In mid-March 2017 Aegis equipped warships from the United States, South Korea and Japan participated in a LINKEX (trilateral missile warning informational link exercise) off the east coast of South Korea. This exercise was to test if all three destroyers (a U.S. Burke, a South Korean Sejong and Japanese Kirishima class) could indeed communicate and coordinate using their Aegis anti-missile system to defeat an enemy ballistic missile attack. Details of the LINKEX were not released, as that would let a potential enemy (namely North Korea, Iran, China or Russia) know just how well the linked warship anti-missile systems worked. Apparently well enough to seriously degrade the effectiveness of an attack using a lot of ballistic missiles.
This international LINKEX comes after Japan and South Korea spent nearly half a billion dollars to install the Baseline (BL) 9 software and hardware upgrade on five of their Aegis equipped warships. BL 9 not only enables ships to use the anti-missile features of Aegis but includes IAMD (integrated air and missile defense) which allows all IAMB ships to share Aegis related information with other IAMD equipped ships. This enables IAMB ships to instantly share target information as well as deciding quickly who will fire on which incoming missiles or aircraft. When trying to destroy incoming ballistic missiles seconds count. All this instantaneous digital communications is what the Internet generation of naval officers expect and this sort of combat connectivity is being achieved in all the services. Not only that but the United States has been holding similar successful link exercises between army, navy and air force units.
What is different about Aegis is that it is a major naval system used by a growing number of countries. The U.S. currently has 84 Aegis equipped warships, many of them also receiving similar BL 9 upgrades. There are 19 Aegis equipped ships with allied navies and this number is rapidly increasing, usually with the anti-missile and IAMB upgrades. Japan and South Korea want IAMB because that enables these ships to network with American Aegis ships to create a more effective defense against Chinese or North Korean ballistic missile attack. Aegis equipped ships are well suited for this because they can quickly move to where they might be needed and it was that capability that caused many other nations to build Aegis equipped warships as well as most of the updates.
One of the recent upgrades for foreign Aegis users is the new (since 2015) SM-6 (Standard Missile 6) anti-aircraft missile, which is more capable that the older SM-2 and SM-3 and is getting more new features. For example in early 2016 the U.S. Navy revealed that it had successfully modified its new SM-6 so that it could hit surface ships. At first many wondered how effective this could be given that warhead of the 1.3 ton SM-6 missile weighs less than a hundred kilograms (220 pounds). Actually more than the warhead is involved but the amount of explosives is small. What makes a big difference is that the warhead and a large part of the missile hits the ship from above moving faster than a rifle bullet. In early 2014 the U.S. Navy tested the SM-6 against a recently retired American frigate. This was a 4,000 ton ship and while the exact results of the “SINKEX” (sinking exercise where a retired warships is used as the target) are classified it was not a surprise (to anyone who could do the math) that the warhead travelling at high speed did a lot of damage to the frigate. The damage was so great that the frigate was judged to be out of action had the SM-6 hit occurred in wartime. The U.S. Navy wants to buy nearly 2,000 SM-6s by the mid-2020s. SM-6 missiles cost $4.3 million each and will replace many of the SM-2 missiles currently carried by American and allied warships.
Giving anti-aircraft missiles a surface-to-surface capability is nothing new. The SM-2 ER, which entered service in 1980 and was also capable of being used against ships. SM-6 has longer range and more effective guidance (and resistance to countermeasures like jamming) than the SM-2 and is meant to deal with aircraft, cruise missile and ballistic missiles. Max range of the SM-6 is given as 240 kilometers. The longer range and higher speed of the SM-6 make it particularly effective against other ships. 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 general improvements in the electronics and other components. IAMB equipped ships can also coordinate the use of their anti-aircraft missiles to go after a large number of surface targets.
The SM-6 is a 1.5 ton, 6.55 meter (21.5 foot) long, 533mm (21 inch) diameter missile. It has a max altitude of 33 kilometers (110,000 feet). The older SM-2 is 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 main change for the SM-6 is the guidance system which is self-contained and will seek out any target it comes within range of. The 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.
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 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. To achieve this, two similar models of the U.S. Navy Standard anti-aircraft missile are in service, in addition to a modified (to track incoming ballistic missiles version) version of the Aegis radar system.
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 optimized for anti-missile work, while the SM-2 Block IV was designed to be used against both ballistic missiles and aircraft. The SM-2 Block IV also costs less than half of what an SM-3 costs. So going after aircraft with SM-3s is discouraged unless absolutely necessary.