The Effects of a Low-Altitude Nuclear Burst on Millimeter Wave Propagation
ROME AIR DEVELOPMENT CENTER GRIFFISS AFB NY
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This report examines the limitations imposed on mm wave propagation by the dust produced by a low altitude nuclear burst. The closer the burst is to the surface, the larger will be the dust loaded into the fireball. The fireball absorbs, scatters and refracts the propagated wave and may also produce scintillations. In this study, only losses due to absorption and scattering are calculated, Since there is a great deal of uncertainty as to how representative the dust model is of the true nuclear environment, a sensitivity analysis of attenuation dependence of the pertinent dust parameters was first conducted. It was found that the dust attenuation is heavily dependent on the maximum particle radius, the number of large particles in the distribution and the real and imaginary components of the index of refraction over the range from dry sand to clay. The attenuation is also proportional to the fraction of the atmosphere filled with dust. The total attenuation produced by a 1 megaton burst at the surface is then computed using the WESCOM code. The attenuation includes losses due to fireball ionization, dust and atmospheric oxygen and water vapor. Results are obtained as a function of time after burst, distance from burst, elevation angle and frequency up to 95 GHZ It is found that very high attenuations occur within about 20 sec after the burst if the path intersects the fireball, At later times attenuations of the order of tens of dB are possible due to dust alone. After several minutes the larger dust particles have settled and attenuations of several dB are present.
- Radiofrequency Wave Propagation