Collision Induced Loads in Pro-Injectors of ADDA Rocket Motors

Abstract

The major improvement introduced by ADDA in space propulsion is the new Compound Rocket Motor concept (CRM), where, in contrast to the inefficient hybrid motors, the completion of combustion is very high. This new motor construction is also remarkable through its new injector type called pro-injector, currently under examination for patenting, with the capability of cutting out the dangerous reversed flow of the liquid component in a definitely short amount of time. The pro-injector device, quite critical when instable, high energy compounds like nitrous oxide are sprayed into the CRM combustion chamber, was designed, tested and successfully applied within the NERVA-ORVEAL project coordinated by the ADDA research team in cooperation with the AEROFINA partner. The results of the research regarding the pro-injector behavior are described. It was observed that unexpectedly high dynamic loads appear upon the seat of the pro-injector due to the collision-type motion when a shock wave in the combustion chamber develops. It is shown that such occurrence impedes application of fragile materials in the construction of the injector seat which otherwise would better serve the construction. Numerical simulations are presented as performed under rational assumptions regarding the mechanical behavior of mobile parts, in order to secure a smooth work of the device at the fast response required to downwind gas pressure shocks. The pro-injector proved being an innovative device currently submitted for patenting