Anti-ballistic missile

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An anti-ballistic missile (ABM) 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 ballistic missiles. However the term is more commonly used for ABM systems designed to counter long range, nuclear-armed Intercontinental ballistic missiles (ICBMs).

Only two ABM systems have previously been operational against ICBMs, the U.S. Safeguard system, which utilized the LIM-49A Spartan and Sprint missiles, and the Russian A-35 anti-ballistic missile system which used the Galosh interceptor. Safeguard was only briefly operational; the Russian system has been improved and is still active, now called A-135 and using two missile types, Gorgon and Gazelle. However the U.S. Ground-Based Midcourse Defense (GMD, previously called NMD) system has recently reached initial operational capability.

Three shorter range tactical ABM systems are currently operational: the U.S. Patriot, Navy Aegis combat system/Standard SM-3, and the Israeli Arrow. The longer-range U.S. Terminal High Altitude Area Defense (THAAD) system is scheduled for deployment in 2011. In general short-range tactical ABMs cannot intercept ICBMs, even if within range. The tactical ABM radar and performance characteristics do not allow it, as an incoming ICBM warhead moves much faster than a tactical missile warhead. However it is possible the higher performance THAAD missile could be upgraded to intercept ICBMs.

Latest versions of the U.S. Hawk missile have a limited capability against tactical ballistic missiles, but is usually not described as an ABM. Similar claims have been made about the Russian long-range surface-to-air S-300 and S-400 series.

For current US developments, see Missile Defense Agency. For other short-range missiles, see Sea Wolf, Aster 15 and Crotale missile.

[edit] Early history of ABMs

[edit] From World War II through the 1950s

The idea of shooting down rockets before they can hit their target dates from the first use of modern missiles in warfare, the German V-1 and V-2 program of World War II. British and American fighters attempted to destroy V-1 “buzz bombs” in flight prior to impact, with some success, although concentrated barrages of heavy anti-aircraft artillery had greater success. The V-2, the first true ballistic missile, was impossible to destroy using aircraft or artillery. Instead, the Allies launched Operation Crossbow to find and destroy V-2s before launch. The operation was largely ineffective, as was a similar operation during the first Persian Gulf War nearly fifty years later against the V-2’s direct descendant, the Russian Scud missile. The V2s were eventually dealt with by the launch sites being over-run by the rapid advance of the Allied armies through Belgium and the Netherlands.

The American armed forces began experimenting with anti-missile missiles shortly after World War II, as the extent of German research into rocketry became clear. But defenses against Soviet long-range bombers took priority until the later 1950s, when the Soviets began to test their missiles (most notably via the Sputnik launch in October 1957). The first experimental ABM system was the soviet V-1000 system (part of the experimental "A-35" ABM programme), closely followed by Nike Zeus, a modification of then-existing air defense systems. Nike Zeus proved unworkable, and so work proceeded with Nike X.

Launch of a Nike Zeus missile

Another avenue of research by the U.S. was the test explosions of several low yield nuclear weapons at very high altitudes over the southern Atlantic ocean, launched from ships. The devices used were the 1.7 kt boosted fission W25 warhead.^[1] When such an explosion takes place a burst of X-rays are released that strike the Earth's atmosphere, causing secondary showers of charged particles over an area hundreds of miles across. The movement of these charged particles in the Earth’s magnetic field causes a powerful EMP which induces very large currents in any conductive material. The purpose was to determine how much the EMP would interfer with radar tracking and other communications and the level of destruction of electronic circuitry aboard missiles and satellites. The project's results are not known, although similar so-called 'effects tests' were a regular feature of underground tests at the Nevada Test Site up to 1992. These 'effects tests' are used to determine how resistant specific warheads, RVs and other components are to exoatmospheric ABM bursts.

Other countries were also involved in early ABM research. A more advanced project was at CARDE in Canada, which researched the main problems of ABM systems. This included developing several advanced infrared detectors for terminal guidance, a number of missile airframe designs, a new and much more powerful solid rocket fuel, and numerous systems for testing it all. After a series of drastic budget cuts in the late 1950s the research wound down. One offshoot of the project was Gerald Bull’s system for inexpensive high-speed testing, consisting of missile airframes fired from a sabot round, which would later form the basis of Project HARP.

[edit] Developments in the 1960s and 1970s

[edit] Nike-X, Sentinel and Safeguard

Dual launch of Sprint missiles during a salvo test at Meck island

Nike X was a US system of two missiles, radars and their associated control systems. The original Nike Zeus (later called Spartan) was upgraded for longer range and a much larger 5 megatonne warhead intended to destroy warheads with a burst of x-rays outside the atmosphere. A second shorter-range missile called Sprint with very high acceleration was added to handle warheads that evaded longer-ranged Spartan. Sprint was a very fast missile (some sources claimed it accelerated to 8,000 mph (13 000 km/h) within 4 seconds of flight--an average acceleration of 100 g) and had a smaller W66 enhanced radiation warhead in the 1-3 kiloton range for in-atmosphere interceptions.

The new Spartan changed the deployment plans as well. Previously the Nike systems were to have been clustered near cities as a last-ditch defense, but the Spartan allowed for interceptions at hundreds of miles range. Therefore the basing changed to provide almost complete coverage of the United States in a system known as Sentinel. Later Sentinel was restructured to a more limited defense of ICBM sites against incoming warheads. That system used the same Spartan/Sprint missiles and radar, and was called Safeguard.

[edit] Moscow ABM system

The first real and successful ABM hit-to-kill test was conducted by the Soviet PVO forces on the 1st of March 1961. An experimental V-1000 missile (part of the "A" ABM programme) launched from the Sary-Shagan test range, destroyed at an altitude of 25 km a dummy warhead released by a R-12 ballistic missile launched from the Kapustin Yar cosmodrome. The dummy warhead was destroyed by the impact of 18 thousand tungsten-carbide spherical impactors 140 seconds after launch. The first US similar test was conducted on the 19th of July 1962 and involved an Nike Zeus ABM simulating a nuclear hit by passing close to the target dummy, i.e. not a direct hit. The V-1000 missile system was nonetheless considered not reliable enough and abandoned in favour of nuclear-tipped ABMs.

The only other ICBM ABM system to reach production was the Soviet A-35 system. It was initially a single-layer exoatmospheric (outside the atmosphere) design, using the Galosh (SH-01/ABM-1) interceptor. It was deployed at four sites around Moscow in the early 1970s.

Originally intended to be a larger deployment, the system was downsized to the two sites allowed under the 1972 ABM treaty. It was upgraded in the 1980s to a two-layer system, the A-135. The Gorgon (SH-11/ABM-4) long-range missile was designed to handle intercepts outside the atmosphere, and the Gazelle (SH-08/ABM-3) short-range missile endoatmospheric intercepts that eluded Gorgon. The system as it existed during the 1970s is thought to have been similar in capability to that of the former U.S. Safeguard system.

[edit] The problem of defense against MIRVs

Testing of the LGM-118A Peacekeeper re-entry vehicles, all eight fired from only one missile. Each line represents the path of a warhead which, were it live, would detonate with the explosive power of twenty-five Hiroshima-style weapons.

ABM systems were initially developed to counter single warheads from large Intercontinental ballistic missiles (ICBMs). The economics seemed simple enough: since rocket costs increase rapidly with size, interceptor cost should be less than the attacking ICBMs (which had much longer range and heavier payloads). In an arms race the defense would always win.

Things changed dramatically with the introduction of Multiple independently targetable reentry vehicle (MIRV) warheads. Suddenly each launcher was throwing not one warhead, but several. The defense would still require a rocket for every warhead, as they would be re-entering over a wide space and could not be attacked by several warheads from a single antimissile rocket. Suddenly the defense was more expensive than offense: it was much less expensive to add more warheads, or even decoys, than it was to build the interceptor needed to shoot them down.

The experimental success of Nike X persuaded the Lyndon B. Johnson administration to propose a thin ABM defense. In a September 1967 speech, Defense Secretary Robert McNamara described it as Sentinel. McNamara, a private ABM opponent because of cost and feasibility (see cost-exchange ratio), claimed that Sentinel would be directed not against the Soviet Union's missiles (since the USSR had more than enough missiles to overwhelm any American defense), but rather against the potential nuclear threat of the People's Republic of China.

In the meantime a public debate over the merit of ABMs broke out. Even before the MIRV problem made ABM effectiveness non-workable in the late 1960s, some technical difficulties had already made an ABM system questionable for a large sophisticated attack. One problem was the Fractional Orbital Bombardment System (FOBS) that would give little warning to the defense. Another problem was high altitude EMP (whether from offensive or defensive nuclear warheads) which could degrade defensive radar systems.

Technical difficulties aside, the debate turned to an odd position: that no defense at all was better than any defense. Namely, a false sense of security might encourage ABM-defended nations to escalate against minor threats, believing they would be protected against any response. By this reasoning simply starting to deploy such a system could prompt a full-scale attack before it could become operational and thereby render such an attack useless. This curious set of arguments thus put the system in a terrible position: it couldn't possibly work, but if it did that would be even worse.

[edit] The Anti-Ballistic Missile Treaty of 1972

Various technical, economic and political problems led to the ABM treaty of 1972, which restricted the deployment of strategic (not tactical) anti-ballistic missiles.

Under the ABM treaty and a 1974 revision, each country was allowed to deploy a single ABM system with only 100 interceptors to protect a single target. The Soviets deployed a system named A-35 (using Galosh interceptors), designed to protect Moscow. The U.S. deployed Safeguard (using Spartan/Sprint interceptors) to defend ballistic missile sites at Grand Forks Air Force Base, North Dakota, in 1975. The U.S. Safeguard system was only briefly operational. The Russian system (now called A-135) has been improved and is still active around Moscow.

On June 13, 2002, the United States withdrew from the Anti-Ballistic Missile Treaty and subsequently recommenced developing missile defense systems that would have formerly been prohibited by the bilateral treaty. This action was taken under the auspices of needing to defend against the possibility of a missile attack conducted by a rogue state.

[edit] ABM developments in the 1980s and Persian Gulf War

The Reagan-era Strategic Defense Initiative (often referred to as “Star Wars”), along with research into various energy-beam weaponry, brought new interest in the area of ABM technologies.

SDI was an extremely ambitious program to provide a total shield against a massive Soviet ICBM attack. The initial concept envisioned large sophisticated orbiting laser battle stations, space-based relay mirrors, and nuclear-pumped X-ray laser satellites. Later research indicated that some planned technologies such as X-ray Lasers were not feasible with then-current technology. As research continued, SDI evolved through various concepts as designers struggled with the difficulty of such a large complex defense system. SDI remained a research program and was never deployed. However several SDI technologies were used in follow on ABM systems.

The Patriot antiaircraft missiles was the first deployed tactical ABM system, although it was not designed from the outset for that task and consequently had limitations. It was used in the 1991 Gulf War to attempt to intercept Iraqi Scud missiles. Post-war analyses show that the Patriot was much less effective than initially thought because of its radar and control system's inability to discriminate warheads from other objects when the Scud missiles broke up during reentry. On the other hand, the Scud itself was highly inaccurate and not very reliable. It was more a psychological than real threat to military targets.

[edit] Post Gulf War ABM developments in the 1990s

[edit] Tactical ABMs deployed

Developed in the late 1990s, the Lightweight Exo-Atmospheric Projectile (LEAP) attaches to a modified SM-2 Block IV missile used by the U.S. Navy

Testing of ABMs and ABM technology continued through the 1990s with mixed success. However, following the Gulf War, improvements were made to several U.S. air defense systems. Patriot PAC-3 was developed and tested following the Gulf War. The PAC-3 is a complete redesign of the system deployed during the war, including a totally new missile. The improved guidance, radar and missile performance improves the probablility of kill over the earlier PAC-2. In operation Iraqi Freedom, the Patriot PAC-3 had a near 100% success rate at intercepting short range tactical ballistic missiles (TBMs). However since no longer range Iraqi Scud missiles were fired, PAC-3 effectiveness against those was untested. Also the PAC-3 was involved in two fratricide incidents: two incidents of Patriot firings at coalition aircraft and one of U.S. aircraft firing on a Patriot battery [1].

From 1992 to 2000 a demonstration system for the US Army Terminal High Altitude Area Defense was deployed at White Sands Missile Range. Tests were conducted on a regular basis and resulted in early failures, but successful intercepts occurred in 1999. A new version of the Hawk missile was tested in the early to mid 90’s and by the end of 1998 the majority of US Marine Corps Hawk systems were modified to support basic theater anti-ballistic missile capabilities[2]. Following the Gulf war, the Aegis combat system was expanded to include ABM capabilities. The Standard missile system was also enhanced and tested for ballistic missile interception. In the late 90’s SM-2 block IVA missiles were tested in a theater ballistic missile defense role.[3] Standard Missile 3 (SM3) systems have also been tested for an ABM role. In 1998, Defense secretary William Cohen proposed spending an additional $6.6 billion on ballistic missile defense programs to build a system to protect against attacks from North Korea or accidental launches from Russia or China[4]. The Israeli Arrow system was initially tested in 1990, before the first Gulf War. The Arrow was supported by the United States throughout the nineties.

[edit] Brilliant Pebbles

Approved for acquisition by the Pentagon in 1991 but never realized, Brilliant Pebbles was a proposed space-based anti-ballistic system that tried to avoid some of the problems of the earlier SDI concepts. Rather than use sophisticated large laser battle stations and nuclear-pumped X-ray laser satellites, Brilliant Pebbles consisted of a thousand very small, highly intelligent orbiting satellites with kinetic warheads. The system relied on advances in computer technology, avoided problems with overly centralized command and control and risky, expensive development of large, complicated space defense satellites. It promised to be much less expensive to develop and have less technical development risk.

The name Brilliant Pebbles comes from the small size of the satellite interceptors and great computational power enabling more autonomous targeting. Rather than rely exclusively on ground-based control, the many small interceptors would cooperatively communicate among themselves and target a large swarm of ICBM warheads in space or in the late boost phase. Development was later discontinued in favor of a limited ground-based defense.

[edit] SDI changed to NMD

In the early 1990s, President G. H. W. Bush called for a more limited version using rocket-launched interceptors based on the ground at a single site. In 1993, SDI was reorganized as the Ballistic Missile Defense Organization. Deployment of the more limited system, called the National Missile Defense (NMD) was planned to protect all 50 states from a rogue missile attack. Research and development of the NMD system continued under the Clinton administration from 1992 to 2000.

[edit] Current ABM developments

A renewed interest in missile defense coincided with the election of President George W. Bush in 2000. In several tests, the U.S. military has demonstrated the feasibility of shooting down long and short range ballistic missiles. Combat effectiveness of newer systems against tactical ballistic missiles seems very high, as the Patriot PAC-3 had a 100% success rate in Operation Iraqi Freedom. However NMD real-world effectiveness against longer range ICBMs is less clear.

While the Reagan era Strategic Defense Initiative was intended to shield against a massive Soviet attack, the current National Missile Defense has the more limited goal of shielding against a limited attack by a rogue state.

The Bush administration has accelerated development and deployment of a system proposed in 1998 by the Clinton administration. The system is a dual purpose test and interception facility in Alaska, and as of 2006 is operational with a few interceptor missiles. The Alaska site provides more protection against North Korean missiles or accidental launches from Russia or China, but is likely less effective against missiles launched from Iran. The Alaska interceptors may be later augmented by the naval Aegis Ballistic Missile Defense System, by ground-based missiles in other locations, or by the Boeing Airborne Laser. President Bush has referenced the September 11, 2001 Terrorist Attacks and the proliferation of ballistic missiles as reasons for missile defense.

[edit] International ABM efforts

An Arrow anti-ballistic missile interceptor

In 1993, a symposium was held by western European nations to explore potential future ballistic missile defense programs. In the end, the council recommended deployment of early warning and surveillance systems as well as regionally controlled defense systems. [5] In 1998 the Israeli military conducted a successful test of their Arrow ABM, developed in Israel with American assistance. Designed to intercept incoming missiles traveling at up to 2 mile/s (3 km/s), the Arrow is expected to perform much better than the Patriot did in the Gulf War. Taiwan is also engaged in the development of an anti-ballistic missile system, based on its indigenously developed Tien Kung-II (Sky Bow) SAM system. Although reports suggest a promising system, the ROC government continues to show strong interest towards the American Terminal High Altitude Area Defense (THAAD) program.

[edit] India's ABM Development

India has an active ABM development effort using local derivatives of the Elta Green pine radars and locally designed missiles. In November of 2006, India successfully conducted the PADE (Prithvi Air Defence Exercise) in which an Anti-ballistic missile, called the Exoatmospheric interceptor system intercepted a Prithvi-II ballistic missile.^[2] India became the fourth nation in the world to acquire such a capability and the third nation to develop it through indigenous effort.^[3] India also became the second nation after the U.S.A to use the Hit to Kill technology in its Anti ballistic missile.

[edit] Footnotes

1. ^ http://nuclearweaponarchive.org/Usa/Tests/Argus.html
2. ^ India fires new interceptor missile in air defence test
3. ^ India develops new anti-missile system

[edit] See also

• National Missile Defense
• nuclear disarmament
• nuclear proliferation
• nuclear warfare
• atmospheric reentry
• Terminal High Altitude Area Defense
• Aegis Ballistic Missile Defense System
• Sprint (missile)
• Spartan (missile)
• Safeguard/Sentinel ABM system

[edit] External links

• Video of the Endo-Atmospheric Interceptor missile system test by India
• The Center for Defense Information has many resources on ABMs and NMD.
• The Federation of American Scientists, as usual, is a wonderful resource for technical data, full-text of key documents, and analysis.
• MissileThreat.com, a listing and descriptions of ABM systems around the world.
• The unofficial website of the Stanley R. Mickelson Safeguard complex contains relevant images and history of the Safeguard program.
• History of U.S. Air Defense Systems