May 6,2008: Japan has agreed to help the United States develop a multiple warhead version of the SM-3 anti-ballistic missile (ABM) system. This system, the RIM-161A, also known as the Standard Missile 3 (or SM3), has a range of over 500 kilometers and max altitude of 160 kilometers. The Standard 3 is based on the failed anti-missile version of the Standard 2, and costs over nine million dollars each. The 22 foot long, one ton 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 (heat seeking) sensors to close on the target and ram it. The SM-3 Block IIA version wound have three LEAP kill vehicles in the warhead. Each would be lighter than the current one, but would be just as effective. That's because hitting an incoming warhead, which is moving faster than a rifle bullet, with anything weighing more than a few ounces, will cause a major mess, and destroy the warhead. Other stages of the SM-3Block IIA will be heavier, a plan already in the works (to produce the SM-3 Block II). This version would have a longer range (about 1,000 kilometers) and higher operating altitude. That would enable the SM-3 to knock out ICBMs.

All this will cost the Japanese over a billion dollars. At first the Japanese turned down the American invitation to join in (that is, help pay for) developing the SM-3 Block IIA. The reason was that the North Koreans did not have multiple warheads on their missiles, and were unlikely to develop multiple warheads before the communist government running the country fell from power. There was also concern that this would delay work on the longer range SM-3 Block II. But apparently the Japanese reconsidered when they took a closer look at China, which is developing multiple warheads for its ICBMs, and has expressed hostile intent towards Japan (whose atrocious behavior there during World War II is still remembered with much bitterness.) In any event, China apparently has ICBMs aimed at Japan, or at least many Japanese politicians and military officials think so. Better safe than sorry. The SM-3Block IIA is not expected to be ready to go for another six years or so.

The Aegis system, and the SM series of missiles, only operate from 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. The U.S. has two other land based anti-missile systems. The U.S. Army THAAD anti-ballistic- missile (ABM) system has a range of 200 kilometers, against targets as high as 150 kilometers. THAAD is intended for short (like SCUD) or medium range (up to 2,000 kilometer) range ballistic missiles. The 18 foot long THAAD missiles weigh 1,400 pounds each. This is about the same size as the Patriot anti-aircraft missile, but twice the weight of the anti-missile version of the Patriot. Ultimately, the army would like to buy at least 18 launchers, 1,400 missiles, and 18 radars. THAAD is a step up from the Patriot PAC-3 anti-missile (which is an anti-aircraft missile adapted to take out incoming missiles). The PAC-3 works, but it has limited range (20 kilometers).