Editing Nuclear bunker buster

{{Short description|Earth-penetrating nuclear weapon}}
{{use dmy dates|date=April 2014}}
[[File:Nevada Test Site craters.jpg|thumb|250px|[[Subsidence crater]]s remaining after underground nuclear (test) explosions at the north end of the [[Yucca Flat]], [[Nevada]] test site]]

A '''nuclear bunker buster''',<ref>{{cite arXiv |last=Gsponer |first=Andre |title=The B61-based "Robust Nuclear Earth Penetrator:" Clever retrofit or headway towards fourth-generation nuclear weapons? |date=2005-11-19 |eprint=physics/0510052}}</ref> also known as an '''earth-penetrating weapon''' ('''EPW'''), is the [[nuclear weapon|nuclear]] equivalent of the conventional [[bunker buster]]. The non-nuclear component of the weapon is designed to penetrate [[soil]], [[Rock (geology)|rock]], or [[concrete]] to deliver a nuclear warhead to an underground target. These weapons would be used to destroy hardened, underground [[military]] [[bunker]]s or other below-ground facilities. An underground explosion releases a larger fraction of its energy into the ground, compared to a [[surface burst]] or [[air burst]] explosion at or above the surface, and so can destroy an underground target using a lower [[nuclear weapon yield|explosive yield]]. This in turn could lead to a reduced amount of [[radioactive fallout]]. However, it is unlikely that the explosion would be completely contained underground. As a result, significant amounts of rock and soil would be rendered radioactive and lofted as dust or vapor into the atmosphere, generating significant [[Nuclear fallout|fallout]].

== Base principle ==
While conventional bunker busters use several methods to penetrate concrete structures, these are for the purpose of destroying the structure directly, and are generally limited in how much of a bunker (or system of bunkers) they can destroy by depth and their relatively low explosive force (compared to nuclear weapons).

The primary difference between conventional and nuclear bunker busters is that, while the conventional version is meant for one target, the nuclear version can destroy an entire underground bunker system.

The main principles in modern bunker design are largely centered around survivability in nuclear war. As a result of this both American and Soviet sites reached a state of "super hardening", involving defenses against the effects of a nuclear weapon such as spring- or counterweight-mounted (in the case of the R-36) control capsules and thick concrete walls ({{convert|3|to|4|ft|m|1}} for the [[LGM-30 Minuteman|Minuteman ICBM]] launch control capsule) heavily reinforced with [[rebar]]. These systems were designed to survive a near miss of 20 megatons.<ref>{{Cite web |last=Uppal |first=Rajesh |title=Reemergence of Underground Warfare, hard and deeply buried targets (HDBTs) Vs Earth-Penetrating weapons (EPW) |url=https://idstch.com/geopolitics/reemergence-underground-warfare-hard-deeply-buried-targets-hdbts-vs-earth-penetrating-weapons-epw/ |access-date=2025-04-19 |website=International Defense Security & Technology |language=en-US}}</ref>

Liquid-fueled missiles such as those historically used by Russia are more fragile and easily damaged than solid-fueled missiles such as those used by the United States. The complex fuel storage facilities and equipment needed to fuel missiles for launch and de-fuel them for frequent maintenance add additional weaknesses and vulnerabilities. Therefore, a similar degree of silo "hardening" does not automatically equate to a similar level of missile "survivability".{{citation needed|date=August 2016}}

Major advancements in the accuracy and precision of nuclear and conventional weapons subsequent to the invention of the missile silo itself have also rendered many "hardening" technologies useless. With modern weapons capable of striking within several feet of their intended targets, a modern "near miss" can be much more effective than a "hit" decades ago. A weapon need only cover the silo door with sufficient debris to prevent its immediate opening to render the missile inside useless for its intended mission of rapid strike or counter-strike deployment.{{citation needed|date=August 2016}}

A nuclear bunker buster negates most of the countermeasures involved in the protection of underground bunkers by penetrating the defenses prior to detonating. A relatively low yield may be able to produce seismic forces beyond those of an air burst or even ground burst of a weapon with twice its yield.{{Citation needed|date=June 2013}} Additionally, the weapon has the ability to impart more severe horizontal [[shock wave]]s than many bunker systems are designed to combat by detonating at or near the bunker's depth, rather than above it.

Geologic factors also play a major role in weapon effectiveness and facility survivability. Locating facilities in hard rock may appear to reduce the effectiveness of bunker-buster type weapons by decreasing penetration, but the hard rock also transmits shock forces to a far higher degree than softer soil types. The difficulties of drilling into and constructing facilities within hard rock also increase construction time and expense, as well as making it more likely construction will be discovered and new sites targeted by foreign militaries.{{citation needed|date=August 2016}}

== Methods of operation ==

=== Penetration by explosive force ===
[[Concrete]] structure design has not changed significantly in the last 70 years.{{citation needed|date=October 2022}} The majority of protected concrete structures in the US military are derived from standards set forth in ''[[Fundamentals of Protective Design]]'', published in 1946 (US Army Corps of Engineers). Various augmentations, such as [[glass]], [[fiber]]s, and [[rebar]], have made concrete less vulnerable, but far from impenetrable.

When explosive force is applied to concrete, three major fracture regions are usually formed: the initial crater, a crushed aggregate surrounding the crater, and "scabbing" on the surface opposite the crater. Scabbing, also known as [[spall]]ing, is the violent separation of a mass of material from the opposite face of a plate or slab subjected to an impact or impulsive loading, without necessarily requiring that the barrier itself be penetrated.

While soil is a less dense material, it also does not transmit shock waves as well as concrete. So while a penetrator may actually travel further through soil, its effect may be lessened due to its inability to transmit shock to the target.

=== Hardened penetrator ===
[[File:Secant ogive.svg|thumb|A secant ogive]]
Further thinking on the subject envisions a hardened penetrator using kinetic energy to defeat the target's defenses and subsequently deliver a nuclear explosive to the buried target.

The primary difficulty facing the designers of such a penetrator is the tremendous heat applied to the penetrator when striking the shielding at high speed. This has partially been solved by using metals such as [[tungsten]] (the metal with the highest melting point), and altering the shape of the projectile (such as an [[ogive]]).

Altering the shape of the projectile to incorporate an ogive shape has yielded substantial improvement in penetration ability. [[Rocket sled]] testing at [[Eglin Air Force Base]] has demonstrated penetrations of {{convert|100|to|150|ft|m}} in concrete {{Citation needed|date=March 2007}} when traveling at {{convert|4000|ft/s|m/s|abbr=on}}. The reason for this is [[liquefaction]] of the concrete in the target, which tends to flow over the projectile. Variation in the speed of the penetrator can either cause it to be vaporized on impact (in the case of traveling too fast), or to not penetrate far enough (in the case of traveling too slowly). An approximation for the penetration depth is obtained with an [[Impact depth|impact depth formula]] derived by [[Isaac Newton|Sir Isaac Newton]].

=== Combination penetrator-explosive munitions ===
Another school of thought on nuclear bunker busters is using a light penetrator to travel {{convert|15|to|30|m|ft|order=flip|sigfig=1}} through shielding, and detonate a nuclear charge there. Such an explosion would generate powerful shock waves, which would be transmitted very effectively through the solid material comprising the shielding (see "scabbing" above).

== Policy and criticism of fallout ==
The main criticisms of nuclear bunker busters regard fallout and nuclear proliferation. The purpose of an earth-penetrating nuclear bunker buster is to reduce the required yield needed to ensure the destruction of the target by coupling the explosion to the ground, yielding a shock wave similar to an earthquake. For example, the United States retired the [[B53 nuclear bomb|B-53 warhead]], with a yield of nine [[TNT equivalent|megatons]], because the [[B61 nuclear bomb|B-61 Mod 11]] could attack similar targets with much lower yield (400 [[kiloton]]s),{{Citation needed|date=September 2007}} due to the latter's superior ground penetration. By burying itself into the ground before detonation, a much higher proportion of the explosion energy is transferred to [[seismic shock]]<ref>{{Cite journal |last=Nelson |first=Robert W. |date=January–February 2001 |title=Low-Yield Earth-Penetrating Nuclear Weapons |url=https://www.fas.org/faspir/2001/v54n1/weapons.htm |url-status=dead |journal=The Journal of the Federation of American Scientists |publisher=[[Federation of American Scientists]] |volume=54 |issue=1 |archive-url=https://web.archive.org/web/20060107023338/https://www.fas.org/faspir/2001/v54n1/weapons.htm |archive-date=7 January 2006}}</ref> when compared to the [[surface burst]] produced from the B-53's [[laydown delivery]]. Moreover, the globally dispersed fallout of an underground B-61 Mod 11 would likely be less than that of a [[surface burst]] B-53. Supporters note that this is one of the reasons nuclear bunker busters should be developed. Critics claim that developing new nuclear weapons sends a proliferating message to non-nuclear powers, undermining non-proliferation efforts.{{who|date=October 2020}}

Critics also worry that the existence of lower-yield nuclear weapons for relatively limited tactical purposes will lower the threshold for their actual use, thus blurring the sharp line between conventional weapons intended for use and weapons of mass destruction intended only for hypothetical deterrence, and increasing the risk of escalation to higher-yield nuclear weapons.<ref>{{Citation |url=http://www.hsfk.de/index.php?id=9&no_cache=1&detail=3124&no_cache=0&cHash=0991198fec |title=Intervention und Kernwaffen – Zur neuen Nukleardoktrin der USA |access-date=2008-02-15 |place=[[Germany|DE]] |first=Stephanie Sonius|last=Harald Müller |year=2006 |language=de |archive-url=https://web.archive.org/web/20110719042934/http://www.hsfk.de/index.php?id=9&no_cache=1&detail=3124&no_cache=0&cHash=0991198fec |archive-date=2011-07-19 |url-status=live}}</ref>

Local fallout from any nuclear detonation is increased with proximity to the ground. While a megaton-class yield [[surface burst]] will inevitably throw up many tons of (newly) radioactive debris, which falls back to the earth as fallout, critics contend that despite their relatively minuscule explosive yield, nuclear bunker busters create more local fallout per kiloton yield.{{citation needed|date=May 2014}} Also, because of the subsurface detonation, radioactive debris may contaminate the local groundwater.

The [[Union of Concerned Scientists]] advocacy group points out that at the [[Nevada Test Site]], the depth required to contain fallout from an average-yield [[underground nuclear test]] was over {{convert|100|m|ft|order=flip|sigfig=1}}, depending upon the weapon's yield. They contend that it is improbable that penetrators could be made to burrow so deeply. With yields between 0.3 and 340 kilotons, they argue, it is unlikely the blast would be completely contained.

Critics further state that the testing of new nuclear weapons would be prohibited by the proposed [[Comprehensive Test Ban Treaty]]. Although Congress refused to ratify the CTBT in 1999, and therefore this treaty has no legal force in the US, the US has adhered to the spirit of the treaty by maintaining a moratorium on nuclear testing since 1992.<ref>{{Citation |title=Comprehensive Nuclear Test Ban Treaty (CTBT) |publisher=MIIS |url=http://cns.miis.edu/inventory/pdfs/ctbt.pdf |date=10 May 2012 |archive-url=https://web.archive.org/web/20111025003946/http://cns.miis.edu/inventory/pdfs/ctbt.pdf |archive-date=2011-10-25 |url-status=live}}</ref>

Proponents, however, contend that lower explosive yield devices and subsurface bursts would produce little to no climatic effects in the event of a nuclear war, in contrast to multi-megaton air and surface bursts (that is, if the [[nuclear winter]] hypothesis proves accurate). [[air burst|Lower fuzing heights]], which would result from partially buried warheads, would limit or completely obstruct the range of the burning [[Effects of nuclear explosions|thermal rays]] of a nuclear detonation, therefore limiting the target, and its surroundings, to a fire hazard by reducing the range of thermal radiation with fuzing for subsurface bursts.<ref>{{Cite book |last1=Solomon |first1=Fredric |url=https://books.google.com/books?id=NUUrAAAAYAAJ&dq=radioactive+fallout+particles+surface+volume&pg=PA106 |title=The Medical Implications of Nuclear War |last2=Marston |first2=Robert Q. |date=1986-01-01 |publisher=National Academies Press |isbn=978-0-309-03692-4 |language=en}}</ref><ref name=":0">{{Cite book |last=Badash |first=Lawrence |url=https://www.worldcat.org/title/246200101 |title=A nuclear winter's tale: science and politics in the 1980s |date=2009 |publisher=MIT Press |isbn=978-0-262-01272-0 |series=Transformations : studies in the history of science (p. [317]-388) and technology |location=Cambridge, MA |oclc=246200101}}</ref>{{Rp|page=235}} Professors Altfeld and Cimbala have suggested that belief in the possibility of nuclear winter has actually made nuclear war more likely, contrary to the views of [[Carl Sagan]] and others, because it has inspired the development of more accurate, and lower explosive yield, nuclear weapons.<ref name=":0" />{{Rp|page=242}}

== Targets and the development of bunker busters ==
[[File:B-61 bomb.jpg|thumb|200px|[[B61 nuclear bomb]]]]
As early as 1944, the Barnes Wallis [[Tallboy bomb]] and subsequent [[Grand Slam bomb|Grand Slam]] weapons were designed to penetrate deeply fortified structures through sheer explosive power. These were not designed to directly penetrate defences, though they could do this (for example, the [[Valentin submarine pens]] had [[ferrous concrete]] roofs {{convert|4.5|m|ft|order=flip}} thick which were penetrated by two Grand Slams on 27 March 1945), but rather to penetrate under the target and explode leaving a [[camouflet]] (cavern) which would undermine foundations of structures above, causing it to collapse, thus negating any possible hardening. The destruction of targets such as the [[V-3 cannon|V3 battery]] at [[Fortress of Mimoyecques|Mimoyecques]] was the first operational use of the Tallboy. One bored through a hillside and exploded in the [[Saumur]] rail tunnel about {{convert|18|m|ft|order=flip|sigfig=1}} below, completely blocking it, and showing that these weapons could destroy any hardened or deeply [[Earthworks (engineering)|excavated]] installation. Modern targeting techniques allied with multiple strikes could perform a similar task.<ref>{{Citation| place = United Kingdom | publisher = Ministry of Defence | title = RAF Bomber Command Grand Slam raids | url = http://www.raf.mod.uk/history/bombercommandgrandslamraids.cfm | archive-url=https://web.archive.org/web/20140226053516/http://www.raf.mod.uk/history/bombercommandgrandslamraids.cfm |archive-date=2014-02-26 |url-status=live}}.</ref><ref>{{Citation | url = http://www.raf.mod.uk/bombercommand/jul44.html | title = RAF Bomber Command Campaign Diary July 1944 | place = UK | contribution = July 1944 | at = (6 July "Mimoyecques V-Weapon Site" photograph shows clearly the camouflet effect) | publisher = Ministry of Defence |archive-url=https://web.archive.org/web/20050514061638/http://www.raf.mod.uk/bombercommand/jul44.html |archive-date=2005-05-14 |url-status=dead}}</ref><ref>{{Citation | url =http://www.raf.mod.uk/history/bombercommandsaumurtunnel9thjune1944.cfm | title = RAF Bomber Command Saumur Tunnel Raid| contribution = Saumur | publisher = Ministry of Defence | place = UK |archive-url=https://web.archive.org/web/20140226011740/http://www.raf.mod.uk/history/bombercommandsaumurtunnel9thjune1944.cfm |archive-date=2014-02-26 |url-status=live}}.</ref>

Development continued, with weapons such as the nuclear [[B61 nuclear bomb|B61]], and conventional thermobaric weapons and [[GBU-28]]. One of the more effective housings, the GBU-28 used its large mass ({{convert|2130|kg|lb|abbr=on|disp=or|order=flip}}) and casing (constructed from barrels of surplus 203&nbsp;mm [[howitzer]]s) to penetrate {{convert|6|m|ft|abbr=off|order=flip}} of concrete, and more than {{convert|30|m|ft|order=flip|sigfig=1}} of earth.<ref>{{Citation | publisher = Rice | url = http://es.rice.edu/projects/Poli378/Gulf/gwtxt_ch6.html#GBU-28 | type = report to Congress | title = The Conduct of the Persian Gulf War | contribution = GBU-28 | archive-url = https://web.archive.org/web/20070202221842/http://es.rice.edu/projects/Poli378/Gulf/gwtxt_ch6.html#GBU-28 | archive-date = 2 February 2007 | url-status = dead | access-date = 14 January 2006 }}.</ref> The B61 Mod 11, which first entered military service after the Cold war had ended, in January 1997, was specifically developed to allow for bunker penetration, and is speculated to have the ability to destroy hardened targets a few hundred feet beneath the earth.<ref>{{Citation | title = USA weapons | publisher = Nuclear weapon archive | url = http://nuclearweaponarchive.org/Usa/Weapons/B61.html | contribution = The B61 (Mk-61) Bomb |archive-url=https://web.archive.org/web/20090227003412/http://nuclearweaponarchive.org/Usa/Weapons/B61.html |archive-date=2009-02-27 |url-status=live}}.</ref>

While penetrations of {{convert|20|to|100|ft|m|0}} were sufficient for some shallow targets, both the [[Soviet Union]] and the United States were creating bunkers buried under huge volumes of soil or reinforced concrete in order to withstand the multi-megaton thermonuclear weapons developed in the 1950s and 1960s. Bunker penetration weapons were initially designed within this [[Cold War]] context. One likely Soviet Union/Russian target, [[Mount Yamantau]], was regarded in the 1990s by Maryland Republican congressman, [[Roscoe Bartlett]], as capable of surviving "half a dozen" repeated nuclear strikes of an unspecified yield, one after the other in a "direct hole".<ref>{{cite web |url=http://viewzone2.com/yamantaux.html |title=Yamantau Whats going on in the Yamantau mountain complex?}}</ref><ref>{{cite web |url=http://www.thelivingmoon.com/45jack_files/03files/Yamantau_Mountain_Complex_Russia.html |title=Secret Bases Russia Yamantau Mountain Complex Beloretsk, Russia}}</ref>

The Russian [[continuity of government]] facility at [[Kosvinsky Mountain]], finished in early 1996, was designed to resist US earth-penetrating warheads and serves a similar role as the American [[Cheyenne Mountain Complex]].<ref>{{cite web|url=http://www.windowonheartland.net/2012/02/russias-top-secret-bases.html |title=WINDOW ON HEARTLAND Geopolitical notes on Eastern Europe, the Caucasus and Central Asia |url-status=dead |archive-url=https://web.archive.org/web/20130424050959/http://www.windowonheartland.net/2012/02/russias-top-secret-bases.html |archive-date=24 April 2013 }}</ref><ref>[http://www.globalsecurity.org/wmd/library/news/russia/1997/bmd970404a.htm  "Moscow builds bunkers against nuclear attack"], by [[Bill Gertz]], ''[[Washington Times]]'', 1 April 1997</ref> The timing of the Kosvinsky completion date is regarded as one explanation for US interest in a new nuclear bunker buster and the declaration of the deployment of the B-61 Mod 11 in 1997. Kosvinsky is protected by about {{convert|300|m|ft|order=flip|sigfig=1}} of [[granite]].<ref>{{cite web |url=http://www.globalsecurity.org/wmd/world/russia/kosvinsky.htm |title=Global Security.org Kosvinsky Mountain, Kos'vinskiy Kamen', Gora, MT 59°31'00"N 59°04'00"E}}</ref>

The weapon was revisited{{dubious|date=May 2014}} after the Cold War during the 2001 [[War in Afghanistan (2001–present)|US invasion of Afghanistan]], and again during the [[2003 invasion of Iraq]]. During the campaign in [[Tora Bora]] in particular, the United States believed that "vast underground complexes," deeply buried, were protecting opposing forces. Such complexes were not found. While a nuclear penetrator (the "Robust Nuclear Earth Penetrator", or "RNEP") was never built, the US [[United States Department of Energy|DOE]] was allotted budget to develop it, and tests were conducted by the US [[Air Force Research Laboratory]]. The RNEP was to use the 1.2&nbsp;megaton [[B83 nuclear bomb|B83]] physics package.<ref>{{cite web |last=Beljac |first=Marco |date=21 September 2006 |title=Does Divine Strake Live On? |url=http://sciencesecurity.livejournal.com/2003.html |website=Science and Global Security}}</ref>

The [[George W. Bush|Bush]] administration removed its request for funding<ref>{{Citation | url = http://news.bbc.co.uk/1/hi/4377446.stm | title = US cancels bunker bomb programme | date = 26 October 2005 | work= BBC |archive-url=https://web.archive.org/web/20140424223521/http://news.bbc.co.uk/2/hi/4377446.stm |archive-date=2014-04-24 |url-status=live}}</ref> of the weapon in October 2005. Additionally, then [[United States Senate|US Senator]] [[Pete Domenici]] announced funding for the nuclear bunker-buster has been dropped from the US [[United States Department of Energy|Department of Energy]]'s 2006 budget at the department's request.<ref>{{Citation  | url=https://news.yahoo.com/s/ap/20051026/ap_on_go_pr_wh/bunker_buster | title=Bush Admin. Drops 'Bunker-Buster' Plan | work=Yahoo! News | date=25 October 2005 | agency=Associated Press | access-date=2014-03-06 | author=Hebert, H. Josef | archive-url=https://web.archive.org/web/20051027195236/http://news.yahoo.com/s/ap/20051026/ap_on_go_pr_wh/bunker_buster | archive-date=2005-10-27}}</ref>

While the project for the RNEP seems to be in fact canceled, [[Jane's Information Group]] speculated in 2005 that work might continue under another name.<ref>{{Citation | archive-url = https://web.archive.org/web/20071022215958/http://janes.com/defence/news/jid/jid051117_1_n.shtml | title = US dumps bunker-buster – or not? | publisher = Jane's | archive-date = 2007-10-22 | url = http://janes.com/defence/news/jid/jid051117_1_n.shtml}}.</ref>

A more recent development (c. 2012) is the [[GBU-57]] Massive Ordnance Penetrator, a {{convert|30000|lb|kg|adj=on}} conventional gravity bomb. The USAF's B-2 Spirit bombers can each carry two such weapons.

==Notable US nuclear bunker busters==
Note that with the exception of strictly earth penetrating weapons, others were designed with air burst capability and some were depth charges as well.

*[[Mark 8 nuclear bomb]] (1952–1957): earth penetrating
*[[Mark 8 nuclear bomb|W8]] for [[SSM-N-8 Regulus]] (cancelled): earth penetrating
*[[Mark 11 nuclear bomb]] (1956–1960): earth penetrating
*[[Mk 105 Hotpoint]] (1958–1965): laydown delivery
*[[B28 nuclear bomb]] (1958–1991): laydown delivery and ground burst
*[[Mark 39 nuclear bomb]] (1958–1962) laydown delivery and ground burst
*[[B43 nuclear bomb]] (1961–1990): laydown delivery and ground burst
*[[B53 nuclear bomb]] (1962–1997): laydown delivery
*[[B57 nuclear bomb]] (1963–1993): laydown delivery
*[[B61 nuclear bomb]] (1968–present): laydown delivery and ground burst 
**Mod 11 (1997–present): earth penetrating, laydown delivery, and ground burst
*[[B61 nuclear bomb#W61 Earth Penetrator Warhead|W61]] for [[MGM-134 Midgetman]] (cancelled): earth penetrating
*[[B77 nuclear bomb]] (cancelled): laydown delivery
*[[B83 nuclear bomb]] (1983–present): laydown delivery and ground burst
*[[W86]] for [[Pershing II]] (cancelled): earth penetrating
*Robust Nuclear Earth Penetrator (cancelled): earth penetrating

== See also ==
{{Commons|Tactical nuclear weapons}}
* [[Bunker buster]] (conventional, non-nuclear)
* [[Earthquake bomb]]
* [[Underground nuclear weapons testing]]
* [[Nuclear strategy]]
* [[Thermobaric weapon]]
* [[Nuclear weapon]]
* [[List of nuclear weapons]]

== Citations ==
{{Reflist|32em}}

== References ==
* {{Citation | title = Penetration Resistance of Concrete: A Review | first = James R | last = Clifton | publisher = The Physical Security and Stockpile Directorate, Defense Nuclear Agency}}.
* {{Citation | title = Nuclear Weapon Initiatives: Low-yield R&D, Advanced Concepts, Earth Penetrators, Test Readiness | last1 = Ernest | first1 = Jonathan V  | year = 2005 | publisher = Nova Publishers | isbn = 1-59454-203-1|display-authors=etal}}.
* {{Citation | title = Barrier Penetration Tests | last = Moore | first = RT | publisher = National Bureau of Standards}}.
* {{Citation | title= U.S. Nuclear Weapons: Changes In Policy And Force Structure | last = Woolf | first = Amy F | isbn = 1-59454-234-1| year = 2005 | publisher = Nova Science Publishers, Incorporated }}.

== External links ==
* [http://nuclearweaponarchive.org/Usa/Weapons/Allbombs.html Allbombs.html] list of all US nuclear warheads at [http://nuclearweaponarchive.org nuclearweaponarchive.org]
* {{Citation | url = http://www.ucsusa.org/nuclear_weapons_and_global_security/solutions/us-nuclear-weapons/earth-penetrating-weapons.html | title = Earth Penetrating Weapons | first1 = Lisbeth | last1 = Gronlund |author1-link= Lisbeth Gronlund | first2 = David | last2 = Wright | first3 = Robert | last3 = Nelson | publisher = Union of Concerned Scientists |date=May 2005 | place = US}}.
* {{Citation | url = http://www.nap.edu/catalog/11282/ | title = Effects of Nuclear Earth-Penetrator and Other Weapons | date = 2005| publisher = The National Academies Press | doi = 10.17226/11282 | isbn = 978-0-309-09673-7 }}.
* {{Citation | url = https://www.newscientist.com/article.ns?id=dn3016 | title = Bunker-busters set to go nuclear | first = David | last = Hambling | newspaper = New Scientist | date = 7 November 2002}}.
* {{Citation | url = http://www.fas.org/faspir/2001/v54n1/weapons.htm | title = Low-Yield Earth-Penetrating Nuclear Weapons | first = Robert W | last = Nelson | journal = Federation of American Scientists |date=January–February 2001 | volume = 54 | number = 1}}/
* {{Citation | arxiv = physics/0510052 | title = The B61-based "Robust Nuclear Earth Penetrator:" Clever retrofit or headway towards fourth-generation nuclear weapons? | first = Andre | last = Gsponer | publisher = Independent Scientific Research Institute | date = 31 March 2007| bibcode = 2005physics..10052G }}.

{{DEFAULTSORT:Nuclear Bunker Buster}}
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