Japan will expand its force of warships equipped with anti-missile systems by building two more Aegis equipped destroyers. Japan is quite pleased with its Aegis anti-missile system. In 2010, a Japanese Kongo class destroyer shot down a ballistic missile off Hawaii, using its Aegis anti-missile system. That made three successful Aegis tests for Japan's Aegis equipped destroyers, out of four attempts. Japan already has four destroyers equipped to use Aegis anti-missile systems and two more are having their Aegis upgraded to have anti-missile capability.
With the two new destroyers Japan will have eight warships with Aegis anti-missile capability. The upgrade process mainly involves software modifications to the Aegis radar and fire control system and replacing some of the SM-2 anti-aircraft missiles with SM-3 anti-missile missiles. Not counting the cost of the SM-3 missiles, the upgrade costs about $15 million per ship.
Encouraged by the success, the U.S. Navy continues developing new features. In 2013, it completed testing of the new Standard Missile 6 (SM-6) anti-aircraft missile. In 2013, two years after receiving the first production SM-6, the U.S. Navy successfully tested it hitting an aircraft (a BQM-74 target UAV) over the horizon. The SM-6 is basically the existing SM-2 anti-aircraft missile with the more capable guidance system of the AMRAAM air-to-air missile, as well as other improvements in the electronics and other components. The SM-6 is a 1.5 ton, 6.55 meter (21.5 foot) long, 533mm (21 inch) diameter missile. It has a max range of 240 kilometers and a max altitude of 33 kilometers (110,000 feet).
The older SM-2 is a 1.35 ton, 8 meter (26.2 foot) long missile with a max range of 190 kilometers and max altitude of 24.4 kilometers (80,200 feet). The AMRAAM guidance system is self-contained and will seek out any target it comes within range of. The current SM-2 uses a "semi-active" guidance system, which requires that a special targeting radar "light up" the target with a radar beam, which the SM-2 guidance system detects and homes in on. The "active" guidance system of the SM-6 is thus harder to jam and can home in on targets beyond the range of targeting radars. The SM-6 can attack anti-ship missiles as well.
The SM-6 took 9 years to develop and is now in production, with the initial order for 1,200 missiles at a cost of $4.3 million each. SM-6 will replace many of the SM-2 missiles currently carried by American and Australian warships and eventually other SM-2 users (like Japan) as well.
Meanwhile, the navy has been continuing years of improvements in the Aegis radar and fire control system that controls SM-2, SM-6, and the smaller SM-3 anti-missile version. The SM-3 can destroy ballistic missiles and low earth-orbit satellites. The Aegis anti-missile system has had a success rate of over 80 percent in knocking down incoming ballistic missile warheads during test firings. Aegis equipped ships are now getting version 4.0 and the next major upgrade (5.0) will make the anti-missile capabilities a standard feature of Aegis software. New destroyers are having anti-missile Aegis software installed as standard equipment. Much of the anti-missile capability of the original Aegis anti-aircraft system came from upgrades to the Aegis software.
There are actually two models of the U.S. Navy Standard anti-aircraft missile that can hit 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-3 missile has a shorter range than the SM-2, which can destroy a warhead that is more than 200 kilometers up. 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.