A Theory of Unstable Combustion in Liquid Propellant Rocket Systems

On the basis of an hypothesis that low-frequency oscillat ions (chugging) somet imes observed in l iquid propellant rocket engines , are the result of oscillatory propellant flow induced by a combust ion t ime lag, condit ions for the suppression of such oscil lations are derived. It is found that stability can be achieved by increases in the l ength of feed l ine, the velocity of the propellant in the feed l ine, the ratio of feed pressure to chamber pressure, and the ratio of chamber volume to nozzle area. Equations are given for the frequencies of osci l lation. Examinat ion of the equation for stability indicates that selfigniting propellant combinat ions are likely to be more stable than n o n self-igniting systems.