The Pentagon is studying ways of countering the threat of an electromagnetic pulse attack.
By Patrick Chisholm
http://www.military-information-technology.com/article.cfm?DocID=1185
Amid increasing reliance on computer networks and other electronic technology and the rise of new and technologically sophisticated potential adversaries, military officials are taking a renewed look at ways of countering the threat of an electromagnetic pulse (EMP) attack. During the Cold War, the possibility of an EMP attack was a prominent concern for U.S. defense planners. In such an attack scenario, a nuclear bomb is exploded miles—typically hundreds of miles—above the target area. The explosion generates an EMP that disrupts or destroys electronic devices everywhere in the target area, which could include an area as large as the continental United States.
With the downfall of the Soviet Union, the threat of EMP from that part of the world has greatly receded. However, since the end of the Cold War, new EMP vulnerabilities have emerged, the most obvious of which is terrorism. As a 2004 report by a panel of experts warned, terrorists or other adversaries could launch an EMP attack without having a high level of sophistication, such as through a short-range Scud missile. Also of concern are non-nuclear, small-scale E-bombs that target localized areas. (See MIT, Volume 8, Issue 8, page 8.)
The EMP generated from nuclear and E-bombs could pass through protective cages that shield electronics and critical infrastructure against lightning and other electromagnetic interference (EMI). And a byproduct of EMPs is said to be huge magnetic fields that collapse, generating a massive power surge that would render many electronic devices inoperable.
Newly nuclear-armed nations pose another EMP threat. If countries such as Iran and North Korea do not already have nuclear weapons and E-bombs, they could be well on their way to acquiring them, analysts say. Iran has conducted flight tests of its Shahab III medium-range missile. The missiles reportedly were deliberately exploded at high altitude, and were deemed by the Iranian government as successful tests. One interpretation points to the possibility of plans for EMP.
A second major development since the end of the Cold War is the U.S. military’s widespread use of and dependency on computers and other electronics for weapons systems, command and control systems, and business process systems. The push toward network-centric warfare—from command centers stateside down to soldiers in the field—means that dependency on electronics will only intensify.
Military Standard
These new vulnerabilities to EMP raise the question of how well the Department of Defense is prepared for such an attack. The answer, observers say, is mixed and difficult to discern, because information regarding which U.S. military systems are hardened against EMP is classified. However, clues suggest that more resources could be devoted to EMP hardening than is currently the case. For example, many EMP testing facilities have been closed since the end of the Cold War, according to William A. Radasky, president of Metatech Corp. and an expert on protecting electronics from EMP.
In addition, the Construction Engineering Research Laboratory of the Army Corps of Engineers used to investigate materials and processes for EMP shielding applications. But, according to a spokesman, “All the money for that research dried up after the Berlin Wall came down.”
Literature warning about the dangers of EMP conveys the impression that an EMP would ruin every electronic device in the target area. It is less frequently pointed out, however, that most electronic components enjoy some built-in protection from electromagnetic interference, albeit not necessarily from EMP. Government standards require such protection.
To be sure, commercial EMI standards are probably too weak to protect against an EMP. But military standards are much stronger than commercial standards because of the more hazardous environments that military electronics are exposed to. Along with protecting against the various electromagnetic interferences that one encounters on the battlefield, some—but by no means all—military EMI standards are designed to withstand EMP as well. The most common EMI standard is Military Standard 461 (MIL-STD-461).
For military electronics, “We are typically trying to protect nearby radio communications or navigation receivers from being jammed by our equipment…. We are [also] trying to protect our own sensitive circuits against the fields from nearby radio or radar transmitters. “Shielding may also be needed for other threats, such as lightning or nuclear EMP,” according to Daryl Gerke and William Kimmel, principals at Kimmel Gerke Associates, an EMC consulting and training firm, writing in Interference Technology magazine.
They continued, “Military equipment may be subjected to very high levels of RF energy (radar and radio transmitters), lightning and nuclear EMP effects. MIL-STD-461E, the key military EMC specification, addresses these multiple environments through a matrix of recommended requirements. For example, an electronic device used in a submarine will have different requirements than a device used in a helicopter.”
A vulnerability arises, however, with the military’s increasing use of COTS devices in warfighting, C4I and business process systems. The key is to ensure either that those COTS items have been modified to comply with military EMI standards, or that, once those COTS items are acquired, they are housed in rooms or buildings that protect against EMP and other EMI.
EMI Shielding
If electronics are not designed correctly or shielded properly, they can jam reception of television, radio and other telecommunications. Therefore, as mentioned above, electronic gear cannot be sold without having to meet some sort of regulations controlling the electromagnetic noise coming out of the device. In the U.S., the Federal Communications Commission (FCC) sets the regulations. Europe has even stronger regulations.
EMI shielding is designed to both keep electromagnetic radiation from escaping from the device, and from getting into it. “Most of the regulations are aimed at keeping whatever noise that the box generates, by virtue of its operation, from getting out and affecting somebody else’s box or licensed radio or TV,” said Joe Butler, new business development manager at Chomerics, which manufactures EMI shielding materials. “However, given that there are all types of sources of electromagnetic radiation in the air, if you want your box to operate properly, you have to build it so that it’s protected from noise getting into it. So the shielding works both ways.”
In EMI parlance, an electronic box may be anything from a cell phone housing, a laptop housing, a PC housing, or even housing for a large server rack.
To shield electronics from EMP or EMI, the equipment needs to be encased in a metal housing, often in the form of what is known as a Faraday cage. The openings to that housing would be sealed with electrically conductive gaskets. The housings can range from tiny, such as the metal soldered on printed circuit boards, to housings that are the size of rooms that protect critical electronic equipment inside.
The cables and/or wires entering the housing need to be shielded as well, because without such shielding, a cable or wire acts as an antenna that carries an EMP or other EMI directly into the device. The shielding of such cables typically consists of a wire mesh. conduit—the metal case through which wires and cables can be placed—may work as well, for facility-level shielding.
“It’s a lot cheaper sometimes to lay lots of cables in a cable conduit or cable box, rather than shielding each one. In military installations, they probably have a lot of that,” said Butler.
Protecting electronic equipment from EMI/EMP does not necessarily entail hardening the equipment itself, but rather the room in which the equipment resides, or even the entire building. There are EMI/EMP-hardened transportable tactical shelters as well.
Products or technologies used to harden electronics include metallic shielding; for tiny devices, this can take the form of a spray-on metal coating. Shielding and filter products also include gaskets and surge protectors.
EMI/EMP shielding can erode over time, so maintenance and testing should be done regularly.
The continued replacement of copper wire with fiber optic cable is a positive development with regard to EMP vulnerability, since fiber optic cable is not viewed as vulnerable to EMP.
In both the commercial and military sectors, general EMI shielding requirements have gotten more stringent over time, according to Butler. In the commercial world, European Union regulations, rather than FCC regulations, are the industry drivers for the most part. Most companies that make hardware wish to sell them worldwide, so they design their equipment to meet the toughest (commercial) regulations in the world. And the EU’s regulations are tougher than those of the U.S.
As electronics get smaller, they become less of an issue for EMP in one sense. The new, more sophisticated, smaller electronic devices that are becoming more available actually make EMI shielding easier, because as things get smaller, the effective “antenna” leading into that component gets smaller along with it. So the ability of such as device to broadcast or pick up signals that may interfere with other it or with other electronics is lessened.
On the flip side, however, is the fact that smaller sizes mean less energy is required to cause an upset, according to Dennis Friday and Perry Wilson of the Electromagnetics Division of the National Institute of Standards and Technology (NIST).
Antenna Systems
Nevertheless, commercial EMI standards are not designed to protect against EMP attacks. During such an event, therefore, there could be widespread disruption of electronics. Not all electronics would be affected, however, because in order to do so, they would need to be connected to some larger “antenna.”
For example, a turned-off computer without any cables or wires attached to it would likely avoid damage from an EMP, since the physical size of the computer may be small enough that it may not collect enough energy to cause a problem. But when it is plugged in, and/or when other cables are attached to it, it gets tied into a much larger network of wires, which form an antenna.
In the event of an EMP, that antenna system collects the signal and pumps it into the computer. Even then, however, because computers have some degree of protection, they only may temporarily go down, according to Butler. But it would depend on how powerful and/or close the EMP is. A powerful enough pulse could ruin a computer.
Butler says that in the civilian sector, critical infrastructure would not necessarily withstand an EMP attack. Power lines act as large antennas, and with an EMP, the pulse rides on those antennas to whatever is connected to them. If there are not sufficient surge suppression devices in place, some equipment could be burned out, or at least disrupted.
Current protection against lightning strikes would not be enough to protect against EMP. The rise time and pulse width of an EMP event is much faster and shorter than that of lightning, explained Butler. So, separate EMP suppressors would be needed, in addition to lightning suppressors.
The electronics in aircraft are subject to severe EMI associated with aviation, and therefore need robust shielding. So airplanes would be expected to escape severe damage from an EMP attack. Likewise, automobiles enjoy substantial shielding because of the EM hazards they often encounter on the roadways. “The roadways are a pretty ugly environment for electronics,” said Gerke. Moreover, the metal in and on the car could block out some of the EMP.
The extent to which vehicles, aircraft, power supplies, and other devices and equipment would survive an EMP attack remains unknown, however. In the civilian sector, while most items are tested for EMI, few if any items are tested against EMP. “It’s anyone’s guess, what would happen in the EMP event,” said Wilson of NIST.
It is possible to test for EMP using special simulators. But the main users of such simulators are military, not civilian. As indicated above, the number of such simulators is very few.
Effective protection against EMI/EMP entails testing. “At the end of the day, you have to verify the performance that you have actually achieved your goals,” said Friday, adding that since EMI shielding can degrade over time, testing has to take place periodically.
Of course, standard COTS equipment used by the military would not have EMP protection. Although some manufacturers make two versions of products—one with commercial standards and one with military standards—this frequently is not the case. But that does not mean the equipment cannot be protected. “The hardening could be done external to the equipment,” said Gerke. This includes hardening at the room level or even at the building level.
The Pentagon has a “Balanced Electromagnetic Hardening” program. According to a budget item justification sheet, the program “provides the science and technology to ensure protection and survival of military battlefield and civilian infrastructure electronic systems against multiple electromagnetic environments, including nuclear electromagnetic pulse, high-power microwaves, as well as WMD threats. Designs and develops innovative, low-cost, balanced EM protection and test technologies for weapon systems; C3; and supporting infrastructure systems to the CINCs, services and other DoD agencies.”
Although information on military EMI/EMP hardening is classified, Wilson suggested that DoD is paying attention to the issue. “It is not something they are ignoring,” he said.
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