United States national missile defense
National missile defense refers to the nationwide antimissile program the United States has had under development since the 1990s. After the renaming in 2002, the term now refers to the entire program, not just the ground-based interceptors and associated facilities.
File:EKV prototype launch.jpg|thumb|300px|A Payload Launch Vehicle carrying a prototype exoatmospheric kill vehicle is launched from Meck Island at the Kwajalein Missile Range on 3 December 2001, for an intercept of a ballistic missile target over the central Pacific Ocean.
Other elements that could potentially be integrated into NMD include anti-ballistic missiles, or sea-based, space-based, laser, and high altitude missile systems. The NMD program is limited in scope and designed to counter a relatively small ICBM attack from a less sophisticated adversary. Unlike the earlier Strategic Defense Initiative program, it is not designed to be a robust shield against a large attack from a technically sophisticated adversary.
Definitions
The term "national missile defense" has several meanings:- U.S. National Missile Defense, the limited ground-based nationwide antimissile system in development since the 1990s. In 2002 this system was renamed to Ground-Based Midcourse Defense, to differentiate it from other missile defense programs, such as space-based, sea-based, laser, robotic, or high-altitude intercept programs. As of 2006, the GMD system is operational with limited capability. GMD is designed to intercept a small number of nuclear-armed ICBMs in the mid-course phase, using Ground-based interceptor missiles launched from within the United States in Alaska and California. GMD uses non-nuclear GBIs with a kinetic warhead. Other [|components of the national missile defense] are listed below.
- Any national ICBM defense by any country, past or present. The U.S. Sentinel program was a planned national missile defense during the 1960s, but was never deployed. Elements of Sentinel were actually deployed briefly as the Safeguard Program, although it wasn't national in scope. The Russian A-135 anti-ballistic missile system is currently operational only around the city of Moscow, the national capital, and is far from being national in scope in Russia.
- Any national missile defense by any country. Israel currently has a national missile defense against short and medium-range missiles using their Arrow missile system.
History of national missile defense systems
When the United States Air Force was split from the United States Army in 1947, the Army retained the role of ground based air defenses that would evolve into National missile defense. The Army retained the lead role in this area until the success of the Aegis system shifted the focus to the United States Navy in the 21st century.Nike-Zeus
In the 1950s, a series of anti-aircraft missiles were developed as part of Project Nike. The latest in the series, Nike-Zeus, offered extremely long-range interception and very high performance. In the late 1950s, the program investigated the use of Nike-Zeus missiles as interceptors against Soviet ICBMs. A Nike warhead would be detonated at high altitudes above the polar regions in the near vicinity of an incoming Soviet missile.The problem of how to quickly identify and track incoming missiles proved intractable, especially in light of easily envisioned countermeasures such as decoys and chaff. At the same time, the need for a high-performance anti-aircraft weapon was also seriously eroded by the obvious evolution of the Soviet nuclear force to one based almost entirely on ICBMs. The Nike-Zeus project was canceled in 1961.
Project Defender
The Nike-Zeus use of nuclear warheads was necessary given the available missile technology. However, it had significant technical limitations such as blinding defensive radars to subsequent missiles. Also, exploding nuclear warheads over friendly territory was not ideal. In the 1960s Project Defender and the Ballistic Missile Boost Intercept concept replaced land-launched Nike missiles with missiles to be launched from satellite platforms orbiting directly above the USSR. Instead of nuclear warheads, the BAMBI missiles would deploy huge wire meshes designed to disable Soviet ICBMs in their early launch phase. No solution to the problem of how to protect the proposed satellite platforms against attack was found, however, and the program was canceled in 1968.Sentinel Program
In 1967, U.S. Defense Secretary Robert McNamara announced the Sentinel Program, providing a defense against attack for most of the continental United States. The system consisted of a long range Spartan missile, the short range Sprint missile, and associated radar and computer system. However, U.S. military and political strategists recognized several problems with the system:- Deployment of even a limited defensive ABM system might invite a preemptive nuclear attack before it could be implemented
- Deploying ABM systems would likely invite another expensive arms race for defensive systems, in addition to maintaining existing offensive expenditures
- Then-current technology did not permit a thorough defense against a sophisticated attack
- Defended coverage area was very limited due to the short range of the missiles used
- Use of nuclear warheads on antimissile interceptors would degrade capability of defensive radar, thus possibly rendering defense ineffective after the first few interceptions
- Political and public concern about detonating defensive nuclear warheads over friendly territory
- An ICBM defense could jeopardize the Mutual Assured Destruction concept, thus being a destabilizing influence
Safeguard Program
- It was less expensive to develop due to its limited geographic coverage and fewer required missiles.
- It avoided a lot of hazards to the public of defensive nuclear warheads detonated in the atmosphere nearby, since the Safeguard system was located in and near sparsely populated areas of the Dakotas, Montana, Manitoba, Saskatchewan, and Alberta.
- It provided better interception probabilities due to dense coverage by the shorter-range Sprint missiles, which were unable to cover the entire defended area under the larger and earlier proposed Sentinel program.
ABM treaty
These above issues drove the United States and the USSR to sign the Anti-Ballistic Missile Treaty of 1972. Under the ABM treaty and the 1974 revision of it, each country was allowed to deploy only two ABM systems with only 100 interceptors each - one to protect the national command authority or capitol, the other to protect a deterrent force such as a missile field. The Soviets deployed a system named the A-35 "Galosh" missile system, and it was deployed to protect Moscow, its capital city. The U.S. deployed the Safeguard system to defend the ICBM launch sites around the Grand Forks Air Force Base, North Dakota, in 1975. The American Safeguard system was only briefly operational. The Soviet system has been improved over the decades, and it is still operational around Moscow.Homing Overlay Experiment
Given concerns about the previous programs using nuclear armed interceptors, in the 1980s the U.S. Army began studies about the feasibility of hit-to-kill vehicles, where an interceptor missile would destroy an incoming ballistic missile just by colliding with it, the so-called "Kinetic Kill Vehicles", or KKV.The first program which actually tested a hit-to-kill missile interceptor was the Army's Homing Overlay Experiment. "Overlay" was the Army's term for exo-atmospheric interceptions, which would have to declutter any decoys, "underlay" was their term for high-altitude interceptions within the atmosphere. The KKV was equipped with an infrared seeker, guidance electronics and a propulsion system. Once in space, the KKV extended a diameter structure similar to an umbrella skeleton to enhance its effective cross section. This device would destroy the ICBM reentry vehicle on collision. After test failures with the first three flight tests, the fourth and final test on 10 June 1984 was successful, intercepting the Minuteman RV with a closing speed of about at an altitude of more than.
Strategic Defense Initiative
On 23 March 1983, President Ronald Reagan announced a new national missile defense program formally called the Strategic Defense Initiative but soon nicknamed "Star Wars" by detractors. President Reagan's stated goal was not just to protect the U.S. and its allies, but to also provide the completed system to the USSR, thus ending the threat of nuclear war for all parties. SDI was technically very ambitious and economically very expensive. It would have included many space-based laser battle stations and nuclear-pumped X-ray laser satellites designed to intercept hostile ICBMs in space, along with very sophisticated command and control systems. Unlike the previous Sentinel program, the goal was to totally defend against a robust, all out nuclear attack by the USSR.A partisan debate ensued in Congress, with Democrats questioning the feasibility and strategic wisdom of such a program, while Republicans talked about its strategic necessity and provided a number of technical experts who argued that it was in fact feasible. Advocates of SDI prevailed and funding was initiated in fiscal year 1984.