ULTRAFAST DIAGNOSTICS FOR NOVEL ENERGETIC MATERIALS IN ROCKET ENGINE ENVIRONMENTS

The objectives of this Phase-II research effort is focused on transitioning noninvasive diagnostic techniques based on ultrafast lasers for characterizing nanoenergetic materials and their performance in rocket engine environments. Through the use of ultrafast laser imaging and spectroscopy, it is possible to isolate and characterize each physical process from initiation through energy release and to do so noninvasively. The specific objectives of this effort are (1) in-situ characterization of nanoenergetic ignition and heat release using picosecond (ps) and femtosecond (fs) time-resolved spectroscopy in bench-scale micro- and macroscale reactors, and (2) development of high-bandwidth (1-10 kHz) femtosecond CARS thermometry for directly measuring the effects of novel energetic materials on energy release in transient, high-pressure rocket engine environments. These studies will focus on the effects of nanoparticle characteristics, such as passivation and agglomeration, on performance metrics, such as heat release rate and flame propagation. During this effort, various commercial nanoparticles as well as specially synthesized nanoparticles will be evaluated to assess their potential for rocket propulsion applications. The improved diagnostic capability will play a key role in the synthesis of novel energetic materials, development and validation of predictive numerical models, and the design of propulsion systems that utilize these materials. BENEFIT: The reliability and performance of rocket combustors can be severely degraded by dynamic system behavior that is enhanced under high energy density conditions. Predicting and controlling this behavior becomes even more critical with the use of novel energetic materials and new additized propellants. The proposed research effort will provide new diagnostic capabilities that will enable the Air Force and original equipment manufacturers to address the challenges associated with nanoenergetic initiation, ignition, hot-spot formation, shock-wave formation, propagation, and energy release. New capabilities afforded by ultrafast diagnostics include the measurement of reactions with picosecond resolution, measurement of temperatures and species with high spatial resolution, measurement of surface phenomena relevant to solid- and gas-phase chemistry, and measurement in unsteady, high-pressure environments. The diagnostic systems developed in this work will transition emerging instrumentation based on ultrafast laser technology for use in educational institutions, DoD laboratories, and industry. This will play a key role in the development of novel energetic materials, validation of predictive numerical models, and the design of propulsion systems that utilize these materials. Ultimately, this will lead to improved control strategies ensuring rapid and stable combustion during critical phases of rocket propulsion.