针对火箭基组合循环(RBCC)动力飞行器上升段轨迹快速规划问题，提出了一种基于降阶模型燃耗最优推力近似解和高度-速度剖面解析设计跟踪的燃耗近最优轨迹快速规划方法。首先，基于奇异摄动和能态近似理论对上升段动力学模型进行降阶，推导了燃耗最优模态切换方程和推力近似解。随后，基于飞行机理分析，设计了三段解析形式的高度-速度剖面并给出了过程约束施加方法；考虑轨迹最优性，将燃耗最优模态切换方程作为分段参数求解依据，设计了基于多段轨迹序贯迭代的剖面参数求解策略以满足终端高度、速度约束；最终，设计了基于二分法的剖面参数闭环迭代校正算法以满足终端弹道倾角约束，进而实现燃耗近最优的上升段多约束轨迹快速规划。以某型RBCC飞行器为例开展上升段轨迹规划仿真，验证了本文方法的有效性、快速性以及多任务适用性；且与传统优化方法相比，本文方法能够保持相近的燃料消耗并具备更高的计算效率。

To address the rapid trajectory planning problem for the ascent phase of Rocket-Based Combined Cycle (RBCC) powered vehicles, this paper proposes a fuel-near-optimal trajectory planning method based on reduced-order model-derived fuel-optimal thrust approximation solutions and analytical altitude-velocity profile tracking. First, the ascent dynamics model is reduced through singular perturbation theory and energy-state approximation, deriving fuel-optimal mode switching equations and thrust approximation solutions. Subsequently, based on flight mechanism analysis, a three-segment analytical altitude-velocity profile is designed with constraint enforcement methods. Considering trajectory optimality, the fuel-optimal mode switching equations are employed as basis for segment parameter determination, developing a sequential iterative strategy for multi-segment profile parameter calculation to satisfy terminal altitude and velocity constraints. Finally, a bisection-based closed-loop correction algorithm is designed to meet terminal flight path angle constraints, thereby achieving rap-id multi-constrained fuel-near-optimal ascent trajectory planning. Simulation studies on an RBCC vehicle validate the method's effectiveness, computational efficiency, and multi-mission adaptability. Compared with conventional optimization methods, the proposed approach maintains comparable fuel consumption while demonstrating superior computational efficiency.