Application of the RIT Model to Mateiral Selection for Zero Erosion Throats for Rockets Firing Aluminized Propellants

"The erosion of four transition metal carbides in a 6100F rocket nozzle test has been correlated with predicted thermochemical reactions with the alumina formed by an aluminized propellant. Correlation with the reaction initiation temperature model (RITmodel) will permit improved compositions to be predicted. Extension of the model to both lower and higher alulminized propellants, longer firing times, higher chamber pressures and to the onset of cavitation loss is needed before the model can be usedmost effectively.Current design of throats for 21% aluminized propellants use massive tungsten inserts to conduct the heat away to maintain a surface temperature below the melting point of tungsten at 6170F. This restriction is removed with carbides that often melt above7000F. Replacement of tungsten (density 0,7 lbs/inch^3) wuth niobium carbide plus graphite could reduce the weight of the Mark 104 nozzle from 43 to 32 lbs, as well as allow an increase to 6500F flame temperatures.Establishment of the RIT model will permit clean sheet nozzle designs to be made, will permit higher aluminized propellants to be used for longer firing times, and will reduce both weight and cost compared with nozzles using tungsten inserts. In additionto the prediction of improved compositions to allow higher temperatures, longer times and higher pressures, the program will lead to better understanding of reacitons at the throat. Understanding often lends to im