July 5, 2012: On June 27th, for the second time, a U.S. Navy SM-3 Block IB anti-missile missile successfully intercepted an incoming warhead. A year ago the U.S. Missile Defense Agency (MDA) bought twenty SM-3 Block 1B anti-missile missiles. This included research and development work on the Block 1B improvements. Aegis has been very successful at knocking down incoming ballistic missile warheads.
At the moment, Aegis anti-missile systems are hot. The U.S. government, encouraged by the high success rate (82 percent) of Aegis SM-3 missile tests, has been expanding the number of SM-3 equipped ships. With 18 Aegis anti-missile equipped ships in service now and plans to have more than twice as many in the next few years.
Converting Aegis ships to fire anti-missile missiles costs about $15 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 an Aegis equipped ship uses two similar models of the U.S. Navy Standard anti-aircraft missile, in addition to a modified version of the Aegis radar system, tweaked to also track incoming ballistic missiles.
Now the government wants to use Aegis more aggressively to block Iranian or North Korean ballistic missiles. This means buying over a thousand SM-3 missiles. These currently cost about $10 million each, and the next upgrade (which will deliver more accuracy and reliability) will raise that to $15 million each. While the expanded Aegis program will cost about $20 billion, it's seen as the cheapest way to provide reliable anti-missile defense against Iran and North Korea.
SM-3 is also known as the RIM-161A. 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 version 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 of 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 9 kg (20 pound) LEAP kill vehicle, which uses infrared sensors to close on the target and ram it.