598. Prediction of Mass Properties for Solid Rocket Motors

Paper

Abstract

The success of a solid rocket motor program often hinges on the Mass Properties Engineer’s ability to accurately predict mass properties from initial design drawings. The mean average (nominal) weight and the weight variation about the nominal of the total motor, propellant, and the expended inerts, are generally the most critical of the mass properties. Costly redesigns and schedule slips can result from the failure to accurately predict these values.
Prediction accuracies (calculated versus actual) of within 0.5% for both the nominal values and the variations have been achieved by Aerojet-General. Two sources of information which are often overlooked have been found to be essential in obtaining and maintaining this accuracy. The first is the utilization of historical data from previous programs, and the second is the close coordination and communication between weights personnel and other program personnel.
Historical data from past programs are utilized in the prediction of the variables which must be determined for each motor component. The total variations are then derived by a statistical summation.
Effective communication and coordination are greatly enhanced by participation of the weights personnel in design review meetings and by documentation controls, including: the specifying of maximum weight on drawings (for items where control of the dispersion is necessary); the receipt and monitoring of all actual weight records; the preparation and publication of Loading Data Reports required for each motor log prior to acceptance by the customer, and the requirement for a weights activity signoff before a drawing or revision is released.