Theory of Liquid PropelIant Rocket Combustion Instability and Its Experimental Verification

A straightforward theoretical formulat ion of the longitudinal h igh frequency rocket stability criteria is presented. Based on Crocco's sensitive combust ion t i m e lag theory, the derivation ii considerably simpler, a l though somewhat less rigorous, than previously published detailed treatm e n t s . A series of rocket motor experiments is described, demonstrat ing t h a t there exists ar upper l imit to the chamber length at which each mode of longitudinal h igh frequency pressure oscil lations will occur, and that this l imit is accurately predicted by the theory over a wide rang* of mixture ratios on two different injectors. The method used to compare experimental result! wi th the theoretical stability l imit predictions ( including a s imple experimental technique fo] determinat ion of the sensitive t i m e lag) is described.