Air Defense: Iron Dome Keeps Moving


February 25, 2013: Israel has moved a third Iron Dome anti-rocket system north, to deal with any possible attacks coming out of Syria. There, the two year old civil war is leading to weapons storage sites being captured by rebels and the contents disappearing. Israel fears that someone will grab some rockets and someone to operate them and launch attacks on Israel. Northern Israel is sparsely populated and not very vulnerable to the many 122mm artillery rockets favored by terrorists because these only have a range of about 20 kilometers. But the Syrians have hundreds of longer range missiles and rockets that can reach Israel’s largest cities farther south. Another problem with this is that the cities are easier to hit because the populated area is so large. This caused some unexpected problems with Iron Dome last November.

Although the Iron Dome system succeeded in shooting down about 85 percent of the rockets Hamas fired at Israeli populated areas last November, the number that had to be shot down was something of a shock. It was originally believed that only ten percent of rockets fired at smaller towns and villages would need to be intercepted by Iron Dome missiles. The rest would fall into unpopulated areas that are common near the northern and southern borders. But the eight day bombardment by Hamas rockets last November saw 1,500 larger or longer ranged rockets fired at larger targets (cities). This meant a third of the rockets headed for populated areas and thus needing an Iron Dome interceptor missile. Even though Israel has ordered more Iron Dome missiles, too many rockets headed for populated areas in a short time means some incoming rockets that should get an interceptor missile won’t.

A solution may lie in Iron Dome’s software. Iron Dome uses two radars to quickly calculate the trajectory of the incoming rocket and does nothing if the rocket trajectory indicates it is going to land in an uninhabited area. But if the computers predict a rocket coming down in an inhabited area, a Tamir guided missile is fired to intercept the rocket. This makes the system cost-effective. Further improvements in the software may make it less necessary to fire missiles. That's mainly because most of these unguided rockets land in uninhabited areas, but the few of those that do land in populated areas inflict casualties. The system was so successful and reliable that it was found safe to fire one missile, instead of two, at each incoming rocket. In addition, during the eight day campaign last November, the Iron Dome software was updated almost daily as users reported any problems which were collected and fixed quickly and a new version of the software created, tested, and issued.

There’s nothing special about the rest of the Iron Dome system. The Tamir missiles each weigh 90 kg (200 pounds), are three meters (9.8 feet) long, and 160mm in diameter. They have the usual components of a guided missile (rocket motor, electronics, and mechanical devices to actuate the fins and batteries). Without the predictive software Iron Dome would quickly run out of missiles and be much more expensive to operate as well.

The first real rocket threat for Iron Dome was from a terrorist organization (Hamas) operating out of an area (Gaza) that is basically home for Palestinian refugees who have been there for over 60 years and want nothing less than the destruction of Israel. A similar organization (Hezbollah) controls southern Lebanon and is also dedicated to the destruction of Israel, using 40,000 unguided rockets they received from Iran. Hezbollah last attacked with rockets in 2006.

Israel is organizing a force of 13 Iron Dome batteries to defeat Hezbollah and Hamas rocket attacks. Israel keeps moving these batteries around, making them less of a target for missiles or terrorists. Each of the five existing Iron Dome batteries has radar and control equipment and three or four missile launchers (each containing twenty missiles). Two more batteries are on order. Each battery costs about $40 million, which includes up to a hundred Tamir missiles (costing $90,000 each). The U.S. contributed nearly $300 million for development of Iron Dome.




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