P80 SRM Pressure Oscillations Reconstruction

Large solid rocket motors (SRMs) may exhibit pressure oscillations (PO) during their quasi-steady-state due to the coupling between chamber acoustic, usually the longitudinal modes, and other typical physical phenomena related to the combustion products flow, leading to a resonant condition. Although dissipative effects, occurring inside the motor chamber, prevent the reaching of high PO level, oscillating phenomena induce a dynamic environment on the launcher which could reduce payload comfort and safety. Both large segmented SRMs - e.g. Ariane 5 and Space Shuttle boosters - and monolithic finocyl SRMs - e.g. P80 of VEGA, exhibit pressure oscillations phenomena but in different functioning phases: the second half of the SRM operative life for segmented SRMs and the first half for aft-finocyl ones. This study aims to discuss and analyze the signatures and the associated dispersion of PO phenomena in P80 SRM, exploiting data provided by the 11 flights (VV01-VV11) successfully accomplished by VEGA launcher. Pressure oscillations are characterized both in time and frequency domain. The experimental P80 SRM PO signature are then reconstructed by means of the Q1D model named AGAR, showing the capability of the model to represent with good correlation the whole PO scenario and to recover also the data dispersion