Internal Ballistics Simulation of NAWC Tactical Motors with SPINBALL Model

In the design and development of solid propellant rocket motors, the use of numerical tools able to simulate, predict and reconstruct the behavior of a given motor in all its operative conditions is particularly important in order to decrease all the planning times and costs. This paper is devoted to present the results of the internal ballistics numerical simulation of the NAWC tactical motors (motors n. 6 and n. 13) for their entire combustion time (ignition transient, quasi steady state and tail-off) by means of a Q1D unsteady numerical simulation model, named SPINBALL (Solid Propellant rocket motor INternal BALListic model). In particular, the attention is focused on the effects on the SRM behavior of the erosive burning, total pressure drops and the possible nature of the pressure overpeak, occurring during the last part of the ignition transient for both the SRMs. The final objective is, to develop an analysis/simulation capability of SRM internal ballistic for the entire combustion time, with simplified physical models, in order to reduce the computational cost required, but ensuring, in the meanwhile, an accuracy of the simulation greater than the one usually given by 0D models. The results of the simulations performed for the two NAWC tactical motors indicates a good agreement with the experimental data, as no attempt of sub-models calibration has been made, enforcing the ability of the proposed approach to predict the internal ballistics of SRMs. The numerical simulations shows that whereas the NAWC n. 6 overall internal ballistics is completely led by the erosive burning, which dominates the burning rate, causing the pressure peak occurring immediately after SRM start-up, the NAWC n. 13 instead is not driven by the erosive burning, which however is not completely negligible. Copyright © 2010 by . Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.