Preliminary Analysis of an Airbreathing and Rocket Combined-Cycle Engine

Abstract

In this paper the characteristics of the rocket engines are compared with those of the airbreathing combined-cycle engines. The types of airbreathing engines are classie ed based on their e ight Mach numbers. The optimization of an airbreathing combined-cycle engine is presented. Based on the analyses of individual characteristics of hydrogen fuel, a rocket, and an airbreathing engine, a new combined engine cycle, known as the high-pressure hydrogen-expansion liquee ed oxygen cycle engine (LOCE), is presented. It is one type of rocket-based airbreathing combined-cycle engines whose specie c impulse can reach up to 3000 s, accounting for inlet air momentum loss, and 5300 s, without accounting for inlet air momentum loss. It successfully overcomes the inconsistency of the chamber pressure of a rocket engine and that of an airbreathing engine. Its liquefaction efe ciency is 5 ‐7 times higher than that of the typical liquee ed air cycle engine cycle. It has a high specie c impulse and a high thrust-to-weight ratio. The payload-totakeoff weight ratio of a two stage to orbit reusable launch vehicle with LOCE is 3.13%, based on current analyses. This cycle, integrated with the advantages of rocket and airbreathing engines, is one of the most promising means of achieving high performance at the low-speed phase (Ma = 0‐5) of e ight.