Written Statement by Dr. Michael P. Bernardin
Provost for the Theoretical Institute for Thermonuclear and Nuclear Studies
Applied Theoretical and Computational Physics Division
Los Alamos National Laboratory
I have been employed in the nuclear weapon design division at Los Alamos National Laboratory since 1985 to work on nuclear weapon design, nuclear outputs, and high-altitude electromagnetic pulse (EMP) assessment. I discovered the impact of x-rays on EMP and quantified the impact of two-stage shadowing effects on it as well, revolutionizing the understanding of realistic EMP environments. From 1992 1995, I was the Laboratory Project Leader for the Joint DoD/DOE Phase 2 Feasibility Study of a High Power Radio Frequency (HPRF) Weapon. This study effort focused on the feasibility and effectiveness of developing an HPRF weapon for offensive purposes. Since 1996, I have been the Provost for a post-graduate nuclear weapon design Institute within the Laboratory, chartered with training the next generation of nuclear weapon designers.
The issue to be addressed this morning is the impact to the civilian and military infrastructure of a high-altitude nuclear detonation over the United States. A high-altitude nuclear detonation would produce an electromagnetic pulse (EMP) that would cover from one- to several-million square kilometers, depending upon the height of burst, with electric fields larger than those typically associated with lightning. In such an event, would military equipment deployed within the area of EMP exposure be seriously impaired? Would civilian communications, the power grid, and equipment connected to the power grid catastrophically fail?
The answers to these questions depend on (1) the types of threat weapons deployed, (2) the EMP produced by these weapons and (3) the effects that are caused by the EMP.
Types of Threat Weapons
The types of threat weapons deployed in foreign arsenals are discussed in closed session. It is noted here that the Department of Energy nuclear design labs, Los Alamos and Lawrence Livermore National Laboratories, work closely with the Defense Intelligence Agency (DIA) and the Central Intelligence Agency (CIA), along with other members of the intelligence community, to computationally model foreign nuclear weapons. The Labs each have over 25 years of experience in modeling foreign nuclear weapons.
With Russia included in the list of countries possessing nuclear weapons that could potentially be detonated over the United States, the list of potential nuclear weapon technologies of interest for evaluation ranges from single-stage, unboosted weapons, through modern, two-stage thermonuclear weapons. Through an understanding of how EMP is produced, it is possible to correlate the severity of the EMP environments with the appropriate class of nuclear weapon technology. This correlation will be presented in closed testimony.
The EMP produced by these weapons is also a topic delegated largely to closed session. However, it is possible to discuss in an open forum the process by which high-altitude EMP is produced in the atmosphere, its propagation down to the earths surface, and some of the generic features of the resultant EMP.
The Defense Threat Reduction Agency (DTRA), through contractors that it employs, is the principal DoD organization for EMP assessment. Los Alamos also has a capability for assessing the large-amplitude portion of the EMP, and has provided the Joint Staff with independent EMP threat assessments since 1987.
The production and characterization of EMP is a highly technical subject. To assist the discussion of this subject, I have brought some graphics for illustration.
Graphic 1 illustrates the area coverage of direct EMP exposure from a 200-km height of burst over the United States. The area coverage varies with the height of burst. For a 200-km height of burst, which might be appropriate for a hypothetical multi-Mt weapon, the horizon is located at about 1600 km (or 1000 miles) from the point on the ground directly beneath the burst. For a 50-km height of burst, which might be appropriate for a 10-kt fission weapon, the horizon is located at about 800 km from the ground point beneath the burst.
Graphic 2 illustrates the temporal features of an EMP waveform at the earths surface resulting from a high-altitude burst. The EMP has three temporal components, designated as E1, E2, and E3. The early-time or E1 component is defined as the first microsecond of the pulse. It is produced largely by prompt gamma rays generated in the explosion. A characteristic amplitude of the electric field is 30,000 volts per meter (V/m) (Longmire, 1978). The intermediate-time component is defined as the portion of the pulse from one microsecond to one second, and it is produced primarily through prompt gamma rays that have been scattered in the atmosphere and by neutrons produced in the explosion. This component is characterized by a peak electric field value of 100 V/m (Radasky, 1988). The third component, the late-time component, is defined as the portion of the pulse beginning at one second and lasting up to several hundred seconds. It is produced primarily through the interaction of the expanding and rising fireball with the earths geomagnetic field lines. This EMP component is characterized by a peak field of 0.01 V/m. The E3 component is thought to couple well to very long lines, on the order of 100 km or greater.
Graphic 3 illustrates details of some additional specifics of the EMP generation process for the E1 portion of the pulse. A high-altitude nuclear explosion produces gamma rays, x-rays, neutrons, and debris. Some of the gamma rays propagate down into the earths atmosphere, where they collide with air molecules, producing recoil electrons. The electrons are created with a velocity directed principally radially outward from the burst. The electrons are turned by the earths magnetic field, which results in synchrotron radiation. The radiation adds coherently to form the electromagnetic pulse. As the electrons traverse their trajectories, they collide with other electrons, creating a sea of electrons known as ionization. Ionization can be enhanced by atmospheric breakdown or avalanching due to the presence of the EMP electric field. The ionization shorts out the EMP, limiting its value to typically 30,000 V/m.
High-energy x-rays produced by the exploding weapon can also enhance the ionization in the high-altitude EMP source region. This source of ionization was largely ignored in EMP assessments until 1986. Inclusion of the x-rays lowered the assessed values of the peak field for many weapons.
Note in graphic 3 that a thermonuclear weapon consists of two stages. The primary stage is typically of relatively low yield and is used to drive the secondary stage that produces a relatively large yield. Each weapon stage produces its own E1 EMP signal. But the primary stage gamma rays leave behind an ionized atmosphere from their EMP generation that is present when the secondary stage gamma rays arrive. Thus, the primary stage can degrade the EMP associated with the secondary stage.
Graphic 4 shows the spatial distribution of the peak EMP fields for a hypothetical weapon detonated over the United States. The directionality of the earths magnetic field causes the largest peak-field region to occur to the south of the burst point. The larger numbers on the plot are peak electric field values, in thousands of volts per meter (kV/m), and the smaller numbers are distance increments in kilometers. Note that the peak field ranges from 12 to about 25 kV/m.
EMP Effects on Infrastructure
Given an understanding of the resultant EMP field levels from a high-altitude nuclear detonation, the effects of those fields on military and commercial infrastructure remains to be determined. There are many organizations that have expertise and experience in evaluating the effects of EMP on commercial and military systems. These organizations include the Military Services, DTRA, and the DOE National Laboratories, among others. I urge the Committee to consult with these organizations for additional information.
The effects of EMP on the infrastructure cannot be quantified simply by drawing upon nuclear testing experience. High-altitude EMP was produced on ten atmospheric nuclear tests conducted by the United States in 1958 and 1962, and damage or upset (i.e., temporary glitches) of electronics was noted on a number of systems. However, these weapons are not truly representative of the foreign nuclear weapons in existence today, and the electronics of the modern era is vastly different from that which existed in 1958 1962. Moreover, the U.S. atmospheric tests were conducted over large bodies of ocean, and thus, the exposure of extended, landline systems to EMP fields was quite limited.
It is worthwhile reviewing the most famous of the EMP effects from U.S. atmospheric testing, namely the simultaneous failure of 30 strings of streetlights in Oahu during the Starfish event. Starfish was detonated at 400 km above Johnston Island in the Pacific on July 9, 1962. It had a yield of 1.4 Mt (about 115 times the yield of the bomb dropped on Hiroshima). Oahu was located approximately 1300 km from the designated ground zero of the burst, which was within line of sight of the detonation. A post-mortem following the event indicated that the failure of the strings of streetlights resulting from the Starfish event was due to damaged fuses. This event was analyzed by Charles Vittitoe, a Sandia National Laboratory scientist, in a report published in 1989 (SAND88-3341, April 1989). He notes that the observed damage is consistent with the magnitude and orientation of the EMP fields impinging on the streetlight strings that suffered damage. More importantly, he notes that the 30 strings of failed streetlights represented only about 1% of the streetlights that existed on Oahu at the time. Thus, the effects were not ubiquitous.
A much more extensive set of vulnerability data has been accumulated over the years through EMP testing in laboratory simulators. Tested items include aircraft, tanks, automobiles, computers, telecommunication equipment, etc. Both upset and damage have been obtained for some of the systems at certain field levels. DTRA and the Military Services should be consulted for a review of these data. A limitation with this type of testing is that the simulators are of finite volume and are not able to expose electric lines of length greater than about 50 m to EMP. Systems connected to power or communication lines are frequently tested with current injection, but even these tests are limited.
The most authoritative study to date on the likely impact of EMP on the U.S. power grid was published in an Oak Ridge National Laboratory report (Barnes, 1993). The report summarizes work performed from 1983 through 1992, and it includes a list of review panel members, which includes both leading experts in EMP and in the commercial power industry, who reviewed the work. The study examined the effects from all three high-altitude EMP environment components, namely E1, E2, and E3. The third witness on our panel will address the study results.
Electronic systems can be protected against EMP. Standard protection techniques include enclosing systems or subsystems in metal enclosures, and adding surge arrestors to power lines, cables, etc. Simulator and line-driven testing have shown that EMP protection is effective. There are cost and practical considerations associated with implementing EMP protection. The Services, DTRA and others should be consulted for more detail.
The conclusions to be drawn are dependent on the validity of the EMP environments imposed on military and commercial systems of interest. These are to be examined in closed session. It is clear that EMP is a real effect and that damage is virtually certain.
To establish that the problem is well understood, one must begin with a model of, say, Starfish, and demonstrate that the predicted EMP environments, EMP coupling, and effects match observation. Then, one must be able to establish that the model retains its fidelity when the warhead model is changed, when the burst location is moved over land and changed in elevation, when the electromagnetic coupling paths change, when the vintage of electronics changes, and with the incorporation of EMP test simulator data, that the results are reliable. While it is conceivable for a model to achieve all of this, any such model should be peer-reviewed by a high-level review group (e.g., National Academy of Science or Defense Science Board) before predictions of catastrophic damage are to be believed.
Barnes, P.R., et al, (1993). Electromagnetic Pulse Research on Electric Power Systems: Program Summary and Recommendations, Oak Ridge National Laboratory report ORNL-6708.
Longmire, C.L., (1978). On the Electromagnetic Pulse Produced by Nuclear Explosions, IEEE Transactions on Antennas and Propagation, Vol. AP-26, No. 1, p. 3.
Radasky, W.A., et al, (1988). High-Altitude Electromagnetic Pulse Theory and Calculations,
Defense Nuclear Agency technical report DNA-TR-88-123. See figure on page 2.
Vittitoe, C.N., (1989). Did High-Altitude EMP Cause the Hawaiian Streetlight Incident? Sandia National Laboratories report SAND88-3341.