Dynamic Responses of Solid Rockets during Rapid Pressure Change

Abstract

Solid rocket performance during rapid pressure excursions differs greatly from predictions based on steady-state burning rate data. Rapid pressurization (150-250 kpsi/sec) following a sudden throat area decrease in a low L* combustor produces pressure overshoots of 10% and indicated burning rate overshoots in excess of 50%. A transient internal ballistics model was developed incorporating nonsteady continuity and energy equations for the chamber, nonsteady energy equation for the propellant condensed phase, and a modified Zeldovich heat feedback function for the propellant (which for the conditions considered is known to burn with a thin quasi-steady reaction zone). Sensitivity analyses using the model indicate that accurate surface temperature and temperature sensitivity data are needed. With reasonable estimates of surface reaction zone temperature and measurements of temperature sensitivity of burning rate, good agreement between the measured and the calculated p vs t was found for a nonmetallized composite propeliant in a low L* combustor. High pressure exponent, high temperature sensitivity of burning rate, high dAJdt, low burning rate, and low L* prominently increase the dynamic effects.