Roll torque prediction in SRM: Practical applications

The production of an unpredicated roll torque, during the launch phase of solid rocket motor (SRM), is not an uncommon event. One of the possible reason of this phenomenon can be attributed to the complex flow field inside the combustion chamber. Anyhow, at the moment, the mechanism at the origin of roll torque has not yet been fully clarified. Available fligh data, obtained from existing launchers, have shown the presence of a significant roll torque, expecially when SRM are used. In most cases roll torque is stronger during the initial phase of fligh when slots in the combustion chamber are still present. Unfortunately, a model for prediction of roll torque in SRM is not yet clearly established. Analogously, CFD simulation as a tool for roll torque prediction is not a common tecnique, even if it is not a complete novelty. Aim of the present work is to investigate and better understand, by means of CFD simulations, the relation between internal geometry of the combustion chamber of a slotted SRM and the presence of roll torque. The complex mechanism governing this phenomenon has been reproduced by means of CFD simulation. Several numerical simulations have be conducted using X-259 Antares II and Castor I as reference motors, showing the basic mechanism of roll torque generation in SRM. As result, a good agreement in the qualitative behaviour and in particular in variation with time of roll moment has been found. Copyright © (2012) by the International Astronautical Federation.