Air Defense: Teaching Old Aegis New Tricks


March 20, 2009: The U.S. Navy is equipping 17 of its 18 Aegis anti-missile system ships with a new feature that enables the older SM-2 missile to destroy the warheads, of short range ballistic missiles, as they enter the atmosphere. The 18th U.S. Aegis anti-missile ship will be equipped with the next upgrade (more powerful Aegis computers and an updated SM-3 missile).

Two Japanese warships also have the Aegis anti-missile capability, and they get all upgrades as well. There are currently 88 Aegis equipped warships in the world, most of them American. Aegis has been around for over three decades, and Aegis equipped ships have fired over 3,500 missiles so far, most of them for training exercises. The U.S. Navy is converting three more Aegis ships to fire anti-missile missiles by the end of the year. This costs about $12 million a ship, mainly for new software and a few new hardware items.

The Aegis anti-missile system has had a success rate of over 80 percent, in knocking down incoming ballistic missile warheads during test firings. To achieve this, two similar models of the U.S. Navy Standard anti-aircraft missile are used, 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 has a shorter range than the SM-3, which 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). However, there is also a land based version that Israel is interested in buying.




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