In this work, a method for experimentally determining a local characteristic velocity, , is presented for purposes of analyzing rocket combustion progress based on in-situ laser absorption spectroscopy measurements of temperature and gas composition. Measuring from spatially-varying thermochemical properties provides an alternative to the classical evaluation, which uses global chamber pressure and mass flow rate measurements. Accordingly, the novel method provides more detailed insight to the underlying mechanisms (multi-phase thermochemistry, diffusive mixing, turbulence, etc) governing combustion performance in the spatial domain. The method is demonstrated on an RP-2/O2 liquid-propellant rocket engine (LRE) and a PMMA/O2 hybrid rocket combustion experiment. Localized results for the LRE are obtained via in-chamber measurements of temperature, CO, and CO2 and are presented over a range of pressures ( 28–83 bar) and mixture ratios (MR = 2.5–5). For the hybrid rocket combustion experiment, one-dimensional tomographic reconstruction techniques are used to spatially-resolve the flow-field thermochemistry and obtain spatially-resolved measurements of temperature, CO, CO2, and H2O. These measurements are compiled to obtain spatially-resolved images of the combustion zone. The results from both experiments are compared to the theoretical expected from chemical equilibrium, providing for a method to assess combustion performance or progress locally within the combustion zone.

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