A Fully Three Dimensional Analysis of Pre-Ignition Transient in Solid Rocket Motors

Ignition transient of SRM with a 3D star-shaped finocyl region and high energy igniter is an operative phase characterized by a very strong unsteady behavior that often causes net thrust and pressure oscillations, possible over-pressures, possible hang-fires or misfires, transient of pressure loads on the propellant grain, dynamic loads on the launch vehicle and on the ground structure. A numerical code has been developed to analyze and to predict these strong unsteady phenomena. The code is a three dimensional, compressible, inviscid and multifluid solver. The third stage of the new European small launcher Vega, Zefiro 9, and the prototype Zefiro 16, will be analyzed. A detailed analysis of ignition transient of Zefiro 16 has been shown; a preliminary analysis of Zefiro 9's ignition transient has been presented.