ELECTROMAGNETIC PULSE PROTECTION CONSIDERATIONS
1. Background
The EMP resulting from a nuclear weapon detonation can adversely affect
unhardened electrical devices. When the detonation is well above the earth, EMP can cover
the entire battlespace. The same detonation on or near the earth causes more intense, but
more localized EMP. For these reasons, equipment supporting critical missions must, as a
minimum, survive high altitude EMP effects. Such equipment survivability can be
achieved by hardening the equipment or by using other mitigation techniques.
2. Electromagnetic Pulse
Electromagnetic pulse is a nuclear weapons effect that can have an adverse impact on
electrical and electronic equipment. Although it represents roughly 1 percent of the total
energy produced by a nuclear burst, EMP can destroy or cause serious damage to electronic
equipment through electrical-current surges. Digital electronics can also suffer upset
conditions that are also serious. Unfortunately, standard devices that protect equipment
against lightning do not necessarily provide protection against EMP. Units must ensure
that OPLANs include mitigation techniques to reduce EMP effects on operations.
3. Electromagnetic Pulse Mitigation Techniques
a. EMP mitigation procedures use hardened equipment and/or unhardened
equipment. Correct maintenance and operational procedures help ensure that the
hardness of built-in equipment remains intact. Improper maintenance can readily reduce
or eliminate EMP hardening. Unhardened equipment relies on operator mitigation to
reduce EMP coupling to levels below upset or damage.
(1) Exercise caution when adding components to already hardened equipment,
such as placing new systems in a hardened van or mobile shelter.
(2) As a general rule, making an addition to stand-alone equipment that does
not have wires or connectors running outside the protected enclosure does not interfere
with the EMP hardening of the shelter. However, any addition of new connectors (such as
running a telephone wire or extra air-conditioning or ventilation hoses into a shelter) that
does not go through an approved surge arrestor and penetration shield or connector can
adversely affect the hardness of the protected area. The addition of more sensitive
electrons inside the protected enclosure can also affect hardness.
b. Many EMP hardening designs create shields between the electronic equipment
and external EMP environments. Any cable or other penetration in a hardened system that
creates a hole or gap in the shield can degrade system survivability. Gaps, seals, and
closures should be intact and fully engaged. Necessary maintenance or modifications made
to systems should attempt to reseal and restore any breaks in the shielding.
c. When possible, EMP effects can be mitigated by having approved nonelectronic
or alternative electronic procedures, backup systems, and backup copies of critical
electronic data available for use. Multiple electronic systems of similar function can
provide alternate or backup systems to supplement the functionality of potentially
vulnerable high- and ultra-high frequency radios. Full restoration of EMP-damaged or
disrupted computer information systems requires that replacement or repaired systems
have operationally critical data from backups for immediate installation. Stored, backup
CISs can provide replacement hardware. Frequent backups of critical operational data in
durable media formats further provide the data needed to resume any disrupted operations
d. Other mitigation measures can include?
? Making maximum use of the least vulnerable equipment when possible.
? Providing redundant, multiple-mode communication links between positions.
? Preplanning and training to use backup and alternate communications
networks. When possible, establish two or more communications paths and have a
contingency plan to reestablish communications.
? Maintaining a stock of critical spare parts. In some cases, EMP damage may
affect only one part of a system, which if replaced, will allow the device to function as
before. Fuses are particularly important; therefore, personnel need to know the location of
all fuses in their equipment and maintain and keep spares on hand. Critical spares and
parts should be sealed in their original, electrostatic discharge (ESD) containers or bags
until needed for use.
? Integrating EMP concerns into safety plans and drills. For example,
personnel need to practice the skills needed to extinguish sudden, multiple, EMP-induced
electrical fires inside shelters and enclosures and have appropriate life-support and firefighting
equipment at hand.
e. Components, such as antennas and other metallic surfaces can be EMPconcentrating
items. Potential antennas include such objects as gun tubes, heating and
ventilation ducts, water pipes, fuel pipelines, conduits, grounding rods and wires,
commercial phone and power lines, missiles, guy wires, fences, railroad tracks, and power
lines from generators.
(1) When possible, personnel should disconnect and collapse collectors or
antennas. Simply turning off the equipment is not sufficient; damaging energy can still
enter through antennas.
(2) Where possible, personnel should avoid use of the most vulnerable
antennas, which include long wires or rods, wide-angle doublets, and omnidirectional
antennas. Less vulnerable antennas include those with smaller radiating elements.
(3) Additionally, personnel should avoid the creating loops in wire and other
antennas or collectors. Loops act as magnetic dipole antennas, allowing EMP energy to
affect the systems connected to them. Operators and supervisors should also recognize the
different types of systems that might be linked in loops that are not immediately obvious.
For example, a phone line may run from a van to a switchboard; the switchboard may be
linked by wire to a CP, the CP may have a power line connection to a generator, and the
same generator may have a power line to the van, thus resulting in an effective loop
antenna or collector.
(4) Laying cables on the ground or shallow burial of cables for physical
protection is recommended when practical for EMP mitigation purposes. Cables strung in
the air can pick up more EMP energy than cables on the earth?s surface. Only very deeply
buried cables (10 feet or more) have significant EMP protection, but they are often not
worth the construction effort.
f. Dispersed operations, to include the use of remotes, increase survivability by
reducing a unit?s single-point signatures and increasing the number of targets an enemy
must find and engage.
g. Mitigation measures also include procedures for damage assessment, repair, and
testing of equipment. In a unit that has been subjected to EMP effects, electronic
equipment may be functionally damaged, operationally upset, or unaffected, depending on
the shielding and effectiveness of EMP mitigation postures.
(1) Even though electronic equipment has suffered functional damage from
EMP, repairs may include operator maintenance procedures such as resetting circuit
breakers or replacing fuses.
(2) Mission-critical computers can also be affected by EMP at levels that are
far lower than the intensities required to inflict functional damage. The effects may only be
revealed when it becomes evident that critical information is incorrect or unavailable. An
effective practice would be to assume that the computer memory has been upset and have
the operators automatically reload backup files.
(3) Consistent with command priorities, all electronic equipment should be
tested and inspected for operational upset and/or functional damage. This includes items
that have been shielded or hardened against EMP effects. In some cases, upset or
functional damage may not be immediately evident.
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