I was pretty impressed when I read about the Israeli Iron Dome missile defense system and how effective it has been during the latest conflict between Israel and Hamas in Gaza. At first, I believed that it was a derivative of the Raytheon Patriot missile system and, although they share the same mission, there are some key differences related to embedded processing that make perfect sense when you consider them.
A single Patriot missile costs somewhere in the area of $2-3 Million and, in some tactical situations using one would be in many ways like trying to kill hornets with a sledgehammer. The Iron Dome missiles on the other hand are said to cost ~$62 Thousand and are much smaller. The cost of the entire battery of missiles is also significantly less expensive. Therefore, the cost and agility of these smaller, less expensive Iron Dome missiles make it much more feasible to use on smaller incoming rockets like the ones currently being fired by Hamas.
The architecture of the Iron Dome system appears to be different than the Patriot system. The entire Patriot battery is intended to be mobile and can be operated autonomously as all of the Radar and command and control are part of the mobile installation. While some of this is likely true on the Iron Dome, more of its system elements are stationary and the areas it protects are well known and defined. This is significant because although the Israelis claimed a hit accuracy of ~70% in 2009, but, as of Saturday they have only intercepted 245 of the 737 rockets that have been launched toward them. You would think that this ~33% hit rate makes the 2009 claim inflated but it is likely that they have actually improved in intervening 3 years.
Why the difference in hit rate? Instead of engaging every inbound missile, the Iron Dome system tracks each one and determines whether it will hit something that needs to be protected as opposed to an unpopulated area of low value. If the system determines that interception is needed, it then calculates the best place to perform this as the falling debris from the in-air destruction can itself be a hazard. Then an interceptor missile is programmed to be at a certain spot at a certain time and is launched from the optimal battery to accomplish this task. No doubt there is a significant amount of embedded electronics to allow the Iron Dome missile to be controlled and maintain the correct path but these systems are likely less powerful and costly than the Patriot versions.
How is does the system work? Obviously and for good reason many details are secret. This does not mean we can’t speculate. We think that in addition to the localized processing and radar capabilities at the launcher, the Iron Dome system uses a very high powered centralized computing core that takes data from multiple radar systems and has overall control of multiple missile batteries. This makes sense particularly since the planned number of missile batteries has not been deployed yet. If so, this is not unlike Smart-Phone processing where user voice commands are captured by the phone but the heavy processing that occurs when the questions are interpreted are performed using centralized computing systems. Another significant advantage to having centralized computing architecture is that the situational awareness derived from multiple sources can be leveraged for multiple Iron Dome sites. As a result, less processing capabilities would be required at the missile battery and inside the missiles.