关键词: 航天运输系统;火箭发动机;空气喷气发动机;组合发动机

Abstract: The requirements on advanced aerospace transportation system is clearly stated. Inthis paper., the characteristics of the rocket are compared with those of the airbreathing combinedengine. The type of airbreathing engines, which performance is better than that of the rocket engine,must be classified by their flight Mach number. Reusable single stage to orbit spacecraft will emergeas a result of two-in-one combination of these two types of engines. It is to be expeted that the onlyway in the future development is the integration of advantages of the two types of engines. Theoptimal principles of airbreathing combined engine is presented. The thrust to weight ratio is moreimportant than the specific impulse in the course of flight. A new optimal combined engine cycle, highpressure hydrogen expansion Liquefying Oxygen Cycle Engine (LOCE), is put forward by analyzingindividual characteristics of the rocket and the airbreathing engine. It is a type of rocket based onairbreathing combined cycle engines (RBCC) which specific impulse can reach up to 35000m/s. Itsuccessfully solves the inconsistency of chamber pressure of rocket engine and that of airbreathingengine. Its liquefaction efficiency is 5-7 times higher than that of ordinary LACE cycle. It has highspecific impulse and high thrust to weight ratio. This cycle, integrated the advantages of rocket andairbreathing engines, is one of the best ways at low speed phases (Ma= 0~5).

Key words: Earth-orbit transportation system;Rrocket engine;Air breathing engine;Combination engine