Abstract Onboard computation of a fuel-optimal trajectory is an indispensable technology for future lunar and planetary missions with pinpoint landings. This paper proposes a throttled explicit guidance (TEG) scheme under bounded constant thrust acceleration. TEG is capable of achieving fuel-optimal large diversions with good accuracy and can find optimal solutions. Thus far, the TEG algorithm is unique as it offers an explicit and simultaneous search method for the fuel-optimal thrust direction and thrust magnitude switching in predictor-corrector iterations. Fast numerical search is realized with a straightforward computation of seven final states (position, velocity, and the Hamiltonian) from seven unknowns (six adjoint variables for position and velocity and one final time). In addition, global convergence capability is enhanced by implementing the damped Newton's method. A number of simulations of large diversions show the excellent convergence of the TEG algorithm within at most 15 iterations from a cold start. The experimental results of the runtime measurement of the TEG algorithm support its real-time feasibility on a flight processor. These features of the TEG are suitable for onboard guidance of pinpoint landings.

中文翻译：

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在有界推力加速度下精确着陆的节流显式引导

摘要 燃料最优轨迹的机载计算是未来月球和行星精确着陆任务不可或缺的技术。本文提出了一种在有界恒定推力加速度下的节流显式制导（TEG）方案。TEG 能够以良好的精度实现燃料优化的大改道，并且可以找到最佳解决方案。到目前为止，TEG 算法是独一无二的，因为它为预测器-校正器迭代中的燃料最佳推力方向和推力大小切换提供了一种明确且同时的搜索方法。通过从七个未知数（位置和速度的六个伴随变量和一个最终时间）直接计算七个最终状态（位置、速度和哈密顿量）来实现快速数值搜索。此外，通过实施阻尼牛顿法增强了全局收敛能力。许多大型改道的模拟表明，从冷启动开始，TEG 算法在最多 15 次迭代内具有出色的收敛性。TEG 算法运行时间测量的实验结果支持其在飞行处理器上的实时可行性。TEG 的这些功能适用于精确着陆的机载引导。