August 29,2008:  The U.S. Navy Aegis anti-missile system has had an 88 percent success rate (14 out of 16) in knocking down incoming ballistic missile warheads. To achieve this, two similar models of the U.S. Navy Standard anti-aircraft missile are use, in addition to a modified version of the Aegis radar system, which can now track incoming ballistic missiles.

The RIM-161A, also known as the Standard Missile 3 (or SM-3), has a range of over 500 kilometers and max altitude of over 160 kilometers. The Standard 3 is based on the anti-missile version of the Standard 2 (SM-2 Block IV). This SM-2 missile turned out to be effective against ballistic missiles ballistic missile warheads that are closer to their target. A test last June saw a SM-2 Block IV missile destroy a warhead that was only 19 kilometers up. An SM-3 missile can destroy a warhead that is more than 200 kilometers up. But the SM-3 is only good for anti-missile work, while the SM-2 Block IV can be used against both ballistic missiles and aircraft. The SM-2 Block IV also costs less than half what an SM-3 costs.

The Standard 3 has four stages. The first two stages boost the interceptor out of the atmosphere. The third stage fires twice to boost the interceptor farther beyond the earth's atmosphere. Prior to each motor firing it takes a GPS reading to correct course for approaching the target. The fourth stage is the 20 pound LEAP kill vehicle, which uses infrared sensors to close on the target and ram it. The Aegis system was designed to operate aboard warships (cruisers and destroyers that have been equipped with the special software that enables the AEGIS radar system to detect and track incoming ballistic missiles).

By the end of the year, the U.S. Navy will have completed equipping 18 ships with the Aegis anti-missile system. One reason the navy recently cancelled its expensive new DDG-1000 class of destroyers was because these were built to support amphibious and coastal operations, and did not have a radar that could easily be converted to use SM-3 missiles. The DDG-1000 also cost 2-3 times as much as current Aegis destroyers. With missile defense seen as a higher priority than providing new coastal combat capability, the DDG-1000 was killed, and money saved could be used to build more Aegis destroyers, and convert more current destroyers and cruisers to use SM-3.