The insurgents fighting in Iraq use improvised explosive devices (IEDs) extensively. They take the form of charges laid in or alongside roads, of fillings for suicide bombers' cars and vests, and even, albeit in more sophisticated form, of bombs used against airplanes. Now there may be a countermeasure. In October, the Naval Surface Warfare Center at Dahlgren announced it had developed a weapon that would neutralize IEDs. The Center hoped to ship units to Iraq before Christmas. Meanwhile, the Army has been working on a means of jamming bombs detonated remotely. The Weapons Center would not describe its approach for fear the insurgents might work against it, but its spokesman said it exploits common IED weaknesses. There also is a Defense Department task force working on ways of detecting and defeating IEDs. Quite aside from ground combat in Iraq, something that negates an IED would be extremely valuable for ships operating in potentially hostile ports, such as Aden; it might have protected the USS Cole (DDG-67). All other means of countering potential attackers run afoul of some form of rules of engagement, which require that an enemy display hostile intent before being attacked. The only current way out of this problem is to use nonlethal mechanisms, such as running-gear entanglement, to keep a suspicious boat away from a potential target. That cannot be altogether satisfactory, because it is impossible to treat all boats as suspicious, even in a harbor teeming with anti-American groups.
Because IEDs are a broader problem than that we face in Iraq, many groups outside the military are trying to deal with them. For example, a Justice Department solicitation for ways of detecting and neutralizing vehicle bombs had a return date of December 2004. It is not clear to what extent such civilian efforts are either known to, or are being exploited by, the Defense Department, but the ongoing development of an intragovernment secure net would make it much easier for a researcher in one to find out about projects being pursued by the others.
The Marine Corps Warfighting Laboratory issued a presolicitation notice for a next-generation IED change detector on 21 October. The idea is that changes on the ground may indicate the emplacement of an IED. The detector is to fly on board an unmanned aerial vehicle (UAV) with a high-capacity digital data link with a 30 kilometer range. Two UAVs and a ground station form a three-demention volumetric change detection unit. The detection system comprises a 14.4 megapixel camera, a fixed video camera, digital media storage, a Global Positioning System unit, and an image computer linked to a ground control and processing station. The cameras are expected to register changes on the ground to indicate the presence of a suspicious object. The system is to locate and characterize IED threats along a route or in an area to within an accuracy of ten meters. Given the system's output, an operational commander should be able to identify the most appropriate mixture of IED countermeasures for a given IED threat; decide which routes to use to avoid or minimize exposure to IED attack; and make informed decisions as to employment of explosive ordnance disposal personnel and assets.
There are several likely approaches to the IED problem. One, typified by the Marine Corps project, is to examine any change in the environment to see if it represents an IED. Hyperspectral imagers, for example, can see changes in soil because of the burial of a charge. They may spot footprints leading to the spot where an IED has been placed or buried. Simply comparing images taken days or hours apart can be revealing. Comparison demands that the images be taken from exactly the same place, which is why the Marines want GPS in their special UAV.
A second approach is to attack the fuzing technique. That is why the Army (and others) is interested in jamming cell phones and lasers. It is possible that the Dahlgren system also attacks fuzing. For example, it might be possible to set off a bomb prematurely by using enough radio power to generate a false detonation signal. Such a device would deter suicide bombers, because it might detonate their weapons well before they had left their friends to attack us. Presumably they would not find it attractive if most of those they killed were their colleagues.
A third possibility is to use the character of the explosive to detect it. There is now considerable interest in the airline security industry in neutron-activation devices, which detect explosives by their chemical structure. The neutrons involved can pass through metal, so it is difficult or impossible to shield a bomb against them. On the other hand, such radiation can be deadly, so it is difficult to justify using it on people, the great majority of whom are innocent. Moreover, current neutron activation devices are relatively massive.
Another possibility would be to exploit the chemical structure of the explosive by probing it with a strong microwave beam. The energy levels of the explosive molecules cause resonances in the reflection of the microwaves. It is even possible that a strong enough signal would set off the explosive. This technique can be worthless if the explosive is encased in metal, but in that situation an X-ray system will detect a suspicious object. Combining X-rays and microwaves could be quite effective, on the theory that the measure used to defeat one would lay the bomber open to the other. Another possibility is ultrasonics. No ultrasonic beam can be strong enough to set off an explosive or to resonate with the important chemical bonds, but a material's response to different ultrasonic frequencies might be a good indication of its character.
Explosives exude subtle chemical trails. That is why explosive-sniffing dogs are so effective. Apparently, it is impossible to seal a case of explosives so well that the dog is entirely frustrated. An electronic sniffer may not be as sophisticated as a dog, but it can be put in places dogs cannot. This is not a new idea, but technology probably makes it far more viable than in the past. Sniffers have had important roles in naval warfare. For example, during the Cold War, some NATO maritime patrol aircraft were equipped with sniffers designed to pick up the exhaust trails of snorkeling Soviet submarines. The submarines could sometimes be detected tens of miles away. The practice died only because the sniffers could not distinguish submarines from coastal cities, which smelled to them like vast numbers of submarines. More recently, chemical trails have been proposed as a means of distinguishing mines from nonmines on the seafloor.
That something works is strongly suggested by Dahlgren's announcement. The reference to consistent weaknesses in the insurgents' IEDs in Iraq suggests that the insurgents follow few techniques, and that as long as their weaknesses are unknown to them, we have a considerable advantage. That also means that whatever device or technique Dahlgren has produced will not be too useful elsewhere, unless virtually all of those we currently oppose share much the same limited range of explosive designs and concepts.
Tactically, the talk of negating the IEDs suggests neutralizing them rather than prematurely exploding them. Perhaps premature detonation is distasteful because of its potential for collateral damage. Yet, it might be argued that if the bombers found themselves compelled to cause collateral damage among their usual supporters, they might quickly find themselves unpopular.
Sophisticated bombers probably can defeat any system we deploy. However, to do so they must work harder, and they generally need more elaborate materials and facilities. That in turn makes them easier to detect by intelligence techniques. Sources of more exotic materials can be tracked. The number of people capable of making elaborate or sophisticated bombs is quite limited. On a simpler level, merely observing changes to a road forces bomb makers to bury their weapons. That requires the bomb makers to spend more time at a bombing site, which makes them more vulnerable to detection and could reduce the number of bombs they can emplace.
That is, incidentally, a wider idea. Think about ship self-defense. Normally it is translated as means of defeating incoming weapons either by destroying them or by jamming them. That leaves out two vital elements. One is the ability of the ship to absorb damage. The other is the ability to deal with the platforms launching the weapons. Anything that raises the bar for weapons effects makes it necessary for the attacker to use a more powerful weapon-which may be easier to detect, and which cannot be carried in such large numbers by the attacker. An attacking platform suited to larger weapons will be larger and hence easier to detect and, hopefully, to destroy before it can attack.
In recent decades, unfortunately, the role of passive protection in simplifying the threat generally has been neglected; to the extent that ships are provided with passive survivability measures, they are associated with weapons that leak through an ideally airtight defense. That no such defense can be erected is often forgotten. There will often be some leaks. The smaller the warhead an enemy must provide to achieve his ends, the more weapons he can afford to fire at one ship, and the better the chance some will get through. The harder the target, the bigger the weapons the enemy must use, and the better the chance the enemy and his weapons can be countered.
The Cole is a case in point. She demonstrated that even a oneton shaped charge could not destroy a modern U.S. destroyer. It is true that it took only a small boat to carry that massive charge, but the sheer mass of the charge itself made it likely that some method, such microwaves or neutron activation, could detect a similar charge in the future. Significantly smaller charges, perhaps equivalent to the warheads of small antiship missiles, might be much more difficult to detect in the first place. Moreover, assembling a ton of explosives requires efforts that may well be visible to an alert intelligence service. The smaller the charges, the better the chance they can be assembled covertly.
Can we ensure that no Cole incident happens again? Probably not, unless we never enter potentially hostile harbors or allow boats to approach us. But we can make it difficult for our enemies to achieve great results at low risk. That idea, that raising the bar in itself makes detection of attackers more likely, applies to homeland security as well as to survivability in Iraq and in the Third World.