Using Missile Defense Against Terrorist Attack
Israel’s Iron Dome and the Future of Rocket Shields

Alan Isom

On April 7, 2011, a Tamir missile streaked into the sky and intercepted a Grad rocket fired by Hamas terrorists in Gaza and aimed at Ashkelon. This marked the first time the Iron Dome system was fired by Israel against an enemy. It performed flawlessly, destroying the terrorist rocket and sprinkling fragments harmlessly across barren terrain. Since that time it has been challenged by Hamas and Hezbollah and has risen to those challenges with a ninety percent success rate against terrorist rocket, artillery and mortar — referred to as RAM — attacks. Because rockets are both a huge chunk of the threat and commonly shown on world media, we will refer to rockets here for simplicity.

Iron Dome leads the way as the first combat-proven air defense shield effective against rocket, artillery, and mortar attacks. It successfully counters one goal of warfighters — “getting inside the enemy’s decision cycle”— that has long been a goal of Islamic terrorists — to goad their enemy, be it Israel, the United States, or another, into striking at them in such a way that they can then cry to the world that they are the victims. With Israel frequently getting a poor reception in the Western press, such incidents have been frequent sources of trouble for Israel. The options have not been good: allow Hamas and Hezbollah to continue to kill Israeli citizens; or to strike back, risking collateral damage, and creating political stress with Israel’s allies due to international public disapproval from perceived Israeli heavy-handedness.

Iron Dome pushes the continuing terrorist rocket attacks outside the terrorists' decision cycle, giving Israeli leadership the precious gift of time to consider responses to Hamas, Hezbollah and other provocateurs, and make good decisions. Furthermore, Iron Dome limits the ability of these provocateurs to draw Israel into ill-considered responses to their rocket provocations. The result is an air defense system that provides not just physical protection, but also a morale boost of hope for the citizens it protects, and also opens the door to future developments that with implications far beyond simply countering rocket attacks—possibly rendering conventional rockets, artillery and mortars as well as air-to-surface, surface-to-surface, and ballistic missile systems obsolete.

Iron Dome is an air defense system consisting of three or four launchers, each holding twenty Tamir missiles, controlled by a single Battle Management Center and supported by a dedicated radar system. The number of major pieces is kept to a minimum — three (rolling launchers into a single count) — and each piece is critical to the fight.

Iron Dome’s S-band, phased array radar can detect aerial tracks up to 210 miles away and the Battle Management Center can process up to 1,200 targets per minute—giving it the ability to track a barrage of incoming rounds and determine which rounds threaten the defended asset. The Tamir interceptor missile can engage targets with ranges between two and a half miles and forty-two miles; it receives updates from the BMC and then its internal seeker takes over for the terminal phase—while designed to counter rocket attacks, it is also effective against conventional aircraft. The radar, Battle Management Center, and launchers are mobile, truck-towed pieces that are all-weather capable, providing flexibility of employment based on location of the defended asset and the flight path of the incoming rocket munitions.

The small sizes, high rates of speed, and short flight times of rocket munitions make them a technologically difficult puzzle to solve. There are two solutions to this puzzle — a hit-to-kill and a proximity kill. The hit-to-kill aims to strike the enemy air frame for a kinetic kill, as it is sometimes called, “hitting a bullet with a bullet.” The proximity kill solution has a fuse that explodes when the missile gets close to its target, throwing shrapnel causing catastrophic damage to the incoming rocket and detonates the enemy warhead—the Tamir missile is of this type. The proximity kill is a technically simpler solution. Consider the difference between guiding the missile to a physical meeting with the incoming rocket versus getting the missile relatively close to the incoming rocket and then blasting it with a shotgun effect.

Iron Dome must contend with two main limitations, time and money, when setting the conditions for the successful intercept of an enemy rocket. Time is a critical feature because of the sheer number of events that must take place, usually sequentially, to successfully engage incoming rocket: detection; tracking; destination calculation; engagement decision; missile launch; guidance; and interception—all before the projected intercept reaches a point where shrapnel and falling debris threaten collateral damage. Each step may only take a few seconds, but those seconds quickly add up. The proximity solution seems to be not only the simpler solution but also the better advised solution to getting an interceptor into position due to the limited engagement window induced by short range rocket. After all, it is easier to get close to a target than it is to actually hit a target, and a shotgun type blast is an area effect. On the flip side, a missile body-to-body intercept carries more kinetic energy with it than does a single piece of shrapnel from the proximity warhead. With a technically feasible intercept solution in hand, a decision must be made about each incoming rocket: to engage or not to engage.

Despite the fact that Israel is paying roughly $50,000 per missile, the decision about whether or not to engage an incoming rocket is based on its destination. When the system is emplaced, it is programmed with areas to defend – any incoming RAM projected to land outside the defended area is ignored. By definition a rocket is an unguided munition. In the past, many of the rockets were homemade. While this is still the case in some instances, the vast majority of rockets used by Hamas and Hezbollah today are made in Iran and supplied via smugglers through Syria or other avenues to the terrorists. Even with the greater range, accuracy and lethality provided by the Iranian rockets, the individual cost of each rocket is, though higher than the homemade versions, far lower than the Israeli interceptor. Those points, coupled with the fact that terrorists launch many of the rockets from homemade, one-shot rails, means that the typical rocket is far cheaper than the Tamir interceptor. Thus money is a major factor in the ongoing conflict. While Hamas and Hezbollah are paying nothing for Iranian-provided arms, or a few hundred to a few thousand for other sourced rockets, Israel’s cost is many factors higher on a per round basis. So the question becomes what can Israel afford to pay?

In an offensive in 2006, Hezbollah launched more than 4000 rockets at Israeli cities in one month, more than four times as many rounds per day and lasting twice as long as the previous record-holding offensive from a decade before. This 2006 offensive resulted in more than fifty Israeli deaths and millions of dollars in damage —and triggered the decision to pursue development of Iron Dome. Thankfully, even with the Iranian rockets, the accuracy is fairly low — even a couple of degrees off for a target thirty or forty miles away results in an error that more often than not puts the rocket into relatively unpopulated areas. Current estimates are that two out of three rockets miss their targets. Even with that great a margin of error, one out of every three rockets does not. That number may not sound too awful until the total numbers of rockets available to the terrorists are considered. Hezbollah is estimated to have between 30,000 and 50,000 rockets stockpiled. Hamas has far fewer, maybe 10,000, but Gaza is also a far smaller place to hide the stockpiles. Iron Dome was pushed through development, testing and initial production in only three years — an amazingly short time. The first system was emplaced only days before the first combat intercept.

Mass, Mix, Mobility, and Integration

U.S. Army Air Defense doctrine considers four employment principles: Mass, Mix, Mobility, and Integration (affectionately referred to as M3I).

Mass is defined simply as the ability to bring as much firepower to bear as possible. For Iron Dome, this converts to how many launchers are in position to intercept rockets and mortars fired from a particular location in Gaza or Lebanon.

Mobility is exactly what it sounds like: the ability to move from one place to another. Specifically, from wherever it is located to wherever it is needed. Timeliness of breakdown and setup of a system is also important. The Iron Dome launchers are mobile and quick to emplace and make ready to fire; this gives Israel the ability to shift locations and follow the terrorists from one general location to another to better protect her citizens. Should Hamas or Hezbollah attempt to mass fires to saturate Israeli defenses, this mobility gives them the ability to mass Iron Dome defensive fires in response. Additionally, mobility gives the Iron Dome system the ability to move with land forces if and when the Israeli Defense Force must go to war.

Just as warriors of the ancient world combined helmets with their shields to exploit the weaknesses inherent in swords, modern Air Defense warriors seek to combine more than one defensive system to take advantage of the weaknesses of rocket and ballistic missile weapons. In the case of Israeli Air Defenders, they are combining Iron Dome with Arrow 2, Arrow 3, HAWK and Patriot — and working to develop additional systems such as David’s Sling. This combination of systems is what Air Defenders call "mix," where one system covers the weakness of another.

Another common use of mix is to employ different types of systems to cover weaknesses within a single threat set; for instance, adding gun systems such as Vulcan to cover a missile system. Teaming these systems together brings us to a fourth principle, integration.

Integration of different systems supporting one another to maximize coordination and minimize confusion increases the effectiveness of the integrated system of systems several fold. This integrated teamwork allows prioritization of fires and ensures that multiple systems do not unintentionally engage the same target while leaving other critical targets unengaged and assets undefended.

Other considerations are what the U.S. Army refers to as employment guidelines. These consist of overlapping fires, mutual support, defense in depth, balanced fires, weighted coverage, and early warning. Each of these has to do with how each individual launcher system is located with respect to others and how they interact with one another. When two launchers are situated such that their engagement zones have no gap between them, they have overlapping fires. If their engagement zones overlap enough that one can engage an enemy airframe above its neighboring launcher, they are in mutual support. Defense in depth means that if the rocket gets past the primary defensive system, another system can engage and destroy the rocket. Balanced fires are accomplished when the available launchers are arrayed such that each avenue of approach is equally defended. In contrast, weighted coverage is accomplished when more launchers are shifted to provide a heavier defense of the most likely avenue of approach, thus massing fires and obviously linked to the concept of Mass. Early warning is exactly what it sounds like, a detection system designed to detect incoming air traffic as soon as possible.

While Iron Dome can operate in a solo role, it is designed to be part of an integrated air defense system where each system on the team defends against a particular threat. Overlap between system capabilities provides both mix and defense in depth. Defense in depth is also applicable to how the air defense is laid out. The simplest description is that of different belts, each providing a layer of defense, and any encroaching object must successfully pass through multiple belts to threaten the defended asset. These belts can be comprised of the same type of system arranged geographically to provide the layout. Or they can be comprised of different systems supporting one another. The best layouts use both.

Both Patriot and Arrow use radar systems that can be tied into the Iron Dome command and control system, providing much longer range coverage than its organic radar can. Tying into the radar feeds of its sister units is another source of additional data. This additional coverage provides early warning for Iron Dome. This early warning may or may not be useful, but for anything within its designated threat set any early warning is the gift of time to prepare to engage. For instance, the Arrow radar can relay information to Iron Dome regarding an incoming ballistic missile, but that is a threat Iron Dome is not designed to counter. Or an Arrow radar may be situated such that it can “see” behind a ridgeline Iron Dome cannot and pass data about short range rocket launches, giving Iron Dome a few extra, precious seconds to process and engage.

Iron Dome and her sister air defense systems are all missile systems. HAWK (Homing All the Way Killer), initially developed in the United States in the 1960s, is the eldest, and has been completely phased out of the U.S. inventory. Patriot, also developed in the United States, was introduced to Israel during the early 1990s during the Gulf War. The Arrow family of systems, like Iron Dome, was developed in Israel. Interestingly, there are no gun systems. The venerable Vulcan gun system, utilized heavily by the United States during the Vietnam conflicts, is only used by U.S. forces for air defense by the U.S. Navy; upgraded, automated and known as the Phalanx Close In Weapon System, it is designed as a last ditch defense against incoming aircraft and missiles. A land-based version, known as C-RAM has been utilized with some success in Afghanistan and Iraq. However, the U.S. Navy is firing over water, making collateral damage unlikely. It is the highly populated urban centers of modern day Israel that terrorists target. As the old adage goes, what goes up must come down. Additionally, such gun systems have a prodigious appetite for ammunition. While even a few thousand rounds is cheaper than a Tamir missile, they are also much shorter ranged. Israel has chosen to go with systems that both have longer legs and a lesser likelihood of collateral damage even though it reduces the possible mix of systems.

Each and every weapon/system ever developed has both strengths and weaknesses. Just as warriors of the ancient world sought the weaknesses inherent in swords, modern warriors are looking for a defense against short-range rocket, artillery and mortar (RAM) indirect fire weapons. Iron Dome provides this defense and, with a ninety percent success rate, it is a very effective system.

Countermeasures

Just as the ancient weapon designers developed the crescent axe in response to the advent of helmets. Hamas and Hezbollah seek to develop counters to the Iron Dome shield. The Hamas terrorists have four basic options to overcome the capabilities of Iron Dome. First, they can probe to find locations where Iron Dome coverage is either weak or missing. Second, they can mass fires, flooding the skies with rockets, artillery rounds and mortars to saturate Iron Dome’s capability to intercept or to deplete Iron Dome’s available missiles. The terrorists have tried both.

The second option is not as easy as it sounds. It requires the terrorists to bring many launchers and rockets, artillery shells or mortars together at one time, which also makes them vulnerable to Israeli counterattack. If Hamas or Hezbollah attempts to mass enough rockets for saturation fire, the IDF is likely to have forewarning and be prepared to hit them as they come into the open. Any prolonged bombardment gives the IDF the opportunity to dial in counter-battery fire from their artillery and call in air strikes.

From a purely air defense perspective, Israel’s tactical options are as varied as the attacks and are based on the parameters of the IDF mission, how the terrain constrains both combatants, and how the terrorists coordinate their attack. They range from simply changing her shot doctrine (dictating how many missiles target each incoming rocket) to massing fires to create more defensive depth and possibly weighting coverage towards the primary avenues of attack. Finding weak locations to attack, therefore, has thus far been the terrorists’ preferred counter to Iron Dome.

The move and countermove dance continues, with the Israelis adapting to the shifting firing patterns of Hamas and Hezbollah by moving the Iron Dome assets to meet each new threat axis. This does not mean that they will not try to saturate the Israeli defenses, only that they have not yet done so in a massive offensive—they did succeed in at least one incident in the early days of the Iron Dome program. Since that time, the terrorists have stockpiled more rockets, artillery shells and mortars while the IDF has, of course, also improved Iron Dome’s capabilities.

A third option is for Hamas and Hezbollah to turn to weapons Iron Dome is not designed to counter. As the terrorists are heavily vested in their current arms, with large caches stockpiled, and cannot compete technologically with Israel—even with Iran supporting them—this option seems unlikely. A fourth option, rendered unfeasible by Israeli security, is a conventional attack such as a ground assault to destroy Iron Dome assets. Such an attempt is unlikely to succeed and most likely to be a suicide mission for the terrorists. While they do make use of suicide bombers, the run-of-the-mill terrorists do not seem particularly enamored with that idea—they prefer to murder and run away, to murder again another day. Thus we are brought back to the first two options, probing for chinks in the armor, or saturating the defenses as avenues of exploration for Hamas and Hezbollah to attempt to counter Iron Dome.

Because Iron Dome is part of an integrated air defense system, its success has implications well beyond rockets, artillery and mortars. Essentially, if Iron Dome works as advertised, it is likely the other systems do also—although the sister systems have not yet been definitively proven in combat—and those other threat sets, such as ballistic missiles, are likely rendered obsolete by a working air defense shield. Iran leads the region in development of ballistic missiles (short, medium and intermediate range weapons) as well as nuclear capability, all with the avowed goal of destroying Israel. They are technologically capable, as are others in the region, and the advent of a functional air defense shield in the Levant has kicked off an arms race in the Middle East.

To understand where this arms race might lead, we must have an idea how things developed to this point. First, the larger an explosive warhead, the more fuel (gun powder or rocket fuel) and therefore the larger airframe required. Rocket munitions are at one end of the spectrum—they are the shortest ranged and have the smallest warheads. Iron Dome is designed to counter these. Stepping up the threat possibilities we come to longer ranged rockets and the short range ballistic missiles, as well as conventional aircraft. HAWK and Patriot were designed to counter the conventional aircraft and rockets; Patriot was upgraded to defend against short range ballistic missiles. Up from there we find medium and intermediate range ballistic missiles which the Arrow family of systems are designed to counter. Intercontinental ballistic missiles are a threat deemed beyond the immediate needs of Israel—their bitterest enemies are close to home.

We have already mentioned the HAWK system which was purchased in the 1960s by Israel. Iraqi use of SCUD ballistic missiles during the Gulf War introduced Patriot to Israel, albeit with fairly low success rates—the systems have now been upgraded substantially, as have the missiles. Iran’s growing threat with more capable ballistic missiles generated the Arrow 2 and Arrow 3 systems currently fielded. Hamas and Hezbollah’s successful employment of rocket attacks led to the development of Iron Dome, which has severely blunted the general efficacy of the terrorists’ attacks.

From Iron Dome to Iron Beam

Israel is not waiting on new or improved threats to emerge; she is leveraging her technological superiority to find more efficient methods of dealing with existing threats and researching ways to counter projected threats. Already, based on the lessons learned with Iron Dome, Israel has introduced improvements to her other systems (Arrow and Patriot), raising their probability of kill commensurately. She has continued to develop other systems, such as David’s Sling, which is nearing the stage of completion and is intended to replace the aging Patriot, and possibly HAWK, systems and will overlap the capabilities of Arrow.

Israel’s adversaries continue to search for counters. Some involve technical solutions such as multiple warheads that split from the missile to seek individual targets and Homing Anti-Radiation Missiles designed to seek and kill radar systems -- both already developed by the United States and Russia.

Penetration aids, with salvos of missiles carrying an Electronic Counter Measure bird for a select number of attack rounds, are on the horizon for larger missiles. Munitions with erratic flight paths or capable of evasive maneuvers adds strain to the tracking and defensive control systems; such additions are applicable to missiles—controlled flight weapons—not to rocket munitions. Likewise, utilizing faster projectiles typically yields longer ranged or larger projectiles—leading us back to research and development against threats from technologically capable opponents such as Iran. As miniaturization of electronics continues, such advancements may one day be available for rockets, but the costs are will render such bells and whistles too expensive. Advanced systems such as rail guns to replace artillery or mortars are unlikely to be within the reach of Iran, much less Hamas or Hezbollah, in the next several decades, but that does not mean that new twists and heretofore unforeseen advances are not possible.

Israel is already looking for the next step in rocket defense with the development of Iron Beam, a laser system, similar in concept to the United States Navy LaWS (Laser Weapon System), which began testing on the USS Ponce in 2014 against boats and Unmanned Aerial Vehicles; the intent is to prove it as a scalable system capable of warning personnel in boats off with heat at the non-lethal end of the spectrum, to burning out engines and detonating explosives at the other end, and with an end state goal of being able to destroy anti-ship missiles (see this link).

The use of lasers in combat is moving inexorably from science fiction to science fact. The advantages are obvious: an unlimited ability to engage incoming threats because there are zero physical munitions; an ability to engage more threats because the engagement window for any individual threat is at light-speed; the ability to engage sooner than even Iron Dome can engage; and an ability to remain hidden from enemy eyes, since there is no vapor trail pointing back to the launcher.

Iron Beam is expected to initially require two lasers co-targeting an incoming rocket for four to five seconds to cause detonation (see this link). Obviously the goal is to increase power to reduce the lasing time from a few seconds to a simple pulse from a single source. Ultimately, if proven a feasible technology, it is planned to, at least partially, replace Iron Dome. A better solution might be to utilize both systems for a better mix. This future air defense team will see an integrated system including Arrow 2, Arrow 3, David’s Sling, Iron Beam and possibly Iron Dome. Scaling up the power should allow both a shorter pulse and a longer reach, potentially allowing more robust systems to replace Arrow and further reduce the efficacy of ballistic missile attacks.

Iran and other developers of ballistic missiles will look for ways to render such laser systems less effective, perhaps painting their missiles white to increase reflectivity—possibly going to an extreme and chroming them to a mirror like surface—in the hopes that the coherent light beam will reflect off the missile. More likely counters are smoke rounds designed to create atmospheric scatter of the light beam and increasingly effective electronic counter measures designed not to counter the weapon but to confuse the tracking and command and control elements. New stealth technology is also possible, to simply hide the weapon in flight. In the tight timelines involved in missile engagements, a few seconds confusion in the defensive control system may well be the difference between an incoming rocket or ballistic missile finding its target, or not.

A functional laser system to counter rocket attacks will be truly game-changing and shift the balance of power firmly to Israel by making the rocket stockpiles obsolete. If Israel can increase the stability of the tracking system to allow a shoot-on-the-move capability, mobile assets such as military units and convoys can be protected as easily as static assets such as towns, while providing the launcher the added security of mobility. Should scaling up the system to counter ballistic missiles also prove feasible, the impact on the balance of power in the Middle East will be tremendous.

The author would like to thank Major Kevin Burnette and Captain Ben Bracewell for their feedback during the composition of this article, and Master Sergeant Christina Morris for proofing it to ensure I did not stray into classified territory.

Copyright © 2015 Alan Isom

Lieutenant Colonel Alan Isom is a citizen-soldier with one career as a structural engineer with Fluor Corporation, an international engineering, procurement and construction (EPC) company, and a second as an Air Defense Artillery (ADA) officer with the 263d Army Air & Missile Defense Command (AAMDC), South Carolina Army National Guard. As a structural engineer, he is responsible for designing structures to resist gravity, wind and seismic loads and has had the opportunity to work on projects both at home and abroad. As an ADA officer, he is responsible for planning and conducting air defense operations to protect assigned assets, and has served multiple tours of duty with the National Capital Region Integrated Air Defense System (NCR-IADS) mission designed to prevent another 9-11 style attack from striking our nation’s capital.

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