Thrust Anomalies at Ignition Transient of Solid Propellant Rockets

VEGA is the new launcher of the European Space Agency, currently in its final phase of development. Tailored for small payloads and low earth orbit missions, VEGA is a single-body four-staged launcher with three solid propellant rockets and one liquid propulsion upper module. The three SRMs, the first stage P80 (Europropulsion), the second Zefiro 23 (Avio Group) and the third Zefiro 9 (Avio Group) share the same finocyl configuration, characteristics and technologies. A fourth SRM, Zefiro 16 (Avio Group), has been developed in the past as a technological demonstrator of the Zefiro motor family. During the development and the qualification of the Zefiros and P80 SRMs, the characterisation and the analysis of the ignition transient phase has been carried out by a numerical simulation code SPIT (Solid Propellant Rocket Motor Ignition Transient), developed by the authors (SPqR Team). As a matter of fact, these numerical simulations proved to be useful to predict the behaviour of the motors during the ignition phase but also, through the analysis of the experimental results of the performed static firing tests, they can give a very deep insight of the physical phenomenology and the complex succession of events that characterize the ignition transient. Experimental results and quasi-ID simulations (SPIT) confirmed that the ignition transient can be characterized by strong unsteady phenomena and complex gas dynamic features as effects of the pressurizing gas on the acoustic excitation of the motor chamber. These phenomena will be discussed and the comparison between numerical simulations and experimental data will be presented. Copyright © 2010 by the International Astronautical Federation. All rights reserved.