A study on pre-cooled turbojet-scramjet-rocket combined engines

The combined engines of air-breathing engine and rocket engine are promising as engines for single stage spaceplanes. High thrust to weight ratio at acceleration phase and high specific impulse at landing phase is required for the engines. The authors examine the engine concept that combines the pre-cooled turbojet engine with supersonic combustion ramjet engine and rocket engine. The precooled turbojet engine can achieve both high thrust to weight ratio and high specific impulse by controlling the equivalence ratio. In this study, the change of thrust to weight ratio and specific impulse is calculated with parameter of the equivalence ratio on the pre-cooled turbojet engine. The weight that can be left for the following flight is estimated with an assumed flight condition. The test that combined the pre-cooling heat exchanger with the turbojet engine was carried out on the fuel lean combustion mode for landing phase.