The Electromagnetic Bomb - a Weapon of Electrical Mass
Destruction

Carlo
Kopp

Defence Analyst

Melbourne, Australia

[email-masked]

http://www.cs.monash.edu.au/~carlo/

ABSTRACT

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. This paper discusses aspects of the
technology base, weapon delivery techniques and proposes a doctrinal
foundation for the use of such devices in warhead and bomb
applications.

1. Introduction

The prosecution of a successful Information Warfare (IW) campaign against an
industrialised 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 [SZAFRANSKI95].

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 delivery 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 specialised 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.

2.The EMP Effect

The ElectroMagnetic Pulse (EMP) effect [1]
was first observed during the early testing of high altitude airburst nuclear
weapons [GLASSTONE64]. The effect is characterised 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 ElectroMagnetic Pulse 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. What is
significant about MOS devices is that very little energy is required to
permanently wound or destroy them, any voltage in typically in excess of tens of
Volts can produce an effect termed gate breakdown which effectively destroys the
device. Even if the pulse is not powerful enough to produce thermal damage, the
power supply in the equipment will readily supply enough energy to complete the
destructive process. Wounded devices may still function, but their reliability
will be seriously impaired. Shielding electronics by equipment chassis provides
only limited protection, as any cables running in and out of the equipment will
behave very much like antennae, in effect guiding the high voltage transients
into the equipment.

Computers used in data processing systems, communications systems, displays,
industrial control applications, including road and rail signalling, and those
embedded in military equipment, such as signal processors, electronic flight
controls and digital engine control systems, are all potentially vulnerable to
the EMP effect.

Other electronic devices and electrical equipment may also be destroyed by
the EMP effect. Telecommunications equipment can be highly vulnerable, due to
the presence of lengthy copper cables between devices. Receivers of all
varieties are particularly sensitive to EMP, as the highly sensitive miniature
high frequency transistors and diodes in such equipment are easily destroyed by
exposure to high voltage electrical transients. Therefore radar and electronic
warfare equipment, satellite, microwave, UHF, VHF, HF and low band
communications equipment and television equipment are all potentially vulnerable
to the EMP effect.

It is significant that modern military platforms are densely packed with
electronic equipment, and unless these platforms are well hardened, an EMP
device can substantially reduce their function or render them unusable.

3. The Technology Base for Conventional Electromagnetic Bombs

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.

3.1. Explosively Pumped Flux Compression Generators

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 [FOWLER60]. 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.

The FCG is a device capable of producing electrical energies of tens of
MegaJoules in tens to hundreds of microseconds of time, in a relatively compact
package. With peak power levels of the order of TeraWatts to tens of TeraWatts,
FCGs may be used directly, or as one shot pulse power supplies for microwave
tubes. To place this in perspective, the current produced by a large FCG is
between ten to a thousand times greater than that produced by a typical
lightning stroke [WHITE78].

The central idea behind the construction of FCGs is that of using a fast
explosive to rapidly compress a magnetic field, transferring much energy from
the explosive into the magnetic field.

The initial magnetic field in the FCG prior to explosive initiation is
produced by a start current. The start current is supplied by an external
source, such a a high voltage capacitor bank (Marx bank), a smaller FCG or an
MHD device. In principle, any device capable of producing a pulse of electrical
current of the order of tens of kiloAmperes to MegaAmperes will be suitable.

A number of geometrical configurations for FCGs have been published (for
examples see REINOVSKY85, CAIRD85, FOWLER89) The most commonly used arrangement
is that of the coaxial FCG. The coaxial arrangement is of particular interest in
this context, as its essentially cylindrical form factor lends itself to
packaging into munitions.

In a typical coaxial FCG , a cylindrical copper tube forms the armature. This
tube is filled with a fast high energy explosive. A number of explosive types
have been used, ranging from B and C-type compositions to machined blocks of
PBX-9501. The armature is surrounded by a helical coil of heavy wire, typically
copper, which forms the FCG stator. The stator winding is in some designs split
into segments, with wires bifurcating at the boundaries of the segments, to
optimise the electromagnetic inductance of the armature coil.

The intense magnetic forces produced during the operation of the FCG could
potentially cause the device to disintegrate prematurely if not dealt with. This
is typically accomplished by the addition of a structural jacket of a
non-magnetic material. Materials such as concrete or Fibreglass in an Epoxy
matrix have been used. In principle, any material with suitable electrical and
mechanical properties could be used. In applications where weight is an issue,
such as air delivered bombs or missile warheads, a glass or Kevlar Epoxy
composite would be a viable candidate.

It is typical that the explosive is initiated when the start current peaks.
This is usually accomplished with a explosive lense plane wave generator which
produces a uniform plane wave burn (or detonation) front in the explosive. Once
initiated, the front propagates through the explosive in the armature,
distorting it into a conical shape (typically 12 to 14 degrees of arc). Where
the armature has expanded to the full diameter of the stator, it forms a short
circuit between the ends of the stator coil, shorting and thus isolating the
start current source and trapping the current within the device. The propagating
short has the effect of compressing the magnetic field, whilst reducing the
inductance of the stator winding. The result is that such generators will
producing a ramping current pulse, which peaks before the final disintegration
of the device. Published results suggest ramp times of tens to hundreds of
microseconds, specific to the characteristics of the device, for peak currents
of tens of MegaAmperes and peak energies of tens of MegaJoules.

The current multiplication (ie ratio of output current to start current)
achieved varies with designs, but numbers as high as 60 have been demonstrated.
In a munition application, where space and weight are at a premium, the smallest
possible start current source is desirable. These applications can exploit
cascading of FCGs, where a small FCG is used to prime a larger FCG with a start
current. Experiments conducted by LANL and AFWL have demonstrated the viability
of this technique [KIRTLAND94, REINOVSKY85].

The principal technical issues in adapting the FCG to weapons applications
lie in packaging, the supply of start current, and matching the device to the
intended load. Interfacing to a load is simplified by the coaxial geometry of
coaxial and conical FCG designs. Significantly, this geometry is convenient for
weapons applications, where FCGs may be stacked axially with devices such a
microwave Vircators. The demands of a load such as a Vircator, in terms of
waveform shape and timing, can be satisfied by inserting pulse shaping networks,
transformers and explosive high current switches.

3.2. Explosive and Propellant Driven MHD Generators

The design of explosive and propellant driven Magneto-Hydrodynamic generators
is a much less mature art that that of FCG design. Technical issues such as the
size and weight of magnetic field generating devices required for the operation
of MHD generators suggest that MHD devices will play a minor role in the near
term. In the context of this paper, their potential lies in areas such as start
current generation for FCG devices.

The fundamental principle behind the design of MHD devices is that a
conductor moving through a magnetic field will produce an electrical current
transverse to the direction of the field and the conductor motion. In an
explosive or propellant driven MHD device, the conductor is a plasma of ionised
explosive or propellant gas, which travels through the magnetic field. Current
is collected by electrodes which are in contact with the plasma jet
[FANTHOME89].

The electrical properties of the plasma are optimised by seeding the
explosive or propellant with with suitable additives, which ionise during the
burn [FANTHOME89, FLANAGAN81]. Published experiments suggest that a typical
arrangement uses a solid propellant gas generator, often using conventional
ammunition propellant as a base. Cartridges of such propellant can be loaded
much like artillery rounds, for multiple shot operation.

3.3. High Power Microwave Sources - The Vircator

Whilst FCGs are potent technology base for the generation of large electrical
power pulses, the output of the FCG is by its basic physics constrained to the
frequency band below 1 MHz. Many target sets will be difficult to attack even
with very high power levels at such frequencies, moreover focussing the energy
output from such a device will be problematic. A HPM device overcomes both of
the problems, as its output power may be tightly focussed and it has a much
better ability to couple energy into many target types.

A wide range of HPM devices exist. Relativistic Klystrons, Magnetrons, Slow
Wave Devices, Reflex triodes, Spark Gap Devices and Vircators are all examples
of the available technology base [GRANATSTEIN87, HOEBERLING92]. From the
perspective of a bomb or warhead designer, the device of choice will be at this
time the Vircator, or in the nearer term a Spark Gap source. The Vircator is of
interest because it is a one shot device capable of producing a very powerful
single pulse of radiation, yet it is mechanically simple, small and robust, and
can operate over a relatively broad band of microwave frequencies.

The physics of the Vircator tube are substantially more complex than those of
the preceding devices. The fundamental idea behind the Vircator is that of
accelerating a high current electron beam against a mesh (or foil) anode. Many
electrons will pass through the anode, forming a bubble of space charge behind
the anode. Under the proper conditions, this space charge region will oscillate
at microwave frequencies. If the space charge region is placed into a resonant
cavity which is appropriately tuned, very high peak powers may be achieved.
Conventional microwave engineering techniques may then be used to extract
microwave power from the resonant cavity. Because the frequency of oscillation
is dependent upon the electron beam parameters, Vircators may be tuned or
chirped in frequency, where the microwave cavity will support appropriate modes.
Power levels achieved in Vircator experiments range from 170 kiloWatts to 40
GigaWatts over frequencies spanning the decimetric and centimetric bands
[THODE87].

The two most commonly described configurations for the Vircator are the Axial
Vircator (AV) (Fig.3), and the Transverse Vircator (TV). The Axial Vircator is
the simplest by design, and has generally produced the best power output in
experiments. It is typically built into a cylindrical waveguide structure. Power
is most often extracted by transitioning the waveguide into a conical horn
structure, which functions as an antenna. AVs typically oscillate in Transverse
Magnetic (TM) modes. The Transverse Vircator injects cathode current from the
side of the cavity and will typically oscillate in a Transverse Electric (TE)
mode.

Technical issues in Vircator design are output pulse duration, which is
typically of the order of a microsecond and is limited by anode melting,
stability of oscillation frequency, often compromised by cavity mode hopping,
conversion efficiency and total power output. Coupling power efficiently from
the Vircator cavity in modes suitable for a chosen antenna type may also be an
issue, given the high power levels involved and thus the potential for
electrical breakdown in insulators.

4. The Lethality of Electromagnetic 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.

4.1. Coupling Modes

In assessing how power is coupled into targets, two principal coupling modes
are recognised in the literature:

Front Door Coupling occurs typically when power from a electromagnetic
weapon is coupled into an antenna associated with radar or communications
equipment. The antenna subsystem is designed to couple power in and out of the
equipment, and thus provides an efficient path for the power flow from the
electromagnetic weapon to enter the equipment and cause damage.

Back Door Coupling occurs when the electromagnetic field from a weapon
produces large transient currents (termed spikes, when produced by a low
frequency weapon ) or electrical standing waves (when produced by a HPM
weapon) on fixed electrical wiring and cables interconnecting equipment, or
providing connections to mains power or the telephone network [TAYLOR92,
WHITE78]. Equipment connected to exposed cables or wiring will experience
either high voltage transient spikes or standing waves which can damage power
supplies and communications interfaces if these are not hardened. Moreover,
should the transient penetrate into the equipment, damage can be done to other
devices inside.

A low frequency weapon will couple well into a typical wiring infrastructure,
as most telephone lines, networking cables and power lines follow streets,
building risers and corridors. In most instances any particular cable run will
comprise multiple linear segments joined at approximately right angles. Whatever
the relative orientation of the weapons field, more than one linear segment of
the cable run is likely to be oriented such that a good coupling efficiency can
be achieved.

It is worth noting at this point the safe operating envelopes of some typical
types of semiconductor devices. Manufacturer's guaranteed breakdown voltage
ratings for Silicon high frequency bipolar transistors, widely used in
communications equipment, typically vary between 15 V and 65 V. Gallium Arsenide
Field Effect Transistors are usually rated at about 10V. High density Dynamic
Random Access Memories (DRAM), an essential part of any computer, are usually
rated to 7 V against earth. Generic CMOS logic is rated between 7 V and 15 V,
and microprocessors running off 3.3 V or 5 V power supplies are usually rated
very closely to that voltage. Whilst many modern devices are equipped with
additional protection circuits at each pin, to sink electrostatic discharges,
sustained or repeated application of a high voltage will often defeat these
[MOTO3, MICRON92, NATSEMI86].

Communications interfaces and power supplies must typically meet electrical
safety requirements imposed by regulators. Such interfaces are usually protected
by isolation transformers with ratings from hundreds of Volts to about 2 to 3 kV
[NPI93].

It is clearly evident that once the defence provided by a transformer, cable
pulse arrestor or shielding is breached, voltages even as low as 50 V can
inflict substantial damage upon computer and communications equipment. The
author has seen a number of equipment items (computers, consumer electronics)
exposed to low frequency high voltage spikes (near lightning strikes, electrical
power transients), and in every instance the damage was extensive, often
requiring replacement of most semiconductors in the equipment [2].

HPM weapons operating in the centimetric and millimetric bands however offer
an additional coupling mechanism to Back Door Coupling. This is the ability to
directly couple into equipment through ventilation holes, gaps between panels
and poorly shielded interfaces. Under these conditions, any aperture into the
equipment behaves much like a slot in a microwave cavity, allowing microwave
radiation to directly excite or enter the cavity. The microwave radiation will
form a spatial standing wave pattern within the equipment. Components situated
within the anti-nodes within the standing wave pattern will be exposed to
potentially high electromagnetic fields.

Because microwave weapons can couple more readily than low frequency weapons,
and can in many instances bypass protection devices designed to stop low
frequency coupling, microwave weapons have the potential to be significantly
more lethal than low frequency weapons.

What research has been done in this area illustrates the difficulty in
producing workable models for predicting equipment vulnerability. It does
however provide a solid basis for shielding strategies and hardening of
equipment.

The diversity of likely target types and the unknown geometrical layout
and electrical characteristics of the wiring and cabling infrastructure
surrounding a target makes the exact prediction of lethality impossible.

A general approach for dealing with wiring and cabling related back door
coupling is to determine a known lethal voltage level, and then use this to find
the required field strength to generate this voltage. Once the field strength is
known, the lethal radius for a given weapon configuration can be calculated.

A trivial example is that of a 10 GW 5 GHz HPM device illuminating a
footprint of 400 to 500 metres diameter, from a distance of several hundred
metres. This will result in field strengths of several kiloVolts per metre
within the device footprint, in turn capable of producing voltages of hundreds
of volts to kiloVolts on exposed wires or cables [KRAUS88, TAYLOR92]. This
suggests lethal radii of the order of hundreds of metres, subject to weapon
performance and target set electrical hardness.

4.2. Maximising Electromagnetic Bomb Lethality

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

The first step in maximising bomb lethality is is to maximise 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 maximising 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 maximise 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. One possible scheme is for a bomb approaching its programmed firing
altitude to deploy five linear antenna elements. These are produced by firing
off cable spools which unwind several hundred metres of cable. Four radial
antenna elements form a "virtual" earth plane around the bomb, while an axial
antenna element is used to radiate the power from the FCG. The choice of element
lengths would need to be carefully matched to the frequency characteristics of
the weapon, to produce the desired field strength. A high power coupling pulse
transformer is used to match the low impedance FCG output to the much higher
impedance of the antenna, and ensure that the current pulse does not vapourise
the cable prematurely.

Other alternatives are possible. One is to simply guide the bomb very close
to the target, and rely upon the near field produced by the FCG winding, which
is in effect a loop antenna of very small diameter relative to the wavelength.
Whilst coupling efficiency is inherently poor, the use of a guided bomb would
allow the warhead to be positioned accurately within metres of a target. An area
worth further investigation in this context is the use of low frequency bombs to
damage or destroy magnetic tape libraries, as the near fields in the vicinity of
a flux generator are of the order of magnitude of the coercivity of most modern
magnetic materials.

Microwave bombs have a broader range of coupling modes and given the small
wavelength in comparison with bomb dimensions, can be readily focussed against
targets with a compact antenna assembly. Assuming that the antenna provides the
required weapon footprint, there are at least two mechanisms which can be
employed to further maximise lethality.

The first is sweeping the frequency or chirping the Vircator. This can
improve coupling efficiency in comparison with a single frequency weapon, by
enabling the radiation to couple into apertures and resonances over a range of
frequencies. In this fashion, a larger number of coupling opportunities are
exploited.

The second mechanism which can be exploited to improve coupling is the
polarisation of the weapon's emission. If we assume that the orientations of
possible coupling apertures and resonances in the target set are random in
relation to the weapon's antenna orientation, a linearly polarised emission will
only exploit half of the opportunities available. A circularly polarised
emission will exploit all coupling opportunities.

The practical constraint is that it may be difficult to produce an efficient
high power circularly polarised antenna design which is compact and performs
over a wide band. Some work therefore needs to be done on tapered helix or
conical spiral type antennas capable of handling high power levels, and a
suitable interface to a Vircator with multiple extraction ports must devised. A
possible implementation is depicted in Fig.5. In this arrangement, power is
coupled from the tube by stubs which directly feed a multi-filar conical helix
antenna. An implementation of this scheme would need to address the specific
requirements of bandwidth, beamwidth, efficiency of coupling from the tube,
while delivering circularly polarised radiation.

Another aspect of electromagnetic bomb lethality is its detonation altitude,
and by varying the detonation altitude, a tradeoff may be achieved between the
size of the lethal footprint and the intensity of the electromagnetic field in
that footprint. This provides the option of sacrificing weapon coverage to
achieve kills against targets of greater electromagnetic hardness, for a given
bomb size (Fig.7, 8). This is not unlike the use of airburst explosive devices.

In summary, lethality is maximised by maximising power output and the
efficiency of energy transfer from the weapon to the target set. Microwave
weapons offer the ability to focus nearly all of their energy output into the
lethal footprint, and offer the ability to exploit a wider range of coupling
modes. Therefore, microwave bombs are the preferred choice.

5. Targeting Electromagnetic 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.

Mobile and camouflaged targets which radiate overtly can also be readily
engaged. Mobile and relocatable air defence equipment, mobile communications
nodes and naval vessels are all good examples of this category of target. 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 datalinked 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)
[HERSKOWITZ96]. UE has attracted most attention in the context of TEMPEST [3]
surveillance, where transient emanations leaking out from equipment due poor
shielding can be detected and in many instances demodulated to recover useful
intelligence. Termed Van Eck radiation [VECK85], such emissions can only be
suppressed by rigorous shielding and emission control techniques, such as are
employed in TEMPEST rated equipment.

Whilst the demodulation of UE can be a technically difficult task to perform
well, in the context of targeting electromagnetic bombs this problem does not
arise. To target such an emitter for attack requires only the ability to
identify the type of emission and thus target type, and to isolate its position
with sufficient accuracy to deliver the bomb. Because the emissions from
computer monitors, peripherals, processor equipment, switchmode power supplies,
electrical motors, internal combustion engine ignition systems, variable duty
cycle electrical power controllers (thyristor or triac based), superheterodyne
receiver local oscillators and computer networking cables are all distinct in
their frequencies and modulations, a suitable Emitter Locating System can be
designed to detect, identify and track such sources of emission.

A good precedent for this targeting paradigm exists. During the SEA (Vietnam)
conflict the United States Air Force (USAF) operated a number of night
interdiction gunships which used direction finding receivers to track the
emissions from vehicle ignition systems. Once a truck was identified and
tracked, the gunship would engage it [4].

Because UE occurs at relatively low power levels, the use of this detection
method prior to the outbreak of hostilities can be difficult, as it may be
necessary to overfly hostile territory to find signals of usable intensity [5].
The use of stealthy reconnaissance aircraft or long range, stealthy Unmanned
Aerial Vehicles (UAV) may be required. The latter also raises the possibility of
autonomous electromagnetic warhead armed expendable UAVs, fitted with
appropriate homing receivers. These would be programmed to loiter in a target
area until a suitable emitter is detected, upon which the UAV would home in and
expend itself against the target.

6. The Delivery of Conventional Electromagnetic Bombs

As with explosive warheads, electromagnetic warheads will occupy a volume of
physical space and will also have some given mass (weight) determined by the
density of the internal hardware. Like explosive warheads, electromagnetic
warheads may be fitted to a range of delivery vehicles.

Known existing applications [6]
involve fitting an electromagnetic warhead to a cruise missile airframe. The
choice of a cruise missile airframe will restrict the weight of the weapon to
about 340 kg (750 lb), although some sacrifice in airframe fuel capacity could
see this size increased. A limitation in all such applications is the need to
carry an electrical energy storage device, eg a battery, to provide the current
used to charge the capacitors used to prime the FCG prior to its discharge.
Therefore the available payload capacity will be split between the electrical
storage and the weapon itself.

In wholly autonomous weapons such as cruise missiles, the size of the priming
current source and its battery may well impose important limitations on weapon
capability. Air delivered bombs, which have a flight time between tens of
seconds to minutes, could be built to exploit the launch aircraft's power
systems. In such a bomb design, the bomb's capacitor bank can be charged by the
launch aircraft enroute to target, and after release a much smaller onboard
power supply could be used to maintain the charge in the priming source prior to
weapon initiation.

An electromagnetic bomb delivered by a conventional aircraft [7]
can offer a much better ratio of electromagnetic device mass to total bomb mass,
as most of the bomb mass can be dedicated to the electromagnetic device
installation itself. It follows therefore, that for a given technology an
electromagnetic bomb of identical mass to a electromagnetic warhead equipped
missile can have a much greater lethality, assuming equal accuracy of delivery
and technologically similar electromagnetic device design.

A missile borne electromagnetic warhead installation will comprise the
electromagnetic device, an electrical energy converter, and an onboard storage
device such as a battery. As the weapon is pumped, the battery is drained. The
electromagnetic device will be detonated by the missile's onboard fusing system.
In a cruise missile, this will be tied to the navigation system; in an
anti-shipping missile the radar seeker and in an air-to-air missile, the
proximity fusing system. The warhead fraction (ie ratio of total payload
(warhead) mass to launch mass of the weapon) will be between 15% and 30%
[8].

An electromagnetic bomb warhead will comprise an electromagnetic device, an
electrical energy converter and a energy storage device to pump and sustain the
electromagnetic device charge after separation from the delivery platform.
Fusing could be provided by a radar altimeter fuse to airburst the bomb, a
barometric fuse or in GPS/inertially guided bombs, the navigation system. The
warhead fraction could be as high as 85%, with most of the usable mass occupied
by the electromagnetic device and its supporting hardware.

Due to the potentially large lethal radius of an electromagnetic device,
compared to an explosive device of similar mass, standoff delivery would be
prudent. Whilst this is an inherent characteristic of weapons such as cruise
missiles, potential applications of these devices to glidebombs, anti-shipping
missiles and air-to-air missiles would dictate fire and forget guidance of the
appropriate variety, to allow the launching aircraft to gain adequate separation
of several miles before warhead detonation.

The recent advent of GPS satellite navigation guidance kits for conventional
bombs and glidebombs has provided the optimal means for cheaply delivering such
weapons. While GPS guided weapons without differential GPS enhancements may lack
the pinpoint accuracy of laser or television guided munitions, they are still
quite accurate (CEP \(~~ 40 ft) and importantly, cheap, autonomous all weather
weapons.

The USAF has recently deployed the Northrop GAM (GPS Aided Munition) on the
B-2 bomber [NORTHROP95], and will by the end of the decade deploy the
GPS/inertially guided GBU-29/30 JDAM (Joint Direct Attack Munition)[MDC95] and
the AGM-154 JSOW (Joint Stand Off Weapon) [PERGLER94] glidebomb. Other countries
are also developing this technology, the Australian BAeA AGW (Agile Glide
Weapon) glidebomb achieving a glide range of about 140 km (75 nmi) when launched
from altitude [KOPP96].

The importance of glidebombs as delivery means for HPM warheads is threefold.
Firstly, the glidebomb can be released from outside effective radius of target
air defences, therefore minimising the risk to the launch aircraft. Secondly,
the large standoff range means that the aircraft can remain well clear of the
bomb's effects. Finally the bomb's autopilot may be programmed to shape the
terminal trajectory of the weapon, such that a target may be engaged from the
most suitable altitude and aspect.

A major advantage of using electromagnetic bombs is that they may be
delivered by any tactical aircraft with a nav-attack system capable of
delivering GPS guided munitions. As we can expect GPS guided munitions to be
become the standard weapon in use by Western air forces by the end of this
decade, every aircraft capable of delivering a standard guided munition also
becomes a potential delivery vehicle for a electromagnetic bomb. Should weapon
ballistic properties be identical to the standard weapon, no software changes to
the aircraft would be required.

Because of the simplicity of electromagnetic bombs in comparison with weapons
such as Anti Radiation Missiles (ARM), it is not unreasonable to expect that
these should be both cheaper to manufacture, and easier to support in the field,
thus allowing for more substantial weapon stocks. In turn this makes saturation
attacks a much more viable proposition.

In this context it is worth noting that the USAF's possesion of the JDAM
capable F-117A and B-2A will provide the capability to deliver E-bombs against
arbitrary high value targets with virtual impunity. The ability of a B-2A to
deliver up to sixteen GAM/JDAM fitted E-bomb warheads with a 20 ft class CEP
would allow a small number of such aircraft to deliver a decisive blow against
key strategic, air defence and theatre targets. A strike and electronic combat
capable derivative of the F-22 would also be a viable delivery platform for an
E-bomb/JDAM. With its superb radius, low signature and supersonic cruise
capability an RFB-22 could attack air defence sites, C3I sites, airbases and
strategic targets with E-bombs, achieving a significant shock effect. A good
case may be argued for the whole F-22 build to be JDAM/E-bomb capable, as this
would allow the USAF to apply the maximum concentration of force against
arbitrary air and surface targets during the opening phase of an air campaign.

7. Defence Against Electromagnetic 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. However,
most such equipment must communicate with and be fed with power from the outside
world, and this can provide entry points via which electrical transients may
enter the enclosure and effect damage. While optical fibres address this
requirement for transferring data in and out, electrical power feeds remain an
ongoing vulnerability.

Where an electrically conductive channel must enter the enclosure,
electromagnetic arresting devices must be fitted. A range of devices exist,
however care must be taken in determining their parameters to ensure that they
can deal with the rise time and strength of electrical transients produced by
electromagnetic devices. Reports from the US [9]
indicate that hardening measures attuned to the behaviour of nuclear EMP bombs
do not perform well when dealing with some conventional microwave
electromagnetic device designs.

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.

An interesting aspect of electrical damage to targets is the possibility of
wounding semiconductor devices thereby causing equipment to suffer repetitive
intermittent faults rather than complete failures. Such faults would tie down
considerable maintenance resources while also diminishing the confidence of the
operators in the equipment's reliability. Intermittent faults may not be
possible to repair economically, thereby causing equipment in this state to be
removed from service permanently, with considerable loss in maintenance hours
during damage diagnosis. This factor must also be considered when assessing the
hardness of equipment against electromagnetic attack, as partial or incomplete
hardening may in this fashion cause more difficulties than it would solve.
Indeed, shielding which is incomplete may resonate when excited by radiation and
thus contribute to damage inflicted upon the equipment contained within it.

Other than hardening against attack, facilities which are concealed should
not radiate readily detectable emissions. Where radio frequency communications
must be used, low probability of intercept (ie spread spectrum) techniques
should be employed exclusively to preclude the use of site emissions for
electromagnetic targeting purposes [DIXON84]. Appropriate suppression of UE is
also mandatory.

Communications networks for voice, data and services should employ topologies
with sufficient redundancy and failover mechanisms to allow operation with
multiple nodes and links inoperative. This will deny a user of electromagnetic
bombs the option of disabling large portions if not the whole of the network by
taking down one or more key nodes or links with a single or small number of
attacks.

8. Limitations of Electromagnetic Bombs

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.

In the context of targeting military equipment, it must be noted that
thermionic technology (ie vacuum tube equipment) is substantially more resilient
to the electromagnetic weapons effects than solid state (ie transistor)
technology. Therefore a weapon optimised to destroy solid state computers and
receivers may cause little or no damage to a thermionic technology device, for
instance early 1960s Soviet military equipment. Therefore a hard electrical kill
may not be achieved against such targets unless a suitable weapon is used.

This underscores another limitation of electromagnetic weapons, which is the
difficulty in kill assessment. Radiating targets such as radars or
communications equipment may continue to radiate after an attack even though
their receivers and data processing systems have been damaged or destroyed. This
means that equipment which has been successfully attacked may still appear to
operate. Conversely an opponent may shut down an emitter if attack is imminent
and the absence of emissions means that the success or failure of the attack may
not be immediately apparent.

Assessing whether an attack on a non radiating emitter has been successful
is more problematic. A good case can be made for developing tools specifically
for the purpose of analysing unintended emissions, not only for targeting
purposes, but also for kill assessment.

An important factor in assessing the lethal coverage of an electromagnetic
weapon is atmospheric propagation. While the relationship between
electromagnetic field strength and distance from the weapon is one of an inverse
square law in free space, the decay in lethal effect with increasing distance
within the atmosphere will be greater due quantum physical absorption effects [10].
This is particularly so at higher frequencies, and significant absorption peaks
due water vapour and oxygen exist at frequencies above 20 GHz. These will
therefore contain the effect of HPM weapons to shorter radii than are ideally
achievable in the K and L frequency bands.

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 [AAP1003].

9. The Proliferation of Electromagnetic Bombs

At the time of writing, the United States 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 labour rates [REINOVSKY85]. This cost could be even lower in a Third
World or newly industrialised 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.

Of major concern is the vulnerability resulting from increasing use of
communications and data communications schemes based upon copper cable media. If
the copper medium were to be replaced en masse with optical fibre in order to
achieve higher bandwidths, the communications infrastructure would become
significantly more robust against electromagnetic attack as a result. However,
the current trend is to exploit existing distribution media such as cable TV and
telephone wiring to provide multiple Megabit/s data distribution (eg cable
modems, ADSL/HDSL/VDSL) to premises. Moreover, the gradual replacement of
coaxial Ethernet networking with 10-Base-T twisted pair equipment has further
increased the vulnerability of wiring systems inside buildings. It is not
unreasonable to assume that the data and services communications infrastructure
in the West will remain a "soft" electromagnetic target in the forseeable
future.

At this time no counter-proliferation regimes exist. Should treaties be
agreed to limit the proliferation of electromagnetic weapons, they would be
virtually impossible to enforce given the common availability of suitable
materials and tools.

With the former CIS suffering significant economic difficulties, the
possibility of CIS designed microwave and pulse power technology leaking out to
Third World nations or terrorist organisations should not be discounted. The
threat of electromagnetic bomb proliferation is very real.

10. A Doctrine for the Use of Conventional Electromagnetic Bombs

A fundamental tenet of IW is that complex organisational systems such as
governments, industries and military forces cannot function without the flow of
information through their structures. Information flows within these structures
in several directions, under typical conditions of function. A trivial model for
this function would see commands and directives flowing outward from a central
decisionmaking element, with information about the state of the system flowing
in the opposite direction. Real systems are substantially more complex.

This is of military significance because stopping this flow of information
will severely debilitate the function of any such system. Stopping the outward
flow of information produces paralysis, as commands cannot reach the elements
which are to execute them. Stopping the inward flow of information isolates the
decisionmaking element from reality, and thus severely inhibits its capacity to
make rational decisions which are sensitive to the currency of information at
hand.

The recent evolution of strategic (air) warfare indicates a growing trend
toward targeting strategies which exploit this most fundamental vulnerability of
any large and organised system [11].
The Desert Storm air war of 1991 is a good instance, with a substantial effort
expended against such targets. Indeed, the model used for modern strategic air
attack places leadership and its supporting communications in the position of
highest targeting priority [WARDEN95]. No less importantly, modern Electronic
Combat concentrates upon the disruption and destruction of communications and
information gathering sensors used to support military operations. Again the
Desert Storm air war provides a good illustration of the application of this
method.

A strategy which stresses attack upon the information processing and
communications elements of the systems which it is targeting offers a very high
payoff, as it will introduce an increasing level of paralysis and disorientation
within its target. Electromagnetic bombs are a powerful tool in the
implementation of such a strategy.

10.1 Electronic Combat Operations using Electromagnetic Bombs

The central objective of Electronic Combat (EC) operations is the command of
the electromagnetic spectrum, achieved by soft and hard kill means [12]
against the opponent's electronic assets. The underlying objective of commanding
the electromagnetic spectrum is to interrupt or substantially reduce the flow of
information through the opponent's air defence system, air operations
environment and between functional elements of weapon systems.

In this context the ability of electromagnetic bombs to achieve kills against
a wide range of target types allows their general application to the task of
inflicting attrition upon an opponent's electronic assets, be they specialised
air defence assets or more general Command-Control-Communications (C3) and other
military assets.

Electromagnetic bombs can be a means of both soft and hard electrical kill,
subject to the lethality of the weapon and the hardness of its target. A hard
electrical kill by means of an electromagnetic device will be achieved in those
instances where such severe electrical damage is achieved against a target so as
to require the replacement of most if not all of its internal electronics.

Electronic combat operations using electromagnetic devices involve the use of
these to attack radar, C3 and air defence weapon systems. These should always be
attacked initially with an electromagnetic weapon to achieve soft or hard
electrical kills, followed up by attack with conventional munitions to preclude
possible repair of disabled assets at a later time. As with conventional SEAD
operations, the greatest payoff will be achieved by using electromagnetic
weapons against systems of strategic importance first, followed in turn by those
of operational and tactical importance [KOPP92].

In comparison with an AntiRadiation Missile (ARM - a missile which homes on
the emissions from a threat radar), the established and specialised tool in the
conduct of SEAD operations, an electromagnetic bomb can achieve kills against
multiple targets of diverse types within its lethal footprint. In this respect
an electromagnetic device may be described as a Weapon of Electrical Mass
Destruction (WEMD). Therefore electromagnetic weapons are a significant force
multiplier in electronic combat operations.

A conventional electronic combat campaign, or intensive electronic combat
operations, will initially concentrate on saturating the opponent's electronic
defences, denying information and inflicting maximum attrition upon electronic
assets. The force multiplication offered by electromagnetic weapons vastly
reduces the number of air assets required to inflict substantial attrition, and
where proper electronic reconnaissance has been carried out beforehand, also
reduces the need for specialised assets such as ARM firing aircraft equipped
with costly emitter locating systems.

The massed application of electromagnetic bombs in the opening phase of an
electronic battle will allow much faster attainment of command of the
electromagnetic spectrum, as it will inflict attrition upon electronic assets at
a much faster rate than possible with conventional means.

Whilst the immaturity of conventional electromagnetic weapons precludes an
exact analysis of the scale of force multiplication achievable, it is evident
that a single aircraft carrying an electromagnetic bomb capable of concurrently
disabling a SAM site with its colocated acquisition radar and supporting radar
directed AAA weapons, will have the potency of the several ARM firing and
support jamming aircraft required to accomplish the same result by conventional
means. This and the ability of multirole tactical aircraft to perform this task
allows for a much greater concentration of force in the opening phase of the
battle, for a given force size.

In summary the massed application of electromagnetic weapons to Electronic
Combat operations will provide for a much faster rate of attrition against
hostile electronic assets, achievable with a significantly reduced number of
specialised and multirole air assets [13].
This will allow even a modestly sized force to apply overwhelming pressure in
the initial phase of an electronic battle, and therefore achieve command of the
electromagnetic spectrum in a significantly shorter time than by conventional
means.

10.2. Strategic Air Attack Operations using Electromagnetic Bombs

The modern approach to strategic air warfare reflects in many respects
aspects of the IW model, in that much effort is expended in disabling an
opponent's fundamental information processing infrastructure. Since we however
are yet to see a systematic IW doctrine which has been tested in combat, this
paper will approach the subject from a more conservative viewpoint and use
established strategic doctrine.

Modern strategic air attack theory is based upon Warden's Five Rings model
[WARDEN95], which identifies five centres of gravity in a nation's warfighting
capability. In descending order of importance, these are the nation's leadership
and supporting C3 system, its essential economic infrastructure, its
transportation network, its population and its fielded military forces.

Electromagnetic weapons may be productively used against all elements in this
model, and provide a particularly high payoff when applied against a highly
industrialised and geographically concentrated opponent. Of particular
importance in the context of strategic air attack, is that while electromagnetic
weapons are lethal to electronics, they have little if any effect on humans.
This is a characteristic which is not shared with established conventional and
nuclear weapons.

This selectivity in lethal effect makes electromagnetic weapons far more
readily applicable to a strategic air attack campaign, and reduces the internal
political pressure which is experienced by the leadership of any democracy which
must commit to warfare. An opponent may be rendered militarily, politically and
economically ineffective with little if any loss in human life.

The innermost ring in the Warden model essentially comprises government
bureaucracies and civilian and military C3 systems. In any modern nation these
are heavily dependent upon the use of computer equipment and communications
equipment. What is of key importance at this time is an ongoing change in the
structure of computing facilities used in such applications, as these are
becoming increasingly decentralised. A modern office environment relies upon a
large number of small computers, networked to interchange information, in which
respect it differs from the traditional model of using a small number of
powerful central machines.

This decentralisation and networking of information technology systems
produces a major vulnerability to electromagnetic attack. Whereas a small number
of larger computers could be defended against electromagnetic attack by the use
of electromagnetic hardened computer rooms, a large distributed network cannot.
Moreover, unless optical fibre networking is used, the networking cables are
themselves a medium via which electromagnetic effects can be efficiently
propagated throughout the network, to destroy machines. Whilst the use of
distributed computer networks reduces vulnerability to attack by conventional
munitions, it increases vulnerability to attack by electromagnetic weapons.

Selective targeting of government buildings with electromagnetic weapons will
result in a substantial reduction in a government's ability to handle and
process information. The damage inflicted upon information records may be
permanent, should inappropriate backup strategies have been used to protect
stored data. It is reasonable to expect most data stored on machines which are
affected will perish with the host machine, or become extremely difficult to
recover from damaged storage devices.

The cost of hardening existing computer networks is prohibitive, as is the
cost of replacement with hardened equipment. Whilst the use of hardened
equipment for critical tasks would provide some measure of resilience, the
required discipline in the handling of information required to implement such a
scheme renders its utility outside of military organisations questionable.
Therefore the use of electromagnetic weapons against government facilities
offers an exceptionally high payoff.

Other targets which fall into the innermost ring may also be profitably
attacked. Satellite link and importantly control facilities are vital means of
communication as well as the primary interface to military and commercial
reconnaissance satellites. Television and radio broadcasting stations, one of
the most powerful tools of any government, are also vulnerable to
electromagnetic attack due the very high concentration of electronic equipment
in such sites. Telephone exchanges, particularly later generation digital
switching systems, are also highly vulnerable to appropriate electromagnetic
attack.

In summary the use of electromagnetic weapons against leadership and C3
targets is highly profitable, in that a modest number of weapons appropriately
used can introduce the sought state of strategic paralysis, without the
substantial costs incurred by the use of conventional munitions to achieve the
same effect.

Essential economic infrastructure is also vulnerable to electromagnetic
attack. The finance industry and stock markets are almost wholly dependent upon
computers and their supporting communications. Manufacturing, chemical,
petroleum product industries and metallurgical industries rely heavily upon
automation which is almost universally implemented with electronic PLC
(Programmable Logic Controller) systems or digital computers. Furthermore, most
sensors and telemetry devices used are electrical or electronic.

Attacking such economic targets with electromagnetic weapons will halt
operations for the time required to either repair the destroyed equipment, or to
reconfigure for manual operation. Some production processes however require
automated operation, either because hazardous conditions prevent human
intervention, or the complexity of the control process required cannot be
carried out by a human operator in real time. A good instance are larger
chemical, petrochemical and oil/gas production facilities. Destroying automated
control facilities will therefore result in substantial loss of production,
causing shortages of these vital materials.

Manufacturing industries which rely heavily upon robotic and semiautomatic
machinery, such as the electronics, computer and electrical industry, precision
machine industry and aerospace industries, are all key assets in supporting a
military capability. They are all highly vulnerable to electromagnetic attack.
Whilst material processing industries may in some instances be capable of
function with manual process control, the manufacturing industries are almost
wholly dependent upon their automated machines to achieve any useful production
output.

Historical experience
[14] suggests that manufacturing industries are highly resilient to air
attack as production machinery is inherently mechanically robust and thus a very
high blast overpressure is required to destroy it. The proliferation of
electronic and computer controlled machinery has produced a major vulnerability,
for which historical precedent does not exist. Therefore it will be necessary to
reevaluate this orthodoxy in targeting strategy.

The finance industry and stock markets are a special case in this context, as
the destruction of their electronic infrastructure can yield, unlike
manufacturing industries, much faster economic dislocation. This can in turn
produce large systemic effects across a whole economy, including elements which
are not vulnerable to direct electromagnetic attack. This may be of particular
relevance when dealing with an opponent which does not have a large and thus
vulnerable manufacturing economy. Nations which rely on agriculture, mining or
trade for a large proportion of the their gross domestic product are prime
candidates for electromagnetic attack on their finance industry and stock
markets. Since the latter are usually geographically concentrated and typically
electromagnetically "soft" targets, they are highly vulnerable.

In summary there is a large payoff in striking at economic essentials with
electromagnetic weapons, particularly in the opening phase of a strategic air
attack campaign, as economic activity may be halted or reduced with modest
expenditure of the attacker's resources. An important caveat is that centres of
gravity within the target economy must be properly identified and prioritised
for strikes to ensure that maximum effect is achieved as quickly as possible.

Transport infrastructure is the third ring in the Warden model, and also
offers some useful opportunities for the application of electromagnetic weapons.
Unlike the innermost rings, the concentration of electronic and computer
equipment is typically much lower, and therefore considerable care must be taken
in the selection of targets.

Railway and road signalling systems, where automated, are most vulnerable to
electromagnetic attack on their control centres. This could be used to produce
traffic congestion by preventing the proper scheduling of rail traffic, and
disabling road traffic signalling, although the latter may not yield
particularly useful results.

Significantly, most modern automobiles and trucks use electronic ignition
systems which are known to be vulnerable to electromagnetic weapons effects,
although opportunities to find such concentrations so as to allow the profitable
use of an electromagnetic bomb may be scarce.

The population of the target nation is the fourth ring in the Warden model,
and its morale is the object of attack. The morale of the population will be
affected significantly by the quality and quantity of the government propaganda
it is subjected to, as will it be affected by living conditions.

Using electromagnetic weapons against urban areas provides the opportunity to
prevent government propaganda from reaching the population via means of mass
media, through the damaging or destruction of all television and radio receivers
within the footprint of the weapon. Whether this is necessary, given that
broadcast facilities may have already been destroyed, is open to discussion.
Arguably it may be counterproductive, as it will prevent the target population
from being subjected to friendly means of psychological warfare such as
propaganda broadcasts.

The use of electromagnetic weapons against a target population is therefore
an area which requires requires careful consideration in the context of the
overall IW campaign strategy. If useful objectives can be achieved by isolating
the population from government propaganda, then the population is a valid target
for electromagnetic attack. Forces constrained by treaty obligations will have
to reconcile this against the applicable regulations relating to denial of
services to non-combatants [AAP1003].

The outermost and last ring in the Warden model are the fielded military
forces. These are by all means a target vulnerable to electromagnetic attack,
and C3 nodes, fixed support bases as well as deployed forces should be attacked
with electromagnetic devices. Fixed support bases which carry out depot level
maintenance on military equipment offer a substantial payoff, as the
concentration of computers in both automatic test equipment and administrative
and logistic support functions offers a good return per expended weapon.

Any site where more complex military equipment is concentrated should be
attacked with electromagnetic weapons to render the equipment unservicable and
hence reduce the fighting capability, and where possible also mobility of the
targeted force. As discussed earlier in the context of Electronic Combat, the
ability of an electromagnetic weapon to achieve hard electrical kills against
any non-hardened targets within its lethal footprint suggests that some target
sites may only require electromagnetic attack to render them both undefended and
non-operational. Whether to expend conventional munitions on targets in this
state would depend on the immediate military situation.

In summary the use of electromagnetic weapons in strategic air attack
campaign offers a potentially high payoff, particularly when applied to
leadership, C3 and vital economic targets, all of which may be deprived of much
of their function for substantial periods of time. The massed application of
electromagnetic weapons in the opening phase of the campaign would introduce
paralysis within the government, deprived of much of its information processing
infrastructure, as well as paralysis in most vital industries. This would
greatly reduce the capability of the target nation to conduct military
operations of any substantial intensity.

Because conventional electromagnetic weapons produce negligible collateral
damage, in comparison with conventional explosive munitions, they allow the
conduct of an effective and high tempo campaign without the loss of life which
is typical of conventional campaigns. This will make the option of a strategic
bombing campaign more attractive to a Western democracy, where mass media
coverage of the results of conventional strategic strike operations will
adversely affect domestic civilian morale.

The long term effects of a sustained and concentrated strategic bombing
campaign using a combination of conventional and electromagnetic weapons will be
important. The cost of computer and communications infrastructure is
substantial, and its massed destruction would be a major economic burden for any
industrialised nation. In addition it is likely that poor protection of stored
data will add to further economic losses, as much data will be lost with the
destroyed machines.

From the perspective of conducting an IW campaign, this method of attack
achieves many of the central objectives sought. Importantly, the massed
application of electromagnetic weapons would inflict attrition on an opponent's
information processing infrastructure very rapidly, and this would arguably add
a further psychological dimension to the potency of the attack. Unlike the
classical IW model of Gibsonian CyberWar, in which the opponent can arguably
isolate his infrastructure from hostile penetration, parallel or hyperwar style
massed attack with electromagnetic bombs will be be extremely difficult to
defend against.

10.3. Offensive Counter Air (OCA) Operations using Electromagnetic
Bombs

Electromagnetic bombs may be usefully applied to OCA operations. Modern
aircraft are densely packed with electronics, and unless properly hardened, are
highly vulnerable targets for electromagnetic weapons.

The cost of the onboard electronics represents a substantial fraction of the
total cost of a modern military aircraft, and therefore stock levels of spares
will in most instances be limited to what is deemed necessary to cover
operational usage at some nominal sortie rate. Therefore electromagnetic damage
could render aircraft unusable for substantial periods of time.

Attacking airfields with electromagnetic weapons will disable communications,
air traffic control facilities, navigational aids and operational support
equipment, if these items are not suitably electromagnetic hardened.
Conventional blast hardening measures will not be effective, as electrical power
and fixed communications cabling will carry electromagnetic induced transients
into most buildings. Hardened aircraft shelters may provide some measure of
protection due electrically conductive reinforcement embedded in the concrete,
but conventional revetments will not.

Therefore OCA operations against airfields and aircraft on the ground should
include the use of electromagnetic weapons as they offer the potential to
substantially reduce hostile sortie rates.

10.4. Maritime Air Operations using Electromagnetic Bombs

As with modern military aircraft, naval surface combatants are fitted with a
substantial volume of electronic equipment, performing similar functions in
detecting and engaging targets and warning of attack. As such they are
vulnerable to electromagnetic attack, if not suitably hardened. Should they be
hardened, volumetric, weight and cost penalties will be incurred.

Conventional methods for attacking surface combatants involve the use of
saturation attacks by anti-ship missiles or coordinated attacks using a
combination of ARMs and anti-ship missiles. The latter instance is where
disabling the target electronically by stripping its antennae precedes lethal
attack with specialised anti-ship weapons.

An electromagnetic warhead detonated within lethal radius of a surface
combatant will render its air defence system inoperable, as well as damaging
other electronic equipment such as electronic countermeasures, electronic
support measures and communications. This leaves the vessel undefended until
these systems can be restored, which may or may not be possible on the high
seas. Therefore launching an electromagnetic glidebomb on to a surface
combatant, and then reducing it with laser or television guided weapons is an
alternate strategy for dealing with such targets.

10.5. Battlefield Air Interdiction Operations using Electromagnetic
Bombs

Modern land warfare doctrine emphasises mobility, and manoeuvre warfare
methods are typical for contemporary land warfare. Coordination and control are
essential to the successful conduct of manoeuvre operations, and this provides
another opportunity to apply electromagnetic weapons. Communications and command
sites are key elements in the structure of such a land army, and these
concentrate communications and computer equipment. Therefore they should be
attacked with electromagnetic weapons, to disrupt the command and control of
land operations.

Should concentrations of armoured vehicles be found, these are also
profitable targets for electromagnetic attack, as their communications and fire
control systems may be substantially damaged or disabled as a result. A useful
tactic would be initial attack with electromagnetic weapons to create a maximum
of confusion, followed by attack with conventional weapons to take advantage of
the immediate situation.

10.6. Defensive Counter-Air (DCA) and Air Defence Operations using
Electromagnetic Warheads

Providing that compact electromagnetic warheads can be built with useful
lethality performance, then a number of other potential applications become
viable. One is to equip an Air-Air Missile (AAM) with such a warhead. A weapon
with datalink midcourse guidance, such as the AIM-120, could be used to break up
inbound raids by causing soft or hard electrical kills in a formation (raid) of
hostile aircraft. Should this be achieved, the defending fighter will have the
advantage in any following engagement as the hostile aircraft may not be fully
mission capable. Loss of air intercept or nav attack radar, EW equipment,
mission computers, digital engine controls, communications and electronic flight
controls, where fitted, could render the victim aircraft defenceless against
attack with conventional missiles.

This paradigm may also be applied to air defence operations using area
defence SAMs. Large SAMs such as the MIM-104 Patriot, RIM-66E/M and RIM-67A
Standard, 5V55/48N6 (SA-10) and 9M82/9M83 (SA-12) could accommodate an
electromagnetic warhead comparable in size to a bomb warhead. A SAM site
subjected to jamming by inbound bombers could launch a first round under
datalink control with an electromagnetic warhead to disable the bombers, and
then follow with conventional rounds against targets which may not be able to
defend themselves electronically. This has obvious implications for the
electromagnetic hardness of combat aircraft systems.

10.7. A Strategy of Graduated Response

The introduction of non-nuclear electromagnetic bombs into the arsenal of a
modern air force considerably broadens the options for conducting strategic
campaigns. Clearly such weapons are potent force multipliers in conducting a
conventional war, particularly when applied to Electronic Combat, OCA and
strategic air attack operations.

The massed use of such weapons would provide a decisive advantage to any
nation with the capability to effectively target and deliver them. The
qualitative advantage in capability so gained would provide a significant
advantage even against a much stronger opponent not in the possession of this
capability.

Electromagnetic weapons however open up less conventional alternatives for
the conduct of a strategic campaign, which derive from their ability to inflict
significant material damage without inflicting visible collateral damage and
loss of life. Western governments have been traditionally reluctant to commit to
strategic campaigns, as the expectation of a lengthy and costly battle, with
mass media coverage of its highly visible results, will quickly produce domestic
political pressure to cease the conflict.

An alternative is a Strategy of Graduated Response (SGR). In this strategy,
an opponent who threatens escalation to a full scale war is preemptively
attacked with electromagnetic weapons, to gain command of the electromagnetic
spectrum and command of the air. Selective attacks with electromagnetic weapons
may then be applied against chosen strategic targets, to force concession.
Should these fail to produce results, more targets may be disabled by
electromagnetic attack. Escalation would be sustained and graduated, to produce
steadily increasing pressure to concede the dispute. Air and sea blockade are
complementary means via which pressure may be applied.

Because electromagnetic weapons can cause damage on a large scale very
quickly, the rate at which damage can be inflicted can be very rapid, in which
respect such a campaign will differ from the conventional, where the rate at
which damage is inflicted is limited by the usable sortie rate of strategic air
attack capable assets [15].

Should blockade and the total disabling of vital economic assets fail to
yield results, these may then be systematically reduced by conventional weapons,
to further escalate the pressure. Finally, a full scale conventional strategic
air attack campaign would follow, to wholly destroy the hostile nation's
warfighting capability.

Another situation where electromagnetic bombs may find useful application is
in dealing with governments which actively implement a policy of state sponsored
terrorism or info-terrorism, or alternately choose to conduct a sustained low
intensity land warfare campaign. Again the Strategy of Graduated Response, using
electromagnetic bombs in the initial phases, would place the government under
significant pressure to concede.

Importantly, high value targets such as R&D and production sites for
Weapons of Mass Destruction (nuclear, biological, chemical) and many vital
economic sites, such as petrochemical production facilities, are critically
dependent upon high technology electronic equipment. The proliferation of WMD
into developing nations has been greatly assisted by the availability of high
quality test and measurement equipment commercially available from First World
nations, as well as modern electronic process control equipment. Selectively
destroying such equipment can not only paralyse R&D effort, but also
significantly impair revenue generating production effort. A Middle Eastern
nation sponsoring terrorism will use oil revenue to support such activity.
Crippling its primary source of revenue without widespread environmental
pollution may be an effective and politically acceptable punitive measure.

As a punitive weapon electromagnetic devices are attractive for dealing with
belligerent governments. Substantial economic, military and political damage may
be inflicted with a modest commitment of resources by their users, and without
politically damaging loss of life.

11. Conclusions

Electromagnetic bombs are Weapons of Electrical Mass Destruction with
applications across a broad spectrum of targets, spanning both the strategic and
tactical. As such their use offers a very high payoff in attacking the
fundamental information processing and communication facilities of a target
system. The massed application of these weapons will produce substantial
paralysis in any target system, thus providing a decisive advantage in the
conduct of Electronic Combat, Offensive Counter Air and Strategic Air Attack.

Because E-bombs can cause hard electrical kills over larger areas than
conventional explosive weapons of similar mass, they offer substantial economies
in force size for a given level of inflicted damage, and are thus a potent force
multiplier for appropriate target sets.

The non-lethal nature of electromagnetic weapons makes their use far less
politically damaging than that of conventional munitions, and therefore broadens
the range of military options available.

This paper has included a discussion of the technical, operational and
targeting aspects of using such weapons, as no historical experience exists as
yet upon which to build a doctrinal model. The immaturity of this weapons
technology limits the scope of this discussion, and many potential areas of
application have intentionally not been discussed. The ongoing technological
evolution of this family of weapons will clarify the relationship between weapon
size and lethality, thus producing further applications and areas for study.

E-bombs can be an affordable force multiplier for military forces which are
under post Cold War pressures to reduce force sizes, increasing both their
combat potential and political utility in resolving disputes. Given the
potentially high payoff deriving from the use of these devices, it is incumbent
upon such military forces to appreciate both the offensive and defensive
implications of this technology. It is also incumbent upon governments and
private industry to consider the implications of the proliferation of this
technology, and take measures to safeguard their vital assets from possible
future attack. Those who choose not to may become losers in any future wars.

12. Acknowledgements

Thanks to Dr D.H. Steven for his insightful comment on microwave coupling and
propagation, and to Professor C.S. Wallace, Dr Ronald Pose and Dr Peter
Leigh-Jones for their most helpful critique of the drafts. Thanks also to the
RAAF Air Power Studies Centre and its then Director, Group Captain Gary Waters,
for encouraging the author to investigate this subject in 1993. Some material in
this paper is derived from RAAF APSC Working Paper 15, "A Doctrine for the Use
of Electromagnetic Pulse Bombs", published in 1993 [KOPP93], and is posted with
permission.

An earlier version of this paper was presented at InfoWarCon V and first
published in "Information Warfare - Cyberterrorism: Protecting Your Personal
Security In the Electronic Age", 1996, Thunder's Mouth Press, 632 Broadway 7th
FL, New York, NY, ISBN: 1-56025-132-8, http://www.infowar.com, posted with
permission.

13. References

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Manual 1-1, Volume 1, March 1992.

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FOWLER89 - C. M. Fowler,R. S. Caird, The Mark IX Generator, Digest of
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Space Technology, February 22, 1993.

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GOFORTH89 - Goforth J.H. et al, Experiments with Explosively Formed Fuse
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HERSKOVITZ96 - Herskowitz D., The Other SIGINT/ELINT, Journal of Electronic
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Countermeasures Handbook, 10th Edition, Cardiff Publishing, Colorado, 1985.

ICH14 - International Countermeasures Handbook, 14th Edition, Cardiff
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Defence, September, 1995.

JED96 - Hughes to Build HPM SEAD Demonstrator, pp.29, Journal of Electronic
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Combat Doctrine for the RAAF, Working Paper No.8, Air Power Studies Centre,
Royal Australian Air Force, Canberra, November 1992.

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Working Paper No.15, Air Power Studies Centre, Royal Australian Air Force,
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KOPP96 - Kopp C., Australia's Kerkanya Based Agile Gliding Weapon, pp.28,
Australian Aviation, Aerospace Publications, Canberra, June 1996.

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Douglas Corporation, 1995, unpublished material.

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Arizona, 1983.

NATSEMI78 - CMOS Databook, National Semiconductor Corporation, Santa Clara,
1978

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Corporation, September, 1995, unpublished material.

NPI93 - NPI Local Area Network Products, SMD Transformers, Nano Pulse
Industries, Brea, 1993.

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briefing, Texas Instruments, Inc., December 1994, unpublished material.

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York, John Wiley & Sons, 1965

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Stage Flux Compression Generator System, Digest of Technical Papers, 5th IEEE
Pulsed Power Conference, pp.216, IEEE, New York, 1985.

SANDER86 - Sander K. F. and G.A.L. Reed, Transmission and Propagation of
Electromagnetic Waves, Cambridge University Press, 1986.

STAINES93 - Staines, G.W., High Power Microwave Technology - Part IV,
Military Applications of High Power Microwaves, Salisbury, DSTO ERL, EWD, 1993,
draft paper.

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in Schneider B.R, Grinter L.E., Battlefield of the Future, 21st Century Warfare
Issues, Air University Press, Maxwell AFB, September 1995.

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to Wire Structures, IEEE Transactions on Electromagnetic Compatibility, Vol. 34,
No. 3, 183, August 1992.

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and Simulation, Chapter 14 in High Power Microwave Sources, 1987.

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Eavesdropping Risk", Computers and Security, 1985, pp. 269.

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Century, Chapter 4 in Schneider B.R, Grinter L.E., Battlefield of the Future,
21st Century Warfare Issues, Air University Press, Maxwell AFB, September 1995.

WATERS92 - Waters Gary, Gulf Lesson One, Canberra, Air Power Studies Centre,
1992

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Electromagnetic Interference and Compatibility, Don White Consultants, Maryland,
1978.

Carlo Kopp Born in Perth, Western Australia, the author
graduated with first class honours in Electrical Engineering in 1984, from the
University of Western Australia. In 1996 he completed an MSc in Computer Science
and is currently working on a PhD in the same discipline, at Monash University
in Melbourne, Australia. He has over a decade of diverse industry experience,
including the design of high speed communications equipment, optical fibre
receivers and transmitters, communications equipment including embedded code,
Unix computer workstation motherboards, graphics adaptors and chassis. More
recently, he has consulted in Unix systems programming, performance engineering
and system administration. Actively publishing as a defence analyst in
Australia's leading aviation trade journal, Australian Aviation, since 1980, he
has become a locally recognised authority on the application of modern military
technology to operations and strategy. His work on electronic combat doctrine,
electromagnetic weapons doctrine, laser remote sensing and signature reduction
has been published by the Royal Australian Air Force's Air Power Studies Centre
since 1992, and he has previously contributed to CADRE Air Chronicles.

1 - Electromagnetic pulse or EMP device is a generic term
applied to any device, nuclear or conventional, which is capable of generating a
very intense but short electromagnetic field transient. For weapons
applications, this transient must be sufficiently intense to produce
electromagnetic power densities which are lethal to electronic and electrical
equipment. Electromagnetic weapons are electromagnetic devices specifically
designed as weapons. Whilst the terms 'conventional EMP weapon' and 'High Power
Microwave or HPM weapon' have been used interchangeably in trade journals (see
FULGHUM93), this paper will distinguish between microwave band and low frequency
weapons. The term 'electromagnetic bomb' or 'E-bomb' will be used to describe
both microwave and low frequency non-nuclear bombs. This paper will not address
the use of nuclear EMP, or alternate uses of HPM technology. HPM technology has
a broad range of potential applications in EW, radar and directed energy weapons
(DEW). The general conclusions of this paper in the areas of infrastructure
vulnerability and hardening are also true for microwave directed energy weapons.
This paper extends the scope of earlier work by the author on this subject
[KOPP93].

2 - One bizzare instance of lightning strike electrical damage
was described to the author by an eyewitness technician, tasked with assessing
the damage on the site. A lightning bolt impacted in the close vicinity of a
transmitter shed. RF and power cables ran from the transmitter shed to a
transmission tower through a rectangular, metal shielded tunnel. The effect of
the lightning strike was to produce an electromagnetic standing wave in the
tunnel, much like in a microwave waveguide. All cables within the tunnel were
burned through at regular spacings along the tunnel, corresponding precisely to
the half wavelength of the standing wave in the tunnel.

3 - The NACSIM 5100A standard specifies acceptable emission
levels for TEMPEST (Transient ElectroMagnetic Pulse Emanation Standard) rated
equipment.

4 - The Northrop/Lockheed ASD-5 Black Crow DF receiver was
fitted to the AC-130A Pave Pronto gunships, rebuilt from obsoleted C-130
transports [ICH10].

5 - A noteworthy technical issue in this context is that even
equipment not-rated to TEMPEST standards will radiate energy at very low power
levels, in comparison with intentional transmissions by radar or communications
equipment. A receiver designed to detect, identify and locate sources of UE
radiation will either need to be highly sensitive, or deployed very close to the
emitter. It is worth noting that UE from computer monitors and networks exhibit
known regular patterns, and correlation techniques could be used to
significantly improve receiver sensitivity [DIXON84].

6 - Fulghum D.A., ALCMs Given Non Lethal Role, AW&ST, Feb
22, 1993. This recent report indicates that the US has progressed significantly
with its development work on electromagnetic warhead technology. An
electromagnetic warhead was fitted to the USAF AGM-86 Air Launched Cruise
Missile airframe, involving both structural and guidance system modifications.
The description in this report suggests the use of an explosive pumped flux
generator feeding a device such as a Vircator. References to magnetic coils
almost certainly relate to the flux compression generator hardware.

7 - The Journal of Electronic Defence [JED96] recently reported
on the USAF Phillips Laboratory at Kirtland awarding a $6.6M HPM SEAD weapon
technology demonstration program contract to Hughes Missile Systems Co. This
contract will see Hughes conduct design studies in order to define design goals,
and then fabricate brassboard demonstration hardware using government developed
technology. JED speculate that the weapon will be a FCG driven microwave tube,
which is most likely the case given the USAF's prior research activities in this
area [REINOVSKY85]. An earlier report [JED95] indicated the existence of a
related program which addresses command and control warfare and counter-air
capabilities. In any event, the devices produced by these programs are likely to
become the first operationally fielded HPM electromagnetic bombs for delivery by
combat aircraft.

8 - This may be readily determined by calculating the ratio of
warhead mass to total weapon launch mass, for representative missile types.
Taking the AGM-78 Standard as a lower limit yields 15.9%, whereas taking the
AGM/BGM-109 Tomahawk as an upper limit yields about 28%. Figures are derived
from manufacturers' brochures and reference publications eg Jane's Air-Launched
Weapons.

9 - Staines, Fulghum. This is entirely consistent with
theoretical expectations, as the different spectral characteristics of microwave
electromagnetic warheads, compared to nuclear electromagnetic weapons, will
significantly affect the effectiveness of protective filters. What is important
from an electrical engineering viewpoint is that a filter designed to stop
signals in the lower frequency bands may perform very poorly at microwave
frequencies.

10 - See International Countermeasures Handbook, 14th Edition,
pp 104.

11 - Gary Waters, Gulf Lesson One. Chapter 16 of this
reference provides a good discussion of both the rationale and implementation of
this strategy.

12 - Soft kill means will inhibit or degrade the function of a
target system during their application, leaving the target system electrically
and physically intact upon the cessation of their application. Hard kill means
will damage or destroy the target system, and are thus a means of inflicting
attrition.

13 - This is also the stated intent of the USAF HPM SEAD
technology demonstration program. The fact that the first application of a HPM
bomb is electronic combat underscores the tactical, operational and strategic
importance of first defeating an air defence system when prosecuting a strategic
air war.

14 - The classical argument here is centred upon Allied
experience in bombing Germany during WW2, where even repeated raids on
industrial targets were unable to wholly stop production, and in many instances
only served to reduce the rate of increase in production. What must not be
overlooked is that both the accuracy and lethality of weapons in this period
bore little comparison to what is available today, and automation of production
facilities was almost non-existent.

15- This constraint primarily results from limitations in
numbers. Strategic air attack requires precision delivery of substantial
payloads, and is thus most effectively performed with specialised bomber assets,
such as the B-52, B-1, B-2, F-111, F-15E, F-117A, Tornado or Su-24. These are
typically more maintenance intensive than less complex multirole fighters, and
this will become a constraint to the sortie rate achievable with a finite number
of aircraft, assuming the availability of aircrew. Whilst multirole fighters may
be applied to strategic air attack, their typically lesser payload radius
performance and lesser accuracy will reduce their effectiveness. In the
doctrinal context, this can be directly related to existing USAF aerospace
doctrine [AFM1-1], in several areas.

A version of this article was first published in: "Information Warfare -
Cyberterroism: Protecting Your Personal Security in the Electronic Age" by Winn
Schwartau, 1996 Thunder's Mouth Press, 632 Broadway 7th Fl, New York, New York,
ISBN: 1-56025-132-8, http://www.infowar.com

The conclusions and opinions expressed in this document are those of the
author cultivated in the freedom of expression, and academic environment of Air
University. They do not reflect the official position of the US Government,
Department of Defense, the United States Air Force or the Air University.

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