Editing LGM-30 Minuteman (section)

== History ==
[[File:Minuteman I.jpg|thumb|Minuteman I missile]]

=== Edward Hall and solid fuels ===
Minuteman owes its existence largely to Air Force Colonel [[Edward N. Hall]], who in 1956 was given charge of the solid-fuel-propulsion division of [[Bernard Adolph Schriever|General Bernard Schriever's]] [[Western Development Division]], created to lead development of the [[SM-65 Atlas]] and [[HGM-25A Titan I]] ICBMs. Solid fuels were already commonly used in short-range rockets. Hall's superiors were interested in [[short range ballistic missile|short-]] and [[medium range ballistic missile|medium]]-range missiles with solids, especially for use in Europe where the fast reaction time was an advantage for weapons that might be attacked by Soviet aircraft. But Hall was convinced that they could be used for a true ICBM with a {{convert|5500|nmi|adj=on}} range.<ref name="1990_MacKenzie" />{{rp|page=152}}

To achieve the required energy, that year Hall began funding research at [[Boeing]] and [[Thiokol]] into the use of [[ammonium perchlorate composite propellant]]. Adapting a concept developed in the [[United Kingdom|UK]], they cast the fuel into large cylinders with a star-shaped hole running along the inner axis. This allowed the fuel to burn along the entire length of the cylinder, rather than just the end as in earlier designs. The increased burn rate meant increased thrust. This also meant the heat was spread across the entire motor, instead of the end, and because it burned from the inside out it did not reach the wall of the missile fuselage until the fuel was finished burning. In comparison, older designs burned primarily from one end to the other, meaning that at any instant one small section of the fuselage was being subjected to extreme loads and temperatures.<ref name="Maugh" />

Guidance of an ICBM is based not only on the direction the missile is traveling but the precise instant that thrust is cut off. Too much thrust and the warhead will overshoot its target, too little and it will fall short. Solids are normally very hard to predict in terms of burn time and their instantaneous thrust during the burn, which made them questionable for the sort of accuracy required to hit a target at intercontinental range. While this initially appeared to be an insurmountable problem, it ended up being solved in an almost trivial fashion. A series of ports were added inside the rocket nozzle that were opened when the guidance systems called for engine cut-off. The reduction in pressure was so abrupt that the remaining fuel broke up and blew out the nozzle without contributing to the thrust.<ref name="Maugh" />

The first to use these developments was the US Navy. It had been involved in a joint program with the [[US Army]] to develop the liquid-fueled [[PGM-19 Jupiter]], but had always been skeptical of the system. The Navy felt that liquid fuels were too dangerous to use onboard ships, especially submarines. Rapid success in the solids development program, combined with [[Edward Teller]]'s promise of much lighter [[nuclear warhead]]s during [[Project Nobska]], led the Navy to abandon Jupiter and begin development of their own solid-fuel missile. Aerojet's work with Hall was adapted for their [[UGM-27 Polaris]] starting in December 1956.<ref name="2001Teller" />

===Missile farm concept===
The US Air Force saw no pressing need for a solid fuel ICBM. Development of the [[SM-65 Atlas]] and [[SM-68 Titan]] ICBMs was progressing, and "storable" ([[Hypergolic propellant|hypergolic]]) liquid propellants were being developed that would allow missiles to be left in a ready-to-shoot form for extended periods. These could be placed in [[missile silo]]s for added protection, and launch in minutes. This met their need for a weapon that would be safe from sneak attacks; hitting all of the silos within a limited time window before they could launch simply did not seem possible.<ref name="1990_MacKenzie" />{{rp|page=153}}

But Hall saw solid fuels not only as a way to improve launch times or survivability, but part of a radical plan to greatly reduce the cost of ICBMs so that thousands could be built. He envisioned a future where ICBMs were the primary weapon of the US, not in the supporting role of "last ditch backup" as the Air Force saw them at the time. This would require huge deployments, which would not be possible with existing weapons due to their high cost and operational manpower requirements. A solid fuel design would be simpler to build, and easier to maintain.<ref name="1990_MacKenzie" />{{rp|page=153}}

Hall's ultimate plan was to build a number of integrated missile "farms" that included factories, [[Missile launch facility|missile silos]], transport and recycling. He was aware that new computerized [[assembly line]]s would allow continual production, and that similar equipment would allow a small team to oversee operations for dozens or hundreds of missiles, radically reducing the manpower requirements. Each farm would support between 1,000 and 1,500 missiles being produced in a continuous low rate cycle. Systems in a missile would detect failures, at which point it would be removed and recycled, while a newly built missile would take its place.<ref name="1990_MacKenzie" />{{rp|page=153}} The missile design was based purely on lowest possible cost, reducing its size and complexity because "the basis of the weapon's merit was its low cost per completed mission; all other factors – accuracy, vulnerability, and reliability – were secondary."<ref name="1990_MacKenzie" />{{rp|page=154}}

Hall's plan did not go unopposed, especially by the more established names in the ICBM field. [[TRW Inc.|Ramo-Wooldridge]] pressed for a system with higher accuracy, but Hall countered that the missile's role was to attack Soviet cities, and that "a force which provides numerical superiority over the enemy will provide a much stronger deterrent than a numerically inferior force of greater accuracy."<ref name="1990_MacKenzie" />{{rp|page=154}} Hall was known for his "friction with others" and in 1958 Schriever removed him from the Minuteman project, sending him to the UK to oversee deployment of the [[PGM-17 Thor|Thor IRBM]].<ref name="1990_MacKenzie" />{{rp|page=152}} On his return to the US in 1959, Hall retired from the Air Force. He received his second [[Legion of Merit]] in 1960 for his work on solid fuels.<ref name="Maugh" />

Although he was removed from the Minuteman project, Hall's work on cost reduction had already produced a new design of {{convert|71|in|m}} diameter, much smaller than the Atlas and Titan at {{convert|120|in|m}}, which meant smaller and cheaper silos. Hall's goal of dramatic cost reduction was a success, although many of the other concepts of his missile farm were abandoned.<ref name="1990_MacKenzie" />{{rp|page=154}}

===Guidance system===
{{main|Missile guidance}}
[[File:Autonetics D-17.JPG|thumb|Autonetics D-17 guidance computer from a Minuteman I missile.]]

Previous long-range missiles used liquid fuels that could be loaded only just prior to firing. The loading process took from 30 to 60 minutes in typical designs. Although lengthy, this was not considered to be a problem at the time, because it took about the same amount of time to spin up the [[inertial guidance system]], set the initial position, and program in the target coordinates.<ref name="1990_MacKenzie" />{{rp|page=156}}

Minuteman was designed from the outset to be launched in minutes. While solid fuel eliminated the fueling delays, the delays in starting and aligning the guidance system remained. For the desired quick launch, the guidance system would have to be kept running and aligned at all times. This was a serious problem for the mechanical systems, especially the gyroscopes which used [[ball bearing]]s.<ref name="1990_MacKenzie" />{{rp|page=157}}

[[Autonetics]] had an experimental design using [[air bearing]]s that they claimed had been running continually from 1952 to 1957.<ref name="1990_MacKenzie" />{{rp|page=157}} Autonetics further advanced the [[state of the art]] by building the platform in the form of a ball which could rotate in two directions. Conventional solutions used a shaft with ball bearings at either end that allowed it to rotate around a single axis only. Autonetics' design meant that only two gyros would be needed for the inertial platform, instead of the typical three.<ref name="1990_MacKenzie" />{{rp|page=159}}{{NoteTag|A third gyro was later added for other reasons.<ref name="1990_MacKenzie" />{{rp|page=159}}}}

The last major advance was to use a general-purpose digital computer in place of the analog or custom designed digital computers. Previous missile designs normally used two single-purpose and very simple electromechanical computers; one ran the [[autopilot]] that kept the missile flying along a programmed course, and the second compared the information from the inertial platform to the target coordinates and sent any needed corrections to the autopilot. To reduce the total number of parts used in Minuteman, a single faster computer was used, running separate [[Function (computer programming)|subroutines]] for these functions.<ref name="1990_MacKenzie" />{{rp|page=160}}

Since the guidance program would not be running while the missile sat in the silo, the same computer was also used to run a program that monitored the various sensors and test equipment. With older designs this had been handled by external systems, requiring miles of extra wiring and many connectors to locations where test instruments could be connected during servicing. Now these could all be accomplished by communicating with the computer through a single connection. In order to store multiple programs, the computer, the [[D-17B]], was built in the form of a [[magnetic drum|drum machine]] but used a [[hard disk]] in place of the drum.<ref name="1990_MacKenzie" />{{rp|page=160}}

Building a computer with the required performance, size and weight demanded the use of [[transistor]]s, which were at that time very expensive and not very reliable. Earlier efforts to use computers for guidance, [[BINAC]] and the system on the [[SM-64 Navaho]], had failed and were abandoned. The Air Force and Autonetics spent millions on a program to improve transistor and component reliability 100 times, leading to the "Minuteman high-rel parts" specifications. The techniques developed during this program were equally useful for improving all transistor construction, and greatly reduced the failure rate of transistor production lines in general. This improved yield, which had the effect of greatly lowering production costs, had enormous spin-off effects in the electronics industry.<ref name="1990_MacKenzie" />{{rp|pages=160–161}}

Using a general-purpose computer also had long-lasting effects on the Minuteman program and the US's nuclear stance in general. With Minuteman, the targeting could be easily changed by loading new trajectory information into the computer's hard drive, a task that could be completed in a few hours. Earlier ICBMs' custom wired computers, on the other hand, could have attacked only a single target, whose precise trajectory information was hard-coded directly in the system's logic.<ref name="1990_MacKenzie" />{{rp|page=156}}

===Missile gap===
In 1957, a series of intelligence reports suggested the Soviet Union was far ahead in the missile race and would be able to overwhelm the US by the early 1960s. If the Soviets were building missiles in the numbers being predicted by the CIA and others within the defense establishment, by as early as 1961 they would have enough to attack all SAC and ICBM bases in the US in a single [[Pre-emptive nuclear strike|first strike]]. It was later demonstrated that this "[[missile gap]]" was just as fictional as the "[[bomber gap]]" of a few years earlier,<ref name="myths">{{cite web |first=Dwane |last=Day |url = http://www.thespacereview.com/article/523/1 |title = Of myths and missiles: the truth about John F. Kennedy and the Missile Gap |website = The Space Review |date=3 January 2006 }}</ref> but through the late 1950s, it was a serious concern.

The Air Force responded by beginning research into survivable strategic missiles, starting the [[WS-199]] program. Initially, this focused on [[air-launched ballistic missile]]s, which would be carried aboard aircraft flying far from the Soviet Union, and thus impossible to attack by either ICBM, because they were moving, or long-range [[interceptor aircraft]], because they were too far away. In the shorter term, looking to rapidly increase the number of missiles in its force, Minuteman was given crash development status starting in September 1958. Advanced surveying of the potential silo sites had already begun in late 1957.<ref name="2010_Yengst" />{{rp|page=46}}

Adding to their concerns was a Soviet [[anti-ballistic missile]] system which was known to be under development at [[Sary Shagan]]. WS-199 was expanded to develop a [[maneuvering reentry vehicle]] (MARV), which greatly complicated the problem of shooting down a warhead. Two designs were tested in 1957, [[Alpha Draco]] and the Boost Glide Reentry Vehicle. These used long and skinny arrow-like shapes that provided aerodynamic lift in the high atmosphere, and could be fitted to existing missiles like Minuteman.<ref name="2010_Yengst" />

The shape of these reentry vehicles required more room on the front of the missile than a traditional reentry vehicle design. To allow for this future expansion, the Minuteman silos were revised to be built {{convert|13|feet}} deeper. Although Minuteman would not deploy a [[boost-glide]] warhead, the extra space proved invaluable in the future, as it allowed the missile to be extended and carry more fuel and payload.<ref name="2010_Yengst" />{{rp|page=46}}

===Polaris===
{{main|UGM-27 Polaris}}
[[File:Polaris missile launch from HMS Revenge (S27) 1983.JPEG|thumb|The Polaris SLBM could ostensibly fill the role of the Minuteman, and was perceived as significantly less vulnerable to attack.]]

During Minuteman's early development, the Air Force maintained the policy that the manned [[strategic bomber]] was the primary weapon of nuclear war. Blind bombing accuracy on the order of {{convert|1500|feet|km}} was expected, and the weapons were sized to ensure even the hardest targets would be destroyed as long as the weapon fell within this range. The USAF had enough bombers to attack every military and industrial target in the USSR and was confident that its bombers would survive in sufficient numbers that such a strike would utterly destroy the country.<ref name="1990_MacKenzie" />{{rp|page=202}}

Soviet ICBMs upset this equation to a degree. Their accuracy was known to be low, on the order of {{convert|4|nmi}}, but they carried large warheads that would be useful against [[Strategic Air Command]]'s bombers, which parked in the open. Since there was no system to detect the ICBMs being launched, the possibility was raised that the Soviets could launch a sneak attack with a few dozen missiles that would take out a significant portion of SAC's bomber fleet.<ref name="1990_MacKenzie" />{{rp|page=202}}

In this environment, the Air Force saw their own ICBMs not as a primary weapon of war, but as a way to ensure that the Soviets would not risk a sneak attack. ICBMs, especially newer models that were housed in silos, could be expected to survive an attack by a single Soviet missile. In any conceivable scenario where both sides had similar numbers of ICBMs, the US forces would survive a sneak attack in sufficient numbers to ensure the destruction of all major Soviet cities in return. The Soviets would not risk an attack under these conditions.<ref name="1990_MacKenzie" />{{rp|page=202}}

Considering this ''[[countervalue]]'' attack concept, strategic planners calculated that an attack of "400 equivalent megatons" aimed at the largest Soviet cities would promptly kill 30% of their population and destroy 50% of their industry. Larger attacks raised these numbers only slightly, as all of the larger targets would already have been hit. This suggested that there was a "[[finite deterrent]]" level around 400 megatons that would be enough to prevent a Soviet attack no matter how many missiles they had of their own. All that had to be ensured was that the US missiles survived, which seemed likely given the low accuracy of the Soviet weapons.<ref name="1990_MacKenzie" />{{rp|page=199}} Reversing the problem, the addition of ICBMs to the US Air Force's arsenal did not eliminate the need, or desire, to attack Soviet military targets, and the Air Force maintained that bombers were the only suitable platform in that role.<ref name="1990_MacKenzie" />{{rp|page=199}}

Into this argument came the Navy's [[UGM-27 Polaris]]. Launched from submarines, Polaris was effectively invulnerable and had enough accuracy to attack Soviet cities. If the Soviets improved the accuracy of their missiles this would present a serious threat to the Air Force's bombers and missiles, but none at all to the Navy's submarines. Based on the same 400 equivalent megatons calculation, they set about building a fleet of 41 submarines carrying 16 missiles each, giving the Navy a finite deterrent that was unassailable.<ref name="1990_MacKenzie" />{{rp|page=197}}

This presented a serious problem for the Air Force. They were still pressing for the development of newer bombers, like the supersonic [[North American XB-70 Valkyrie|B-70]], for attacks against military targets, but this role seemed increasingly unlikely in a nuclear war scenario. A February 1960 memo by [[RAND]], entitled "The Puzzle of Polaris", was passed around among high-ranking Air Force officials. It suggested that Polaris negated any need for Air Force ICBMs if they were also being aimed at Soviet cities. If the role of the missile was to present an unassailable threat to the Soviet population, Polaris was a far better solution than Minuteman. The document had long-lasting effects on the future of the Minuteman program, which, by 1961, was firmly evolving towards a [[counterforce]] capability.<ref name="1990_MacKenzie" />{{rp|page=197}}

===Kennedy===
Minuteman's final tests coincided with the start of [[John F. Kennedy]]'s presidency. His new [[United States Secretary of Defense|Secretary of Defense]], [[Robert McNamara]], was tasked with continuing the expansion and modernisation of the US nuclear deterrent while limiting spending. McNamara began to apply [[cost/benefit analysis]], and Minuteman's low production cost ensured its selection. Atlas and Titan were soon scrapped, and the storable liquid fueled [[LGM-25C Titan II|Titan II]] deployment was severely curtailed.<ref name="1990_MacKenzie" />{{rp|page=154}} McNamara also cancelled the [[North American XB-70 Valkyrie|XB-70]] bomber project.<ref name="1990_MacKenzie" />{{rp|page=203}}

Minuteman's low cost had spin-off effects on non-ICBM programs. The Army's [[LIM-49 Nike Zeus]], an interceptor missile capable of shooting down Soviet warheads, provided another way to prevent a sneak attack. This had initially been proposed as a way to defend the SAC bomber fleet. The Army argued that upgraded Soviet missiles might be able to attack US missiles in their silos, and Zeus would be able to blunt such an attack. Zeus was expensive and the Air Force said it was more cost-effective to build another Minuteman missile. Given the large size and complexity of the Soviet liquid-fueled missiles, an ICBM building race was one the Soviets could not afford. Zeus was canceled in 1963.<ref name="2008_Kaplan" />

===Counterforce===
{{main|Counterforce|Pre-emptive nuclear strike}}
Minuteman's selection as the primary Air Force ICBM was initially based on the same "[[second strike]]" logic as their earlier missiles: that the weapon was primarily one designed to survive any potential Soviet attack and ensure they would be hit in return. But Minuteman had a combination of features that led to its rapid evolution into the US's primary weapon of nuclear war.

Chief among these qualities was its digital computer, the D-17B. This could be updated in the field with new targets and better information about the flight paths with relative ease, gaining accuracy for little cost. One of the unavoidable effects on the warhead's trajectory was the mass of the Earth, which contains many [[mass concentration (astronomy)|mass concentrations]] that pull on the warhead as it passes over them. Through the 1960s, the Defense Mapping Agency (now part of [[National Geospatial-Intelligence Agency]]) mapped these with increasing accuracy, feeding that information back into the Minuteman fleet. The Minuteman was initially deployed with a [[circular error probable]] (CEP) of about {{convert|1.1|nmi}}, but this had improved to about {{convert|0.6|nmi}} by 1965.<ref name="1990_MacKenzie" />{{rp|page=166}} This was accomplished without any mechanical changes to the missile or its navigation system.<ref name="1990_MacKenzie" />{{rp|page=156}}

At those levels, the ICBM begins to approach the manned bomber in terms of accuracy; a small upgrade, roughly doubling the accuracy of the INS, would give it the same {{convert|1500|feet}} CEP as the manned bomber. Autonetics began such development even before the original Minuteman entered fleet service, and the Minuteman II had a CEP of {{convert|0.26|nmi}}. Additionally, the computers were upgraded with more memory, allowing them to store information for eight targets, which the missile crews could select among almost instantly, greatly increasing their flexibility.<ref name="1990_MacKenzie" />{{rp|page=152}} From that point, Minuteman became the US's primary deterrent weapon, until its performance was matched by the Navy's [[Trident (missile)|Trident missile]] of the 1980s.<ref name="2010_Brookings" />

Questions about the need for the manned bomber were quickly raised. The Air Force began to offer a number of reasons why the bomber offered value, in spite of costing more money to buy and being much more expensive to operate and maintain. Newer bombers with better survivability, like the [[North American XB-70 Valkyrie|B-70]], cost many times more than the Minuteman, and, in spite of great efforts through the 1960s, became increasingly vulnerable to [[surface-to-air missile]]s. The [[Rockwell B-1 Lancer|B-1]] of the early 1970s eventually emerged with a price tag around $200 million (equivalent to ${{Inflation|US-GDP|200|1980|fmt=c|r=-2}} million in {{Inflation-year|US-GDP}}){{Inflation-fn|US-GDP}} while the Minuteman IIIs built during the 1970s cost only $7 million (${{Inflation|US-GDP|7|1978|fmt=c|r=-1}} million in {{Inflation-year|US-GDP}}).{{citation needed|date=May 2016}}

The Air Force countered that having a variety of platforms complicated the defense; if the Soviets built an effective [[anti-ballistic missile]] system of some sort, the ICBM and SLBM fleet might be rendered useless, while the bombers would remain. This became the [[nuclear triad]] concept, which survives into the present. Although this argument was successful, the number of manned bombers has been repeatedly cut and the deterrent role increasingly passed to missiles.<ref name="2009_Triad" />

=== Minuteman I (LGM-30A/B or SM-80/HSM-80A) ===
:''See also [[W56|W56 Warhead]]''

==== Deployment ====
The '''LGM-30A Minuteman I''' was first test-fired on 1 February 1961 at [[Cape Canaveral Air Force Station|Cape Canaveral]],<ref name="bbthmj" /><ref name="mmmfs61" /><ref name="6555th" /><ref name="lmtpit" /> entering into the [[Strategic Air Command]]'s arsenal in 1962. After the first batch of Minuteman I's were fully developed and ready for stationing, the [[United States Air Force]] (USAF) had originally decided to put the missiles at [[Vandenberg AFB]] in California, but before the missiles were set to officially be moved there it was discovered that this first set of Minuteman missiles had defective boosters which limited their range from their initial {{convert|6300|mi}} to {{convert|4300|mi}}. This defect would cause the missiles to fall short of their targets if launched over the [[North Pole]] as planned. The decision was made to station the missiles at [[Malmstrom AFB]] in [[Montana]] instead.<ref name="mmmfs61" /> These changes would allow the missiles, even with their defective boosters, to reach their intended targets in the case of a launch.<ref name="1996_dtic" />

The "improved" '''LGM-30B''' '''Minuteman I''' became operational at [[Ellsworth AFB]], [[South Dakota]], [[Minot AFB]], [[North Dakota]], [[F.E. Warren AFB]], [[Wyoming]], and [[Whiteman AFB]], [[Missouri]], in 1963 and 1964. All 800 Minuteman I missiles were delivered by June 1965. Each of the bases had 150 missiles emplaced; F.E. Warren had 200 of the Minuteman IB missiles. Malmstrom had 150 of the Minuteman I, and about five years later added 50 of the Minuteman II similar to those installed at [[Grand Forks AFB]], ND.

==== Specifications ====
The Minuteman I's length varied based on which variation one was to look at. The Minuteman I/A had a length of {{convert|53|ft|8|in|m|abbr=on|sp=us}} and the Minuteman I/B had a length of {{convert|55|ft|11|in|m|abbr=on|sp=us}}. The Minuteman I weighed roughly {{convert|65000|lb|kg|abbr=on|sp=us}}, had an operational range of {{convert|5500|nmi|mi km|abbr=on|sp=us}}<ref name="FAS_LGM-30-1" /> with an accuracy of about {{convert|1.5|mi|km|abbr=on|sp=us}}.<ref name="1996_dtic" /><ref name="2009_Polmar" /><ref name="1963_Bowman" />

==== Guidance ====
The Minuteman I Autonetics [[D-17B|D-17 flight computer]] used a rotating air bearing magnetic disk holding 2,560 "cold-stored" [[Word (computer architecture)|words]] in 20 tracks (write heads disabled after program fill) of 24 bits each and one alterable track of 128 words. The time for a D-17 disk revolution was 10 ms. The D-17 also used a number of short loops for faster access to intermediate results storage. The D-17 computational minor cycle was three disk revolutions or 30 ms. During that time all recurring computations were performed. For ground operations, the inertial platform was aligned and gyro correction rates updated.

During a flight, filtered command outputs were sent by each minor cycle to the engine nozzles. Unlike modern computers, which use descendants of that technology for [[secondary storage]] on [[hard disk]], the disk was the active [[computer memory]]. The disk storage was considered hardened to radiation from nearby nuclear explosions, making it an ideal storage medium. To improve computational speed, the D-17 borrowed an instruction look-ahead feature from the Autonetics-built Field Artillery Data Computer ([[M18 FADAC]]) that permitted simple instruction execution every word time.

==== Warhead ====
At its introduction into service in 1962, Minuteman I was fitted with the [[W59]] warhead with a yield of 1 Mt. Production for the W56 warhead with a 1.2 Mt yield began in March 1963 and W59 production was ended in July 1963 with a production run of only 150 warheads before being retired in June 1969. The W56 would continue production until May 1969 with a production run of 1000 warheads. Mods 0 to 3 were retired by September 1966 and the Mod 4 version would remain in service until the 1990s.<ref name=AtomArch>{{cite web|title=Complete List of All U.S. Nuclear Weapons|url=http://nuclearweaponarchive.org/Usa/Weapons/Allbombs.html|publisher=Nuclear Weapons Archive|access-date=12 April 2020}}</ref>

It's not clear exactly why the W59 was replaced by the W56 after deployment but issues with "... one-point safety" and "performance under aged conditions" were cited in a 1987 congressional report regarding the warhead.<ref name=CongReport>{{cite report |last1=Miller | first1=G.H.|last2=Brown|first2=P.S.|last3=Alonso|first3=C.T.|date=1987 |title=Report to Congress on stockpile reliability, weapon remanufacture, and the role of nuclear testing | osti=6032983|url=https://www.osti.gov/scitech/biblio/6032983 }}</ref> [[Chuck Hansen]] alleged that all weapons sharing the [[Tsetse (nuclear primary)|"Tsetse" nuclear primary]] design including the W59 suffered from a critical one-point safety issue and suffered premature tritium aging issues that needed to be corrected after entry into service.<ref name=Hansen>{{cite book | last = Hansen | first = Chuck | title = The Swords of Armageddon |volume=VI | publisher = Chukelea Publications | year = 1995a }}</ref>

=== Minuteman II (LGM-30F) ===
:''See also [[W56|W56 warhead]]''
[[File:Minuteman guidance computer (1).jpg|thumb|The guidance system of the Minuteman II was much smaller due to the use of integrated circuits. The inertial platform is in the top bay.]]

The LGM-30F Minuteman II was an improved version of the Minuteman I missile. Its first test launch took place on September 24, 1964. Development on the Minuteman II began in 1962 as the Minuteman I entered the Strategic Air Command's nuclear force. Minuteman II production and deployment began in 1965 and completed in 1967. It had an increased range, greater [[throw weight]] and guidance system with better azimuthal coverage, providing military planners with better accuracy and a wider range of targets. Some missiles also carried penetration aids, allowing the higher probability of kill against [[A-35 anti-ballistic missile system|Moscow's anti-ballistic missile system]]. The payload consisted of a single Mk-11C reentry vehicle containing a [[W56]] nuclear warhead with a yield of 1.2 megatons of TNT (5 [[petajoule|PJ]]).

==== Specifications ====
The Minuteman II had a length of {{convert|57|ft|7|in|m|abbr=on|sp=us}}, weighed roughly {{convert|73000|lb|kg|abbr=on|sp=us}}, had an operational range of {{convert|10200|km|abbr=on|sp=us|order=flip}}{{sfn|Sandia Weapon Review: Nuclear Weapon Characteristics Handbook|p=65}} with an accuracy of about {{convert|1|mi|km|abbr=on|sp=us}}.<ref name="1996_dtic" /><ref name="2009_Polmar" />

The major new features provided by Minuteman II were:

* An improved first-stage motor to increase reliability.
* A novel, single, fixed [[nozzle]] with liquid injection thrust vector control on a larger second-stage motor to increase missile range. Additional motor improvements to increase reliability.
* An improved guidance system (the [[D-37C|D-37 flight computer]]), incorporating [[microchips]] and miniaturized discrete electronic parts. Minuteman II was the first program to make a major commitment to these new devices. Their use made possible multiple target selection, greater accuracy and reliability, a reduction in the overall size and weight of the guidance system, and an increase in the survivability of the guidance system in a nuclear environment. The guidance system contained 2,000 microchips made by [[Texas Instruments]].
* A penetration aids system to camouflage the warhead during its reentry into an enemy environment. In addition, the Mk-11C reentry vehicle incorporated stealth features to reduce its radar signature and make it more difficult to distinguish from decoys. The Mk-11C was no longer made of titanium for this and other reasons.<ref name="2014_Isaacson" />
* A larger warhead in the reentry vehicle to increase kill probability.

System modernization was concentrated on [[launch facility|launch facilities]] and [[command and control]] facilities. This provided decreased reaction time and increased survivability when under nuclear attack. Final changes to the system were performed to increase compatibility with the expected [[LGM-118A Peacekeeper]]. These newer missiles were later deployed into modified Minuteman silos.

The Minuteman II program was the first mass-produced system to use a computer constructed from integrated circuits (the [[Autonetics]] [[D-37C]]). The Minuteman II integrated circuits were [[diode–transistor logic]] and [[diode logic]] made by [[Texas Instruments]]. The other major customer of early integrated circuits was the [[Apollo Guidance Computer]], which had similar weight and ruggedness constraints. The Apollo integrated circuits were [[resistor–transistor logic]] made by [[Fairchild Semiconductor]]. The Minuteman II flight computer continued to use rotating magnetic disks for primary storage. The Minuteman II included [[diode]]s by [[Microsemi Corporation]].<ref name="1964_microsemi" />

=== Minuteman III (LGM-30G) {{anchor|Minuteman-III|LGM-30G|Minuteman-III (LGM-30G)|reason=For wiki redirects}} ===
[[File:Minuteman-3 Museum.jpg|thumb|Minuteman III]]
[[File:Minuteman III diagram.png|thumb|Side view of Minuteman III ICBM]]
[[File:Minuteman_III_RVs.jpg|thumb|[[Airman|Airmen]] work on a Minuteman III's multiple independently-targetable re-entry vehicle (MIRV) system. Current missiles carry a single warhead.]]
:''See also [[W62|W62 warhead]]''
The LGM-30G Minuteman III program started in 1966 and included several improvements over the previous versions. Its first test launch took place on August 16, 1968. It was first deployed in 1970. Most modifications related to the final stage and reentry system (RS). The final (third) stage was improved with a new fluid-injected motor, giving finer control than the previous four-nozzle system.
Performance improvements realized in Minuteman III include increased flexibility in reentry vehicle (RV) and penetration aids deployment, increased survivability after a nuclear attack, and increased payload capacity. The missile retains a [[gimbal]]led [[inertial navigation system]].

Minuteman III originally contained the following distinguishing features:

* Armed with up to three [[W62]] Mk-12 warheads, having a yield of only 170 kilotons TNT, instead of previous [[W56]]'s yield of 1.2 megatons.<ref name="usa-archive" /><ref>{{cite web|title=Minuteman Missile Nuclear Warheads|url=https://minutemanmissile.com/nuclearwarheads.html|access-date=2020-07-21|website=minutemanmissile.com}}</ref><ref>{{cite web|title=The W62 Warhead|url=https://nuclearweaponarchive.org/Usa/Weapons/W62.html|access-date=2020-07-21|website=nuclearweaponarchive.org}}</ref>
* It was the first<ref name="gwu.edu" /> missile equipped with [[multiple independently targetable reentry vehicle]]s (MIRV). A single missile was then able to target three separate locations. This was an improvement from the Minuteman I and Minuteman II models, which were able to carry only one large warhead.
** An RS capable of deploying, in addition to the warheads, [[penetration aid]]s such as [[Chaff (radar countermeasure)|chaff]] and [[decoy]]s.
** Minuteman III introduced in the post-boost-stage ("bus") an additional liquid-fuel propulsion system rocket engine (PSRE) that is used to slightly adjust the [[trajectory]]. This enables it to dispense decoys or – with MIRV – dispense individual RVs to separate targets. For the PSRE it uses the bipropellant Rocketdyne RS-14 engine.
* The Hercules M57 third stage of Minuteman I and Minuteman II had thrust termination ports on the sides. These ports, when opened by detonation of shaped charges, reduced the chamber pressure so abruptly that the interior flame was blown out. This allowed a precisely timed termination of thrust for targeting accuracy. The larger Minuteman III third-stage motor also has thrust termination ports although the final velocity is determined by PSRE.
* A fixed nozzle with a liquid injection thrust vector control system on the new third-stage motor (similar to the second-stage Minuteman II nozzle) additionally increased range.
* A flight computer (Autonetics [[D37D]]) with larger disk memory and enhanced capability.
** A Honeywell HDC-701 flight computer which employed non-destructive readout [[plated-wire memory]] instead of rotating magnetic disk for primary storage was developed as a backup for the D37D but was never adopted.
** The Guidance Replacement Program, initiated in 1993, replaced the disk-based D37D flight computer with a new one that uses [[radiation hardened|radiation-resistant]] [[semiconductor]] [[RAM]].

The Minuteman III missiles use D-37D computers and complete the 1,000 missile deployment of this system. The initial cost of these computers range from about $139,000 (D-37C) to $250,000 (D-17B).

[[File:Minuteman III MIRV path.svg|thumb|Minuteman III [[MIRV]] launch sequence:<br />
1. The missile launches out of its silo by firing its 1st-stage boost motor (''A'').<br />
2. About 60 seconds after launch, the 1st stage drops off and the 2nd-stage motor (''B'') ignites. The missile shroud (''E'') is ejected.<br />
3. About 120 seconds after launch, the 3rd-stage motor (''C'') ignites and separates from the 2nd stage.<br />
4. About 180 seconds after launch, 3rd-stage thrust terminates and the Post-Boost Vehicle (''D'') separates from the rocket.<br />
5. The Post-Boost Vehicle maneuvers itself and prepares for re-entry vehicle (RV) deployment.<br />
6. The RVs, as well as decoys and chaff, are deployed during back away.<br />
7. The RVs and chaff re-enter the atmosphere at high speeds and are armed in flight.<br />
8. The nuclear warheads initiate, either as air bursts or ground bursts.]]

The existing Minuteman III missiles have been further improved over the decades in service, with more than $7 billion spent in the 2010s to upgrade the 450 missiles.<ref name="2012_Pampe" />

==== Specifications ====
The Minuteman III has a length of {{convert|59.9|ft|m|abbr=on|sp=us}},<ref name="FAS_LGM-30-3" /> weighs {{convert|79,432|lb|kg|abbr=on|sp=us}},<ref name="FAS_LGM-30-3" /> an operational range of {{convert|14000|km|abbr=on|sp=us|order=flip}},{{sfn|Sandia Weapon Review: Nuclear Weapon Characteristics Handbook|p=74}} and an accuracy of about {{convert|800|ft|m|abbr=on|sp=us}}.<ref name="1996_dtic" /><ref name="2009_Polmar" />

==== W78 warhead ====
In December 1979 the higher-yield [[W78]] warhead (335–350 kilotons) began replacing a number of the W62s deployed on the Minuteman IIIs.<ref name="NWA20010901" /> These were delivered in the Mark 12A reentry vehicle. A small, unknown number of the previous Mark 12 RVs were retained operationally, however, to maintain a capability to attack more-distant targets in the south-central Asian republics of the [[USSR]] (the Mark 12 RV weighed slightly less than the Mark 12A).

==== Guidance Replacement Program ====
The Guidance Replacement Program replaces the NS20A Missile Guidance Set with the NS50 Missile Guidance Set. The newer system extends the service life of the Minuteman missile beyond the year 2030 by replacing aging parts and assemblies with current, high reliability technology while maintaining the current accuracy performance. The replacement program was completed 25 February 2008.<ref name="irconnect1"/>

==== Propulsion Replacement Program ====
Beginning in 1998 and continuing through 2009,<ref name="2006_ATK" /> the Propulsion Replacement Program extends the life and maintains the performance by replacing the old solid propellant boosters (downstages).

==== Single Reentry Vehicle ====
The Single Reentry Vehicle modification enabled the United States ICBM force to abide by the now-voided [[START II]] treaty requirements by reconfiguring Minuteman III missiles from three reentry vehicles down to one. Though it was eventually ratified by both parties, START II never entered into force and was essentially superseded by follow-on agreements such as [[Strategic Offensive Reductions Treaty|SORT]] and [[New START]], which do not limit MIRV capability. Minuteman III remains fitted with a single warhead due to the warhead limitations in New START.

==== Safety Enhanced Reentry Vehicle ====
Beginning in 2005, Mk-21/[[W87]] RVs from the deactivated [[LGM-118 Peacekeeper|Peacekeeper]] missile were replaced on the Minuteman III force under the Safety Enhanced Reentry Vehicle (SERV) program. The older [[W78]] did not have many of the safety features of the newer W87, such as [[Insensitive munition|insensitive high explosives]], as well as more advanced safety devices. In addition to implementing these safety features in at least a portion of the future Minuteman III force, the decision to transfer W87s onto the missile was based on two features that improved the targeting capabilities of the weapon: more [[Fuze|fuzing]] options which allowed for greater targeting flexibility, and the most accurate reentry vehicle available, which provided a greater probability of damage to the designated targets.

==== Deployment ====
The Minuteman III missile entered service in 1970, with weapon systems upgrades included during the production run from 1970 to 1978 to increase accuracy and payload capacity. {{As of|2024|06}}, the USAF plans to operate it until the mid-2030s.<ref name="MMIII_Test" />

The [[LGM-118 Peacekeeper|LGM-118A Peacekeeper]] (MX) ICBM, which was to have replaced the Minuteman, was retired in 2005 as part of [[START II]].

A total of 450 LGM-30G missiles are emplaced at [[F.E. Warren Air Force Base]], [[Wyoming]] ([[90th Missile Wing]]), [[Minot Air Force Base]], [[North Dakota]] ([[91st Missile Wing]]), and [[Malmstrom Air Force Base]], [[Montana]] ([[341st Missile Wing]]). All Minuteman I and Minuteman II missiles have been retired. The United States prefers to keep its MIRV deterrents on submarine-launched [[Trident Missile|Trident Nuclear Missiles]]<ref name="2019_Navy_Trident" /> In 2014, the Air Force decided to put fifty Minuteman III silos into "warm" unarmed status, taking up half of the 100 slots in America's allowable nuclear reserve. These can be reloaded in the future if necessary.<ref name="2014_Kirstensen_Obama_Weakens_START" />

==== Testing ====
[[File:Minuteman III in silo 1989.jpg|thumb|A Minuteman III missile in its silo]]
Minuteman III missiles are regularly tested with launches from [[Vandenberg Space Force Base]] in order to validate the effectiveness, readiness, and accuracy of the weapon system, as well as to support the system's primary purpose, [[Deterrence theory|nuclear deterrence]].<ref>{{cite news |last=Burns |first=Robert |date=26 February 2016 |title=U.S. continues to test Cold War-era Minuteman missiles |url=http://www.pressherald.com/2016/02/26/u-s-continues-to-test-cold-war-era-minuteman-missiles/ |newspaper=Portland Press Herald |location=Portland, Oregon |access-date=13 August 2016 |archive-url=https://web.archive.org/web/20160825194801/http://www.pressherald.com/2016/02/26/u-s-continues-to-test-cold-war-era-minuteman-missiles/ |archive-date=25 August 2016 |url-status=live }}</ref> The safety features installed on the Minuteman III for each test launch allow the flight controllers to terminate the flight at any time if the systems indicate that its course may take it unsafely over inhabited areas.<ref>{{cite news |author=<!--Staff writer(s); no by-line.--> |title=Minuteman Test Firing Aborted Over Pacific |url=https://www.latimes.com/archives/la-xpm-1985-02-06-mn-4340-story.html |newspaper=Los Angeles Times |location=Los Angeles, California |date=6 February 1985 |access-date=13 August 2016 |archive-url=https://web.archive.org/web/20160827144925/http://articles.latimes.com/1985-02-06/news/mn-4340_1_minuteman-iii |archive-date=27 August 2016 |url-status=live }}</ref> Since these flights are for test purposes only, even terminated flights can send back valuable information to correct a potential problem with the system.

The test of an unarmed Minuteman III failed on November 1, 2023, from Vandenberg Space Force Base, California. The U.S. Air Force said it had blown up the missile over the Pacific Ocean after an anomaly was detected following its launch.<ref>{{cite web | url=https://www.airandspaceforces.com/icbm-test-failure-nuclear-modernization/ | title=ICBM Test Failure Puts Nuclear Modernization Effort into Focus | date=3 November 2023 }}</ref><ref>{{cite web | url=https://www.reuters.com/world/us/us-air-force-blows-up-minuteman-iii-test-flight-after-post-launch-anomaly-2023-11-01/ | title=US Air Force blows up Minuteman III in test flight after post-launch anomaly | work=Reuters }}</ref>

The [[576th Flight Test Squadron]] is responsible for planning, preparing, conducting, and assessing all ICBM ground and flight tests.