Air Defense: Iron Dome Faces Bad Numbers


January 10, 2013:   Although the new Israeli Iron Dome system succeeded in shooting down about 85 percent of the 500 hundred rockets (of 1,500 launched) headed for Israeli populated areas, this was something of a shock. This was the original situation the system was designed for. It was originally believed that only ten percent of less accurate rockets 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.

Meanwhile, the key to Iron Dome’s success continues to be its 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. 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 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 most recent Israeli rocket threat 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. 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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