Experimental and numerical analysis of narrowband coherent Rayleigh-Brillouin scattering in atomic and molecular species.

Coherent Rayleigh-Brillouin scattering (CRBS) line shapes generated from all narrow-band pump experiment, Direct Simulation Monte-Carlo (DSMC) approach, and published kinetic line shape models are presented for argon, molecular nitrogen, and methane at 300 & 500 K and 1 atm. The kinetic line shape models require uncertain gas properties, such as bulk viscosity, and assume linearization of the kinetic equations from low intensities (<1 x 10¹⁵ W/m²) operating in the perturbative regime. DSMC, a statistical approach to the Boltzmann equation, requires only basic gas parameters available in literature and simulates the forcing function from first principles without assumptions on laser intensity.

Invited article: Time accurate mass flow measurements of solid-fueled systems.

A novel diagnostic method is described that utilizes a thrust stand mass balance (TSMB) to directly measure time-accurate mass flow from a solid-fuel thruster. The accuracy of the TSMB mass flow measurement technique was demonstrated in three ways including the use of an idealized numerical simulation, verifying a fluid mass calibration with high-speed digital photography, and by measuring mass loss in more than 30 hybrid rocket motor firings. Dynamic response of the mass balance was assessed through weight calibration and used to derive spring, damping, and mass moment of inertia coefficients for the TSMB.