Solid-Propellant Combustion Response Function from Direct Measurement Methods: ONERA Experience

Usually, the pressure-coupled response function of a solid propellant is determined using the traditional indirect methods such as T-burner or modulated exhaust jet technique. A few direct methods, based on wave propagation through the solid-propellant grain, exist: microwave and ultrasound techniques. There is also the magnetohydrodynamic technique derived from magnetic velocimetry through the gas phase. The theoretical approaches of each method are explained and are coupled with an acoustic analysis of the pressure oscillations. The response function is determined using these direct and nonintrusive methods for the Ariane V solid propellant (HTPB‐ AP‐ Al) and a nonmetalized propellant. Results obtained for composite propellants, such as that of the Ariane V, show the accuracy of each method and underline the advantages or disadvantages of each method as far as ONERA’ s experience can carry it out. Direct methods are nonintrusive but are limited because of their principle itself. There is a frequency limit above which the measurement cannot be performed. Finally, the objectives of future ONERA work are proposed.