[Infowarrior] - E-Bombs Could Go Mainstream

[Richard Forno]

E-Bombs Could Go Mainstream

Mar 11, 2009

By David Hambling

http://www.aviationweek.com/aw/generic/story_generic.jsp?channel=dti&id=news/EBOMB031109.xml

E-bombs, weapons that destroy electronics with an intense pulse of  
electromagnetic radiation, have been discussed for decades. But  
despite years of research and development, there is little sign of  
their deployment. The prospect of knocking out communications and  
other electronic systems is attractive, but commanders prefer proven  
weapons with known effects. Now the U.S. Army is developing technology  
to provide the best of both worlds, by creating munitions that combine  
conventional and e-bomb effects in one package.

Explosive munitions rely on blast, fragmentation and sometimes armor- 
piercing shaped charges for their effects. Researchers want to add an  
electromagnetic pulse (EMP) damage mechanism as well. This is in  
contrast to previous e-bomb projects that were intended to be  
nonlethal so they could destroy materiel without causing casualties.  
The Army program seeks to enhance existing warheads, adding the  
feature without affecting blast, fragmentation or armor penetration,  
and with minimal extra weight.

The power supply in traditional e-bomb design is a magnetic flux  
compression generator with metal coils carrying current. The coils  
rapidly compress in an explosion, producing an intense pulse of  
energy. The generator is bulky and cannot easily be integrated into  
existing munitions.

An alternative approach explored by the Army is a shockwave  
ferromagnetic generator. This is a magnet that blows up and  
spontaneously demagnetizes, releasing energy as a pulse of power. The  
effect is known as pressure-induced magnetic phase transition, and  
only occurs with some types of magnets in certain situations. In 2005,  
researchers from the U.S. Army Aviation and Missile Research  
Development and Engineering Center (Amrdec), working with contractor  
Loki and scientists from Texas Tech University, demonstrated an  
explosive pulsed-power source based on neodymium alloy magnets, a type  
used in speakers and headphones.

Having proven that the principle works, the researchers moved on to  
more exotic lead zirconate titanate magnets. This enabled them to  
reduce the volume of the power generator from 50 cu. cm. (3 cu. in.)  
to 3 cu. cm., excluding explosives. Army requirements call for  
assembly of the power generator, power conditioning and aerial in a 1- 
in. space. Power output will be measured in hundreds of megawatts for  
microseconds.

The aerial needed to shape and direct the electromagnetic energy is an  
engineering challenge, due to the intense force of the explosion and  
the size required. Allen Stults of Amrdec is working on a “conducting  
aerosol plasma warhead.” A flame conducts electricity due to the  
presence of charged particles in it. By altering the chemical mixture  
of a fireball produced by an explosion, Stults aims to turn it into an  
electrically conductive aerial, a “plasma antenna.”

This builds on previous Army work with explosively generated plasma  
antennas. Stults is working with military explosives and ensuring that  
other blast effects like armor piercing are not compromised by the  
changes. Previous work has also shown that the composition of the  
fireball needs to be matched to the frequency of the desired output.

An explosion takes the shape of a roughly spherical fireball, but a  
plasma antenna needs to be more cylindrical. This is why Stults works  
with shaped charges that produce more linear explosions. An earlier  
project looked at using the jet of metal produced by a shaped charge  
as an antenna, but this has been dropped for the plasma antenna.

An enhanced warhead could knock out a tank even if it did not  
penetrate. The vehicle would be left without ignition, communications  
or other electronics. A warhead would also knock out other electronic  
systems, including mobile phones used by insurgents to detonate bombs  
and circuitry in rocket-propelled grenades.

There is one big question with an EMP weapon: How to tell if it works.  
Carlo Kopp, an assistant professor at Monash University of Melbourne,  
Australia, and cofounder of the Air Power Australia think tank, is an  
authority in this field. He wrote papers that shaped strategic  
thinking on electromagnetic pulse weapons in the 1990s, and coined the  
term “e-bomb.”

“Damage assessment for all electromagnetic weapons, be they e-bombs or  
beam weapons, is problematic,” Kopp says. “Unless the attack fries the  
power supply and you observe related electrical breakdown symptoms,  
you will never know whether you fried the target or the victim  
intentionally shut down. The expectation that such weapons should  
provide easy-to-observe bomb damage assessment mechanisms is not  
realistic.”

The multifunction munition provides more signs of its effects than the  
traditional e-bomb, whose effects are invisible. It is possible to  
determine whether a target has been hit, and a target within the  
radius of blast and fragment damage will also have suffered EMP  
effects. But these are variable, depending on the angle between the  
target and the pulse, the nature of the electronic component and the  
amount of shielding. Effects range from temporary disruption and  
forced rebooting to permanent damage or electrical burnout of  
components similar to that of a lightning strike.

With their comparatively low power output, the Army’s new small  
multifunction munitions are for point targets. Two candidate munitions  
for upgrade are the Tow missile and 2.75-in. rockets fired by  
helicopter. This is unlike previous e-bomb efforts, which have focused  
on large air-delivered bombs or unitary artillery munitions that cover  
a large area, what Kopp terms “weapons of electrical mass destruction.”

A small e-bomb will be qualitatively different than larger versions.  
Radiated power falls off with the square of distance, so a target 3  
meters (10 ft.) away receives 100 times the effect of one 30 meters  
away. An EMP-enhanced Tow missile would produce a pulse strong enough  
to destroy what it hits, but should not disrupt electronics over a  
wide area. The possibilities of electronic “friendly fire” rule out  
more powerful tactical e-bombs, but Kopp warns that even smaller  
versions may cause unpredictable collateral damage. If urban  
electrical power or telephone wiring picks up the pulse, damage could  
extend over a wide area.

The smallest weapon that the Army is looking to upgrade is the M77  
bomblet fired by the Multiple Launch Rocket System (MLRS). A bomblet  
has a shaped-charge warhead and throws out antipersonnel fragments.  
Bomblets cover a wide area—one launcher can fire a 12-rocket salvo  
blanketing an area the size of six football fields—and are used  
against soft targets. An EMP-enhanced version would cover the same  
area, providing even destruction over the target zone.

If the M77 can be upgraded, shoulder-launched rockets and similar  
weapons could be modified to produce an EMP. Small infantry rockets  
have limited effectiveness against modern armor. An EMP-enhanced round  
might not penetrate but could provide a “soft kill” capability that  
immobilizes a vehicle. This damage is hard to repair and would  
probably require the replacement of electronic systems.

The U.S. Air Force has an interest in this area, but few details are  
available. Air-to-air missiles might gain considerably with EMP  
capabilities, if they could be modified without affecting performance.  
Antiradiation missiles that target air-defense radar would be another  
market.

The U.S. Naval Surface Warfare Center’s Indian Head Div. wants to  
build a warhead that knocks out improvised explosive devices (IEDs)  
with a plasma fireball. The aim would be to produce a controlled  
explosion, destroying the IED without detonating it, and so minimizing  
collateral damage.

Tests in 2007 used explosively generated plasma against artillery and  
mortar rounds, which are often the basis for IEDs. Information about  
the project has been removed from the Indian Head web site and no  
details are being released. This suggests the work is at an advanced  
stage, possibly field-testing.

Multifunction warheads may finally bring e-bombs into the mainstream  
of armaments, by making a munition effective against all targets as  
well as electronic ones.