Combustion instability has long been recognized as one of the most important but difficult problems in the development of propulsion systems. The U.S. and the former Soviet Union were simultaneously working during the Cold War to solve the instability problem. However, the scientific basis and engineering approach employed by the Soviets remained largely unknown to the Western world. This book—much of it formerly classified material--is a clear exposition of much of the theoretical work on combustion instabilities, performed in support of the Soviet liquid rocket program during its most vigorous period. While there are similarities between Western and Eastern works, there are many distinct differences. The author was one of the small group of Soviet theorists actively engaged in all of the Soviet liquid rocket programs. His development of the field is firmly grounded in fundamental ideas, and progresses to applications of a general sort.