Three years ago, Japan bought nine American SM3 anti-missile missiles, along with the needed software upgrades to the Aegis radar systems on some of its warships (that use the SM-3 missile.) Japan has since bought more missiles. Now Japan plans to use this new anti-missile capability on a recently announced (or, rather, threatened) North Korean missile launch. If the North Korean missile appears headed for Japanese territory, Japan will try to shoot it down. Maybe.
There's a bit of déjà vu to all this, as North Korea pulled the same stunt three years ago. Back in 2006, North Korea used missile launch preparations to try and get some better aid offers out of its enemies. At the time, the U.S. discussed shooting down the North Korean Taepodong 2 missiles with its Aegis anti-missile systems. Even back then, it was believed North Korea was trying to launch a satellite, in which case AEGIS systems wound have a more difficult time destroying the North Korean missile. This time around, North Korea is again talking about maybe launching a satellite. This time, the Japanese are ready. It was past North Korean missile launches that spurred the Japanese to equip themselves with suitable defenses.
Back in 2006, as now, North Korea was preparing a multi-stage Taepodong 2 missile for launch. This liquid fueled missile takes several days to prepare for launch, and it can't be easily hidden. The missile can reach parts of Alaska, as well as all of Japan. In 2006, the North Korean did launch two Taepodong 2 missiles, and no attempt was made to shoot them down. The two missiles landed 500 kilometers west of Japan, in international waters. This time around, the Japanese would like to knock a Taepodong 2, just to show the North Koreans, and the Japanese tax payers, that the billions they have spent on the anti-missile systems, was worth it.
Since 2006, Japan has equipped four of its warships to use the Aegis SM-3 anti-missile system. Eventually, Japan plans to equip half a dozen, or more, of its Aegis warships with the SM-3, to provide protection from North Korean, or Chinese, ballistic missiles.
The SM-3 missile has been one of the bright spots in the American anti-missile effort. Thus Japan has also agreed to contribute a billion dollars to the three billion dollar development work being done on the next version of the SM-3. The U.S. has already stationed Aegis SM-3 equipped ships off the coast of Korea, to provide protection against North Korean missiles.
The Standard 3 (or SM-3) is designed to reach out 500 kilometers to hit incoming missiles. The Standard 3 is based on the failed anti-missile version of the Standard 2 and costs over three million dollars each. 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 its 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.