The Electromagnetic Bomb - a Weapon
of Electrical Mass Destruction
Source: Air Chronicles
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 unserviceable 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 argeting aspects of using such weapons, as no
historical experience xists as yet upon which to build a doctrinal
model. The immaturity of his weapons technology limits the scope of
this discussion, and many
potential areas of application have intentionally not been discussed.
he ongoing technological evolution of this family of weapons will
larify the relationship between weapon size and lethality, thus
roducing further applications and areas for study.
E-bombs can be an affordable force multiplier for
military forces hich are under post Cold War pressures to reduce force
sizes, ncreasing both their combat potential and political utility in
esolving 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.
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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.
Carlo Kopp
Carlo.Kopp@aus.net
Defence Analyst
http://www.airpower.maxwell.af.mil/airchronicles/kopp/apjemp.html