1 Chapter 1 Revolution in Military Weapons 1.1 Weapons Revolutions From the Stone Age until the Middle Ages, a weapon’s power was limited by the strength of the man wielding it or, in the case of bows, by the strength of material from which it was made. In the late Middle Ages, a revolution in the weaponry occurred when chemical-powered (gunpowder) weapons began to replace swords and bows. This revolution changed the nature of warfare: not just tactics, but also the usefulness of armor, castles, and then-popular weapons.1 Since the invention of gunpowder, a weapon’s effectiveness has no longer depended on the wielder’s strength, but on the chemical energy of the propellant or explosive. While centuries of technological advances have improved the power of these materials, the basic operating principle of chemical-powered weapons ultimately remains the same. Modern battlefield weapons are the descendents of muskets and cannon. Another revolution in weaponry is with directed-energy weapons (DEWs) replacing chemical-powered weapons on the battlefield. DEWs use the electromagnetic spectrum (light and radio energy) to attack pinpoint targets at the speed of light. They are well suited to defending against threats such as missiles and artillery shells, which DEWs can shoot down in mid-flight. In addition, controllers can vary the strength of the energy put on a target, unlike a bullet or exploding bomb, allowing for nonlethal uses. 1.2 Directed-Energy Weapons A directed-energy weapon (DEW) is a type of weapon that emits energy in an aimed direction without the means of a projectile. It transfers energy to a target for a desired
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Chapter 1
Revolution in Military Weapons
1.1 Weapons Revolutions
From the Stone Age until the Middle Ages, a weapon’s power was limited by the strength
of the man wielding it or, in the case of bows, by the strength of material from which it
was made. In the late Middle Ages, a revolution in the weaponry occurred when
chemical-powered (gunpowder) weapons began to replace swords and bows. This
revolution changed the nature of warfare: not just tactics, but also the usefulness of
armor, castles, and then-popular weapons.1
Since the invention of gunpowder, a weapon’s effectiveness has no longer depended on
the wielder’s strength, but on the chemical energy of the propellant or explosive. While
centuries of technological advances have improved the power of these materials, the
basic operating principle of chemical-powered weapons ultimately remains the same.
Modern battlefield weapons are the descendents of muskets and cannon.
Another revolution in weaponry is with directed-energy weapons (DEWs) replacing
chemical-powered weapons on the battlefield. DEWs use the electromagnetic spectrum
(light and radio energy) to attack pinpoint targets at the speed of light. They are well
suited to defending against threats such as missiles and artillery shells, which DEWs can
shoot down in mid-flight. In addition, controllers can vary the strength of the energy put
on a target, unlike a bullet or exploding bomb, allowing for nonlethal uses.
1.2 Directed-Energy Weapons
A directed-energy weapon (DEW) is a type of weapon that emits energy in an aimed
direction without the means of a projectile. It transfers energy to a target for a desired
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effect. Directed-energy weapons take the form of lasers, high-powered microwaves, and
particle beams. These three forms are briefly discussed in the following part.
1.2.1 Lasers
Albert Einstein described the theoretical underpinnings of lasers (an acronym for Light
Amplification by Simulated Emission of Radiation) in 1917. However, the first working
laser was not built until 1960, opening an entirely new avenue of directed- energy
research. Lasers produce narrow, single-frequency (i.e., single color), coherent beams of
light that are much more powerful than ordinary light sources. Laser light can be
produced by a number of different methods, ranging from rods of chemically doped glass
to energetic chemical reactions to semiconductors. One of the most promising laser
devices is the free-electron laser. This laser uses rings of magnetically confined electrons
whirling at the speed of light to produce laser beams that can be tuned up and down the
electromagnetic spectrum from microwaves to ultraviolet light.
Lasers produce either continuous beams or short, intense pulses of light in every
spectrum from infrared to ultraviolet. X-ray lasers may be possible in the not too distant
future. The power output necessary for a weapons-grade laser ranges from 10 kilowatts to
1 megawatt. When a laser beam strikes a target, the energy from the photons in the beam
heats the target to the point of combustion or melting. Because the laser energy travels at
the speed of light, lasers are particularly well-suited for use against moving targets such
as rockets, missiles, and artillery projectiles.
One problem that affects laser beam strength is a phenomenon known as “blooming,”
which occurs when the laser beam heats the atmosphere through which it is passing,
turning the air into plasma. This causes the beam to lose focus, dissipating its power.
However, a variety of optical methods can be used to correct for blooming. Laser beams
also lose energy through absorption or scattering if fired through dust, smoke, or rain.
The number of “shots” a laser weapon can produce is limited only by its power supply.
Depending on the type of laser, this means that the weapon can have an almost “endless
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magazine” of laser bursts. In addition, a laser shot (including the cost of producing the
energy) is much cheaper than a shot from a chemical-powered weapon system. Figure 1.1
shows a schematic of High Power Laser and the method of attack with it. As the laser
travels with the speed of light so the target is first searched for. Once the target is
searched it is tracked in two phases: coarse and fine track and while finally locked in
range, the Laser is shot. The figure 1.2 shows the target being illuminated and it drowns
after a successful hit. [10]
(a) (b)
Figure 1.1 (a): Schematic Diagram of a High Power Laser (b): Targeting with HPL [10]
Figure 1.2: (1) Target before illumination (2) Target being illuminated (3) target after a successful hit[10]
1.2.2 Microwave Weapons
Written off as impractical during World War II, technological advances have now made
microwave weapons feasible. However, current research focuses on using them as a
means of nonlethal area defense and as anti-electronic weapons rather than as “death
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rays.” High-power microwave (HPM) weapons work by producing either beams or short
bursts of high frequency radio energy. Similar in principle to the microwave oven, the
weapons produce energies in the megawatt range. When the microwave energy
encounters unshielded wires or electronic components, it induces a current in them,
which causes the equipment to malfunction. At higher energy levels, the microwaves can
permanently “burn out” equipment, much as a close lightning strike could.
Semiconductors and modern electronics are particularly susceptible to HPM attacks.
Electronic devices can be shielded by putting conductive metal cages around them;
however, enough microwave energy may still get through the shielding to damage the
device.
The short, intense bursts of energy produced by HPM devices damages equipment
without injuring personnel. Mounted on properly shielded aircraft or ships, or dropped in
single-use “e-bombs,” HPM weapons could destroy enemy radars, anti-aircraft
installations, and communications and computer networks and even defend against
incoming antiaircraft and anti-ship missiles. With the ever increasing use of electronics in
weapons systems, HPM devices could have a devastating but nonlethal effect on the
battlefield.
High Power Microwave weapons are dealt in more detail in chapter 2. One most worked
on High Power Microwave weapon –Electromagnetic Bomb- is discussed in detail in
chapter 3.
1.2.3 Particle beam
During the Cold War, the U.S. and the Soviet Union studied the possibility of creating
particle beam weapons, which fire streams of electrons, protons, neutrons, or even neutral
hydrogen atoms. The kinetic energy imparted by a particle stream destroys the target by
heating the target’s atoms to the point that the material literally explodes. These weapons
were considered for both land and space-based systems. However, because beam strength
degrades rapidly as the particles react with the atoms in the atmosphere, it requires an
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enormous power plant to generate a weapons grade beam. The countries abandoned
particle beam weapon research as impracticable.
1.3 Differences between Microwave Weapon system and Electronic warfare system
A common assumption is that microwave weapons systems are similar to electronic warfare
systems. The relationship between a microwave weapon and an electronic warfare system is
that, while both use the frequency spectrum to work against enemy electronics, microwave
weapons are different from the electronic warfare systems on several counts.
Electronic warfare systems are limited to jamming, and will affect enemy systems only when
the electronic warfare system is operating. When the electronic warfare system is turned off,
the enemy capability returns to normal operation. Electronic warfare attacks also require
prior knowledge of the enemy system, because the jamming function will work only at the
enemy system’s frequency or modulation. The enemy system also has to be operating in
order for electronic warfare systems to effectively jam. There are numerous ways to counter
the effects of electronic warfare signals. These countermeasures are often accomplished by
redesigning the internal signal controls or increasing the frequency bandwidth of the system.
Unlike the electronic warfare system, the microwave weapon is designed to “overwhelm a
target’s capability to reject, disperse, or withstand the energy.” In other words, microwave
weapons by their nature will produce significant, and often lethal, effects on their targets.
There are four major distinctive characteristics that differentiate a microwave weapon system
from an electronic warfare system.
1. Microwave weapons do not rely on exact knowledge of the enemy system.
2. They can leave persisting and lasting effects in the enemy targets through damage
and destruction of electronic circuits, components, and subsystems.
3. A microwave weapon will affect enemy systems even when they are turned off.
4. To counter the effects of a microwave weapon, the enemy must harden the entire
system, not just individual components or circuits.
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Chapter 2
High Power Microwave Weapons
2.1 High Power Microwave Weapons
High Power Microwave (HPM) technology relies on the fact that while most types of
matter are transparent to microwaves, metallic conductors (as present in Metal-Oxide
semiconductors) absorb them and get heated up. HPM weapons generate a very short,
intense energy pulse producing a transient surge of thousands of volts that melts the
circuitry and destroys the semiconductor devices. The electromagnetic frequency
spectrum for high power microwave technology ranges from the low megahertz to the
high gigahertz frequencies (106
hertz to 1011
hertz). Invisible to the human eye, these
frequencies range from wavelengths of 0.3 centimeters (the gigahertz frequencies) to 300
meters (the megahertz frequencies) in length. Some of the characteristics which make
these weapons popular are:
1. It enables a speed-of-light attack on enemy electronic system.
2. It is not at all affected by weather.
3. It allows the military commander to effect a surgical strike at selected levels of
combat.
4. In a politically sensitive environment it is preferable to use weapons causing
collateral damage.
5. HPMs have deep magazines, low operating costs and allow simplified pointing and
tracking.
2.2 Electromagnetic Pulse
Electromagnetic Pulse (EMP) is a pulse of electromagnetic energy of extremely short
duration. Initially called radio flash, EMP is similar to the simultaneous transmission of a
large number of radio waves varying from one KHz to 100 MHz and peak field
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amplitudes produced are very large on the order of 50 kilovolts per meter. EMP is of
great concern today. As the field of electronics has evolved from the vacuum tube era to
today's integrated microcircuits which can handle only minute quantities of voltage
current, its susceptibility to EMP has increased significantly. Consequently, this results
in modern communications and electronics equipment being highly vulnerable to the
power surges of EMP.
The EMP effect was first observed during the early testing of high altitude airburst
nuclear weapons. The effect is characterized by the production of a very short (hundreds
of nanoseconds) but intense electromagnetic pulse, which propagates away from its
source with ever diminishing intensity, governed by the theory of electromagnetism. The
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 (i.e. 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.
The significance of these power surges is demonstrated when comparing EMP with
lightning. Both involve a sudden pulse of energy and both are attracted to intentional or
unintentional collectors or antennas. However, EMP and lightning differ in four crucial
ways:
1. EMP pulses much more rapidly. Pulse time for EMP maybe a few billionths of a
second; the comparable interval for lightning pulse involves millionths of seconds.
2. Each field strength can differ radically. Lightning maybe a few thousand volts per
meter; EMP can involve 50,000 volts per meter.
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3. EMP pulses are of short duration--usually less than a thousandth of a second as
opposed to lightning pulses that last hundreds of a millisecond.
4. Lightning occurs at much lower frequencies and in bands well below the frequencies
used by the military communications systems. However, EMP concentrates in some
of the bands most frequently used by the military's tactical communications systems.
The formation of EMP results from the collision of the gamma photons emitted from a
nuclear detonation and interacts with atoms in the outer atmosphere. This result in the
ejection of electrons and the creation of a strong ionized area referred to as the source
field region. This complicated process occurs in a few billionths of a second
(nanoseconds) and last one millionth of a second (millisecond), which produces a strong
electric field that radiates away from the source region. This radiated field is EMP. A
number of parameters including the yield, its height-of-burst, asymmetries in the earth's
atmosphere and location of the burst relative to the earth's magnetic declination directly
affect both the shape or coverage area and the strength of the EMP.
2.3 Types of Electromagnetic Pulse
Based on analysis of the various combinations of the preceding parameters there are four
significant types of EMP.
Surface Burst EMP: The first, surface burst electromagnetic pulse (EMP) , occurs when
the nuclear burst explodes on the earth's surface or up to two kilometers above the
surface. The radiated wave is only propagated to a distance of ten to twenty kilometers
from the burst point due to the higher density of the lower atmosphere. Although the area
over which the low-altitude EMP produces a damaging effect is relatively small, it is
significant on the tactical nuclear battlefield.
High-Altitude EMP: The second type, high-altitude EMP (HEMP), is the most
significant and, potentially, the most hazardous to our security. The explosion of a
nuclear burst at an altitude greater than 30 to over 500 kilometers above the earth's
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surface will produce the above scenario. Due to the very thin to non existent atmosphere
at these altitudes, the gamma rays emitted from the explosion will travel radically
outward for long distances. Those gamma rays traveling toward the earth's atmosphere
are stopped by collisions with atmospheric molecules at altitudes between 20 and 40
kilometers. These collisions generate Compton recoil electrons which interact with the
earth's magnetic field to produce a downward traveling electromagnetic wave. This high
altitude burst will not generate any other nuclear effect at the earth's surface.
However, this type of nuclear explosion also produces vast ground coverage. Significant
HEMP levels occur at the earth's surface out to where the line of sight from the burst
contacts the earth's surface. Consequently, a nuclear burst over the central part of the
United States at an altitude of 500 kilometers would produce an EMP field that would
incapacitate all communications systems in the continental United States.
Source Region EMP: The third type of EMP is source region EMP (SREMP). This is
produced by a nuclear burst within several hundred meters of the earth's surface (the
fireball touches the ground). SREMP is localized three to five kilometers from the burst.
The generation of EMP by a surface blast begins with the gamma rays traveling radically
outward from the burst. This action causes the Compton electrons to move radically
outward and leaves behind immobile positive ions. This produces an electric field and
lasts two to three nano seconds. The final result is a tremendous surge on current in the
air on any communications equipment and the SREMP renders the equipment useless.
System Generated EMP: The last type of EMP is system generated EMP (SGEMP).
SGEMP results from the interaction of x-rays or gamma rays striking an atom on a metal
object. A nuclear blast in outer space sends gamma rays or x-rays out in all directions. If
these rays were to strike an unprotected satellite or missile traveling above the
atmosphere, these rays would knock out electrons from the atoms of the metal skin. This
action would induce an EMP field that would make the satellite and the missiles useless.
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There are two different methods of generating such high powered EMP suitable for HPM
weapons. These are discussed in the sections to follow.
2.4 Nuclear EMP
This idea dates back to nuclear weapons research from the 1950s. In 1958, American
tests of hydrogen bombs yielded some surprising results. A test blast over the Pacific
Ocean ended up blowing out streetlights in parts of Hawaii, hundreds of miles away. The
blast even disrupted radio equipment as far away as Australia. Researchers concluded
that the electrical disturbance was due to the Compton Effect, theorized by physicist
Arthur Compton in 1925. Compton's assertion was that photons of electromagnetic
energy could knock loose electrons from atoms with low atomic numbers. In the 1958
test, researchers concluded, the photons from the blast's intense gamma radiation knocked
a large number of electrons free from oxygen and nitrogen atoms in the atmosphere. This
flood of electrons interacted with the Earth's magnetic field to create a fluctuating electric
current, which induced a powerful magnetic field. The resulting electromagnetic pulse
induced intense electrical currents in conductive materials over a wide area.
Figure 2.1: Nuclear EMP formation
2.5 Non- nuclear EMP
The non-nuclear methods for producing EMP are being developed to have a controlled
EMP. Using these non-nuclear techniques the EMP can be made to vary in strength
depending upon the target enemy type. More over this will help to develop HPM
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weapons for non-lethal use as active-denial system for controlling crowd by heating the
water in the target's skin and thus cause incapacitating pain. The technology base for non-
nuclear EMP production has far grown. The key technologies in the area are:
1. Flux Compression Generators.
2. Explosive or propellant driven Magneto-Hydro Dynamic generators.
3. Virtual cathode Oscillators.
These technologies are discussed in detail in chapter 3 with the discussion of an HPM
weapon- the Electromagnetic Bomb. The non-nuclear EMP generator for HPM is shown
in figure 2.2 with its block diagram.
(a)
(b)
Figure 2.2: (a) Block diagram of Non-nuclear EMP generator for HPM (b) Complete HPM system
Figure 2.3: Comparison of Electromagnetic Pulse shape
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Figure 2.3 shows a comparison of electromagnetic pulse shapes obtained with nuclear
HPM generation, lightning and Flux Generators which is a non-nuclear method of
generation of HPM. It can be clearly seen from the figure 2.3 that the amplitudes for the
three are comparable but the difference appears in the duration of the pulse. Nuclear
method produces the electromagnetic pulse with shortest duration of the three, but the
caused effect due to it is uncontrolled. The other two methods produce the pulse of
greater duration, in contrast to that produced by nuclear method, but the waveforms are
almost opposite in nature as lightning produces a sharp transient but slows down later
whereas the non nuclear method (Flux Compression Generator) produces a slow transient
which decays fast. This helps the non nuclear methods to control the pulse in amplitude
and thus power. This is an important advantage to be exploited for developing HPM for
non-lethal applications.
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Chapter 3
Electromagnetic Bomb
In principle, an electromagnetic weapon is any device which can produce electromagnetic
field of such intensity, that a targeted item or items of electronic equipment experiences
either a soft or hard kill.
A soft kill is produced when the effects of the weapon cause the operation of the target
equipment or system to be temporarily disrupted. A good example is a computer system,
which is caused to reset or transition into an unrecoverable or hung state. The result is a
temporary loss of function, which can seriously compromise the operation of any system
which is critically dependent upon the computer system in question.
A hard kill is produced when the effects of the weapon cause permanent electrical
damage to the target equipment or system, necessitating either the repair or the
replacement of the equipment or system in question. An example is a computer system
which experiences damage to its power supply, peripheral interfaces and memory. The
equipment may or may not be repairable, subject to the severity of the damage, and this
can in turn render inoperable for extended periods of time any system which is critically
dependent upon this computer system.
Electromagnetic bomb is a directed energy, high power and non-nuclear microwave
weapon researched upon for use as non-lethal weapon, by not harming humans but
affecting the warfare electronics thereby leaving the enemy limping. These are actually
not bombs at all but a large microwave oven.
3.1 Technology base for electromagnetic bomb
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
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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.
Due to harmful effects of the nuclear method of EMP generation, it is not used. Most
common technology used for E-Bomb is FCG and Vircator. Using these, the block
diagram of a non-nuclear HPM weapon – E-Bomb- can be shown as in figure 3.2.