This is in contrast to fission bombs, which are limited in their explosive power due to [[Nuclear criticality safety|criticality]] danger (premature nuclear chain reaction caused by too-large amounts of pre-assembled fissile fuel). The largest nuclear weapon ever detonated, the [[Tsar Bomba]] of the USSR, which released an energy equivalent of over {{convert|50|MtonTNT}}, was a three-stage weapon. Most thermonuclear weapons are considerably smaller than this, due to practical constraints from missile warhead space and weight requirements.<ref name="Sublette">{{cite web |url=http://nuclearweaponarchive.org/ |last=Sublette |first=Carey |title=The Nuclear Weapon Archive |access-date=March 7, 2007 |url-status=live |archive-url=https://web.archive.org/web/20070301105632/http://nuclearweaponarchive.org/ |archive-date=March 1, 2007}}</ref> In the early 1950s the [[Lawrence Livermore National Laboratory|Livermore Laboratory]] in the United States had plans for the testing of two massive bombs, Gnomon and [[Sundial (weapon)|Sundial]], 1 gigaton of TNT and 10 gigatons of TNT respectively.<ref>{{Cite web |last=Simha |first=Rakesh Krishnan |date=2016-01-05 |title=Nuclear overkill: The quest for the 10 gigaton bomb |url=https://www.rbth.com/opinion/2016/01/05/nuclear-overkill-the-quest-for-the-10-gigaton-bomb_556351 |access-date=2023-10-08 |website=Russia Beyond |language=en-US |archive-date=November 29, 2023 |archive-url=https://web.archive.org/web/20231129191303/https://www.rbth.com/opinion/2016/01/05/nuclear-overkill-the-quest-for-the-10-gigaton-bomb_556351 |url-status=live }}</ref><ref>{{Cite web |last=Wellerstein |first=Alex |author-link=Alex Wellerstein |date=2021-10-29 |title=The untold story of the world's biggest nuclear bomb |url=https://thebulletin.org/2021/11/the-untold-story-of-the-worlds-biggest-nuclear-bomb/ |access-date=2023-10-08 |website=Bulletin of the Atomic Scientists |language=en-US |archive-date=August 27, 2023 |archive-url=https://web.archive.org/web/20230827130626/https://thebulletin.org/2021/11/the-untold-story-of-the-worlds-biggest-nuclear-bomb/ |url-status=live }}</ref>
[[File:Edward Teller (1958)-LLNL.jpg|thumb|upright|[[Edward Teller]], often referred to as the "father of the hydrogen bomb"]]

Fusion reactions do not create fission products, and thus contribute far less to the creation of [[nuclear fallout]] than fission reactions, but because all [[thermonuclear weapon]]s contain at least one [[Fission barrier|fission]] stage, and many high-yield thermonuclear devices have a final fission stage, thermonuclear weapons can generate at least as much nuclear fallout as fission-only weapons. Furthermore, high yield thermonuclear explosions (most dangerously ground bursts) have the force to lift radioactive debris upwards past the [[tropopause]] into the [[stratosphere]], where the calm non-turbulent winds permit the debris to travel great distances from the burst, eventually settling and unpredictably contaminating areas far removed from the target of the explosion.

=== Other types ===
{{Main|Boosted fission weapon|Neutron bomb|Radiological warfare|Induced gamma emission|Antimatter weapon}}
There are other types of nuclear weapons as well. For example, a [[boosted fission weapon]] is a fission bomb that increases its explosive yield through a small number of fusion reactions, but it is not a fusion bomb. In the boosted bomb, the neutrons produced by the fusion reactions serve primarily to increase the efficiency of the fission bomb. There are two types of boosted fission bomb: internally boosted, in which a deuterium-tritium mixture is injected into the bomb core, and externally boosted, in which concentric shells of lithium-deuteride and depleted uranium are layered on the outside of the fission bomb core. The external method of boosting enabled the [[USSR]] to field the first partially thermonuclear weapons, but it is now obsolete because it demands a spherical bomb geometry, which was adequate during the 1950s arms race when bomber aircraft were the only available delivery vehicles.

The detonation of any nuclear weapon is accompanied by a blast of [[neutron radiation]]. Surrounding a nuclear weapon with suitable materials (such as [[cobalt]] or [[gold]]) creates a weapon known as a [[salted bomb]]. This device can produce exceptionally large quantities of long-lived [[radioactive contamination]]. It has been conjectured that such a device could serve as a "doomsday weapon" because such a large quantity of radioactivities with half-lives of decades, lifted into the stratosphere where winds would distribute it around the globe, would make all life on the planet extinct.

In connection with the [[Strategic Defense Initiative]], research into the [[nuclear pumped laser]] was conducted under the DOD program [[Project Excalibur]] but this did not result in a working weapon. The concept involves the tapping of the energy of an exploding nuclear bomb to power a single-shot laser that is directed at a distant target.

During the [[Starfish Prime]] high-altitude nuclear test in 1962, an unexpected effect was produced which is called a [[nuclear electromagnetic pulse]]. This is an intense flash of electromagnetic energy produced by a rain of high-energy electrons which in turn are produced by a nuclear bomb's gamma rays. This flash of energy can permanently destroy or disrupt electronic equipment if insufficiently shielded. It has been proposed to use this effect to disable an enemy's military and civilian infrastructure as an adjunct to other nuclear or conventional military operations. By itself it could as well be useful to terrorists for crippling a nation's economic electronics-based infrastructure. Because the effect is most effectively produced by high altitude nuclear detonations (by military weapons delivered by air, though ground bursts also produce EMP effects over a localized area), it can produce damage to electronics over a wide, even continental, geographical area.<ref>{{Cite web |date=2021-07-15 |title=Why the U.S. once set off a nuclear bomb in space |url=https://www.nationalgeographic.com/premium/article/why-the-us-once-set-off-a-nuclear-bomb-in-space-called-starfish-prime |access-date=2023-11-27 |website=Premium |language=en |archive-date=November 29, 2023 |archive-url=https://web.archive.org/web/20231129191301/https://www.nationalgeographic.com/premium/article/why-the-us-once-set-off-a-nuclear-bomb-in-space-called-starfish-prime |url-status=live }}</ref>

Research has been done into the possibility of [[pure fusion weapon|pure fusion bombs]]: nuclear weapons that consist of fusion reactions without requiring a fission bomb to initiate them. Such a device might provide a simpler path to thermonuclear weapons than one that required the development of fission weapons first, and pure fusion weapons would create significantly less nuclear fallout than other thermonuclear weapons because they would not disperse fission products. In 1998, the [[United States Department of Energy]] divulged that the United States had, "...made a substantial investment" in the past to develop pure fusion weapons, but that, "The U.S. does not have and is not developing a pure fusion weapon", and that, "No credible design for a pure fusion weapon resulted from the DOE investment".<ref>U.S. Department of Energy, [https://fas.org/sgp/othergov/doe/rdd-8.pdf Restricted Data Declassification Decisions, 1946 to the Present (RDD-8)] {{webarchive |url=https://web.archive.org/web/20150924140708/http://www.fas.org/sgp/othergov/doe/rdd-8.pdf |date=September 24, 2015}} (January 1, 2002), accessed November 20, 2011.</ref>

[[Nuclear isomers]] provide a possible pathway to fissionless fusion bombs. These are naturally occurring [[isotopes]] ([[Isotopes of hafnium|<sup>178m2</sup>Hf]] being a prominent example) which exist in an elevated energy state. Mechanisms to release this energy as bursts of gamma radiation (as in the [[hafnium controversy]]) have been proposed as possible triggers for conventional thermonuclear reactions.

[[Antimatter]], which consists of [[particles]] resembling ordinary [[matter]] particles in most of their properties but having opposite [[electric charge]], has been considered as a trigger mechanism for nuclear weapons.<ref name="arxiv.org">{{cite arXiv|eprint=physics/0510071 |last1=Gsponer |first1=Andre |title=Fourth Generation Nuclear Weapons: Military effectiveness and collateral effects |year=2005}}</ref><ref>{{cite web |url=http://www.nextbigfuture.com/2015/09/details-on-antimatter-triggered-fusion.html|title=Details on antimatter triggered fusion bombs |website=NextBigFuture.com|date=September 22, 2015 |url-status=live |archive-url=https://web.archive.org/web/20170422125419/http://www.nextbigfuture.com/2015/09/details-on-antimatter-triggered-fusion.html|archive-date=April 22, 2017}}</ref><ref>{{cite web |url=http://cui.unige.ch/isi/sscr/phys/anti-BPP-3.html |title=Page discussing the possibility of using antimatter as a trigger for a thermonuclear explosion |publisher=Cui.unige.ch |access-date=May 30, 2013 |url-status=live |archive-url=https://web.archive.org/web/20130424174413/http://cui.unige.ch/isi/sscr/phys/anti-BPP-3.html |archive-date=April 24, 2013}}</ref> A major obstacle is the difficulty of producing antimatter in large enough quantities, and there is no evidence that it is feasible beyond the military domain.<ref>{{Cite book |arxiv=physics/0507114 |last1=Gsponer |first1=Andre |last2=Hurni |first2=Jean-Pierre |chapter=The physics of antimatter induced fusion and thermonuclear explosions |editor1-first=G. |editor1-last=Velarde |editor2-first=E. |editor2-last=Minguez |title=Proceedings of the 4th International Conference on Emerging Nuclear Energy Systems, Madrid, June 30/July 4, 1986 |publisher=World Scientific, Singapore |year=1987 |pages=166–169}}</ref> However, the US Air Force funded studies of the physics of antimatter in the [[Cold War]], and began considering its possible use in weapons, not just as a trigger, but as the explosive itself.<ref>{{cite news |author1=Keay Davidson |author2=Chronicle Science Writer |url=http://sfgate.com/cgi-bin/article.cgi?file=/c/a/2004/10/04/MNGM393GPK1.DTL |title=Air Force pursuing antimatter weapons: Program was touted publicly, then came official gag order |publisher=Sfgate.com |date=October 4, 2004 |access-date=May 30, 2013 |url-status=live |archive-url=https://web.archive.org/web/20120609101650/http://www.sfgate.com/cgi-bin/article.cgi?file=%2Fc%2Fa%2F2004%2F10%2F04%2FMNGM393GPK1.DTL |archive-date=June 9, 2012}}</ref> A fourth generation nuclear weapon design<ref name="arxiv.org" /> is related to, and relies upon, the same principle as [[antimatter-catalyzed nuclear pulse propulsion]].<ref>{{cite web |url=http://nuclearweaponarchive.org/News/INESAPTR1.html|title=Fourth Generation Nuclear Weapons|access-date=October 24, 2014 |url-status=live |archive-url=https://web.archive.org/web/20160323010905/http://nuclearweaponarchive.org/News/INESAPTR1.html|archive-date=March 23, 2016}}</ref>

Most variation in [[nuclear weapon design]] is for the purpose of achieving [[Dial-a-yield|different yields for different situations]], and in manipulating design elements to attempt to minimize weapon size,<ref name="Hansen" /> [[Nuclear fratricide|radiation hardness]] or requirements for special materials, especially fissile fuel or tritium.

====Tactical nuclear weapons====
[[File:ChemicalExercise2018-01.jpg|thumb|right|Soviet [[OTR-21 Tochka]] missile. Capable of firing a 100-kiloton nuclear warhead a distance of 185 km]]
Some nuclear weapons are designed for special purposes; most of these are for non-strategic (decisively war-winning) purposes and are referred to as [[tactical nuclear weapon]]s.

The [[neutron bomb]] purportedly conceived by [[Samuel T. Cohen|Sam Cohen]] is a thermonuclear weapon that yields a relatively small explosion but a relatively large amount of neutron [[radiation]]. Such a weapon could, according to tacticians, be used to cause massive biological casualties while leaving inanimate infrastructure mostly intact and creating minimal fallout. Because high energy neutrons are capable of penetrating dense matter, such as tank armor, neutron warheads were procured in the 1980s (though not deployed in Europe) for use as tactical payloads for US Army artillery shells (200&nbsp;mm [[W79 Artillery-Fired Atomic Projectile|W79]] and 155&nbsp;mm [[W82]]) and [[MGM-52 Lance|short range missile]] forces. Soviet authorities announced similar intentions for neutron warhead deployment in Europe; indeed, they claimed to have originally invented the neutron bomb, but their deployment on USSR tactical nuclear forces is unverifiable.{{citation needed|date=May 2022}}

A type of nuclear explosive most suitable for use by ground special forces was the [[Special Atomic Demolition Munition]], or SADM, sometimes popularly known as a [[Suitcase nuclear device|suitcase nuke]]. This is a nuclear bomb that is man-portable, or at least truck-portable, and though of a relatively small yield (one or two kilotons) is sufficient to destroy important tactical targets such as bridges, dams, tunnels, important military or commercial installations, etc. either behind enemy lines or pre-emptively on friendly territory soon to be overtaken by invading enemy forces. These weapons require plutonium fuel and are particularly "dirty". They also demand especially stringent security precautions in their storage and deployment.{{citation needed|date=May 2022}}

Small "tactical" nuclear weapons were deployed for use as antiaircraft weapons. Examples include the USAF [[AIR-2 Genie]], the [[AIM-26 Falcon]] and US Army [[Nike Hercules]]. Missile interceptors such as the [[Sprint (missile)|Sprint]] and the [[LIM-49 Spartan|Spartan]] also used small nuclear warheads (optimized to produce neutron or X-ray flux) but were for use against enemy strategic warheads.{{citation needed|date=May 2022}}

Other small, or tactical, nuclear weapons were deployed by naval forces for use primarily as [[antisubmarine]] weapons. These included nuclear [[depth charge|depth bombs]] or nuclear armed torpedoes. Nuclear mines for use on land or at sea are also possibilities.{{citation needed|date=May 2022}}