SUBJECT AREA C4
In Partial Fulfillment of Requirements
for Written Communications
The Marine Corps Command and Staff College
Major R. D. Erick
United States Marine Corps
April 6, 1984
Thesis sentence: EMP is a very misunderstood force that will have
a devastating effect in a tactical nuclear war.
I. How EMP was noticed
II. Factors that determine EMP
A. Formation of EMP wave
B. Strength of EMP wave
1. Low-level blasts
2. Surface blasts
3. High-altitude blasts
III. Tactical warfare (low-level or surface blasts)
A. Present stock of tactical nuclear weapons
B. Vulnerability of our tactical systems
C. Vulnerability of the Marine Corps systems
D. Vulnerability of Soviet tactical systems
IV. Protecting against EMP
EMP. What is it and how will it affect us in a tactical nuclear
war? EMP stands for Electromagnetic Pulse. Explosions of conventional
high explosive bombs produce EMP. However, the effects produced by
a nuclear explosion were not fully realized until the "Johnston Is-
land Test" in 1962. This nuclear blast had a yield of 1.4 megatons
at an altitude of 250 miles. The explosion damaged a number of low
earth orbit satellites and caused malfunctions and early failure of
others. Another effect that was noted during the blast was a black-
out up to 600 miles away of high frequency radio communications that
lasted for hours. It was caused by disruption of the ionosphere. It
also popped circuit breakers, street lights went out, burglar alarms
rang, and power lines went down in Honolulu, about 800 miles away. In
Nov. 1962, all above ground testing was halted and our testing and
analysis was limited to underground testing, analysis of the existing
atmospheric test data, nonnuclear simulation, and theoretical calcula-
tions. This is in part why we know so little about the effects of
EMP. The primary effects of a nuclear blast are the blast, thermal,
and radiation. This is where the propensity of effort was put in the
Although most of the information on this subject is classified
as far as what our vulnerabilities are and what we have hardened and
what we are doing to solve the problems, all the information contained
in this report is unclassified and can be discussed freely.
Electromagnetic Pulse, or EMP as we will call it through out the
rest of our discussion is not a unique phenomenon. There are a variety
of factors that determine EMP. However, the first phase is always the
same, a form of energy released by means of a nuclear detonation. This
causes gamma rays to collide with air molecules. Electrons are given
off by the air molecules and the motion is transfered from the gamma
rays to the free electrons. The result is a scattering of these neg-
atively charged electrons and the positive air molecules are left be-
hind. See figure 1.
Click here to view image
Reaching its maximum strength the electric field strength falls off
and becomes quite small in a few tenths of a microsecond. Despite
the relatively short duration of this pulse it has a considerable
amount of energy and it travels away from the blast point at the speed
The next phase of generation is dependent on whether the blast
is a low-altitude air blast, a near-surface or ground blast, or a high-
altitude blast. The low-altitude air blast is usually described as
from three to 19 miles above the earth's surface. See figure 3.
Click here to view image
This type of blast is probably the least destructive as far as EMP is
concerned. It's effects will generally range from three to nine miles
depending on the height of the blast point. Even though our modern
day systems can survive the blast, thermal and overpressure effects
at these distances, EMP could induce operational problems such as burn
out of circuits, erasure of memory and recorded data. The EMP of a
low-altitude blast, even though covering more area is less intense than
in a surface blast.
The surface blast is the most devastating as far as the tactical
Click here to view image
Since the ground is a relatively good conductor of electricity it
provides an alternative path for the electrons. The electric currents
thus flow in the ground and generate strong magnetic fields in the re-
gion of the surface blast point. The electric field produced in this
surface blast is very strong but the radiated field falls off with in-
creasing distance much the same as the low-altitude blast. The poten-
tial hazard to electrical and electronic equipment from the EMP will
be greatest within the disposition region which may extend over a radius
around ground zero out to 10 miles. This is dependent on explosion
High-altitude blasts, above about 19 miles, have two kinds of ef-
fects. First is the gamma rays that move upward from the blast point
because of the low air density at the heights. These gamma rays travel
great distances before they are absorbed. This affect can cause great
damage to satellites since the range of travel of these gamma rays can
be hundreds of miles. See figure 5.
Click here to view image
The other effect of high altitude explosions is that the gamma rays
emitted are generally downward so as to encounter a region where the
atmospheric density is increased. These gamma rays collide with the
air molecules as previously mentioned to create a source region for the
EMP. This region can be up to 50 miles thick and several hundred miles
in diameter. This causes an EMP that generally moves down toward the
earth's surface. The EMP strength of a high-altitude explosion is from
1/10 to 1/100 of that of the surface blast. However, the surface blast's
strength drops off rapidly with distance. The effects of the high al-
titude blast at 200 miles above the center of the United States could
cover all of the United States and parts of Mexico and Canada.
On the tactical battlefield we will probably not see the high
altitude nuclear blast. This will be used by the Soviet Union as the
first step in the escalation from tactical nuclear weapons to a stra-
tegic nuclear war. The effects of this, while being able to knock out
some of our communication satellites and thus disrupting communications
from the battlefield back to the President or Joint Chiefs of Staff,
sould have none of the tactical effect or influence in that it would
knock out all the communications in the United States and would cause
massive failures in systems not hardened against EMP. The system of
greatest interest for the Soviet Union would be the Command and Control
Network which would disrupt communications and launch commands to our
strategic nuclear missiles. It also could disrupt the computer systems
that control these nuclear missiles. Other effects would be to disrupt
the life of the average American citizen by causing massive black outs,
disrupting all radio and television communications and the Civil De-
If we go from peacetime directly into an all out nuclear war we
will never use a tactical nuclear weapon. However, the United States
and the Soviet Union were until several months ago engaged in two sets
of nuclear arms talks, one dealing with the intercontinental range stra-
tegic weapons, and the other dealing with intermediate range strategic
weapons. Both of these talks have since been suspended. However, there
is a very large armory of nuclear weapons which the U.S. and the U.S.S.R.
have not begun to talk about. These are the approximately 8,000, 20 to
1,000 Kiloton range tactical nuclear weapons held by both super powers
not to mention those held by third world countries which may not even
have a strategic capability. Because of the lack of limitations on
these tactical weapons I will be looking at the tactical effects of EMP
on our equipment and the way we fight wars.
Both the low-altitude and the surface blast will probably be used
on the modern tactical battlefield. The low-altitude nuclear blast has
a very small zone of effect and in almost all cases when talking about
nuclear weapons in the kiloton range, the other effects such as blast,
radiation, overpressure and thermal far outweigh the damage caused by EMP.
I will concentrate on the surface blast for the rest of the paper since
it has the greatest potential for causing us problems with EMP at a
As stated previously the EMP is an actual pulse form in the time
domain with peak value and pulse slope characteristics as see in figure
2. One of the biggest problems of EMP is that it creates a pulse, which
may be up to 40 kilovolts per meter and is 50 times faster than lightn-
ing. This means that normal lightning protection is ineffective. The
nature of the problem is that the voltage pulse arising from the EMP
rises to kilovolts in one billionth of a second and currents in the kilo-
amp range.A typical surge arrestor such as used to protect electronic
equipment from lightning can not react this fast to the rise in voltage
nor can it handle the current demands. The EMP is induced into the elec-
tronic equipment the same as lightning or electromagnetic waves but with
greater intensity and over a broader spectrum. In other words, instead
of a very narrow band such as a radio signal which is a specific fre-
quency or lightning which affects a fairly narrow frequency range, EMP
affects a very broad band. Any conducting objects such as metal ob-
jects exposed to the EMP act as collectors or as an antenna even though
it is not intended to be one. Generally, the larger the metal object
the greater the amount of energy that is induced into the system. This
is the difference between radiation and EMP. For other nuclear radia-
tions, such as blast, thermal, and overpressure the energy is only on
the exterior of the structures. The EMP effects are collected and can
be conducted into a metal structure by wires which focus a large amount
of energy to the interior of the system. The equipment reacts by treat-
ing the EMP as noise. The collectors would be not only those items
specifically designed to be antennas but also items such as cables,
gun tubes, missiles, structural members, guy wires, conduction loops,
and even railroad tracks, fences and metal sheets.
There are two kinds of damage EMP can cause to electrical or elect-
ronic systems. First is the actual physical damage caused by electrical
components shorting out or burning out such as capacitors, resistors,
and transistors, thus causing the repair or replacement of the component.
The second is of lesser concern because it causes only temporary oper-
ational upsets such as instabilities, causing the system to shut itself
down, upset computers so they must be started again. Both these effects
increase in direct proportion to the amount of digital technology and
the large scale integrated circuitry designed into our systems. Items
such as motors, power switches, and components that are subject to large
power levels in normal use are relatively uneffected by EMP. Both sides
in a nuclear war are vulnerable to EMP. However, the U.S. will probably
be more vulnerable because of our greater sophistication in transistors
and miniature and micro circuits. We have made everything smaller by
the use of solid state circuits. Yet, this technoloty is particularly
vulnerable to EMP because of its small size and micro geometry.
The Marine Corps in particular will have problems with the EMP.
The battlefield will be extremely difficult to operate in and if tac-
tical nuclear weapons are employed by the opposing forces the situation
will be even more complicated by the effects of EMP. The command and
control systems will be knocked out. The generals and their staff will
not be able to talk to their front line troops and they will not be
able to receive instructions from higher headquarters in the United
Not only will the communications be disrupted but any equipment
which has integrated circuits or transistors will be affected. This
will include such equipment as generators, aircraft electronics systems
and ground electronics systems. Because of our increasing technology,
we have made ourselves even more vulnerable in this area. For example,
all our new family of vehicles which have electronic ignition and com-
puter controlled ignition advance and computer controlled fuel-air
mixture will cease to operate. Not only will we not be able to talk on
the tactical nuclear battlefield we might not even be able to move.
The Soviets, however, have not yet replaced many of their vacuum
tubes with solid state devices. Vacuum tubes are far more resistant to
EMP that the microelectronic devices. This was emphasised when one of the
Soviet's most modern jet fighter, a MIG -25, was flown to Japan by a
Soviet defector in 1976. Subsequent investigation revealed that this
modern fighter used vacuum tube electronics extensively. It should be
mentioned that even though this modern jet had vacuum tubes it may be
that this is more directly related to the lack of Soviet Union's semi-
conductor technology than to any attempt by the Soviets to harden their
aircraft against the effects of EMP.
As put by Daniel L. Stein, assistant professor of physics at
Princeton, " a ground or low-altitude burst generates significant elec-
tromagnetic pulse out to distances corresponding to an overpressure of
about two pounds per square inch, the radius of blast damage to resi-
dences - approximately seven - to - ten miles for a one megaton weapon.
A sophisticated system hardened against blast, thermal and over-pressure
effects of a low-yield weapon could well suffer operational upset, such
as, erasure of memory or recorded data, from electromagnetic pulse.
Disruption of communications and coordination among tactical aircraft
may occure, and their links to a central authority may be temporarily
The big problem is that the next war could be characterized by
this EMP phenomenon which our armed forces have never before experienced
in combat. When it first happens we need to know what we as the forces
on the ground or in the air can do to protect the equipment we have. We
also need to make more people aware of the problem so we can develope
new equipment and weapons that will minimise the effects of EMP. It is
easy to say we can protect against EMP in principle but very difficult
to implement and even more difficult to maintain. There are two basic
methods of providing EMP protection. The first is to provide a shield
which will not allow the EMP to enter. The second is to design and
build the equipment so that the circuit can resist the EMP. Often the
most cost effective way is to use a combination of both methods to de-
feat the EMP. We will look at a few ways to defeat the EMP which are
for the most part combinations of the two basic ways. Features that
need to be designed in are such things as pulse resistant fiber optics,
improved power supply systems using batteries, solar power and thermo-
nuclear power sources, and the use of nodule self-healing network architec-
ture. In the case of computer memory we need to insure that magnetic
tape or some other semipermanent storage device used to store data and
programs for the computer.
The operator can do little to harden his equipment to EMP but he
can do some things that might help lessen the damage to the equipment.
First the equipment should be operated and maintained by the technical
manuals. All equipment access doors should be kept closed. Cables
should be buried under steel sheets to a depth of three feet. Use
the shortest possible cables and disconnect them when not in use.
Keep equipment away from large collectors such as long cable/power lines,
fencing or railroads.
Even though some individual components or circuits may be tested
it is often difficult if not impossible to predict how the entire in-
tegrated system will react to an actual nuclear explosion. We have
seen some movement toward hardening systems in the last few years but
effective hardening of entire systems is simply impossible and not cost
effective. The Joint Chief of Staff last year asked for 7 billion
dollars to upgrade command and control. Only part was spent on the
electromagnetic pulse protection and even less was spent on tactical
systems. In general the understanding of EMP, the means to harden,
and the technological capabilities are all present to make our system
survivable. The problem is to make people aware of the EMP phenomena
and get the funds to do the work. Not only do funds need to be made
available but there are other considerations such as the problem of
hardening the President's E-4B National Airborne Emergency Command
Post. It costs not only dollars but close to 14,000 pounds in added
weight to harden the aircraft as compared to the unhardened aircraft.
Finally, it was stated by Captain Jay Willis, who has a master of
science in nuclear engineering, "One question that is easy to answer is
whether any given air defense system" or any tactical system, "may re-
asonably expect to be subjected to an EMP in a nuclear war. A single
thermonuclear detonation at an altitude of a few hundred kilometers can
blanket an entire theater of war with a strong EMP. EMP could damage
any of our military or critical civilian electrical systems or elec-
tronic equipment. Any potential nuclear advesary probably would not
hesitate to make full use of EMP against our forces."2
1Daniel L. Stein, "Electromagnetic pulse - The uncertain certainty.
The Bulletin of the Atomic Scientists, Mar 83, p. 54.
2Captain Jay C. Willis, "EMP: An Increasingly Important Nuclear
Weapons Effect. Air Defense Magazine, Jan - Mar 82, p.16.
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Cook, K. G. "Fast Gas Filled Surge Arresters for EMP Protection."
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Dean, Johathan. "Battlefield Nuclear Weapons." Arms Control Today,
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Dolan, Philip J. and Samuel Glasstone. The Effects of Nuclear Weapons.
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Lippert, Jorg C. "The Hidden Destroyer." NATO's Sixteen Nations,
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McQuade, K. F. "Improved C3I Systems Needed for Survivability." Defense
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Schemmer, Benjamin F. "Fastest Growing Part of DOD Budget: 'Electronic
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