Zeev's Turnips Talk Politics (ZTTP)

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Statement of

Dr. George W. Ullrich
Deputy Director
Defense Special Weapons Agency

http://www.fas.org/spp/starwars/congress/1997_h/h970716u.htm

INTRODUCTION

Mr. Chairman, I am Dr. George Ullrich, the Deputy Director at the Defense Special Weapons Agency in the Department of Defense. I appreciate the opportunity to appear before you today to discuss this important issue......... snip

....A high altitude burst, detonated at heights ranging from 50 to several hundreds of kilometers above the earth's surface, is also capable of generating a wide variety of effects and disturbed environments, the most far-reaching being EMP. Depending primarily on the burst height and to a lesser extent on yield, a high altitude burst can bathe a continental size region in EMP....snip

...A less well known effect of high altitude bursts, but also one with potentially devastating consequences, is the artificial "pumping" of the Van Allen belt with large numbers of electrons. The bomb-induced electrons will remain trapped in these belts for periods exceeding one year. All unhardened satellites traversing these belts in low earth orbit could demise in a matter of days to weeks following even one high altitude burst....snip



However, due to size and power reductions, modern electronics are inherently more vulnerable to some of the effects produced by a nuclear detonation. And each new generation, smaller and needing less power, exacerbates these vulnerabilities. Furthermore, as we make greater use of more affordable commercial parts and components, we potentially introduce new vulnerabilities into our military systems. Additionally, the military's increasing reliance on commercial space-based systems makes it more vulnerable to the nuclear weapon effects being discussed. ...snip,snip

...In my presentation today, I will provide a brief overview of the effects produced by nuclear weapons, to include lessons learned during both the United States' and Soviet Union's atmospheric nuclear test programs. Particular emphasis will be given to the most significant effects in a scenario in which an adversary uses one or a few nuclear weapons detonated at a high altitude. I will discuss what we have learned about providing affordable protection. Finally, I will mention what we do to simulate these threat level environments and how we perform testing to validate EMP hardness..... snip

....In keeping with your request, Mr. Chairman, I will direct most of my remarks to the topic of high altitude EMP.


High Altitude EMP

A nuclear weapon detonated at high altitude releases some of its energy in the form of gamma rays. These gamma rays collide with air molecules and produce what are called Compton electrons. The Compton electrons, in turn, interact with the earth's magnetic field, producing an intense electromagnetic pulse that propagates downward to the earth's surface. The initial gamma rays and resultant EMP move with the speed of light. The effects encompass an area along the line of sight from the detonation to the earth's horizon. Any system within view of the detonation will experience some level of EMP. For example, if a high-yield weapon were to be detonated 400 kilometers (250 miles) above the United States, nearly the entire contiguous 48 states would be within the line-of-sight. The frequency range of the pulse is enormously wide -- from below one hertz to one gigahertz. Peak electric fields can reach tens of thousands of volts per meter. All types of modern electronics are potentially at risk, from Boston to Los Angeles; from Chicago to New Orleans.

One of our earliest experiences with HEMP dates back to the resumption of atmospheric nuclear testing in 1962 following a three year testing moratorium. Starfish Prime, a 1.4 megaton device, was detonated at an altitude of 400 kilometers over Johnston Island. Failures of electronic systems resulted in Hawaii, 1,300 kilometers away from the detonation. Street lights and fuzes failed on Oahu and telephone service was disrupted on the island of Kauai. Subsequent tests with lower yield devices produced electronic upsets on an instrumentation aircraft that was approximately 300 kilometers away from the detonations.

Soviet scientists had similar experiences during their atmospheric test program. In one test, all protective devices in overhead communications lines were damaged at distances out to 500 kilometers; the same event saw a 1,000 kilometer segment of power line shut down by these effects. Failures in transmission lines, breakdowns of power supplies, and communications outages were wide-spread.



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