Air Defense: Iron Dome Passes The Combat Test


April 5, 2012:  In the last year Israel has seen its Iron Dome anti-rocket system get its first real combat test. Iron Dome has been a success, shooting down over 85 percent of the rockets aimed at Israeli towns and cities.

A year ago Israel deployed its only two Iron Dome anti-missile batteries to defend against rockets being fired from Gaza. One was placed near the town of Beer Sheva (the largest town in the Negev desert and east of Gaza) and another near the coastal city Ashdod (the largest city within range of 122mm rockets fired from Gaza). On April 7th, 2011, a 122mm rocket was intercepted near Ashkelon, which is south of Ashdod. This deployment was prompted by an increase in rockets fired from Gaza and the growing use of longer range (20 kilometers) 122mm rockets. Iron Dome proved that it could work under combat conditions, preventing the longer range, factory made rockets from landing in populated areas.

This year there was an even heavier attack. Of 250 rockets fired out of Gaza 166 made it to Israel and the Iron Dome computer determined that 56 of the rockets would land in an inhabited area, missiles were fired at those, destroying 75 percent of them. Thus only 11 percent of the rockets to make it into Israeli air space actually landed in an inhabited area (the other misfired or otherwise failed and landed inside Gaza). Iron Dome's ability to calculate which rockets (those headed for uninhabited area) to ignore allows the system to concentrate on the minority (less than a third) of the rockets aimed at inhabited areas that are actually going to land near their targets.

The 2011 deployment was a big turnaround for Iron Dome. Four months earlier Israeli revealed that its new Iron Dome anti-rocket system was not meant for defending towns and villages but was for military bases. This came as a big shock to most Israelis. For years politicians touted Iron Dome as a means of defending civilians living close to Gaza in the south and Lebanon in the north. But it turns out that it takes about 15 seconds for Iron Dome to detect and identify targets and fire its missiles. But most of the civilian targets currently under fire from Gaza are so close to the border (within 13 kilometers) that the rockets are fired and land in less than 15 seconds. This means that the town of Sderot, the closest Israeli urban area to Gaza, cannot be helped by Iron Dome. Sderot has been the main target for Palestinian rockets over the last few years.

This range and time problem explains why, after Iron Dome was declared ready for action two years ago, it was surprisingly placed in storage. The air force said they would prefer to save money and put the Iron Dome batteries off line, to be deployed only for regular tests (and for training) and for an actual emergency (an expected large scale attack on southern or northern Israel). Politicians demanded that at least one battery be deployed along the Gaza border. But the military sees more to fear from growing Hamas and Hezbollah supplies of longer range rockets. This enables large numbers of rockets to be fired at military bases. The generals believe it's more important to protect the military forces, who ultimately defend Israel, and that's what Iron Dome was to be used for. Since the military bases are far from the borders, longer range rockets, with longer (than 15 seconds) flight times, would be used. Iron Dome would knock down many of these rockets, as it has already done in tests. But terrorist use of longer range rockets against civilian targets changed these plans. Hamas wants to kill civilians and is aiming longer range rockets at Israeli cities.

Israel has bought seven batteries of Iron Dome, all to be delivered by next year. Three are currently in service and more will be ready by the end of the year. Each battery has radar, control equipment, and four missile launchers. Each battery costs about $37 million, which includes over fifty missiles.

Iron Dome uses two radars to quickly calculate the trajectory of the incoming rocket 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 (crude, short range, and locally made) 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 had 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 about 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. These are not smuggled in much because the locally made Kassam II has about the same range. However, the B-12 is more reliable (more reliable trajectory and fuse, so more are likely to land where aimed and explode).

The B-12 is a 107mm, 19 kg (42 pound), 107mm (4.2 inch) diameter, 84 cm (33 inch) long rocket that is very popular with terrorists. This rocket has a range of about six kilometers and 1.35 kg (3 pounds) of explosives in its warhead. Normally fired from a launcher, in salvoes of dozens at a time, when used individually it is more accurate the closer it is to the target. This 107mm design has been copied by many nations and is very popular with guerillas and terrorists because of its small size and portability. There is a Chinese BM-12 variant which has a smaller warhead and larger rocket motor. This version is supposed to have a range of about 12 kilometers.

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 stopped eight of these longer range missiles aimed at Ashkelon and Ashdod earlier this year. Then that Iron Dome battery was moved around to other cities where the Israeli Air Force planned to eventually install Iron Dome.

The rocket attacks from Gaza have been remarkably ineffective, killing only 40 people (half from rockets, the rest by mortars) in eight years. Hamas has had to fire about 270 rockets or mortar shells for each Israel soldier or civilian they have killed. Israeli counterfire killed or wounded a Palestinian for every three Palestinian rockets or mortar shells fired. One Israeli was killed or wounded for every 40 rockets or mortar shells fired. Israeli fire was much more accurate, with most of the Palestinian casualties being terrorists or others involved in building or firing the rockets and mortars. Hamas has tried to get civilians killed, by storing rockets in residential areas, and firing them from those neighborhoods as well. Although Hamas believes in the concept of "involuntary martyrdom" (getting civilians killed for the cause, even if the victims are not willing), many of its chosen candidates are not eager to die. So civilians stay away from areas where the rockets are launched and try to conceal the fact that rockets are hidden under their homes.

Meanwhile, up north in Lebanon, Hezbollah has stockpiled over 40,000 factory-made rockets, mainly BM-21s brought in from Iran via Syria. This is three times as many rockets as they had in the Summer of 2006, when over 4,000 rockets were fired into northern Israel, killing about fifty people, most of them civilians. Over a thousand Lebanese died from Israeli counterattacks. Hezbollah and Hamas plan to launch a joint rocket attack on Israel eventually. The Israelis have been planning more effective countermeasures, which they have not been discussing openly. There is also the option of installing Iron Dome in the north but that has not been assured yet.




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