November 3, 2009: Recently, the Japanese Navy conducted its third successful test of one of its Aegis equipped ship using a SM-3 missile. The U.S. and Japan are jointly developing the next generation SM-3 missile, which will be more accurate and reliable, than the current ones, in shooting down ballistic missiles. Japan has six Aegis equipped warships.

The U.S. Navy 18 ships with the Aegis anti-missile system. Earlier this year, for the 19th time, a U.S. Navy Aegis equipped ship used one of its SM-3 missiles to shoot down a ballistic missile. At that point, Aegis achieved an 83 percent success rate for these live test firings.

With that in mind, the navy is converting three more Aegis ships to fire anti-missile missiles. This 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 missile, 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 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 missile warheads that are closer to their target. 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 that Israel is interested in buying.