In late October, a Japanese Kongo class destroyer shot down a ballistic missile off Hawaii, using its Aegis anti-missile system. That makes three successful Aegis tests for Japan's Aegis equipped destroyers, out of four attempts. Overall, Aegis has been successful in 85 percent of its test firings.
Currently, the U.S. Navy has 20 ships with the Aegis anti-missile system. Within three years, the navy will have 27 such ships. But in the meantime, the Aegis ABM (Anti-Ballistic Missile)s are in high demand by U.S. commanders, seeking some protection from hostile missiles in their area of operation. Japan has six Aegis ABM equipped warships, and these are used to provide protection from any North Korean mischief. But six isn't enough, and some American ships are doing ABM patrols off Korea as well. However, the navy needs these Aegis ABM ships for other work as well, and this is causing problems when the Department of Defense and the president come seeking some instant ABM protection. Aegis is usually the quickest way of providing it. The navy is a victim of its own success.
Converting an Aegis ship to Aegis ABM costs about $12 million a ship, mainly for new software and a few new hardware items. This is seen as a safe investment. To knock down ballistic missiles, Aegis uses two similar models of the U.S. Navy Standard anti-aircraft missile, in addition to a modified version of the Aegis radar system, which has been modified to track incoming ballistic missiles.
The anti-missile missile is the RIM-161A, also known as the Standard Missile 3 (or SM-3). It 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 shorter range ballistic missiles. One test 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 SM-3 has four stages. The first two 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).
However, there is also a land based version, which is being installed in Poland, Romania and Israel. There has long been a land based version, it's the one originally used to develop the Aegis hardware and software.