The detonation by the United States of a nuclear warhead 30,000 feet above Johnston Atoll in July 1962 lit up the night sky above the Hawaiian Islands, 800 miles away. It also created a power surge that shut down the streetlights and phone system of Oahu as well as triggering circuit breakers and burglar alarms. Such was the power of the electromagnetic pulse created by what was to be one of the last above-ground nuclear tests by the US, prior to the 1963 Limited Test Ban Treaty signed by the United Kingdom, US and the Soviet Union.

Electromagnetic (EM) waves include everything from radio-frequency (RF) waves used to transmit radio and TV signals; to microwaves used to cook food; to infrared, visible light, ultra-violet rays, x-rays and more. All travel at the speed of light, but differences in their wavelengths and vibrations define their utility. In whatever form, though, EM waves can be made to have some effect on man or machines, or both.

The EM pulse from the "Starfish Prime" test that provided such a show to the residents of Hawaii and elsewhere in the area was part of early research by the US that currently includes high power microwaves intended to stop vehicles dead in their tracks, lasers for blowing up enemy missiles, and more. Today, not only the US hopes to harness the photon to build a so-called directed-energy weapon (DEW); private companies and military agencies in Russia, China, the UK and elsewhere are pursuing DEW projects.

Cutting-edge militaries -whether army, air force, or navy - are increasingly turning to computerized battle-management, weapons-tracking, and Internet-like communications systems to better understand where their forces are and where the enemy is, and to more quickly respond to threats like missiles, aircraft, and so on (see "Computing a New Plan of Attack," JED , March 2003, p. 53). Could this growing reliance on computers, in fact, be a weakness for an enemy to exploit? So seems to think the People's Republic of China, according to the latest report from the Office of the US Secretary of Defense on the military power of China. "Captain Shen Zhongchang from the Chinese Navy Research Institute, for example, envisions a weaker military defeating a superior one by attacking its space-based communications and surveillance systems," the report said. "In future wars, Shen highlights radar, radio stations, communications facilities, and command ships as priority targets vulnerable to smart weapons, electronic attack and electromagnetic pulse weapons."

During Operation Allied Force in the Balkans in the late '90s, the Russian news agency Tass ran a story quoting the Russian defense minister at the time as saying the US had dropped an e-bomb from a B-2 stealth bomber over Kosovo for the purpose of destroying radio and electronic equipment. Pentagon officials denied this. Moreover, the US has quelled rumors that it employed e-bombs in the Iraq War. C.N. Ghosh, a senior fellow at the Institute for Defence Studies and Analyses (New Delhi, India), said development of such technology by India would be a quick way for the country to match the threat posed by neighboring countries. "No matter what Pakistan could procure or develop in the future, it will not be in a position to match this capability. Air-defense systems built around EMP weapons could nullify many a Chinese threat of the future," according to Ghosh.

Limiting Collateral Damage

The US views extremely precise weapons as useful for, among other things, taking out phone networks, power grids, and command-and-control centers, while avoiding harming civilians or civilian infrastructure as much as possible. Sometimes, the line between civil and military infrastructure is blurry, as in the case of Iraq, for example. A June 2001 report from the US Office of the Undersecretary of Defense for Acquisition, Technology and Logistics on "High Energy Laser Weapon Systems Applications" found that "high power lasers have the potential to change future military operations in dramatic ways" and that the US can "exploit current high energy laser technology to take advantage of speed-of-light engagement, precisely controlled effects, deep magazines, low cost per shot and reduced logistics footprint." When the death of civilians - "collateral damage," in militarese - can force a country to pull out of a military action, a weapon that can take out aircraft, vehicles, or infrastructure without creating mass destruction can mean the difference between success and failure.

At the recent Dixie Crow Symposium at Warner Robins AFB, GA, Col Bruce Litchfield, deputy director of transformation for the US Air Force Materiel Command, said that any technology or capability that can be provided to help the US military better fulfill its duties should be provided as quickly as possible. "What you really want to do is blind the enemy," he said. "If you can kill electronics or blind them without killing people, that's a key advantage. That gets your mission done without creating unnecessary damage on the civilian side of things."

Of course, directed-energy devices like RF jammers are standard equipment for many aircraft these days, effective for interfering with enemy radar or communications systems. But of the various types of directed-energy weapons under development, the closest to being fielded are those that use lasers. Already well-established as tools for tracking and targeting airborne and ground-based targets, laser weapons are getting powerful and accurate enough to actually themselves do damage to missiles or aircraft - or people. The US Air Force Research Laboratory (AFRL) at Kirtland AFB, NM, for example, in conjunction with the Department of Defense's Joint Non-lethal Weapons Directorate, has developed a laser weapon that produces a burning sensation in people's skin. A project on which the US has spent about $40 million over the last 10 years, the "active denial technology," as it is called, is an alternative to tear gas or rubber bullets, beaming 95-GHz millimeter waves that penetrate just the first layer of skin to create a burning sensation intended to encourage people to move away. Such a weapon might be used during a peacekeeping mission (for example, US soldiers with the "Active Denial Technology" weapon during the 1993 battle in Mogadishu, Somalia, might have been better able to keep armed civilians away at a distance safe for all concerned), and the Air Force's Electronic Systems Center at Hanscom Air Force Base will oversee the acquisition of systems designed to be mounted on vehicles.

Laboratory tests have been underway for several years, but when the US might actually deploy such a weapon has not been announced. Human-rights-group worry that such technology may potentially blind people, despite assurances by the government to the contrary. The AFRL says the energy levels of the technology are too low to permanently burn anyone, unless they remained in the beam for at least 250 seconds. Tests of the technology continue, with Raytheon AET (Cucamonga, CA) acting as the systems integrator and Communications and Power Industries (Palo Alto, CA) as the source developer, while Veridian Engineering (San Antonio, TX) is doing research on the weapon's effect on people.

While the US may be working to make sure its active denial technology is safe, plenty of systems are available for sale around the world that are not, including a Chinese laser weapon called the ZM-87, a truck-mounted high energy laser made in Russia, and a CO2-based system from the University of Tasmania in Hobart that is used to set fire to logging debris from distances of 100 to 1,500 meters, according the Federation of American Scientists' Web site. Over the years, military pilots from Canada and the US performing surveillance of Russian ships have complained of blinding lasers being used against them, presumably as a means of deterrence, with blurred vision, lesions and recurrent headaches the result. US programs to develop weapons that were, in fact, specifically intended to blind enemy combatants were dropped in 1995 following the addition to the Geneva Convention of a protocol banning blinding laser weapons.

Star Wars

But development of laser weapons for shooting down enemy aircraft or missiles continues, with the AFRL at Kirtland AFB reporting in January that the Boeing aircraft to be used in the Airborne Laser (ABL) program - which would employ laser-equipped aircraft to shoot down ballistic missiles in the air but still over enemy territory - was successfully tested for their in-flight refueling capability (Figure 1). In February Northrop Grumman (Los Angeles, CA) delivered to the program a solid-state laser that will be used to illuminate targets as well as gauge and help adjust for turbulence that would otherwise prevent the accompanying chemical laser from doing the actual damage to the missiles (see "Another Milestone for Airborne Laser Program," JED , April 2003, p. 20).

The use of two lasers, including a solid-state laser that measures and helps the ABL adjust for atmospheric changes and a chemical laser that does the actual damage to the enemy missile, means the system is very complicated, though those developing the system say water, dust, or smoke won't interfere with the laser, because the system is designed to operate above the clouds. "All the kilowatt lasers we've built in the past have been on a large optics table that takes a full lab, and here we've compacted it to a package that's about four by five feet and makes a weight allocation that we were given," said Steve Hickson, ABL program manager for Northrop Grumman, one of the project's co-developers. Other work proceeds at Edwards AFB, CA, on overcoming potential countermeasures such as mirrored surfaces on or spinning flight patterns of missiles, with test shootdowns of actual boosting ballistic missiles planned for late 2004, said spokesman Ken Englade of the ABL System Program Office.

Meanwhile, in live-fire tests last fall of the joint US-Israeli Mobile Tactical High Energy Laser (MTHEL) - a ground-based laser for shooting down incoming short-range rockets and artillery projectiles that the governments aim to have in the field by 2007 - the system successfully shot down an artillery projectile in mid-air (Figure 2). Another project involving space-based lasers, which would mount lasers on orbiting satellites, has lately seen budget cuts by the US Congress and is at least decades away from deployment, according to a recent report from the Lexington Institute on directed-energy weapons.

Thus, these and other efforts to develop laser weapons remain in the developmental phase. Meanwhile, even less information is being made available about development of weapons based on the invisible, lower end of the electromagnetic spectrum. Nuclear weapons feature as one of their attributes the emission of large EM waves, which are particularly devastating when released at high altitudes (Figure 3). Because nuclear detonations create such extreme effects, military research agencies of the US and other countries hope to create EM weapons of a non-nuclear variety. A common phenomenon, electromagnetic interference (EMI), happens in a variety of situations: hair dryers interfere with TV reception or cordless phones; car radios in blasting zones can cause accidental detonations; and so on. But can EMI be used as weapon, to zap the electronic circuitry of a vehicle, bring down a plane, or achieve some other military objective?

"It's very obvious that computers and the like, being housed in plastic containers, quite often are practically open," said Dr. Edward Scannell, head of the Advanced Technology group of Alion Science and Technology (McLean, VA) and a former chief of the US Army Research Lab's Directed Energy Branch. "With a very small architecture and high density solid-state electronics, they're susceptible to this kind of thing. In the business, we've used the term 'Visa card threat.' What could a determined terrorist who has an electrical engineering background do with fairly readily available surplus material? Certainly there are things that one can do. After all, anyone who has operated a computer knows that it doesn't take much to get them upset. It's not anything classified to say that as we go to more and more microelectronics, things could become more easily upset by outside electromagnetic influence."

There have long been questions regarding the effect of RF or other EM emissions on aircraft. One of the most notorious incidents: radar on the USS Forestall in 1967 during the Vietnam War accidentally illuminated a plane carrying an air-to-ground rocket. High power microwave energy from the radar accidentally set the rocket off, which blew up the fuel tanks of another jet and started a fire that killed 134 men and destroyed 24 aircraft (see "Directed Energy," JED , November 2000, p. 43). Could someone build a device that could electromagnetically bring down an airplane? "If you can get close enough, yes. It's the same problem as a MANPADS shooter sitting beyond the ends of the runway, sniping at aircraft taking off," according to Dr. Carlo Kopp, a consultant on system engineering and part-time lecturer at Monash University in Melbourne, Australia. Anechoic chambers, including "one large enough to house a fighter aircraft," are being used at the AFRL to study the effects of high power microwaves on US systems, though a lab spokesman, Rich Garcia, declined to say what the results of evaluations have been.

Preventative Measures

Experts say that EMI can be effectively taken care of through shielding, or "hardening," of machines' electronics. The shielding that the skin of a plane provides against air-traffic-control radars that might otherwise affect electronics inside also protects against microwave weapons. "A plane would be an obvious target for a microwave weapon - anything that's got electronics in it. But the skin of the aircraft provides quite a lot of shielding," Scannell said. The weapon would need to have much more powerful radiation than that of the average air-control radar system, and its power would diminish the farther away it is from the aircraft.

Through a "Faraday cage" (named after Michael Faraday, one of the founders of electromagnetic theory), what is basically a metal container surrounds electronics that need to be protected. Electromagnetic waves induce current on the outside, but because of attenuation, remain outside. For example, with a microwave oven, a gasket running around the inside of the door may appear to be rubber, but has metal inside that completes the circuit of the box, so that electromagnetic currents that impinge on it don't penetrate the interior. The problem is that all electronic boxes have cords going in and out, to provide power, communications and so on. In the case of the USS Forrestall, a faulty maintenance door in the rocket allowed the electromagnetic pulses to seep inside. "What military people worry about is that things may be well shielded, but then people operate the electronics inside with the door open," Scannell said. "So obviously more stuff is defeated by the operators in the field than it is by the designers."

The same problem is at work with cell phones or other portable electronic devices that airline passengers are always warned against using during takeoffs and landings. The plane may be shielded on the outside, but not shielded against EMI coming from inside. Furthermore, regarding the general threat posed by EMI toward any electronics located anywhere, from a plane to a vehicle to a command-and-control center, shielding against higher frequency threats such as high power microwaves will not necessarily protect against low frequency electromagnetic pulses (EMP) from nuclear blasts, and because of the costs associated with the hardening of electronics, military planners make decisions about the extent to which they harden equipment based on its relative importance, according to Scannell. Nuclear bunkers are shielded against EMPs, which are very low frequencies. The longer the wavelength, the lower the frequency, the larger the scale of the object it will come to. But with small objects like computers, the concern is with more commonly found high frequencies, since with smaller objects, there is better coupling with higher frequencies, which are better able to slip into small cracks and crevices.

To protect against low as well as high frequencies costs more than protecting against just high. "Just like when you buy insurance, you take chances. You could insure yourself against everything in the world, and Lloyd's of London, I'm sure, would accommodate. But at some point, you weigh your risk versus the cost," Scannell said.

Some press reports have speculated about the potential use by the US of "electromagnetic bombs" against Iraq or Afghanistan in situations where bunkers built deep below ground might be difficult to reach by conventional weapons (see "E-Bombs Away!" JED , March 2003, p. 30). Knocking out the communications and computers within the bunkers would effectively render them useless. In any case, the antennas used on aircraft, military vehicles, or command-and-control posts to receive radio communications cannot themselves be shielded from attack, simply because they must be able to receive signals. Governments working on microwave weapons are not sharing much about their developments.

The Swedish Defence Research Establishment reportedly has carried out tests in which it was able to stop cars from up to 3,000 feet away (though stalling a car is not the same as permanently disabling it) and, through a private company called EME, is attempting to market technology that it says can detect the presence of high power microwave (HPM) radiation. The Pentagon has carried out similar tests in the US using private contractors. In August 2002, the AFRL awarded a $16.4 M contract to Fiore Industries (Albuquerque, NM) to investigate the lethality of HPM devices on target systems and the vulnerability of US systems to HPM threats. By better understanding the effects of HPMs, the program aims to learn how to disrupt them and protect against them, whether the HPM originates from an enemy or comes from a friendly source.

Though it has not announced anything about testing HPM bombs, the AFRL says its HPM technology is "considerably advanced." On its Web site, the laboratory has pictures of its $9 M, 26,000-square-foot High Energy Research and Technology Facility (Figure 4), where it conducts research into the military applications of high energy pulsed-power systems. "The facility's remote location in the Manzano Mountains on Kirtland Air Force Base is coupled with a unique construction, which is designed to withstand blasts and intense radiation from a variety of sources, including high energy microwaves and X-rays," according to a fact sheet. Companies working on HPM weapons reportedly include BAE Systems (Nashua, NH), and the latest report from the Office of the Secretary of Defense to Congress on China's military power warned that China may work together with Russia on a HPM system called Ranets-E to be used to target the electronics of precision-guided weapons. Systems designed to target satellites may also be a future possibility. In January the AFRL awarded a seven-year, $49 M contract to Metatech (Goleta, CA) to study the vulnerability of US satellite systems to directed energies such as lasers.

Reliance on Computers

With militaries and societies in general becoming increasingly dependent on computer chips, the fear arises that such dependence represents a potential weakness. Could political rebels in an undeveloped nation or terrorists in a rich country like Germany or the UK build a high-power microwave bomb with just a few hundred dollars? Books available for sale on the Internet with titles like "The Poor Man's Ray Gun - An Improvised Weapon" may or may not actually provide information useful for building an e-bomb in one's basement. But speaking before the US House of Representatives' Committee on Armed Services in May 2000, Bronius Cikotas, a former EMP division chief at the US Defense Nuclear Agency, noted the vulnerability created by modern society's ever-increasing reliance on computers. "There is a new target set for terrorists that includes our infrastructures which are vulnerable to cyber, radio-frequency, and other forms of attack," he said. "It could be argued that we have deep and extensive infrastructures that could not be attacked in any significant way. The problem is that, if you take the power grid down, the rest of them crumble because of interdependencies. Our almost total dependence on our infrastructures for power, food, water, fuel, telecommunications, transportation, etc., and a general lack of reserves brought about by just-in-time manufacturing makes us particularly vulnerable to infrastructure disruption. The cities typically have a three-day supply of food on supermarket shelves; the rest is on trains and trucks from the processing plants."

But Cikotas concluded that, in the case of terrorists, the need to detonate a nuclear weapon at high altitude to create an EMP wave that could knock out infrastructure probably would dissuade them from doing it in the first place; better to use more readily available conventional weapons, or detonate nuclear devices at ground level, where the resulting damage would be more certain and predictable. A well-placed conventional bomb could just as easily take out a radio-transmission tower or electrical power plant. The use of a suitcase-sized microwave weapon might be able to do damage to electronics, but so could regular explosives. Other types of weapons, in other words, might cause just as much damage and mayhem, and their effects are easier to calculate. Not always is the latest, most advanced form of technology needed to fulfill a wartime goal.