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The fundamental scientific issues impeding the integrataion of laser diffraction particle sizing techniques into intelligent sensors for next generation propulsion systems have been identified. This research contributes to the knowledge base necessary to significantly advance the laser diffraction concept. The research addresses three areas, inverse scattering algorithms, multiple scattering, and the problems of laser beam deflections due to refractive index gradients in hostile propulsion environments. Progress has been made in the development of direct integral transform techniques for the inverse problem which potentially can operate at frequencies on the order of 10 kHz as needed for propulsion system sensors.Adequate inversion performance on bi modal distributions with signal to noise ratios as low as 10% has been demonstrated. The multiple scattering problem has been formulated as a matrix operation, and a corresponding scheme for the inversion of diffraction data under multiple scattering conditions has been proposed. A prototype computer generated hologram which generates a hollow cone of scattered light has been fabricated. Experiments are underway to demonstrate the usefulness of this development to the inverse multiple scattering problem. Finally, a concept to allow laser diffraction particle sizing sensors to function autonomously in environments where transient beam deflections are significant has been proposed and proof of principle experiments have begun.