An Ignition-to-Burn Out Analysis of SRM Internal Ballistic and Performances

The use of numerical tools able to simulate and predict the behavior of a solid rocket motor, in all its operative conditions, is particularly important in order to decrease the experimental, design and development times and costs. In this paper, we present a new numerical tool, named SPINBALL, that comes out from the updating and development of the numerical, mathematical and physical models of the SPIT code. These improvements allow to extend the numerical simulation of SRM internal ballistic from the ignition transient, to quasi steady state and tail-off phases, allowing to use an unique numerical tool, with an quasi-1D unsteady approach, to predict the internal ballistic and performances of a given motor for its entire combustion time. In particular, we will focus our attention on the description of the SPINBALL grain burnback module, named GREG, that, with a Level Set technique, is able to accomplish the grain burnback analysis of 3D complicated grains, directly from STL grain input files. A cylindrical and a finocyl grain will be presented as test of GREG numerical model. Preliminary results of the operative conditions, for all the combustion time, of Zefiro 9, third stage of the Vega launcher, with a comparison between the experimental head-end pressure time history and the numerical one, are also shown.