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Multiple independently targetable reentry vehicle

Multiple independently targetable reentry vehicle

Overview


A multiple independently targetable reentry vehicle (MIRV) warhead is a collection of nuclear weapon
Nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission bomb test released the same amount...

s carried on a single intercontinental ballistic missile
Intercontinental ballistic missile
An intercontinental ballistic missile is a ballistic missile with a long range typically designed for nuclear weapons delivery...

 (ICBM) or a submarine-launched ballistic missile
Submarine-launched ballistic missile
A submarine-launched ballistic missile is a ballistic missile capable of delivering a nuclear warhead that can be launched from submarines. Modern variants usually deliver multiple independently targetable reentry vehicles each of which carries a warhead and allows a single launched missile to...

 (SLBM). Using a MIRV warhead, a single launched missile can strike several targets, or fewer targets redundantly. By contrast a unitary warhead is a single warhead on a single missile.

The military purpose of a MIRV is threefold:
  • Provides greater target damage for a given missile
    Missile
    Though a missile may be any thrown or launched object, it colloquially almost always refers to a self-propelled guided weapon system.-Etymology:The word missile comes from the Latin verb mittere, meaning "to send"...

     payload.
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A multiple independently targetable reentry vehicle (MIRV) warhead is a collection of nuclear weapon
Nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission bomb test released the same amount...

s carried on a single intercontinental ballistic missile
Intercontinental ballistic missile
An intercontinental ballistic missile is a ballistic missile with a long range typically designed for nuclear weapons delivery...

 (ICBM) or a submarine-launched ballistic missile
Submarine-launched ballistic missile
A submarine-launched ballistic missile is a ballistic missile capable of delivering a nuclear warhead that can be launched from submarines. Modern variants usually deliver multiple independently targetable reentry vehicles each of which carries a warhead and allows a single launched missile to...

 (SLBM). Using a MIRV warhead, a single launched missile can strike several targets, or fewer targets redundantly. By contrast a unitary warhead is a single warhead on a single missile.

Purpose


The military purpose of a MIRV is threefold:
  • Provides greater target damage for a given missile
    Missile
    Though a missile may be any thrown or launched object, it colloquially almost always refers to a self-propelled guided weapon system.-Etymology:The word missile comes from the Latin verb mittere, meaning "to send"...

     payload. Radiation (including radiated heat) from a nuclear warhead diminishes as the square of the distance (called the inverse-square law
    Inverse-square law
    In physics, an inverse-square law is any physical law stating that a specified physical quantity or strength is inversely proportional to the square of the distance from the source of that physical quantity....

    ), and blast pressure diminishes as the cube of the distance. For example at a distance of 4 km from ground zero, the blast pressure is only 1/64th that of 1 km. Due to these effects several small warheads cause much more target damage area than a single large one. This in turn reduces the number of missiles and launch facilities required for a given destruction level - much the same as the purpose of a conventional submunition.
  • With single warhead missiles, one missile must be launched for each target. By contrast with a MIRV warhead, the post-boost (or bus) stage can dispense the warheads against multiple targets across a broad area.
  • Reduces the effectiveness of an anti-ballistic missile
    Anti-ballistic missile
    An anti-ballistic missile is a missile designed to counter ballistic missiles .A ballistic missile is used to deliver nuclear, chemical, biological or conventional warheads in a ballistic flight trajectory. The term "anti-ballistic missile" describes any antimissile system designed to counter...

     system that relies on intercepting individual warheads. While a MIRV attacking missile can have multiple (3–12 on United States missiles and 3-10 on Russians) warheads, interceptors may have only one warhead per missile. Thus, in both a military and an economic sense, MIRVs render ABM systems less effective, as the costs of maintaining a workable defense against MIRVs would greatly increase, requiring multiple defensive missiles for each offensive one. Decoy reentry vehicles can be used alongside actual warheads to minimize the chances of the actual warheads being intercepted before they reach their targets. A system that destroys the missile earlier in its trajectory (before MIRV separation) is not affected by this but is more difficult, and thus more expensive to implement.


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 the US's deployable nuclear arsenal and thus the possibility that it would have enough bombs to destroy virtually all of the Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

'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
Throw-weight
Throw-weight is a measure of the effective weight of ballistic missile payloads. It is measured in kilograms or metric tons. Throw-weight equals the total weight of a missile's warheads, reentry vehicles, self-contained dispensing mechanisms, penetration aids, and guidance systems — generally all...

 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 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 SLBMs, which could be outfitted with MIRVs, and helped offset the ICBM disadvantage. It is because of this that this type of weapon was banned under the START II
START II
START II was a bilateral treaty between the United States of America and Russia on the Reduction and Limitation of Strategic Offensive Arms. It was signed by United States President George H. W...

 agreement. However, START II was never ratified by the Russian Duma due to disagreements about the ABM Treaty
Anti-Ballistic Missile Treaty
The Anti-Ballistic Missile Treaty was a treaty between the United States and the Soviet Union on the limitation of the anti-ballistic missile systems used in defending areas against missile-delivered nuclear weapons....

.

The Russian Federation
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

 claims to have developed the most advanced MIRV system as of 2006 for use in the RSM-56 Bulava.

Mode of operation


In a MIRV, the main rocket motor (or booster) pushes a "bus" (see illustration) into a free-flight suborbital ballistic flight path. After the boost phase the bus maneuvers using small on-board rocket motors and a computerised inertial guidance system. It takes up a ballistic trajectory that will deliver a reentry
Atmospheric reentry
Atmospheric entry is the movement of human-made or natural objects as they enter the atmosphere of a celestial body from outer space—in the case of Earth from an altitude above the Kármán Line,...

 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
Propellant
A propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...

 limits the distances between targets of individual warheads to perhaps a few hundred km. Some warheads may use small hypersonic
Hypersonic
In aerodynamics, a hypersonic speed is one that is highly supersonic. Since the 1970s, the term has generally been assumed to refer to speeds of Mach 5 and above...

 airfoils during the descent to gain additional cross-range distance. Additionally, some buses (e.g. the British Chevaline
Chevaline
Chevaline was a system to improve the penetrability of the British Polaris missile warheads. Devised as an answer to the improved Soviet defences around Moscow, the system was intended to increase the probability that at least one warhead would penetrate the city's anti-ballistic missile defences,...

 system) can release decoy
Decoy
A decoy is usually a person, device or event meant as a distraction, to conceal what an individual or a group might be looking for. Decoys have been used for centuries most notably in game hunting, but also in wartime and in the committing or resolving of crimes.-Duck decoy:The term duck decoy may...

s to confuse interception devices and radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...

s, such as aluminized
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

 balloons or electronic noisemakers.
Accuracy 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
Seasat
SEASAT was the first Earth-orbiting satellite designed for remote sensing of the Earth's oceans and had on board the first spaceborne synthetic aperture radar . The mission was designed to demonstrate the feasibility of global satellite monitoring of oceanographic phenomena and to help determine...

 may have a covert purpose to map mass concentrations and determine local gravity anomalies
Gravity anomaly
A gravity anomaly is the difference between the observed acceleration of Earth's gravity and a value predicted from a model.-Geodesy and geophysics:...

, in order to improve accuracies of ballistic missiles. Accuracy is expressed as circular error probable
Circular error probable
In the military science of ballistics, circular error probable is an intuitive measure of a weapon system's precision...

 (CEP). This is simply 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
Trident missile
The Trident missile is a submarine-launched ballistic missile equipped with multiple independently-targetable reentry vehicles . The Fleet Ballistic Missile is armed with nuclear warheads and is launched from nuclear-powered ballistic missile submarines . Trident missiles are carried by fourteen...

 and Peacekeeper
LGM-118A Peacekeeper
The LGM-118A Peacekeeper, also known as the MX missile , was a land-based ICBM deployed by the United States starting in 1986. A total of 50 missiles were deployed. They have since been deactivated....

 missiles.

See also

  • Atmospheric reentry
    Atmospheric reentry
    Atmospheric entry is the movement of human-made or natural objects as they enter the atmosphere of a celestial body from outer space—in the case of Earth from an altitude above the Kármán Line,...

  • M45 SLBM
    M45 SLBM
    The M45 SLBM is the current standard French Navy's submarine launched ballistic missile...

  • M51 SLBM
    M51 SLBM
    The M51 SLBM is a submarine-launched ballistic missile, built by EADS Astrium Space Transportation, and deployed with the French Navy. Designed to replace the M45 SLBM The M51 SLBM is a submarine-launched ballistic missile, built by EADS Astrium Space Transportation, and deployed with the French...

  • Maneuverable reentry vehicle
    Maneuverable reentry vehicle
    The maneuverable reentry vehicle is a type of ballistic missile warhead capable of shifting targets in flight...

     (MARV)
  • Multiple Reentry vehicle
    Multiple Reentry vehicle
    A Multiple Reentry vehicle payload for a ballistic missile deploys multiple warheads in a pattern against a single target. The advantage of an MRV over a single warhead is that the damage produced in the center of the pattern is far greater than the damage possible from any single warhead in the...

  • Nuclear warfare
    Nuclear warfare
    Nuclear warfare, or atomic warfare, is a military conflict or political strategy in which nuclear weaponry is detonated on an opponent. Compared to conventional warfare, nuclear warfare can be vastly more destructive in range and extent of damage...

  • Poseidon missile
  • START II
    START II
    START II was a bilateral treaty between the United States of America and Russia on the Reduction and Limitation of Strategic Offensive Arms. It was signed by United States President George H. W...


External links