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Ballistic missile defense
From Citizendium, the Citizens' Compendium
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Ballistic missile defense (BMD) includes a range of technologies and military doctrines intended to defeat, or reduce the damage caused by, an enemy attack with ballistic missiles. While a ballistic missile could be intercepted in any of the three phases of its flight:
- boost: powered flight into a suborbital trajectory, typically over an area of land or sea either under the enemy's control or that the enemy does not consider contested (e.g., ocean from which a submarine-launched ballistic missile would be fired);
- midcourse: unpowered "coasting" through space or extremely high atmosphere, from which the reentry phase will be triggered by gravitation or a programmed maneuver such as firing retrorockets to slow the trajectory;
- terminal defense: interception of the reentry vehicle(s) as they reenter the atmosphere, at extremely high speed, from the midcourse phase;
each of these phases presents unique challenges for interception of the missile or its warhead. Some BMD systems, recognizing the complexity of each phase, may "layer" defenses, combining, for example, midcourse intercept with terminal defense against those warheads not destroyed in midcourse.
BMD divides into two major classes:
- Theater BMD, against short- to intermediate-range missiles. Depending on the range of the missile, the curvature of the earth may not hide much of the flight path from defensive sensors;
- National BMD, against intercontinental-range missiles, a significant part of the flight path of which will be hidden, from target-area sensors, by the curvature of the earth.
Technical issues and tradeoffs
Early BMD interceptors had nuclear warheads; the Russian 53T6 GRIFFON and possibly 51T6 GAZELLE still do, but no recently designed system uses them. Nuclear warheads have been rendered impractical due to bans against testing in the atmosphere and space. Improvements in guidance also makes the large area of effect of a defensive nuclear burst unnecessary; the kill mechanisms of current systems are either kinetic (i.e., direct collision with the warhead) or directed energy (e.g., laser heating of the warhead). Some endoatmospheric ABMs do use explosive warheads.
Mechanisms to destroy enemy missiles are not limited to anti-ballistic missiles, although those are the most common that have been deployed. Directed energy weapons, especially lasers, are under active development. Autocannon have been proposed for terminal defense of point targets, and may be of increased interest against very short range missiles and unguided rockets, as, for example, on the borders of Israel.
Systems by nation/multinational group
Russian Federation (former Soviet Union)
Sensors
Kill mechanisms
There is a two-layer missile system protecting the Moscow area against small attacks, using 53T6 GORGON and 51T6 (missile)
Israel/United States
Interceptors include the U.S. Army THAAD and MIM-104 Patriot‎, and the joint U.S.-Israeli Arrow 2. Lasers and autocannon are being considered as final defense.
Israel is also actively seeking counter-rocket, artillery and mortar (C-RAM) systems to protect against a short-range threat that, to them, is also national.
United States
At an architectural and system integration level, there is a distinction between U.S. theater and non-theater kill mechanisms, but sensors generally called national or theater routinely feed targeting information to either type.
Sensors
Space-based infrared
Radars
Radars on theater-level platforms include the shipboard AN/SPY-2 and the U.S. Army AN/TPY-2. It must be emphasized that both types feed tracking information into an overall command and control system. There are AN/TPY-2 installations in locations without colocated interceptors, such as Japan.
Theater-level kill mechanisms
SM-3
The U.S. Navy RIM-161 Standard SM-3 has demonstrated anti-satellite as well as ABM capability. It is fired from Ticonderoga-class cruisers and Burke-class destroyers equipped with the AN/SPY-2 enhancement to the AEGIS battle management system. Japan is also acquiring this system for use on their Kongo-class destroyers, which are licensed copies of Burkes.
Israel is considering adapting SM-3 as a land-based system with greater range than THAAD.
THAAD
Patriot
Patriot began as a surface-to-air missile, but the PAC-3 variant is optimized for BMD. Besides the U.S., Egypt, Germany, Greece, Israel, Japan, Kuwait, the Netherlands, Saudi Arabia, South Korea and Taiwan have it, and at least a temporary installation is in Poland/
Airborne Laser (ABL-1)
Still experimental, the U.S. has an evolving laser system in a Boeing 747 aircraft.
NCADE
In advanced development, the NCADE system is intended for boost-phase intercept. It is modified from the AIM-120 AMRAAM missile and potentially can be fired from any of the wide range of aircraft that already have the AMRAAM as an air-to-air missile. The F-15 Eagle radar specifically supports it, but it is primarily a software problem to adapt other radars for it.
Regional-level kill mechanisms
The term "national-level" does not strictly fit the U.S. systems, since there will be a midcourse interceptor installation in Poland as well as the U.S.
