Earlier this month Israel successfully completed tests of new software for its Iron Dome anti-rocket system. The improvements enable the Iron Dome missiles to intercept incoming rockets farther away. The 90 kg (200 pound) three meter (9.8 foot) long missiles are only fired if the fire control system calculates that the incoming rocket could land in an inhabited area.
Israel has bought seven batteries of Iron Dome. Four are in action and a fifth one enters service this month. Each battery has radar and control equipment and four missile launchers. Each battery costs about $37 million, which includes over fifty missiles. In the last two years Iron Dome has intercepted over 100 rockets headed for populated areas.
During tests Iron Dome detected and shot down BM-21 (122mm) and Kassam (locally made) rockets. Iron Dome uses two radars to quickly calculate the trajectory of the incoming rocket (Palestinian Kassams from Gaza or Russian and Iranian designs favored by Hezbollah in Lebanon) and do 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 $40,000 guided missile is fired to intercept the rocket. This makes the system cost-effective. That's because Hezbollah fired 4,000 rockets in 2006, and Palestinian terrorists in Gaza have fired over six thousand Kassam rockets in the past eight years and the Israelis know where each of them landed. Over 90 percent of these rockets landed in uninhabited areas and few of those that did hit inhabited areas caused casualties. Still, a thousand interceptor missiles would cost $40 million. But that would save large quantities of military equipment and avoid many dead and injured troops. Israel already has a radar system in place that gives some warning of approaching rockets. Iron Dome will use that system, in addition to another, more specialized, radar in southern Israel.
The rocket attacks have been around since 2001, but got much worse once Israel pulled out of Gaza in August of 2005. This was a peace gesture that backfired. From 2001 to 2005, about 700 rockets were fired from Gaza into Israel. Since the 2005 withdrawal, nearly 4,000 more rockets were fired into Israel. The rate of firings increased after Hamas took control of Gaza in June, 2007.
Hamas has been bringing in more factory made Iranian and Chinese made BM-21 and BM-12 rockets. Israel believes Hamas currently has, in Gaza, factory-made BM-21 rockets, each with a range of 20-40 kilometers. They also have some shorter range (six kilometers) Russian designed B-12 rockets. The 122mm BM-21s weigh 68.2 kg (150 pounds) and are 2.9 meters (nine feet) long. These have 20.5 kg (45 pound) warheads but not much better accuracy than the 107mm model. However, these larger rockets have a maximum range of 20 kilometers. Again, because they are unguided, they are only effective if fired in salvos or at large targets (like cities, large military bases, or industrial complexes). There are Egyptian and Chinese variants that have smaller warheads and larger rocket motors, giving them a range of about 40 kilometers. Iron Dome has stopped over a dozen of these longer range missiles so far.