Structural Dynamic Analysis of Solid Rocket Motor Resonant Burning

Abstract

Thetermresonantburningisusedbystructuraldynamiciststodescribethecoincidenceofvortex sheddinginside solid rocketmotorswith frequenciesoflongitudinalacousticmodesofthecombustionchamber. Thecorresponding thrust oscillations excite launch vehicles that use solid rocket motors; however, system responses from resonant burningaregenerallyenvelopedbythoseforothere ightevents,and,traditionally,thedesignofprimarylaunchand space vehicle structure has not been established by the resonant-burning dynamic environment. Recently, though, this phenomenon has emerged as a major dynamic event for new small-sized launch vehicles with single-segment motors as stages. An overview of resonant burning is provided, with an emphasis on features that ine uence structural dynamic analyses. Statistical assessments of motor internal pressure oscillations, and of spacecraft loads induced by resonant burning, are conducted. The results indicate that the phenomenon cannot generally be characterized by a normal probability distribution and that care must be taken when dee ning a resonant-burning environment for structural design. It is also shown that this excitation source is quasi periodic and that structural dynamic analyses that use stationary thrust oscillations can severely overpredict spacecraft accelerations.