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28-506: An intercontinental missile, the R-39 had a three-stage solid-fuel boost design with a liquid-fuel post-boost unit carrying up to ten multiple independently targetable reentry vehicle warheads. Like other SLBMs the initial launch was powered by a gas generator in the bottom of the firing tube. During the missile's passage through the water additional motors produce a gaseous wall around the missile, reducing hydrodynamic resistance. The launch system

56-438: A ballistic missile deploys multiple warheads above a single aimpoint which then drift apart, producing a cluster bomb-like effect. These warheads are not individually targetable. The advantage of an MRV over a single warhead is the increased effectiveness due to the greater coverage; this increases the overall damage produced within the center of the pattern, making it far greater than the damage possible from any single warhead in

84-484: A covert purpose to map mass concentrations and determine local gravity anomalies , in order to improve accuracies of ballistic missiles. Accuracy is expressed as circular error probable (CEP). This is the radius of the circle that the warhead has a 50 percent chance of falling into when aimed at the center. CEP is about 90–100 m for the Trident II and Peacekeeper missiles. A multiple re-entry vehicle (MRV) system for

112-612: A factor of 6 while the Soviets increased theirs by a factor of 10. Furthermore, the US had a much smaller proportion of its nuclear arsenal in ICBMs than the Soviets. Bombers could not be outfitted with MIRVs so their capacity would not be multiplied. Thus the US did not seem to have as much potential for MIRV usage as the Soviets. However, the US had a larger number of submarine-launched ballistic missiles , which could be outfitted with MIRVs, and helped offset

140-605: A miniaturized physics package and a lower mass re-entry vehicle, both of which are highly advanced technologies. As a result, single-warhead missiles are more attractive for nations with less advanced or less productive nuclear technology. The United States first deployed MRV warheads on the Polaris A-3 SLBM in 1964 on the USS Daniel Webster . The Polaris A-3 missile carried three warheads each having an approximate yield of 200 kilotonnes of TNT (840 TJ). This system

168-459: A new Oreshnik intermediate-range ballistic missile , striking Dnipro . Analysts stated the missile used a multiple independently targetable reentry vehicle (MIRV), likely marking their first use in combat. The night attack was reported to see six sequential vertical flashes, each comprising a cluster of up to six individual projectiles. Ukraine's air force initially claimed an intercontinental ballistic missile (range greater than 5,500 km)

196-497: A single warhead; ABMs have to be deployed in a spread-out fashion so that one can respond no matter where the warhead appears. Even if a single ABM is needed to shoot down that single new missile, that single new ABM would be needed to be added to multiple bases depending on their range. For short-range weapons like the Sprint , dozens are needed for every new Soviet warhead. Through the 1950s and 60s there were intense ongoing debates about

224-504: A succession of testing failures and was cancelled. Multiple independently targetable reentry vehicle A multiple independently targetable reentry vehicle ( MIRV ) is an exoatmospheric ballistic missile payload containing several warheads , each capable of being aimed to hit a different target. The concept is almost invariably associated with intercontinental ballistic missiles carrying thermonuclear warheads , even if not strictly being limited to them. An intermediate case

252-409: Is crucial because doubling the accuracy decreases the needed warhead energy by a factor of four for radiation damage and by a factor of eight for blast damage. Navigation system accuracy and the available geophysical information limits the warhead target accuracy. Some writers believe that government-supported geophysical mapping initiatives and ocean satellite altitude systems such as Seasat may have

280-571: Is the multiple reentry vehicle (MRV) missile which carries several warheads which are dispersed but not individually aimed. All nuclear-weapon states except Pakistan and North Korea are currently confirmed to have deployed MIRV missile systems. The first true MIRV design was the Minuteman III , first successfully tested in 1968 and introduced into actual use in 1970. The Minuteman III held three smaller W62 warheads, with yields of about 170 kilotons of TNT (710 TJ) each in place of

308-456: The cost-exchange ratio is the ratio of the incremental cost to the aggressor of getting one additional warhead through the defence screen, divided by the incremental cost to the defender of offsetting the additional missile. For instance, a single new ICBM might require a single new ABM to counter it, and if they both cost the same, the cost-exchange ratio would be 1:1. Throughout the Cold War ,

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336-624: The 1972 Anti-Ballistic Missile Treaty in order to avoid a massive arms race . In June 2017 the United States finished converting its Minuteman III missiles back to using a single reentry vehicle system, as part of its obligations under the New START treaty. The military purpose of a MIRV is fourfold: MIRV land-based ICBMs were considered destabilizing because they tended to put a premium on striking first . The world's first MIRV—US Minuteman III missile of 1970—threatened to rapidly increase

364-608: The ICBM disadvantage. It is because of their first-strike capability that land-based MIRVs were banned under the START II agreement. START II was ratified by the Russian Duma on 14 April 2000, but Russia withdrew from the treaty in 2002 after the US withdrew from the ABM treaty . In a MIRV, the main rocket motor (or booster ) pushes a "bus" into a free-flight suborbital ballistic flight path. After

392-498: The MRV cluster; this makes for an efficient area-attack weapon and makes interception by anti-ballistic missiles more challenging due to the number of warheads being deployed at once. Improved warhead designs allow smaller warheads for a given yield, while better electronics and guidance systems allow greater accuracy. As a result, MIRV technology has proven more attractive than MRV for advanced nations. Multiple-warhead missiles require both

420-596: The US's deployable nuclear arsenal and thus the possibility that it would have enough bombs to destroy virtually all of the Soviet Union's nuclear weapons and negate any significant retaliation. Later on the US feared the Soviet's MIRVs because Soviet missiles had a greater throw-weight and could thus put more warheads on each missile than the US could. For example, the US MIRVs might have increased their warhead per missile count by

448-409: The United States phased out the use of MIRVs in ICBMs in 2014 to comply with New START , Russia continues to develop new ICBM designs using the technology. The introduction of MIRV led to a major change in the strategic balance. Previously, with one warhead per missile, it was conceivable that one could build a defense that used missiles to attack individual warheads. Any increase in missile fleet by

476-547: The boost phase, the bus maneuvers using small on-board rocket motors and a computerized inertial guidance system . It takes up a ballistic trajectory that will deliver a re-entry vehicle containing a warhead to a target and then releases a warhead on that trajectory. It then maneuvers to a different trajectory, releasing another warhead, and repeats the process for all warheads. The precise technical details are closely guarded military secrets , to hinder any development of enemy counter-measures. The bus's on-board propellant limits

504-408: The cost-exchange ratio was almost always strongly in favor of the offense. Some of this has to do with the fact that an ICBM can be aimed at any target, which the defender cannot know in advance. To shoot that warhead down, the defender has to wait until it appears on radar , which typically happens only a few hundred miles from the target. This means a single defensive missile cannot be used to counter

532-461: The distances between targets of individual warheads to perhaps a few hundred kilometers. Some warheads may use small hypersonic airfoils during the descent to gain additional cross-range distance. Additionally, some buses (e.g. the British Chevaline system) can release decoys to confuse interception devices and radars , such as aluminized balloons or electronic noisemakers. Accuracy

560-452: The enemy could be countered by a similar increase in interceptors. With MIRV, a single new enemy missile meant that multiple interceptors would have to be built, meaning that it was much less expensive to increase the attack than the defense. This cost-exchange ratio was so heavily biased towards the attacker that the concept of mutual assured destruction became the leading concept in strategic planning and ABM systems were severely limited in

588-411: The exact figures of the cost-exchange ratio. This ended with the introduction of multiple independently targetable re-entry vehicles , or MIRVs. MIRV allowed a single ICBM to launch multiple warheads, each attacking a different target. Now every new ICBM required dozens and dozens of new ABMs to counter it, swinging the cost-exchange ratio so dramatically in favor of the offense that it ended any debate on

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616-581: The single 1.2 megatons of TNT (5.0 PJ) W56 used on the Minuteman II. From 1970 to 1975, the United States would remove approximately 550 earlier versions of the Minuteman ICBM in the Strategic Air Command 's (SAC) arsenal and replace them with the new Minuteman IIIs outfitted with a MIRV payload, increasing their overall effectiveness. The smaller power of the warheads used (W62, W78 and W87)

644-668: The terms of the START I and START II treaties, from 1996 a number of R-39 missiles were destroyed. Throughout the 1990s, Typhoon class submarines and the R-39 missiles they carried were gradually withdrawn from service. All the missiles were decommissioned by 2004 and all the Typhoon class submarines have been retired, except for one which is used as a test platform for the RSM-56 Bulava . A successor design, R-39M Grom ( Russian : Гром , Thunder)/RSM-52V/SS-N-28 for D-19UTTKh launch system, suffered

672-576: The topic. Consideration of cost-exchange ratios was influential in persuading the United States and the Soviet Union to sign the ABM Treaty . The topic was once again a consideration in the era of the Strategic Defense Initiative , SDI or "Star Wars". In this case the defensive weapons attacked the ICBMs before they released their warheads, reducing the exchange ratio to one, although at

700-763: Was also used by the Royal Navy who also retained MRV with the Chevaline upgrade, though the number of warheads in Chevaline was reduced to two due to the ABM counter-measures carried. The Soviet Union deployed 3 MRVs on the R-27U SLBM and 3 MRVs on the R-36P ICBM. Refer to atmospheric re-entry for more details. On November 21, 2024, as part of the Russian invasion of Ukraine , Russia launched

728-524: Was designated "D-19". Development work began at NII Mashinostroyeniya in 1971 and the design gained official approval in 1973. Initial test flights from 1979 found problems in the solid-fuel boost engines, over half of the early flights failed. Later tests aboard a modified Typhoon-class submarine were more successful and deployment began in May 1983, with 20 missiles in each submarine. At full deployment, 120 missiles were deployed with 1,200 total warheads. Under

756-527: Was offset by increasing the accuracy of the system, allowing it to attack the same hard targets as the larger, less accurate, W56. The MMIII was introduced specifically to address the Soviet construction of an anti-ballistic missile (ABM) system around Moscow; MIRV allowed the US to overwhelm any conceivable ABM system without increasing the size of their own missile fleet. The Soviets responded by adding MIRV to their R-36 design, first with three warheads in 1975, and eventually up to ten in later versions. While

784-627: Was used, and Ukrainian media initially reported it was an RS-26 Rubezh ICBM with range 5,800 km. The US and Russia confirmed it was intermediate-range (3,000–5,500 km), but the Pentagon stated it was based on the RS-26 ICBM. It was fired from the Astrakhan region 700 km away. UN spokesperson Stéphane Dujarric called the use of the intermediate-range weapon "concerning and worrying". Cost-exchange ratio In anti-ballistic missile (ABM) defence

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