Predicted optical characteristics of solid rocket motor exhaust in the stratosphere

Optical characteristics of large solid rocket motor exhaust in the stratosphere are predicted for portions of the near-ultraviolet, visible, and near-infrared spectral regions. Mie scattering calculations show that attenuation by the alumina particles is caused principally by the large-particle mode of the trimodal particle size distribution, The local attenuation in the plume as a function of wavelength and the transplume total attenuation due to particles as a function of time are predicted for several wavelengths. An expression for the total surface area of the particles is derived in terms of known parameters and the Sauter mean diameter. Mie theory is then used to show that this Sauter mean diameter can be measured using a two-color transmissometer. The absorption spectra due to the chemical constituents are predicted for the 200-400-nm wavelength interval for several times after vehicle passage. It is predicted that these absorptions are comparable to the attenuations due to particle scattering.