A systematic study has been conducted on a composite solid propellant formulation using hydroxyl-terminated polybutadiene (HTPB) prepolymer with varying molecular weights and hydroxyl values. Fairly extensive regions of resin parameters have been studied. Contours of important propellant properties have been laid down. In this set of experiments, varying levels of diol and triol contents were used at two different NCO/OH ratios to arrive at the optimum level needed for different grades of HTPB resin. It is seen that different grades of HTPB resin require varying levels of diol-triol contents to give similar properties for the end product. Also, for the best performance, varying the diol-triol ratio at the optimum level of the diol-triol content is necessary.