High Power Electromagnetic Pulse generation techniques and High Power Microwave technology have matured to the point where practical E-bombs (Electromagnetic bombs) are becoming technically feasible, with new applications in both Strategic and Tactical Information Warfare. The development of conventional E-bomb devices allows their use in non-nuclear confrontations.

The prosecution of a successful Information Warfare (IW) campaign against an industrialized or post industrial opponent will require a suitable set of tools.

As demonstrated in the Desert Storm air campaign, air power has proven to be a most effective means of inhibiting the functions of an opponent’s vital information processing infrastructure.

This is because air power allows concurrent or parallel engagement of a large number of targets over geographically significant areas.

While Desert Storm demonstrated that the application of air power was the most practical means of crushing an opponent’s information processing and transmission nodes, the need to physically destroy these with guided munitions absorbed a substantial proportion of available air assets in the early phase of the air campaign.

Indeed, the aircraft capable of delivering laser guided bombs were largely occupied with this very target set during the first nights of the air battle.

The efficient execution of an IW campaign against a modern industrial or post-industrial opponent will require the use of specialized tools designed to destroy information systems. Electromagnetic bombs built for this purpose can provide, where delivered by suitable means, a very effective tool for this purpose.

The EMP Effect

The Electro Magnetic Pulse (EMP) effect was first observed during the early testing of high altitude airburst nuclear weapons.

The effect is characterized by the production of a very short (hundreds of nanoseconds) but intense electromagnetic pulse, which propagates away from its source with ever diminishing intensity, governed by the theory of electromagnetism. The EMP is in effect an electromagnetic shock wave.

This pulse of energy produces a powerful electromagnetic field, particularly within the vicinity of the weapon burst. The field can be sufficiently strong to produce short lived transient voltages of thousands of Volts (ie kiloVolts) on exposed electrical conductors, such as wires, or conductive tracks on printed circuit boards, where exposed.

It is this aspect of the EMP effect which is of military significance, as it can result in irreversible damage to a wide range of electrical and electronic equipment, particularly computers and radio or radar receivers.

Subject to the electromagnetic hardness of the electronics, a measure of the equipment’s resilience to this effect, and the intensity of the field produced by the weapon, the equipment can be irreversibly damaged or in effect electrically destroyed.

The damage inflicted is not unlike that experienced through exposure to close proximity lightning strikes, and may require complete replacement of the equipment, or at least substantial portions thereof.

Commercial computer equipment is particularly vulnerable to EMP effects, as it is largely built up of high density Metal Oxide Semiconductor (MOS) devices, which are very sensitive to exposure to high voltage transients.

Technology base

The technology base which may be applied to the design of electromagnetic bombs is both diverse, and in many areas quite mature.

Key technologies which are extant in the area are explosively pumped Flux Compression Generators (FCG), explosive or propellant driven Magneto-Hydrodynamic (MHD) generators and a range of HPM devices, the foremost of which is the Virtual Cathode Oscillator or Vircator.

A wide range of experimental designs have been tested in these technology areas, and a considerable volume of work has been published in unclassified literature.

This paper will review the basic principles and attributes of these technologies, in relation to bomb and warhead applications. It is stressed that this treatment is not exhaustive, and is only intended to illustrate how the technology base can be adapted to an operationally deployable capability.

The explosively pumped FCG is the most mature technology applicable to bomb designs. The FCG was first demonstrated by Clarence Fowler at Los Alamos National Laboratories (LANL) in the late fifties. Since that time a wide range of FCG configurations has been built and tested, both in the US and the USSR, and more recently CIS.

Lethality of E-warheads

The issue of electromagnetic weapon lethality is complex. Unlike the technology base for weapon construction, which has been widely published in the open literature, lethality related issues have been published much less frequently.

While the calculation of electromagnetic field strengths achievable at a given radius for a given device design is a straightforward task, determining a kill probability for a given class of target under such conditions is not.

This is for good reasons. The first is that target types are very diverse in their electromagnetic hardness, or ability to resist damage. Equipment which has been intentionally shielded and hardened against electromagnetic attack will withstand orders of magnitude greater field strengths than standard commercially rated equipment.

Moreover, various manufacturer’s implementations of like types of equipment may vary significantly in hardness due the idiosyncrasies of specific electrical designs, cabling schemes and chassis/shielding designs used.

The second major problem area in determining lethality is that of coupling efficiency, which is a measure of how much power is transferred from the field produced by the weapon into the target. Only power coupled into the target can cause useful damage.

Maximizing lethality

To maximize the lethality of an electromagnetic bomb it is necessary to maximize the power coupled into the target set.

The first step in maximizing bomb lethality is to maximize the peak power and duration of the radiation of the weapon. For a given bomb size, this is accomplished by using the most powerful flux compression generator (and Vircator in a HPM bomb) which will fit the weapon size, and by maximizing the efficiency of internal power transfers in the weapon. Energy which is not emitted is energy wasted at the expense of lethality.

The second step is to maximize the coupling efficiency into the target set. A good strategy for dealing with a complex and diverse target set is to exploit every coupling opportunity available within the bandwidth of the weapon.

A low frequency bomb built around an FCG will require a large antenna to provide good coupling of power from the weapon into the surrounding environment. Whilst weapons built this way are inherently wide band, as most of the power produced lies in the frequency band below 1 MHz compact antennas are not an option.

Targeting E-bombs

The task of identifying targets for attack with electromagnetic bombs can be complex. Certain categories of target will be very easy to identify and engage. Buildings housing government offices and thus computer equipment, production facilities, military bases and known radar sites and communications nodes are all targets which can be readily identified through conventional photographic, satellite, imaging radar, electronic reconnaissance and humint operations.

These targets are typically geographically fixed and thus may be attacked providing that the aircraft can penetrate to weapon release range. With the accuracy inherent in GPS/inertially guided weapons, the electromagnetic bomb can be programmed to detonate at the optimal position to inflict a maximum of electrical damage.

While radiating, their positions can be precisely tracked with suitable Electronic Support Measures (ESM) and Emitter Locating Systems (ELS) carried either by the launch platform or a remote surveillance platform.

In the latter instance target coordinates can be continuously data-linked to the launch platform. As most such targets move relatively slowly, they are unlikely to escape the footprint of the electromagnetic bomb during the weapon’s flight time.

Mobile or hidden targets which do not overtly radiate may present a problem, particularly should conventional means of targeting be employed. A technical solution to this problem does however exist, for many types of target.

This solution is the detection and tracking of Unintentional Emission (UE). UE has attracted most attention in the context of TEMPEST surveillance, where transient emanations leaking out from equipment due to poor shielding can be detected and in many instances demodulated to recover useful intelligence.

Termed Van Eck radiation, such emissions can only be suppressed by rigorous shielding and emission control techniques, such as are employed in TEMPEST rated equipment.

Defence against E-bombs

The most effective defence against electromagnetic bombs is to prevent their delivery by destroying the launch platform or delivery vehicle, as is the case with nuclear weapons. This however may not always be possible, and therefore systems which can be expected to suffer exposure to the electromagnetic weapons effects must be electromagnetically hardened.

The most effective method is to wholly contain the equipment in an electrically conductive enclosure, termed a Faraday cage, which prevents the electromagnetic field from gaining access to the protected equipment.

It is significant that hardening of systems must be carried out at a system level, as electromagnetic damage to any single element of a complex system could inhibit the function of the whole system.

Hardening new build equipment and systems will add a substantial cost burden. Older equipment and systems may be impossible to harden properly and may require complete replacement. In simple terms, hardening by design is significantly easier than attempting to harden existing equipment.

Limitations of E-bomb

The limitations of electromagnetic weapons are determined by weapon implementation and means of delivery. Weapon implementation will determine the electromagnetic field strength achievable at a given radius, and its spectral distribution. Means of delivery will constrain the accuracy with which the weapon can be positioned in relation to the intended target. Both constrain lethality.

Means of delivery will limit the lethality of an electromagnetic bomb by introducing limits to the weapon’s size and the accuracy of its delivery. Should the delivery error be of the order of the weapon’s lethal radius for a given detonation altitude, lethality will be significantly diminished.

This is of particular importance when assessing the lethality of unguided electromagnetic bombs, as delivery errors will be more substantial than those experienced with guided weapons such as GPS guided bombs.

Therefore accuracy of delivery and achievable lethal radius must be considered against the allowable collateral damage for the chosen target. Where collateral electrical damage is a consideration, accuracy of delivery and lethal radius are key parameters.

An inaccurately delivered weapon of large lethal radius may be unusable against a target should the likely collateral electrical damage be beyond acceptable limits. This can be a major issue for users constrained by treaty provisions on collateral damage.

Proliferation of E-bomb

The US and the CIS are the only two nations with the established technology base and the depth of specific experience to design weapons based upon this technology. However, the relative simplicity of the FCG and the Vircator suggests that any nation with even a 1940s technology base, once in possession of engineering drawings and specifications for such weapons, could manufacture them.

As an example, the fabrication of an effective FCG can be accomplished with basic electrical materials, common plastic explosives such as C-4 or Semtex, and readily available machine tools such as lathes and suitable mandrels for forming coils.

Disregarding the overheads of design, which do not apply in this context, a two stage FCG could be fabricated for a cost as low as $1,000-2,000, at Western labor rates. This cost could be even lower in a Third World or newly industrialized economy.

While the relative simplicity and thus low cost of such weapons can be considered of benefit to First World nations intending to build viable war stocks or maintain production in wartime, the possibility of less developed nations mass producing such weapons is alarming.

The dependence of modern economies upon their information technology infrastructure makes them highly vulnerable to attack with such weapons, providing that these can be delivered to their targets.

(The author, a defence analyst, is based in Australia)