Intercontinental ballistic missile

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Image:Minuteman3launch.jpg An intercontinental ballistic missile, or ICBM, is a very long-range (greater than 5,500–km or 3,500 miles) ballistic missile typically designed for nuclear weapons delivery, i.e., delivering one or more nuclear warheads.

ICBMs are differentiated by maximum range from other ballistic missiles: intermediate-range ballistic missiles (IRBMs), short-range ballistic missiles, and the newly named theater ballistic missiles.

The following nations currently have operational ICBM systems: Russia, the United States, France [1], the United Kingdom, and People's Republic of China. India has IRBMs but is developing ICBMs (see ballistic missiles of India). Pakistan has IRBMs but is also researching ICBMs (see Pakistan's ballistic missiles).

In 2002, the United States and Russia agreed in the SORT treaty to reduce their deployed stockpiles to not more than 2,200 warheads each.

1 Flight phases
2 History
3 Modern ICBMs
4 Specific missiles
5 Ballistic missile submarines
6 See also
7 External links

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Flight phases

The following flight phases can be distinguished:

boost phase — 3 to 4 minutes (for a solid rocket shorter than for a liquid-propellant rocket); altitude at the end of this phase is 150 to 200 km, typical burnout speed is 7–km/s
midcourse phase — approx. 25 minutes — suborbital flight in an elliptic orbit, i.e. the orbit is part of an ellipse with vertical major axis; the apogee (halfway the midcourse phase) is at an altitude of typically approx. 1200 km; the semi-major axis is between one half of the radius of the Earth and the radius; the projection of the orbit on the Earth's surface is a great circle—the missile may release several independent warheads, and penetration aids such as metallic-coated balloons, aluminum chaff, and full-scale warhead decoys
reentry phase (starting at an altitude of 100 km) — 2 minutes — impact is at a speed of up to 4 km/s (for early ICBMs less than 1 km/s).

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History

The progenitor of the ICBM was the German A9/10, which was never developed but only proposed by Wernher von Braun. The progenitor of the IRBM was the German V2 (Vergeltung, or "vengeance") rocket designed by von Braun that used liquid propellant and an inertial guidance system. It was launched from a mobile launcher in order to make it less susceptible to Allied air attacks. Following World War 2 von Braun and other lead nazi scientist were secretly transferred to US to work directly for the U.S. Army through Operation Paperclip developing the V2 into the Redstone IRBM and Jupiter IRBM. Due to treaty agreements the U.S. was able to base these IRBMs in countries close to the USSR within strategic range.

The USSR had no similar territory in the 1950s so under the direction of reactive propulsion engineer Sergei Korolev a program to develop an ICBM (which started in Russia well before WWII) was accelerated. Korolev was given access to some captured V2 materials but found V2 design weak and developed his own distinct design, the R-7, that was tested in August 1957 and on October 4, 1957 placed first Sputnik (satellite) in space opening space exploration era for mankind. The R-7 was so successful and reliable that it is still in service.

In USA competition between the U.S. armed services meant that each force developed its own ICBM program, slowing progress. The U.S.'s first ICBM was the Atlas, operational in 1959. Both the R7 and Atlas required a large launch facility making them vulnerable to attack and could not be kept in a ready state. Early ICBMs formed the basis of many space launch systems. Examples include: Atlas, Redstone rocket, Titan, R-7, and Proton, which was derived from the earlier ICBMs but never deployed as an ICBM. The UK built its own ICBM Black Knight but it was never made operational due to the difficulty of finding a launch site away from population centers. Under the direction of Robert McNamara the U.S. initiated the LGM-30 Minuteman, Polaris and Skybolt solid fuel ICBMs. Modern ICBMs tend to be smaller than their ancestors (due to increased accuracy and smaller and lighter warheads) and use solid fuels, making them less useful as orbital launch vehicles. Deployment of these systems was governed by the strategic theory of Mutually Assured Destruction.

In the 1970s development began of Anti-Ballistic Missile Systems by both the U.S. and USSR but these were restricted by treaty in order to preserve the value of the existing ICBM systems. President Ronald Reagan launched the Strategic Defense Initiative as well as the MX and Midgetman ICBM programmes. This led to the agreement of a series of Strategic Arms Reduction Treaty negotiations.

Countries in the early stages of developing ICBMs have all used liquid propellants for the sake of simplicity.

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Modern ICBMs

Modern ICBMs typically carry multiple independently targetable reentry vehicles (MIRVs), each of which carries a separate nuclear warhead, allowing a single missile to hit multiple targets. MIRV was an outgrowth of the rapidly shrinking size and weight of modern warheads and the Strategic Arms Limitation Treaties which imposed limitations on the number of launch vehicles (SALT I and SALT II). It has also proved to be an "easy answer" to proposed deployments of ABM systems – it is far less expensive to add more warheads to an existing missile system than to build an ABM system capable of shooting down the additional warheads; hence, most ABM system proposals have been judged to be impractical. The only operational ABM systems were deployed in the 1970s, the U.S. Safeguard ABM facility was located in North Dakota and was operational from 1975–1976. The USSR deployed its Galosh ABM system around Moscow in the 1970s, which remains in service.

ICBMs can be deployed from multiple platforms:

in missile silos, which offer some protection from military attack (including, the designers hope, some protection from a nuclear first strike)
on submarines: submarine-launched ballistic missiles (SLBMs); most or all SLBMs have the long range of ICBMs (as opposed to IRBMs)
on heavy trucks; this applies to one version of the RT-2UTTH Topol M which may be deployed from a self-propelled mobile launcher, capable of moving through roadless terrain, and launching a missile from any point along its route
mobile launchers on rails; this applies, for example, to РТ-23УТТХ "Молодец" (RT-23UTTH "Molodets" -- SS-24 "Sсаlреl")

The last three kinds are mobile and therefore hard to find.

During storage, one of the most important features of the missile is its serviceability. One of the key features of the first computer-controlled ICBM, the Minuteman missile was that it could quickly and easily use its computer to test itself.

In flight, a booster pushes the warhead and then falls away. Most modern boosters are solid-fueled rocket motors, which can be stored easily for long periods of time. Early missiles used liquid-fueled rocket motors. Liquid-fueled ICBMs were generally not kept fueled all the time, and therefore fueling the rocket was necessary before a launch. This annoying procedure was a source of significant operational delay, and therefore might cause the rockets to be destroyed before they could be used. It also provided opponents with intelligence because it was a definite observable event that indicated the start of an attack.

Once the booster falls away, the warhead falls on an unpowered path much like an orbit, except that it hits the earth at some point. Moving in this way is stealthy. No rocket gases or other emissions occur to indicate the missile's position to defenders. Also, it is the fastest way to get from one part of the Earth to another. This increases the element of surprise. The high speed of a ballistic warhead (near 5 miles per second) also make it difficult to intercept.

Many authorities say that missiles also release aluminized balloons, electronic noisemakers, and other items intended to confuse interception devices and radars.

The high speed can cause the missile to get very hot as it reenters the atmosphere. Ballistic warheads are protected by heatshields constructed of materials such as pyrolytic graphite, and in early missiles, thick plywood. Plywood approaches the strength per weight of carbon fiber/epoxy composites and chars slowly, protecting the missile.

Accuracy is crucial, because doubling the accuracy decreases the needed warhead energy by a factor of four. Accuracy is limited by the accuracy of the navigation system and the available geophysical information. Many authorities believe that most government-supported geophysical mapping initiatives such as GPS, and ocean satellite altitude systems such as Seasat, probably have a covert purpose to map mass concentrations and determine local gravitic anomalies, in order to improve accuracies of ballistic missiles.

Strategic missile systems are thought to use custom integrated circuits designed to calculate navigational differential equations thousands to millions of times per second in order to reduce navigational errors caused by calculation alone. These circuits are usually a network of binary addition circuits that continually recalculate the missile's position. The inputs to the navigation circuit are set by a general purpose computer according to a navigational input schedule loaded into the missile before launch.

One particular weapon developed by the Soviet Union (FOBS) had a partial orbital trajectory, and unlike most ICBMs its target could not be deduced from its orbital flight path. It was decommissioned in compliance with arms control agreements, which address the maximum range of ICBMs and prohibit orbital or fractional-orbital weapons.

Low-flying guided cruise missiles are an alternative to ballistic missiles.

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Specific missiles

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Land-based ICBMs and cruise missiles

The U.S. Air Force currently operates just over 500 ICBMs at around 15 missile complexes located primarily in the northern Rocky Mountain states and the Dakotas. These are of the LGM-30 Minuteman III and Peacekeeper ICBM variants. Peacekeeper missiles were phased out in 2005[2]. All USAF Minuteman II missiles have been destroyed in accordance to START, and their launch silos have been sealed or sold to the public. To comply with the START II most U.S. multiple independently targetable reentry vehicles, or MIRVs, have been eliminated and replaced with single warhead missiles. However, since the abandonment of the START II treaty, the U.S. is said to be considering retaining 800 warheads on 500 missiles.[3]

The United States Air Force awards two badges for performing duty in a nuclear missile silo. The Missile Badge is presented to commissioned officers while the Space and Missile Pin is awarded to silo ground and support personnel.

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Sea-based ICBMs

Image:Trident missile image.jpg

The U.S. Navy currently has 14 Ohio-class SSBNs deployed. Each submarine is equipped with a complement of 24 Trident missiles, eight with Trident I missiles, and ten with Trident II missiles (336 missiles total).

The French Navy constantly maintains at least four active units, relying on two classes of nuclear-powered ballistic submarines (SSBN): the older Redoutable class, which are being progressively decommissioned, and the newer Triomphant class. These carry 16 M45 missiles with TN75 warheads, and are scheduled to be upgraded to M51 nuclear missile around 2010.

The UK's Royal Navy has four Vanguard class submarines, each armed with 16 Trident II SLBMs.

China's People's Liberation Army Navy has one Xia class submarine with 12 single-warhead JL-1 SLBMs. The PLAN is also developing the new Type 094 SSBN that will have up to 16 JL-2 SLBMs (possibly MIRV), which are also in development.

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Current and former U.S. ballistic missiles

Atlas (SM-65, CGM-16) former ICBM launched from silo, the rocket is now used for other purposes
Titan I (SM-68, HGM-25A)
Titan II (SM-68B, LGM-25C) — former ICBM launched from silo, the rocket is now used for other purposes
Minuteman I (SM-80, LGM-30A/B, HSM-80)
Minuteman II (LGM-30F)
Minuteman III (LGM-30G) — launched from silo — as of June 28 2004, there are 517 Minuteman III missiles in active inventory
LG-118A Peacekeeper / MX (LG-118A, MX) — silo-based; 29 missiles were on alert at the beginning of 2004; all are to be removed from service by 2005.
Midgetman — has never been operational — launched from mobile launcher
Polaris A1, A2, A3 — (UGM-27/A/B/C) former SLBM
Poseidon C3 — (UGM-73) former SLBM
Trident — (UGM-93A/B) SLBM — Trident II (D5) was first deployed in 1990 and is planned to be deployed past 2020.