National Missile DefenseNational Missile Defense (NMD) is a military strategy that has been discussed in the United States since the 1960s. The basic idea is to shield the U.S. against incoming missiles by shooting them down as they approach the country, and its role in nuclear strategy has been a heated topic for several decades. (See also: Anti-ballistic missile)
In the 1980s, the primary focus of research and planning for National Missile Defense was as part of a Strategic Defense Initiative designed to shield the United States from a massive attack by the Soviet Union and move the United States and the Soviet Union from a position of mutually assured destruction. The motivation behind this effort largely collapsed with the fall of the Soviet Union and the end of the Cold War.
In the 1990s and early 21st century, the mission of NMD has changed to the more modest goal of preventing the United States from being subject to nuclear blackmail or nuclear terrorism by a so-called rogue state. The feasibility of this more limited goal remains somewhat controversial. Although most (though not all) defense analysts believe that developing a system to intercept a small missile attack is technologically possible, some have questioned whether it is a strategy that is preferable to that of a promise of retaliation.
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3 Recent developments
4 APS report
Skeptics named the U.S. missile defense program of the 1980s "Star Wars" (after the hit movie series), since it seemed to its critics to be a mere science fiction scheme with no hope of success. It has since then gained the support of some of its erstwhile critics.
On the other hand, new critism about the feasibility of the program has been raised very recently. See e.g. the APS report on NMD.
There has been controversy among experts about whether it is technically feasible at all to build a system which intercepts ballistic missiles during their boost phase, as part of the U.S. National Missile Defense program intends.
This technical criticism came especially from US physicists and culminated in the publication of a very critical study on the subject by the American Physical Society.
The study's main point is that it might be possible to develop within several years from now a system with (though limited) capability to destroy a liquid-fuel propelled ICBM during the boost phase. It was also found possibly feasible to destroy some solid-propellant launches, such as those from Iran, but not those from North Korea, because of differences in the boost time and siting possibilities for interceptors. However, at this time it is to be expected that the likely users of ICBMs will switch to solid fuel, which makes acceleration faster and the boost phase so short that only few tens of seconds remain to identify, target and destroy the missile. The study concluded that this is unlikely to be achievable with expected advances in technology over the following 15 years.
Using orbital launchers to provide a reliable defence against solid fuel launches from Iran or North Korea was found to require at least 1,600 interceptors in orbit. Reducing the requirement to liquid-fueled missile interception would reduce the number to 700. To allow for the use of two or more interceptors per missile, many more would be required.
If operating in the region, within 300km of intercept point for a solid fuel missile, 600km for liquid, the use of the airborne laser was found to possibly be credible, though solid fuel launchers are more resistant than liquid-fueled systems. There is considerable uncertainty about the actual capability of the system.
In summary, the report concluded that:
Given the results that follow from our assumptions, we conclude that while the boost phase technologies we studied are potentially capable of defending the United States against liquid-propellant ICBMs at certain ranges of interest, at least in the absence of counter-measures, when all factors are considered none of the boost-phase defense concepts studied would be viable for the foreseeable future to defend the nation against even first-generation solid-propellant ICBMs.
- Report of the APS Study Group on Boost-Phase Intercept Systems for National Missile Defense -July 15, 2003