动力增程型高超声速飞行器的再入轨迹规划

为研究飞行过程中的动力装置启动时刻及燃料消耗情况，对轨迹进行优化，进而提出一种动力增程型弹道的再入模式。推导Sanger弹道的解析解，分析得到高超声速飞行器再入航程最优所必须的迎角及初始速度取值条件等相关前提，利用该结论设计动力装置的启动方式使航程最远、燃料利用率最大。将轨迹设计为Sanger弹道和拟平衡滑翔弹道相结合的混合弹道:再入前期利用助推器间隔点火的方式形成等高类周期跳跃弹道以保证足够远的航程; 再入后期采用拟平衡滑翔弹道，将最优控制问题转化为复杂多约束非线性规划问题，性能指标综合考虑了轨迹平滑和航程。仿真实现了所提出的动力增程型再入弹道; 并在燃料充足、弹道倾角取值合适的条件下，得到“打水漂”弹道形式，该弹道能量损失极慢，具有足够远的飞行能力。仿真表明，与不同点火方式及求解方法得出的弹道相对比，所提动力增程型再入弹道具有3.47~3.84倍的航程、1.04~1.18倍的末端动能以及4.47~15.79倍的燃料利用率。 

Reentry trajectory planning for range-extended hypersonic vehicles with boosters

A reentry trajectory for a hypersonic vehicle with an accessory rocket-powered engine is optimized in terms of the ignition time of boosters and the fuel consumption, based on which a reentry mode of range-extended trajectory is proposed. The analytical solution of Sanger trajectory reveals the conditions of the attack angle and initial velocity for the vehicle to travel the longest distance, which can be used to manipulate the boosters with the goal of maximum travel distance and minimum fuel consumption. The reentry trajectory is designed as a combination of Sanger trajectory and quasi-equilibrium glide trajectory. In the first stage of reentry, the vehicle flies along an equal altitude quasiperiodic trajectory guaranteed by boosters interval ignition, and ensures that the range is longest. In the second stage of reentry, the vehicle flies along a quasi-equilibrium gliding trajectory which is the solution of an optimal control problem with trajectory smoothness and distance as the performance index and the problem is converted and solved by constrained nonlinear programming. Finally, the proposed reentry trajectory is simulated and the results show that the trajectory is quite analogous to the so called "stone skipping" under the conditions of sufficient fuel and appropriate path angle, which can efficiently use its mechanical energy of a stone to long range over a lake. Compared with the trajectories with boosters working in different modes and the trajectories solved in different ways, the proposed reentry trajectory has 3.47-3.84 times range, 1.04-1.18 times end kinetic energy and 4.47-15.79 times fuel availability.