The purpose of this program is the acquisition of detailed analytical and experimental information concerning the mechanisms of energy addition from propellant spray combustion to steady flow fields and propagating pressure disturbances. Data are to be obtained and used to evaluate present or formulate new expressions describing the dynamics that contribute to the coupling processes between the spray and gas flow fields. These expressions appear in steady-state and transient propellant combustion models and bear directly on the prediction of performance and onset of high frequency combustion instability in liquid propellant rocket engines. To overcome past difficulties in comparing analytical and experimental results, an experimental apparatus which produces a monodisperse propellant spray uniformly distributed throughout the combustor has been built. The motor, to be operated as a rocket engine combustor under either stable or transient conditions, provides for optical observation and is extensively instrumented to record pressure wave amplification or decay as a function of parameter variation. Test data (drop diameters, velocity and pressure wave growth or decay as functions of chamber length and initial conditions) can be input to the newly-developed combustion models and the validity of the coupling term expressions evaluated by directly comparing the resulting predictions to experimental data. These newly-developed combustion models are described in detail.