水平起降两级入轨系统的质量估算方法及应用

针对近地轨道运输任务，考虑不同飞行阶段的推阻特性差异和不同发动机模态的比冲变化，提出了适用于水平起降两级入轨（TSTO，Two Stage To Orbit）天地往返运输系统的质量估算方法.以8 t有效载荷为任务需求，对比研究了涡轮基组合循环动力-可重复使用火箭（TBCC-RR，Turbine Based Combined Cycle-Reusable Rocket）、火箭基组合循环动力-可重复使用火箭（RBCC-RR，Rocket Based Combined Cycle-Reusable Rocket）和可重复使用火箭-可重复使用火箭（RR-RR，Reusable Rocket-Reusable Rocket）方案，分析了级间分离点、一级飞行器推阻比和一级飞行器结构质量分数等参数对设计结果的影响.研究结果表明，级间分离点设计对TSTO总体方案影响很大，若使用RBCC型飞行器作为第1级，建议在超燃冲压模态后即进行两级分离；TBCC-RR方案比RBCC-RR方案起飞总质量更小，但RBCC-RR方案一级飞行器结构质量更小；减小TSTO系统起飞总质量的最有效途径是减小飞行器的结构质量分数，其次是提高飞行器的推阻比. 

Mass estimation method and its application for horizontal takeoff horizontal landing two stage to orbit system

Aiming at transportation missions to low global orbit, a mass estimation method was proposed for horizontal takeoff horizontal landing two stage to orbit (TSTO) transportation systems considering thrust-drag characteristics in different flight stages and specific impulse variations in different engine modes. Three schemes of turbine based combined cycle-reusable rocket (TBCC-RR), rocket based combined cycle-reusable rocket (RBCC-RR), and reusable rocket-reusable rocket (RR-RR) were designed and compared for a mission to deliver 8 t payloads to a 200 km orbit. Influences of several parameters on design results were analyzed, including the separation point, throat-drag ratio and structure mass fraction of the first stage vehicle. The position of separation point has a great influence on TSTO schemes. If a RBCC vehicle is used as the first stage, it's recommended that the separation take place when the scramjet is turn off. Though TBCC-RR scheme leads to a smaller gross takeoff mass, RBCC-RR scheme has a smaller structure mass. The most effective way for gross mass reduction is to cut down the structure mass fraction and another approach is to improve throat-drag ratio of the vehicle.