The authors have been developing CAMUI type hybrid rockets which have a new fuel grain design to accelerate burning rate. Regression formulae for CAMUI type rockets have been developed as functions of local O/F. The authors carried out combustion tests with various oxidizer flow rate and burning duration to obtain empirical constants of these regression formulae. Additionally, a simulation model of static firing was built using the fuel regression formulae. In these studies, regression rates were mean values during firing. This paper discusses the effect of firing duration on the accuracy of regression formulae by using the simulation model.
