Electromagnetic Bomb - E-Bombs

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.

INTRODUCTION

The fact that an electromagnetic pulse is produced by a nuclear explosion was known since the earliest days of nuclear weapons testing, but the magnitude of the EMP and the significance of its effects were realized very slowly.

In July, 1962, a 1.44 megaton United States nuclear test in space, 400 km. above the mid-Pacific Ocean, called the Starfish Prime test demonstrated to nuclear scientists that the magnitude and effects of a high altitude nuclear explosion were much larger than had been previously calculated. Starfish Prime also made those effects known to the public by causing electrical damage in Hawaii, more than 800 miles away from the detonation point, knocking out about 300 streetlights, setting off numerous burglar alarms and damaging a telephone company microwave link.

The larger scientific community became aware of the significance of the EMP problem after a series of three articles was published about nuclear electromagnetic pulse in 1981 by William Broad in the weekly publication Science.

PRINCIPLES BEHIND E-BOMB

An electromagnetic bomb, or e-bomb, is a weapon designed to take advantage of this dependency. But instead of simply cutting off power in an area, an e-bomb would actually destroy most machines that use electricity. Generators would be useless, cars wouldn't run, and there would be no chance of making a phone call. In a matter of seconds, a big enough e-bomb could thrust an entire city back 200 years or cripple a military unit. The basic principles behind the working of e-bomb are:

1. The Compton effect (for nuclear e-bomb)

2. Flux compression (for non-nuclear e-bomb)

The basic idea of an e-bomb -- or more broadly, an electromagnetic pulse (EMP) weapon -- is pretty simple. These sorts of weapons are designed to overwhelm electrical circuitry with an intense electromagnetic field.

A low intensity radio transmission only induces sufficient electrical current to pass on a signal to a receiver. But if you greatly increased the intensity of the signal (the magnetic field), it would induce a much larger electrical current. A big enough current would fry the semiconductor components in the radio, disintegrating it beyond repair.

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 has been tested in these technology areas, and a considerable volume of work has been published in unclassified literature. 

NUCLEAR EMP

E-bombs started popping up in headlines only recently, but the concept of EMP weaponry has been around for a long time. 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.

Compton effect

Photons of electromagnetic energy could knock loose electrons from atoms with low atomic numbers.

Einstein's photoelectric discussion of 1905 and his other work including "Special Relativity" led physicists to speculate on the "momentum" of these "packets" of light which became known as "photons". Arthur Compton and Debye both provided in 1922 a very simple mathematical framework for the momentum of these photons with Compton having experimental evidence from firing X-Rays of known frequency into graphite and looking at recoil electrons. 

Let     E = mc2 = hf       for a photon, where f is frequency, and "m" is the mass "equivalent" of the photon given they have no "rest mass". (It is important to recognise that stopping a photon to measure its mass eliminates it -so it has no "at rest" mass - crucial in Special Relativity where, to travel at the speed of light, mass would otherwise become infinite.)

Having "rigged" this mass problem,

p = momentum = mc (mass x velocity) = hf /c = E / c = h / l

The experiment shows that X-Rays and electrons behave exactly like ball bearings colliding on a table top using the same 2D vector diagrams. They enter the graphite at one wavelength and leave at a longer wavelength as they have transfered both momentum and kinetic energy to an electron. Momentum and energy are conserved in the collision if we accept the equation above for momentum of light.

When the photon enters at l0 and leaves at l1, its energy has changed from E0 to E1 and momentum from E0 / c to E1 / c with a change in direction of q. The electron gains Ek = E0 -E1

Using the cos rule on the diagram above, the energy equation, with some Special Relativity (or by approximation) one can derive the change in wavelength as a function of scattered angle q. 

Dl = ( h / mc )( 1 - cosq )      "m" here is the electron mass and the term h / mc is called the "Compton wavelength".

This was corroborated and forced doubting physicists to take the whole photon thing very seriously - which they had not up to this point

NON-NUCLEAR EMP

The technology base, which may be applied to the design of non nuclear 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 has been tested in these technology areas, and a considerable volume of work has been published in unclassified literature.

Flux compression

The flux compression is defined as compressing a large amount of flux within a low inductive region. For a constant intensity magnetic field of magnitude B traversing a surface S, the flux Φ is equal to B x S. Magneto-explosive generators use a technique called "magnetic flux compression", which will be described in detail later. The technique is made possible when the time scales over which the device operates are sufficiently brief that resistive current loss is negligible, and the magnetic flux on any surface surrounded by a conductor (copper wire, for example) remains constant, even though the size and shape of the surface may change.

Elementary description of flux compression

An external magnetic field (blue lines) threads a closed ring made of a perfect conductor (with zero resistance). The nine field lines represent the magnetic flux threading the ring.

After the ring's diameter is reduced, the magnetic flux threading the ring, represented by five field lines, is reduced by the same ratio as the area of the ring. The variation of the magnetic flux induces a current in the ring (red arrows), which in turn creates a new magnetic field, so that the total flux in the interior of the ring is maintained (four green field lines added to the five blue lines give the original nine field lines)

By adding together the external magnetic field and the induced field, the final configuration after compression can be obtained; the total magnetic flux through the ring has been conserved (even though the distribution of the magnetic flux has been modified), and a current has been created in the conductive ring.

Flux compression generator

The explosively pumped FCG is the most mature technology applicable to bomb designs. Clarence Fowler at Los Alamos National Laboratories (LANL) first demonstrated the FCG 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 Mega Joules in tens to hundreds of microseconds of time, in a relatively compact package. With peak power levels of the order of Tera Watts to tens of Tera Watts, 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. 

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 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 kilo Amperes to Mega Amperes will be suitable. 

Helical generators were principally conceived to deliver an intense current to a load situated at a safe distance. They are frequently used as the first stage of a multi-stage generator, with the exit current used to generate a very intense magnetic field in a second generator.

In an e-bomb, the sequences of events in the flux compression can be explained as below:

A longitudinal magnetic field is produced in between a metallic conductor and a surrounding solenoid, by discharging a battery of capacitors into the solenoid; 

After the charge is ignited, a detonation wave propagates in the explosive charge placed in the interior of the central metallic tube (from left to right on the figure); 

Under the effect of the pressure of the detonation wave, the tube deforms and becomes a cone which contacts the helically wrapped coil, diminishing the number of turns not short-circuited, compressing the magnetic field and creating an inductive current; 

At the point of maximal flux compression, the load switch is opened, which then delivers the maximal current to the load. 

STRUCTURE OF E-BOMB

A general structure of a conventional non-nuclear e-bomb based on the principle of flux compression is as shown in figure (5). It has following parts:

Dielectric structural jacket for shielding and structural support. It can be of concrete or peroxy glass materials, which should be strong enough to sustain the blast till the desired time.

Explosive, which is detonated inside the cylindrical structure leading the huge flux compression and energy transfer in a very short duration of time.

Stator coil, which is used to provide initial high voltage.

Expendable copper tube, which contains the high explosive material and forms a conical structure as the blast proceeds in the foreword direction, thus shorting out the progressive windings.

Insulator, to provide the required insulation between the two sections i.e. the section containing the capacitor banks and the other section, which contains the copper windings and the explosives.

Detonator, which is used to detonate the explosive, which initiates the blast.

Capacitor banks, which provides the initial high current to the copper windings to generate high magnetic flux.

Batteries, which provide supply to the capacitor banks and the GPS guidance system.

GPS guidance system, which helps to guide the e-bomb to the target. 

 The lethality of the e-bomb depends chiefly on the strength of the blast that can be achieved from the explosive and the type of polarization. A nuclear explosive material can produce much more lethality than that produced by a non-nuclear explosive material. The amount of the explosive material also contributes to the lethality of the e-bomb effects.

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

The practical constraint is that it may be difficult to produce an efficient high power circularly polarized 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. 

TARGETING AN E-BOMB

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 defense 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 and Emitter Locating Systems carried either by the launch platform or a remote surveillance platform. In the latter instance target coordinates can be continuously data linked to the launch platform. As most such targets move relatively slowly, they are unlikely to escape the footprint of the electromagnetic bomb during the weapon's flight time.

Mobile or hidden targets, which do not overtly radiate may present a problem, particularly should conventional means of targeting be employed. A technical solution to this problem does however exist, for many types of target. This solution is the detection and tracking of Unintentional Emission (UE). UE has attracted most attention in the context of TEMPEST surveillance, where transient emanations leaking out from equipment due poor shielding can be detected and in many instances demodulated to recover useful intelligence. Termed Van Eck radiation, such emissions can only be suppressed by rigorous shielding and emission control techniques, such as are employed in TEMPEST rated equipment[3]. 

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, switch mode power supplies, electrical motors, internal combustion engine ignition systems, variable duty cycle electrical power controllers (thyristor or triac based), super heterodyne 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. 

EFFECTS OF E-BOMB

There is a range of possible attack scenarios. Low-level electromagnetic pulses would temporarily jam electronics systems, more intense pulses would corrupt important computer data and very powerful bursts would completely fry electric and electronic equipment. 

In modern warfare, the various levels of attack could accomplish a number of important combat missions without racking up many casualties. For example, an e-bomb could effectively neutralize: 

vehicle control systems 

targeting systems, on the ground and on missiles and bombs 

communications systems 

navigation systems 

long and short-range sensor systems 

A widespread EMP attack in any country would compromise a military's ability to organize itself. Ground troops might have perfectly functioning non-electric weapons (like machine guns), but they wouldn't have the equipment to plan an attack or locate the enemy. Effectively, an EMP attack could reduce any military unit into a guerilla-type army. 

While EMP weapons are generally considered non-lethal, they could easily kill people if they were directed towards particular targets. If an EMP knocked out a hospital's electricity, for example, any patient on life support would die immediately. An EMP weapon could also neutralize vehicles, including aircraft, causing catastrophic accidents. 

In the end, the most far-reaching effect of an e-bomb could be psychological. A full-scale EMP attack in a developed country would instantly bring modern life to a screeching halt. There would be plenty of survivors, but they would find themselves in a very different world.

CONCLUSION

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.

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

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.