1. to calculate the pressure and mass flow. The performance of the motor( delivered specific impulse, Isp ) i s then calculated by a
2. The two key parameters required of the igniter-ignition model for predictive purposes are the ignition delay time and the peak pressure. To date, the simple model used i n the NPP appears to predict the peak pressure well, but under predicts the ignition delay time significantly. Figures . 2-10 show the ignition sequence for head end, middle, and aft end igniters, respective 1y. The head end pressure trace, velocity prof i1es, and pressure profiles are displayed i n a comparative manner so that the salient features can be secn. The formation of right- and left-running waves i s readily seen as i s the development of a shock wave near the exit of the motor. Head end and middle of the grain igniters posz no problems i n running the computer model. However, the strong shock which forms when the pressure pulse from an aft end igniter i s reflected from the head end closure leads to computational difficulties. The flame speed used in the computations shown i n Figures 4, 7, and 10 was unrealistically high i n order to smooth out the steep fronted pulse from the igniter. Despite the overall poor prediction of the ignition delay, the peak pressure reached after ignition was predicted to within 1%for the DUE0 notor as shown i n Figure 17. Grain Geflection
3. The next set of Figures, 11 - 16, show the effect of grain deformation on the internal ballistics of a nozzleless soli d rocket motors. The calculations shown i n these figures do not include erosive burning or an igniter model (the grain was assumed to be instaneously ignited). Theonly difference i n the calculations are the presence of the grain deformation effects. The condition temperature for these cases was taken to be -65' i n order t o accentuate the grain deflection due to cooldown. The effects of the grain deformation are observed t o be most pronounced during the volume filling transient when visco-elastic effects are most important. The