View source for Nuclear weapons delivery

{{Short description|Type of explosive arms}}
{{Use dmy dates|date=January 2020}}{{More footnotes needed|date=November 2023}}

[[File:Mark-28 bomb being transported to an F-100 via bomb lift truck by the load crew of the 18th Tactical Fighter Wing at Kadena Air Base.jpg|thumb|A [[B28 nuclear bomb]] being transported to a [[United States Air Force]] [[F-100 Super Sabre]] at [[Kadena Air Base]] in Japan]]
{{Nuclear weapons}}
'''Nuclear weapons delivery''' is the technology and systems used to place a [[nuclear weapon]] at the position of [[detonation]], on or near its target. All nine [[nuclear states]] have developed some form of medium- to long-range delivery system for their nuclear weapons. Alongside improvement of weapons, their development and deployment played a key role in the [[nuclear arms race]].

[[Strategic nuclear weapons]] are intended primarily as part of a doctrine of [[Deterrence theory|deterrence]] by threatening large targets, such as [[Countervalue|cities]] or [[Counterforce|military installations]]. These are generally delivered by some combination of land-based [[Intercontinental ballistic missile|intercontinental ballistic missiles]], sea-based [[Submarine-launched ballistic missile|submarine-launched ballistic missiles]], and air-based [[Strategic bomber|strategic bombers]] carrying [[gravity bombs]] or [[cruise missiles]]. The possession of all three is known as a [[nuclear triad]].

[[Tactical nuclear weapons]] are intended for battlefield usage and/or destroying specific military, communications, or infrastructure targets, and generally have lower yields. Delivery systems developed for them include shorter-range ground-, air-, and sea-launched missiles, [[nuclear artillery]], [[Atomic demolition munition|nuclear land mines]], [[Nuclear torpedo|nuclear torpedoes]], and [[Nuclear depth charge|nuclear depth charges]], but they have become less salient since the end of the [[Cold War]].

Delivery systems were occasionally tested [[List of nuclear weapons tests#Tests of live warheads on rockets|with live warheads]] as a provocative form of [[nuclear weapons testing]] and [[live fire exercise]].

Detection and interception of delivery vehicles is a key part of nuclear deterrence. For detection, [[early-warning radar]] and [[Early warning satellite|satellite]] systems were developed. For interception, [[anti-ballistic missile]] and [[air defense]] systems were developed, some of which were themselves nuclear-armed. Warhead countermeasures developed against these include [[Missile defense#Decoys|decoys]], [[Multiple independently targetable reentry vehicle|multiple independently targetable reentry vehicles]], and [[Maneuverable reentry vehicle|maneuverable reentry vehicles]].

Since the end of the Cold War, nuclear weapons delivery has been advanced by [[Stealth bomber|stealth bombers]] and [[Hypersonic weapon|hypersonic weapons]]. 

==Nuclear triad==
{{main|Nuclear triad}}
A '''nuclear triad''' refers to a [[strategic nuclear weapon|strategic nuclear arsenal]] which consists of three components, traditionally [[strategic bomber]]s, [[intercontinental ballistic missile]]s (ICBMs), and [[submarine-launched ballistic missile]]s (SLBMs). The purpose of having a three-branched nuclear capability is to significantly reduce the possibility that an enemy could destroy all of a nation's nuclear forces in a [[Pre-emptive nuclear strike|first-strike]] attack; this, in turn, ensures a credible threat of a [[second strike]], and thus increases a nation's [[nuclear deterrence]].<ref name="NW">{{cite magazine |author=John Barry |url=http://www.newsweek.com/id/226494 |title=Do We Still Need a Nuclear 'Triad'? |magazine=[[Newsweek]] |date=12 December 2009 |access-date=8 October 2010}}</ref><ref>{{cite web |url=http://www.acq.osd.mil/ncbdp/nm/USNuclearDeterrence.html |title=Nuclear Stockpile |publisher=US Department of Defense |author=Office for the Deputy Assistant to the Secretary of Defense for Nuclear Matters |access-date=8 October 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100510015329/http://www.acq.osd.mil/ncbdp/nm/USNuclearDeterrence.html |archive-date=10 May 2010 }}</ref><ref name="Time">{{cite magazine|url=http://www.time.com/time/magazine/article/0,9171,959948,00.html |archive-url=https://web.archive.org/web/20080307080808/http://www.time.com/time/magazine/article/0,9171,959948,00.html |url-status=dead |archive-date=7 March 2008 |title=Toning Up the Nuclear Triad |magazine=Time |date=23 September 1985 |access-date=8 October 2010}}</ref>

==Main delivery mechanisms==

===Gravity bomb===
[[Image:Fat Man (replica of nuclear bomb).jpg|left|thumb|The "[[Little Boy]]" and the "[[Fat Man]]" devices were large and cumbersome [[gravity bomb]]s.]]
Historically the first method of nuclear weapons delivery, and the method used in [[Atomic bombings of Hiroshima and Nagasaki|the twin instances]] of [[nuclear warfare]] in history, was a [[gravity bomb]] dropped by a [[bomber|plane]]. In the years leading up to the development and deployment of nuclear-armed missiles, nuclear bombs represented the most practical means of nuclear weapons delivery; even today, and especially with the [[START I|decommissioning]] [[START II|of nuclear]] [[START III|missiles]], aerial bombing remains the primary means of offensive nuclear weapons delivery, and the majority of [[United States|US]] nuclear warheads are represented in bombs, although some are in the form of missiles.

Gravity bombs are designed to be dropped from planes, which requires that the weapon be able to withstand vibrations and changes in air temperature and pressure during the course of a flight. Early weapons often had a removable core for safety, known as [[Mark 4 nuclear bomb|in flight insertion]] (IFI) cores, being inserted or assembled by the air crew during flight. They had to meet safety conditions, to prevent accidental detonation or dropping. A variety of types also had to have a fuse to initiate detonation. US nuclear weapons that met these criteria are designated by the letter "B" followed, without a hyphen, by the sequential number of the "[[physics package]]" it contains. The "[[B61 nuclear bomb|B61]]", for example, was the primary bomb in the US arsenal for decades.

Various air-dropping techniques exist, including [[toss bombing]], [[parachute]]-retarded delivery, and [[laydown]] modes, intended to give the dropping aircraft time to escape the ensuing blast.

The earliest gravity nuclear bombs ([[Little Boy]] and [[Fat Man]]) of the United States could only be carried, during the era of their creation, by the special ''[[Silverplate]]'' limited production (65 airframes by 1947) version of the [[B-29 Superfortress]]. The next generation of weapons were still so big and heavy that they could only be carried by bombers such as the six/ten-engined, seventy-meter wingspan [[B-36 Peacemaker]], the eight jet-engined [[B-52 Stratofortress]], and jet-powered British RAF [[V bomber]]s, but by the mid-1950s smaller weapons had been developed that could be carried and deployed by [[fighter-bomber]]s. Modern nuclear gravity bombs are so small that they can be carried by (relatively) small [[multirole fighter |multirole fighter aircraft]], such as the single-engined [[General Dynamics F-16 Fighting Falcon|F-16]] and [[Lockheed Martin F-35 Lightning II|F-35]].

===Cruise missile===
{{main|Cruise missile}}
{{Further|Cruise-missile submarine}}[[Image:Tomahawk Block IV cruise missile.jpg|thumb|right|150px|[[Cruise missile]]s have a shorter range than [[ICBM]]s. [[Tomahawk (missile family)|U/RGM-109E Tomahawk]] pictured ([[Intermediate-Range Nuclear Forces Treaty|not nuclear capable anymore]]).]]

A [[cruise missile]] is a [[jet engine|jet-]] or [[rocket engine|rocket-propelled]] [[missile]] that [[Aerodynamic Flight|flies aerodynamically]] at low altitude using an automated guidance system (usually [[Inertial navigation system|inertial navigation]], sometimes supplemented by either [[Global Positioning System|GPS]] or [[Missile guidance|mid-course updates]] from friendly forces) to make them harder to detect or intercept. Cruise missiles can carry a nuclear warhead. They have a shorter range and smaller [[payload]]s than ballistic missiles, so their warheads are smaller and less powerful.

The [[AGM-86 ALCM]] is the [[United States Air Force|US Air Force]]'s current nuclear-armed [[air-launched cruise missile]]. The ALCM is only carried on the [[B-52 Stratofortress]] which can carry 20 missiles. Thus the cruise missiles themselves can be compared with MIRV warheads.  The [[Tomahawk (missile family)|BGM/UGM-109 Tomahawk]] [[submarine-launched cruise missile]] is capable of carrying nuclear warheads, but all nuclear warheads were removed following the [[Intermediate-Range Nuclear Forces Treaty]].

Cruise missiles may also be launched from [[Transporter erector launcher|mobile launchers on the ground]], and from naval ships.

There is no letter change in the US arsenal to distinguish the warheads of cruise missiles from those for ballistic missiles.

Cruise missiles, even with their lower payload, speed, and thus readiness, have a number of advantages over ballistic missiles for the purposes of delivering nuclear strikes:
* Launch of a cruise missile is difficult to detect early from satellites and other long-range means, contributing to a [[surprise attack|surprise factor of attack]].
* That, coupled with the ability to actively maneuver in flight, allows for penetration of [[Anti-ballistic missile|strategic anti-missile systems aimed at intercepting ballistic missiles]], which typically fly on a ballistic arc without complex maneuvers.

However, cruise missiles are vulnerable to typical [[air-defence|air-defence means]] as they are essentially [[kamikaze drone|one-use]] [[unmanned aircraft]]; strategies such as [[Combat air patrol|combat flights of fighter aircraft]], or an integrated air-defence system comprising both CAP and ground-based elements, such as [[Surface-to-air missile|surface-air missiles (SAM)]], can be used to defend against a cruise missile attack.

Prior to the development of nuclear-armed [[submarine-launched ballistic missile]]s, the United States and the Soviet Union conducted their first [[Deterrence theory|at-sea deterrence patrol]]s using modified [[Cruise-missile submarine|submarines armed with very large nuclear-armed cruise missiles]]; The US operated various [[diesel-electric submarine]]s armed with the [[SSM-N-8 Regulus|Regulus missile]], and the Soviets operated [[Whiskey-class submarine#Missile variants|Modified ''Whiskey''-class]] armed with the [[P-5 Pyatyorka|P-5 ''Пятёрка'']]. These early nuclear-armed SSGs served for a few decades until there were enough SSBNs put in service, after which they were retired. Their spiritual successors, armed with larger amounts of more modern, smaller cruise missiles continue to serve to this day serving in a tactical strike role, although they could be rearmed with nuclear cruise-missiles if need be.

[[Air-to-surface missile|Air-]] or [[Transporter erector launcher|Ground-launched]] nuclear-armed cruise missiles (sometimes even [[Nuclear-powered aircraft|nuclear-powered]]) were [[SM-64 Navaho|considered]] [[Supersonic Low Altitude Missile|by]] [[Burya|both]] [[RSS-40 Buran|sides]] early in the Cold War, but both concluded that it was impractical with the technology of the time. Nuclear-powered aircraft were considered due to the nascent [[Aeronautics|aeronautical]] and [[Aerospace engineering|rocketry]] technology of the time, especially when considering the temperamental and inefficient nature of [[History of the jet engine|early jet engines]], which limited the range and use cases of strategic bombers and cruise missiles. Later on in the Cold War both [[Academic discipline|discipline]]s had advanced far enough that it was feasible to create both reliable long-ranged cruise missiles and the strategic bombers able to launch them. Another [[Arms race|arms-race]] began which produced contemporary post-Cold War cruise missiles and launch systems; [[Vertical launching system|VLS technology]] also allowed for surface ships to be armed with nuclear-armed cruise missiles while concealing their true payload. In 2018, the first operational nuclear-powered strategic cruise missile, the [[9M730 Burevestnik|SSC-X-9 "Skyfall" (9М730 ''Буревестник'')]] was revealed by [[President of Russia|Russian President]] [[Vladimir Putin]]. It is under development and is slated to enter service sometime in the [[2020s]].

===Ballistic missile===
{{main|Ballistic missile}}
[[Image:Trident II missile image.jpg|thumb|150px|right|[[Trident II]] [[SLBM]] launched by [[Royal Navy]] {{sclass|Vanguard|submarine|1}} ]]

[[Missile]]s using a [[ballistic missile|ballistic]] trajectory deliver a [[warhead]] over the horizon; in the case of the most capable of these, classified as [[intercontinental ballistic missile]]s (ICBMs) (and [[submarine-launched ballistic missile]]s (SLBMs) if transported by [[Ballistic missile submarine|submarine]]), they can reach distances of nearly tens of thousands of kilometers. Most ballistic missiles exit the Earth's atmosphere and re-enter it in their [[sub-orbital spaceflight]]. Ballistic missiles aren't always nuclear armed, but the conspicuous and alarming nature of their launch often precludes arming ICBMs and SLBMs, the most capable classes of ballistic missiles, [[Prompt Global Strike|with conventional warheads]].

Placement of nuclear missiles on the [[low Earth orbit]] has been banned by the [[Outer Space Treaty]] as early as 1967. Also, the eventual Soviet [[Fractional Orbital Bombardment System]] (FOBS) that served a similar purpose—it was just deliberately designed to deorbit before completing a full circle—was phased out in January 1983 in compliance with the [[SALT II]] treaty.

An ICBM is more than 20 times as fast as a [[bomber]] and more than 10 times as fast as a [[fighter plane]], and also flying at a much higher altitude{{clarify|reason= A note could be here to explain the specific kinematics of ICBM flight|date=November 2023}}, and therefore more difficult to defend against. ICBMs can also be [[High-alert nuclear weapon|fired quickly]] in the event of a surprise attack.

Early ballistic missiles carried a single [[warhead]], often of [[TNT equivalent|megaton]]-range yield. Because of the limited accuracy of the missiles, this kind of high yield was considered necessary in order to ensure a particular target's destruction. Since the 1970s modern ballistic weapons have seen the development of far more accurate targeting technologies, particularly due to improvements in [[inertial guidance system]]s. This set the stage for smaller warheads in the hundreds-of-[[kiloton]]s-range yield, and consequently for ICBMs having [[multiple independently targetable reentry vehicle]]s (MIRV). Advances in technology have enabled a single missile to launch a payload containing several warheads; the number of which depended on the missile's and payload bus' design.  MIRVs has a number of advantages over a missile with a single warhead. With few additional costs, it allows a single missile to strike multiple targets, or to inflict maximum damage on a single target by attacking it with multiple warheads. It makes [[anti-ballistic missile]] defense even more difficult, and even less economically viable, than before.

Missile warheads in the [[United States|American]] arsenal are indicated by the letter "W"; for example, the W61 missile warhead would have the same [[physics package]] as the B61 gravity bomb described above, but it would have different environmental requirements, and different safety requirements since it would not be crew-tended after launch and remain atop a missile for a great length of time.<ref>{{Citation | title = Nav Air | publisher = Navy | url = http://www.navair.navy.mil/index.cfm?fuseaction=home.display&key=F4E98B0F-33F5-413B-9FAE-8B8F7C5F0766| archive-url = https://web.archive.org/web/20100307084742/http://www.navair.navy.mil/index.cfm?fuseaction=home.display&key=F4E98B0F-33F5-413B-9FAE-8B8F7C5F0766| url-status = dead| archive-date = 7 March 2010}}.</ref>

While the [[V-2 rocket|first modern ballistic missile designed]] is the basis of contemporary rocket- and missilery, it never carried a nuclear warhead. The first ICBM ever designed was the [[Soviet Union|Soviet]] [[R-7 Semyorka|R-7]].

The first [[Ballistic missile submarine|SLBM-carrying submarine]] was also Soviet; the [[prototype]] Modified [[Zulu-class submarine|''Zulu''-class]] and the mass-produced [[Golf-class submarine|''Golf''-class ballistic missile submarines]] carried their SLBMs in their sails, but these pioneering designs had to surface to launch their ballistic missiles. The Americans responded with the first "modern design" of ballistic missile subs; the [[George Washington-class submarine|''George Washington''-class]], which launched the [[UGM-27 Polaris|Polaris SLBM]]. The subsequent arms-race culminated in some of the largest submarines ever designed; the [[Trident (missile)|Trident-armed]] 170 meter long [[Ohio-class submarine|''Ohio''-class submarine]] armed with 24 x 8 MIRV [[UGM-133 Trident II|Trident missiles]], and the [[battlecruiser|battlecruiser-sized]] 48,000 [[tonne]] [[List of ships of Russia by project number|Project]] [[Typhoon-class submarine|941 ''Акула'', the ''Typhoon''-class submarine]], armed with 20 [[R-39 Rif|R-39]]s with 10 MIRVs each. After the Cold War, SSBN and subsequently SLBM development have slowed, but nascent nuclear powers are building [[Arihant-class submarine|novel classes]] of [[Sinpo-class submarine|SSB]](N)s, while the established powers, all members of the [[United Nations Security Council]], are plotting the [[Columbia-class submarine|next]]-[[Type 096 submarine|generation]] [[SNLE 3G|of]] [[Dreadnought-class submarine|nuclear-powered]] [[Arcturus-class submarine|nuclear-armed]] ballistic missile submarines.

[[Hypersonic glider|Hypersonically-Gliding]] [[Hypersonic glide vehicle|Warhead]]s are a novel form of warhead to arm ballistic missiles. These maneuverable devices threaten to obsolate current forms of [[Anti-ballistic missile|ABM]] defences, thus various nascent and established nuclear powers are [[Arms race|racing]] to [[Avangard (hypersonic glide vehicle)|field]] [[DF-ZF|examples]] [[Long-Range Hypersonic Weapon|of]] such [[Hwasong-8|systems]].

===Other delivery systems===
[[Image:DavyCrockettBomb.jpg|right|thumb|150px|The [[Davy Crockett (nuclear device)|Davy Crockett]] artillery shell is the smallest known nuclear weapon developed by the US.]]
[[Image:Mk17 bomb.jpg|left|thumb|150px|The [[Mark 17 nuclear bomb|Mk-17]] was an early US thermonuclear weapon and weighed around 21 [[short ton]]s (19,000&nbsp;kg).]]

Other delivery methods included [[nuclear artillery]] shells, [[Land mine|mine]]s such as the [[Medium Atomic Demolition Munition]] and the novel [[Blue Peacock]], [[nuclear depth bomb]]s, and [[nuclear torpedo]]es. An [[Davy Crockett (nuclear device)|'Atomic Bazooka']] was also fielded, designed to be used against large formations of tanks.

In the 1950s the US developed small nuclear warheads for air defense use, such as the [[Nike (rocket)#Nike Hercules|Nike Hercules]]. From the 1950s to the 1980s, the United States and Canada fielded a [[nuclear weapon yield|low-yield]] nuclear armed [[air-to-air rocket]], the [[AIR-2 Genie]].  Further developments of this concept, some with much larger warheads, led to the early [[anti-ballistic missile]]s. The United States have largely taken nuclear air-defense weapons out of service with the fall of the [[Soviet Union]] in the early 1990s. Russia updated its nuclear armed Soviet era anti-ballistic missile (ABM) system, known as the [[A-135 anti-ballistic missile system]] in 1995. It is believed that the, in development successor to the nuclear A-135, the [[A-235 anti-ballistic missile system|A-235 Samolet-M]], will dispense with nuclear interception warheads and instead rely on a conventional ''hit-to-kill'' capability to destroy its target.<ref>{{Cite web | date = 13 April 2013 | url = http://missilethreat.wpengine.netdna-cdn.com/wp-content/uploads/2013/04/Russian-BMD-April-13.pdf | title = Current Developments in Russia's Ballistic Missile Defense | first = Jana | last = Honkova | publisher = George C. Marshall Institute | url-status = dead | archive-url = https://web.archive.org/web/20140426201121/http://missilethreat.wpengine.netdna-cdn.com/wp-content/uploads/2013/04/Russian-BMD-April-13.pdf | archive-date = 26 April 2014 }}</ref>

Small, two-man portable tactical weapons (erroneously referred to as [[suitcase bomb]]s), such as the [[Special Atomic Demolition Munition]], have been developed, although the difficulty to combine sufficient yield with portability limits their military utility.

==Costs==
{{see also|Space Race|Global Positioning System|CorningWare|WD-40}}

According to an audit by the [[Brookings Institution]], between 1940 and 1996, the US spent ${{Format price|{{Inflation|US|5821000000000|1996|r=3}}}} in present-day terms{{Inflation-fn|US}} on nuclear weapons programs. 57 percent of which was spent on building [[nuclear triad|delivery mechanisms]] for nuclear weapons. 6.3 percent of the total, ${{Format price|{{Inflation|US|365000000000|1996|r=3}}}} in present-day terms, was spent on weapon [[Radioactive waste|nuclear waste]] management, for example, cleaning up the [[Hanford site]] with environmental [[Environmental remediation|remediation]], and 7 percent of the total, ${{Format price|{{Inflation |US|409000000000|1996|r=3}}}} was spent on the manufacturing of nuclear weapons themselves.<ref>{{Citation | publisher = Brookings Institution | title = Estimated Minimum Incurred Costs of U.S. Nuclear Weapons Programs, 1940–1996 | url = http://www.brook.edu/fp/projects/nucwcost/figure1.htm | url-status = dead | archive-url = https://web.archive.org/web/20081121144318/http://www.brook.edu/fp/projects/nucwcost/figure1.htm | archive-date = 21 November 2008 }}.</ref>

===Technology spin-offs===
[[File:Ed White with Space Gun maneuvering unit.jpg|thumb|right|Edward White during the first US "Spacewalk" [[Extravehicular activity]] (EVA), [[Project Gemini]] 4, June 1965]]
Strictly speaking however not all this 57 percent was spent solely on "weapons programs" delivery systems.

====Launch vehicles====
For example, two such [[Nuclear triad|delivery mechanisms]], the [[Atlas ICBM]] and [[Titan II]], were re-purposed as human [[launch vehicle]]s for [[human spaceflight]], both were used in the civilian [[Project Mercury]] and [[Project Gemini]] programs respectively, which are regarded as stepping stones in the evolution of US human spaceflight.<ref>{{Citation | contribution = Titan | contribution-url = https://www.fas.org/spp/military/program/launch/titan.htm | quote = The Titan II ICBM was converted into the Titan/Gemini space launch vehicle (SLV) by man-rating critical systems. It served as a significant stepping stone in the evolution of the US human spaceflight program using expendable launch vehicles, culminating in the Apollo program.  Twelve successful Gemini launches occurred between April 1964 and November 1966. | publisher = FAS | title = Military launch program}}</ref><ref>{{Citation | contribution = Titan History | title = Space flight now | contribution-url = http://spaceflightnow.com/titan/b26/titanhistory.html}}.</ref> The Atlas vehicle sent [[John Glenn]], the first American into orbit. Similarly in the [[Soviet Union]] it was the [[R-7 (rocket)|R-7 ICBM]]/[[launch vehicle]] that placed the first artificial satellite in space, [[Sputnik 1|Sputnik]], on 4 October 1957, and the first [[human spaceflight]] in history was accomplished on a derivative of the R-7, the [[Vostok (rocket family)|Vostok]], on [[Cosmonautics Day|12 April 1961]], by [[cosmonaut]] [[Yuri Gagarin]].  A modernized version of the R-7 is still in use as the [[launch vehicle]] for the Russian Federation, in the form of the [[Soyuz (spacecraft)|Soyuz spacecraft]]. The [[Proton (rocket family)|Proton rocket family]] was originally developed as a "super-heavy ICBM" to launch heavy warheads with a 100 megaton yield of the same design used in the 1961 [[Tsar Bomba]] test.

====Weather satellites====
The first true [[weather satellite]], the [[TIROS-1]] was launched on the [[Thor-Able]] launch vehicle in April 1960.<ref>{{Citation | last = Darling | first = David | title = Encyclopedia | contribution = Tiros | contribution-url = http://www.daviddarling.info/encyclopedia/T/TIROS.html}}.</ref> The [[PGM-17 Thor]] was the first operational [[IRBM]] (intermediate ballistic missile) deployed by the US Air Force ([[USAF]]). The [[Soviet Union]]'s first fully operational weather satellite, the [[Meteor (satellite)|Meteor 1]] was launched on 26 March 1969 on the [[Vostok rocket]],{{citation needed|date=February 2023}} a derivative of the [[R-7 (rocket)|R-7 ICBM]].

====Lubricants====
[[WD-40]] was first used by [[Convair]] to protect the outer skin, and more importantly, the paper thin "balloon tanks" of the [[Atlas missile]] from rust and corrosion.<ref name="aboutus">{{cite web | title = Our History | publisher = WD-40 | url = http://www.wd40.com/about-us/history/ | access-date = 16 June 2013 | archive-url = https://web.archive.org/web/20140623152408/http://wd40.com/about-us/history/ | archive-date = 23 June 2014 | url-status = dead }}</ref><ref name="barrynytobit">Martin, Douglas. "[https://www.nytimes.com/2009/07/22/business/22barry1.html?ref=obituaries John S. Barry, Main Force Behind WD-40, Dies at 84]". ''The New York Times'', 22 July 2009.</ref> These stainless steel fuel tanks were so thin that, when empty, they had to be kept inflated with nitrogen gas to prevent their collapse.

====Thermal isolation====
In 1953, Dr. [[S. Donald Stookey]] of the Corning Research and Development Division invented [[Pyroceram]], a white [[glass-ceramic]] material capable of withstanding a thermal shock (sudden temperature change) of up to 450&nbsp;°C (840&nbsp;°F). It evolved from materials originally developed for a US [[ballistic missile]] program, and Stookey's research involved heat-resistant material for [[nose cone]]s.<ref name="missilehistory">{{cite web |url= http://sec.edgar-online.com/2001/04/13/0000912057-01-508691/Section2.asp |publisher= WKI |title= Annual Report: 10-K |type= Securities and Exchange Commission filing |date= 13 April 2001 |access-date= 26 March 2007 |url-status= dead |archive-url= https://web.archive.org/web/20070930201047/http://sec.edgar-online.com/2001/04/13/0000912057-01-508691/Section2.asp |archive-date= 30 September 2007 }}</ref>

====Satellite assisted positioning====
Precise navigation would enable United States [[submarine]]s to get an accurate fix of their positions before they launched their SLBMs, this spurred development of triangulation methods that ultimately culminated in [[GPS]].<ref name="Trimble Navigation Ltd">{{cite web|url= http://www.trimble.com/gps/whygps.shtml#0 |archive-url= https://web.archive.org/web/20071018151253/http://www.trimble.com/gps/whygps.shtml#0|archive-date= 18 October 2007 |title= Why Did the Department of Defense Develop GPS?|publisher=Trimble Navigation |access-date= 13 January 2010}}</ref> The motivation for having accurate launch position fixes, and missile velocities,<ref>{{cite web | url= https://www.rand.org/content/dam/rand/pubs/monographs/MG1200/MG1210/RAND_MG1210.pdf |title= The Future of the U.S. Intercontinental Ballistic Missile Force |first=Lauren |last= Caston | publisher =The RAND corporation |display-authors= etal}}</ref> is twofold. It results in a tighter target impact [[circular error probable]] and therefore by extension, reduces the need for the earlier generation of heavy multi-[[TNT equivalent|megaton]] nuclear warheads, such as the [[W53]] to ensure the target is destroyed. With increased target accuracy, [[MIRV|a greater number]] of lighter, multi-kiloton range warheads can be [[throw weight|packed on a given missile]], giving a higher number of separate targets that can be hit per missile.

====Global positioning system====
{{main |Global Positioning System}}
During a [[Labor Day]] weekend in 1973, a meeting of about twelve military officers at the Pentagon discussed the creation of a ''Defense Navigation Satellite System (DNSS)''. It was at this meeting that "the real synthesis that became GPS was created." Later that year, the DNSS program was named ''Navstar'', or Navigation System Using Timing and Ranging.<ref>{{Citation | url = http://www.au.af.mil/au/cadre/aspj/airchronicles/aureview/1981/may-jun/garwin.htm | archive-url = https://archive.today/20130616042904/http://www.au.af.mil/au/cadre/aspj/airchronicles/aureview/1981/may-jun/garwin.htm | url-status = dead | archive-date = 16 June 2013 | title = MX Deployment Reconsidered | access-date = 7 June 2013 | publisher = Air force | date = May–Jun 1981| journal = Air Chronicles}}.</ref>

During the development of the submarine-launched [[UGM-27 Polaris|Polaris]] missile, a requirement to accurately know the submarine's location was needed to ensure a high [[circular error probable]] warhead target accuracy. This led the US to develop the [[Transit (satellite)|Transit]] system.<ref>{{citation|title=Where good ideas come from, the natural history of innovation| first =Steven | last = Johnson|publisher=Riverhead Books |place= New York|year=2010}}</ref> In 1959, ARPA (renamed [[DARPA]] in 1972) also played a role in Transit.<ref>{{cite book | title = Transit to Tomorrow. Fifty Years of Space Research | publisher = The Johns Hopkins University Applied Physics Laboratory | first1 = Helen E | last1 = Worth | first2 = Mame | last2 = Warren | year = 2009 | url = http://space50.jhuapl.edu/pdfs/book.pdf | archive-url = https://web.archive.org/web/20190901150111/http://space50.jhuapl.edu/pdfs/book.pdf | url-status = dead | archive-date = 1 September 2019 }}</ref><ref>{{cite web | url = http://www.darpa.mil/WorkArea/DownloadAsset.aspx?id=2565 | title = The Story of GPS | first = Catherine | last = Alexandrow | date = Apr 2008 | publisher = Darpa | url-status = dead | archive-url = https://web.archive.org/web/20110629003311/http://www.darpa.mil/WorkArea/DownloadAsset.aspx?id=2565 | archive-date = 29 June 2011 }}</ref><ref name=gap>{{Citation | contribution-url=http://www.darpa.mil/about/history/first_50_years.aspx | publisher = DARPA | title = History | contribution = 50 Years of Bridging the Gap | date= Apr 2008}}</ref>

[[File:ConstellationGPS.gif|frame|A visual example of a 24 satellite [[GPS]] constellation in motion with the Earth rotating. Notice how the number of ''satellites in view'' from a given point on the Earth's surface, in this example at 45°N, changes with time. GPS was initially developed to increase Ballistic Missile [[Circular Error Probable]] accuracy, accuracy which is vital in a [[counterforce]] attack.<ref>{{cite web | publisher = CBO | url= https://www.cbo.gov/sites/default/files/cbofiles/ftpdocs/67xx/doc6714/78-cbo-012.pdf |title= Counterforce issues for the US strategic nuclear forces | year = 1978}}</ref><ref>{{cite web |url=http://web.mit.edu/stgs/pdfs/FordenBeiDouSatelliteArticle1.pdf | publisher = MIT | title= Strategic uses for China's Bei Dou satellite system | first = Geoffrey | last = Forden }}</ref><ref>{{cite web |url= http://home.earthlink.net/~loganscott53/Circular_Error_Probable.htm |title= Circular Error Probable (CEP) mathematics |first= Logan |last= Scott |publisher= Earth link |access-date= 8 March 2014 |archive-url= https://web.archive.org/web/20150102004917/http://home.earthlink.net/~loganscott53/Circular_Error_Probable.htm |archive-date= 2 January 2015 |url-status= dead }}</ref>]]

The first satellite navigation system, [[Transit (satellite)|Transit]], used by the [[United States Navy]], was first successfully tested in 1960. It used a constellation of five satellites and could provide a navigational fix approximately once per hour. In 1967, the US Navy developed the [[Timation]] satellite that proved the ability to place accurate clocks in space, a technology required by the latter [[Global Positioning System]].  In the 1970s, the ground-based [[Omega Navigation System]], based on phase comparison of signal transmission from pairs of stations,<ref>{{cite web| first =Jerry | last = Proc|url= http://www.jproc.ca/hyperbolic/omega.html |title=Omega|publisher=Jerry Proc | place = [[Canada|CA]] |access-date=8 December 2009}}</ref> became the first worldwide radio navigation system. Limitations of these systems drove the need for a more universal navigation solution with greater accuracy.

While there were wide needs for accurate navigation in military and civilian sectors, almost none of those was seen as justification for the billions of dollars it would cost in research, development, deployment, and operation for a constellation of navigation satellites. During the [[Cold War]] [[arms race]], the nuclear threat to the existence of the United States was the one need that did justify this cost in the view of the United States Congress. This deterrent effect is why GPS was funded. The [[nuclear triad]] consisted of the United States Navy's [[submarine-launched ballistic missile]]s (SLBMs) along with [[United States Air Force]] (USAF) strategic bombers and [[intercontinental ballistic missile]]s (ICBMs). Considered vital to the nuclear-deterrence posture, accurate determination of the SLBM launch position was a [[force multiplier]].

Precise navigation would enable United States [[submarine]]s to get an accurate fix of their positions before they launched their SLBMs.<ref name="Trimble Navigation Ltd"/> The USAF, with two-thirds of the nuclear triad, also had requirements for a more accurate and reliable navigation system.  The Navy and Air Force were developing their own technologies in parallel to solve what was essentially the same problem. To increase the survivability of ICBMs, there was a proposal to use mobile launch platforms (such as Russian [[SS-24]] and [[SS-25]]) and so the need to fix the launch position had similarity to the SLBM situation.

In 1960, the Air Force proposed a radio-navigation system called MOSAIC (MObile System for Accurate ICBM Control) that was essentially a 3-D&nbsp;[[LORAN]]. A follow-on study, Project&nbsp;57, was worked in 1963 and it was "in this study that the GPS concept was born". That same year, the concept was pursued as Project&nbsp;621B, which had "many of the attributes that you now see in GPS"<ref>{{cite web | date = Summer 2002 | url = http://www.aero.org/publications/crosslink/summer2002/01.html | title = Charting a Course Toward Global Navigation | publisher = The Aerospace Corporation | access-date = 14 January 2010 | archive-url = https://web.archive.org/web/20120119005341/http://www.aero.org/publications/crosslink/summer2002/01.html | archive-date = 19 January 2012 | url-status = dead }}</ref> and promised increased accuracy for Air Force bombers as well as ICBMs. Updates from the Navy Transit system were too slow for the high speeds of Air Force operation. The Navy Research Laboratory continued advancements with their Timation (Time Navigation) satellites, first launched in 1967, and with the third one in 1974 carrying the first atomic clock into orbit.<ref>{{cite web |url= http://support.radioshack.com/support_tutorials/gps/gps_tmline.htm |work= A Guide to the Global Positioning System (GPS) |title= GPS Timeline |publisher= Radio Shack |access-date= 14 January 2010 |url-status= dead |archive-url= https://web.archive.org/web/20100213100725/http://support.radioshack.com/support_tutorials/gps/gps_tmline.htm |archive-date= 13 February 2010 }}</ref>

Another important predecessor to GPS came from a different branch of the United States military. In 1964, the [[United States Army]] orbited its first Sequential Collation of Range ([[SECOR]]) satellite used for geodetic surveying. The SECOR system included three ground-based transmitters from known locations that would send signals to the satellite transponder in orbit.  A fourth ground-based station, at an undetermined position, could then use those signals to fix its location precisely. The last SECOR satellite was launched in 1969.<ref>{{cite encyclopedia|url=http://www.astronautix.com/craft/secor.htm|title=SECOR Chronology|first=Mark|last=Wade|encyclopedia=Encyclopedia Astronautica|publisher=Astronautix|access-date=19 January 2010|url-status=dead|archive-url=https://web.archive.org/web/20100116213013/http://astronautix.com/craft/secor.htm|archive-date=16 January 2010}}</ref> Decades later, during the early years of GPS, civilian surveying became one of the first fields to make use of the new technology, because surveyors could reap benefits of signals from the less-than-complete GPS constellation years before it was declared operational. GPS can be thought of as an evolution of the SECOR system where the ground-based transmitters have been migrated into orbit.{{citation needed|date=January 2020}}

==See also==
* [[History of nuclear weapons]]
* [[List of nuclear weapons]]
* [[Mutual assured destruction]] doctrine
* [[National missile defense]] of the United States
* [[Nuclear explosion]]
* [[Nuclear strategy]]
* [[Nuclear weapon design]]
* [[Nuclear terrorism]]

==Notes==
{{reflist|30em}}

==References==
* [http://alsos.wlu.edu/adv_rst.aspx?keyword=delivery*systems&creator=&title=&media=all&genre=all&disc=all&level=all&sortby=relevance&results=10&period=15 Annotated bibliography for nuclear weapon delivery systems from the Alsos Digital Library for Nuclear Issues]

==External links==

{{nuclear technology}}

[[Category:Nuclear weapons|*]]
[[Category:Nuclear missiles|*]]
[[Category:Nuclear weapon design|Delivery]]
[[Category:Missile operation]]