Texas Engineering Solutions
Security Implications of High-Power Microwave Technology
IEE International Symposium on Technology and Society 1997
Texas Engineering Solutions
Dallas, Texas 75244 USA
The development of high-power microwave (HPM) weaponry, and its proliferation into subversive organizations, offers the means to commit the "perfect crime." HPM attacks typically leave no residual evidence and their effects can range from nuisance to catastrophic.
This paper highlights some of the unusual aspects of HPM technology and raises issues regarding security of airliners, commercial power systems and other targets. It also discusses strategies to begin mitigating the risks.
High-power microwave (HPM) technology was merely a theoretical possibility until the 1970s. In the last twenty years, advances in plasma physics, energy storage and fast switching devices have made HPM systems effective and the technology is migrating outside classified government research and development laboratories.
The maturation of technologies required for HPM feasibility is shown in Fig. 1. Since the technology is relatively new, and was closely guarded until the demise of the Soviet Union, the societal ramifications of HPM have received little analysis.
Within the past few years, non-military applications have been sought for HPM. These applications often are referred to as "non-lethal technologies." One such employment is the use of HPM by police to disable automobiles in a high-speed chase. Such discussions have further highlighted the capability of HPM, and presumably raised the general awareness of the technologys capability.
The most widely acknowledged effect of high-power microwave energy is disruption of electronic systems. This perturbation is extremely short in duration, generally on the order of a few hundred nanoseconds. This brief disturbance can be sufficient to reset computers, cause complete loss of stored data and/or cause microprocessors to switch operating modes.
Advanced electronic systems are increasingly vulnerable to upset by electromagnetic radiation. Many Department of Defense (DoD) and Department Of Energy (DOE) studies indicate Radio Frequency (RF) power is a threat to the proper operation of modern systems. As circuits have become more densely packaged, more energy efficient and operate at higher speeds, they have experienced an associated increase in vulnerability and susceptibility to perturbations from non-ionizing radiation.
This inherent vulnerability to RF power has spawned international research in optimizing transmitters for use as weapons. NATO and former Soviet nations have developed HPM weapons. These weapons are designed to exploit this inadvertent vulnerability to RF power by concentrating as much power as possible into a controlled field. This has proven very effective, and anecdotal data suggest successful combat deployment.
The effects of a successful HPM weapon attack are unpredictable. The primary goal is merely disruption of the victim system, the results of which are of secondary importance. Consequently, the result varies widely depending upon the victim system. In some cases, computers may be reset. In other cases, local oscillators may be driven off frequency, navigation systems misguided, safety sensors incorrectly set or reset, faulty data recorded and control systems given erroneous inputs.
The significance of the perturbation is proportional to the importance of the system corrupted. A portable compact disc player may react by garbling music or changing the track it was playing. A similar amount of energy directed at a commercial aircraft could corrupt the planes control and navigation systems enough to cause a crash.
Another important similarity shared by vulnerable systems involves post-attack evidence. Typically, there is none. Although the perturbation of the victim system is indisputable while subjected to the electromagnetic field, the affected circuits are rarely permanently damaged. This makes identification of the cause extremely difficult. Failures appear to be anomalies with no traceable cause. An interesting aspect of a successful HPM weapon attack is that no evidence remains to incriminate the perpetrator.
Another feasible effect of an HPM attack, under proper conditions, is an unexplained explosion. The ability of electromagnetic energy to create a spark is undisputed. Inadvertently leaving a metal "twist tie" on a package placed in a common microwave oven can present impressive evidence of this phenomenon. An even more impressive proof can be achieved by filling the oven with an explosive vapor before activating the magnetron with the twist tie in the oven. Whether there will be resulting evidence of a microwave-induced spark causing the resulting explosion is arguable.
Other experiments familiar to scientists and technicians further prove the ability of microwave energy propagating through space to transform to other forms of energy. Tossing steel wool into the main lobe of a search radars antenna can produce a spectacular explosion. Fluorescent light bulbs can be lit without any wired connection at a considerable distance from a radar emitter.
After transoceanic flights, airliners often have more vapors than fuel in their tanks. These tanks also have conductive wiring harnesses inside the fuel tanks. If any of the wires immersed in this explosive vapor has an imperfection resulting in a sharp point, all the conditions are set for an HPM induced spark resulting in an unexplainable explosion. The origin of such an explosion would likely be impossible to discover from residual evidence.
Conditions similar to these were present when TWA 800 exploded shortly after takeoff in 1996. The center fuel tank contained mostly vapor, for reasons based in weight and economics. Although the reason the fuel tank exploded has not been determined, investigators are certain that the forces of that ignition made the incident unsurvivable. This has resulted in consideration within the aviation regulatory community of prohibiting the common practice of flying aircraft with mostly empty fuel tanks. Such a regulation might mitigate the risk on take off, but does not address the situation of tanks emptied in flight.
Most HPM experts acknowledge that at the end of the Cold War the Soviet Union was ahead of Western laboratories in the development of HPM weaponry. This is logical since Western weapon systems (planes, missiles, etc.) tended to be more sophisticated than their Soviet bloc counterparts. Since HPM vulnerability tends to be proportional to a victim systems reliance on microprocessors, the technology would be more attractive to NATO adversaries. Implementation of HPM against sophisticated weaponry transforms that sophistication from an asset to an "Achilles heel".
With the demise of the USSR, the research and the scientists who performed it became less well controlled. This is particularly alarming since, unlike traditional weapons of mass destruction, there are no controllable components in an HPM weapon.
1995 saw the first known use of HPM technology by subversives. Chechnyan rebels used HPM to defeat a Russian security system and gain access to a controlled area. 
Traditional means of improving security are ineffective in preventing an HPM attack. Ordinarily, the integrity of a region, building or other asset can be maintained by limiting physical access to the object of interest. This access control generally takes the form of guards, physical barriers and/or surveillance systems.
An HPM attack, however, uses invisible electromagnetic energy as "ammunition". This implies speed of light velocity, a very "deep magazine", and an effective range that is limited only by the weapons effective radiated power and the victim systems susceptibility.
It is generally unnecessary, then, for an attacker to expose themselves to the secure environment provided by traditional security measures. They can instead remain outside the sterile environment and still disrupt electronic systems a great distance away.
While there are many variables that must be considered to determine the range of an HPM weapon, a reusable system able to disrupt systems hundreds of meters away is certainly achievable.
The important point is that a clandestine attack can be mounted using HPM without having to breach or even account for existing security systems. A less obvious result is that there is very little risk involved in unsuccessful attacks or "dry runs." Unlike traditional attacks, precise execution and planning is unnecessary and tactics can be tested and refined until the perpetrators achieve the desired effect.
Considering the intrinsic qualities of an HPM attack, it is useful to analyze what groups or individuals would be most likely to find such a weapon attractive. Further analysis can concentrate on whether such a population exists in todays society.
The bombing of Pan Am 103 in 1988 was a crime that was intended to be unsolvable. Although physical evidence has provided solid information identifying the bombers, those implicated have denied involvement. Indeed, the critical piece of evidence that led investigators to discover the explosions origin was about the size of a fingernail.
HPM offers a means of attack that doesnt even leave evidence as small as that incriminating the bombers of Pan Am 103. For those desiring anonymity, there can be no better tool than an HPM weapon. Its effects are transient and leave no evidence in their wake.
This invisibility may be extremely attractive to an organization wishing to maintain plausible deniability. This is even truer if the subversives are religious fundamentalists. If science cannot attribute a catastrophes cause, religious zealots can credit an angry Supreme Being.
As an example, a religious leader with ties to Libya could prophesize a communication from his deity denouncing the freezing of Libyan assets in response to Pan Am 103. In his public prophecy, he could express confusion about the meaning, while relaying the message that unless those assets were released by a certain date his god will cause "a large bird to fall from the sky." This prediction could then be followed by an unexplainable and unattributable airliner crash. This process could be repeated as necessary until the Western world capitulates. Of course, the demands would likely only be accelerated after that capitulation.
Other potential users of the technology are rouge countries seeking to expand their borders. If Iraq had even a single reusable HPM weapon in 1990, the United States and its allies could have been excluded from responding to the annexation of Kuwait.
Most troops were transported to the Desert Shield/Desert Storm theatre using commercial aircraft. If Saddam Hussein had HPM capability, those airliners might have crashed on final approach. Public pressure would have then pressured the U.S. to withdraw. Failing that, opposing troops would have been killed by the hundreds, seat belted to their airline seats, before they ever had a chance to fire a shot.
As this paper was being written, Peruvian soldiers ended a four-month hostage crisis by storming the Japanese ambassadors residence in Lima and killing 15 Marxist rebels. Negotiations with the members of Tupac Amaru stalled over a single point of freeing imprisoned guerillas previously convicted of subversive activity.
Tupac Amaru could have achieved their goals if, instead of holding hostages, they used HPM weapons to disrupt crucial infrastructure assets. By attacking the commercial power grid, hospitals, and/or financial centers the small band of subversives could have caused an intolerable environment without any direct loss of life. If Peru remained defiant, similar attacks could be launched against Peruvian allies until world pressure coerced the prisoners release.
There will also be countries or groups who are not as interested a surreptitious attack as they are maximizing the resulting disruption. Those goals can also be met with an entirely different deployment of HPM technology.
Instead of using a reusable, focused and transportable system, these users may use expendable, explosively driven devices.
A virtual cathode oscillator (VIRCATOR) can easily be packaged into a guided missile or free fall bomb. Although these weapons are apparent because of the explosion that drives the HPM device, the electromagnetic emissions will still be extremely difficult to detect.
Explosively driven HPM devices can have footprints that disrupt electronic systems for several hundred meters in all directions. Such a system can be built from commonly available material for less than $2,000 .
HPM represents unique opportunities for subversives. Reusable systems, used against fly by wire airliners, can produce a "virtual windshear" on demand. Single shot, expendable systems can produce "virtual lightning strikes" over a large geographic region. In either case, modern electronic systems are vulnerable to catastrophic disruption.
For centuries, security systems have concentrated on exclusion and detection of intruders. Sophistication has ranged from moats with drawbridges to infrared and laser motion detectors.
In todays world, intrusion detectors and other modern security devices may become as antiquated as the moat without supplemental detection of electronic attacks.
The technology to launch an HPM attack exists, and is cost effective and easily obtainable. Security experts must counter this threat immediately. Until such detection technology is deployed, the opportunity endures to wreak tremendous havoc without fear of identification or recrimination the perfect crime.
A.E. Pevler was born in New York May 16, 1955. He graduated from Southern Methodist University with a BSEE. His employment experience includes the United States Marine Corps, Omni-Spectra, Inc., Texas Instruments, Inc., EG&G Special Projects, Inc. and he founded Texas Engineering Solutions. Mr. Pevler is an expert in the uncooperative detection of high-power microwave emissions and has developed several systems for unique collection environments.