We have heard impressive reports about the efficiency of the Iron Dome, the interceptor defense system that Israel uses to blast Hamas rockets out of the sky so they don’t do their intended damage. Israel claims that 90% of the Hamas rockets are successfully destroyed with the Iron Dome interceptor system. The United States is providing most of the funding for this system. Recently the Senate Armed Services Committee suggested doubling the $175 million budget for the Iron Dome project, in view of its heavy use in this round of the never ending Israeli-Palestinian conflict. But does this system really work?
Theodore Postal, physicist and professor of science, technology, and national security policy at MIT claims that studies of rocket and interceptor contrails (the smoke trails that follow the rockets and interceptors) forces one to conclude that the success rate is probably no more than 5% and perhaps even less. Postal and his colleagues examined the system during the current crisis as well as the 2012 Israeli-Palestinian conflict. Based on his analysis of photographs and imagery of Hamas rocket and Iron Dome interactions, he concluded that the system remains fraught with problems coupled with marginal outcomes. Although his analysis of the July 2014 interceptor accuracy is still underway, it is unlikely that the system has been improved substantially from the 2012 conflict which he argues had an unequivocally high rate of failure. The Postal site has a slide show which provides additional insight into the problems facing the interceptors. Postal argues that the low incidence of Israeli deaths from Hamas rockets can be attributed to the civil warning system that effectively warns citizens in time for them to seek shelter, either in their own homes or within the vast array of public safety shelters. From the Postal Article: ["What performance characteristics make a rocket defense effective? To successfully intercept an artillery rocket of the type Hamas has been firing, an Iron Dome interceptor must destroy the warhead on the front end of the rocket. If the Iron Dome interceptor instead hits the back end of the target rocket, it will merely damage the expanded rocket motor tube, basically an empty pipe, and have essentially no effect on the outcome of the engagement. The pieces of the rocket will still fall in the defended area; the warhead will almost certainly go on to the ground and explode. Destroying an artillery rocket warhead is a considerably more demanding mission than damaging other parts of the targeted rocket—or, in the analogous situation of aircraft defense, successfully damaging an airplane, causing the failure of its mission. Analysis of photographs of contrails left by Iron Dome interceptor missiles can show whether or not an attempted rocket intercept could have been successful. Such analysis focuses on two connected facts: To have a realistic chance of destroying an artillery rocket's warhead, an Iron Dome interceptor must approach the rocket from the front—in fact, almost directly head-on. And for all practical purposes, an Iron Dome interceptor has no chance of destroying the warhead if the interceptor engages the rocket from the side or from the back." ]
Studies of the Hamas and interceptor contrails show that the majority of engagements are either from the side or with the interceptor trailing the rocket: neither of these approaches are likely to result in successful destruction of the rocket warhead. Figure 1 should help to understand what must happen if the interceptor is going to destroy the Hamas rocket warhead. To have a realistic chance of destroying the Hamas rocket, the interceptor must approach the rocket from the front. The Grad artillery rocket illustrated was first produced by the Soviet Union in the 1960s and is now readily available to Hamas. The blue dashed line represents the line of sight of the interceptor’s “laser fuse”. It represents a beam of light that reflects off the rocket. Through its control system the interceptor can determine when the rocket is passing; the interceptor warhead is positioned well behind the light beam; timing mechanisms allow the interceptor warhead to explode at an optimum position for destruction of the rocket warhead. This is why Postal argues that frontal positioning of the Iron Dome interceptor with the approaching rocket is the optimal spatial relationship and positions that deviate from a purely frontal approach have a dramatically lower chance of success. According to Postal, even the frontal positioning of the rocket and interceptor has a slim chance of success, just better than zero because of all the timing issues that come into play in order to get a successful engagement.
Figure 2 shows what a successful interceptor destruction of a Hamas rocket looks like. In this example the Iron Dome interceptor and the Hamas rocket have a frontal approach with one another. You can see the explosion from the Iron Dome interceptor, while the asymmetry of the debris field indicates that there were two explosions in quick succession. The blast from the interceptor produces a forward momentum of debris. The approaching Hamas rocket also explodes with a smoke cloud on the left, while the contrail below probably indicates the path taken by a section of the rocket’s motor. This photograph was the only successful engagement Postal and his colleagues found during their very extensive searches of voluminous photographic and video evidence of Iron Dome interceptor rocket interactions in November 2012.
If the Iron Dome interceptor system has such a low rate of success, why are the Israelis and the Americans touting its effectiveness and lavishly funding it as if it was a well established system? The most obvious answer is that it gives a psychological boost to the Israeli citizens who believe they are benefiting from the system, while at the same time it provides Hamas with the idea that most of their rockets are being destroyed by a system far in advance to the relatively small rockets they are aiming at Israel. And, perhaps we should add that funding it from our budget gives additional largess to our armaments industry. The Hamas rockets only have a 10 to 2o lb explosive. If it hits you or the room you are staying in directly, it will probably kill you, but if it doesn’t make a direct hit you will probably survive and perhaps come away unscathed.
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