Transmissive solar sail designs have been proposed with performance and utility benefits over traditional solar sails, particularly in low Earth orbit. The functional element of these new sails is their refractive or diffractive surface pattern. This paper explores the design of refractive sail patterns using numerical optimisation, and explores the validity of using model-free reinforcement learning algorithms for this purpose. In particular, the performances of triangular prism and semi-cylindrical lightfoil patterns from prior literature are iteratively improved. To do this, a ray tracing optical simulation was developed that models the solar radiation pressure and torque per unit area of illuminated, refractive patterns in a vacuum. Meanwhile, a numerical optimiser was developed to iteratively improve upon simulated patterns according to user-defined fitness functions. Depending on their purpose, patterns were optimised for either tangential-to-sail solar radiation pressure or self-stabilising corrective torque at a Sun-pointing attitude, or range of attitudes. The optimiser was shown to be capable of substantially improving the performance of optical elements, particularly through the harnessing of total internal reflection. In one case, the numerical optimiser was shown to improve the maximum tangential radiation pressure of an analytically optimised polystyrene prism pattern by 58%. In another case, the optimiser improved the peak corrective torque of a pattern of polyethylene terephthalate lightfoils by 74%.

中文翻译：

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透射式太阳帆折射表面图案的建模和数值优化


与传统太阳帆相比，透射式太阳帆设计具有性能和实用优势，尤其是在近地轨道上。这些新帆的功能元素是它们的折射或衍射表面图案。本文探讨了使用数值优化设计折射帆图案，并探讨了为此目的使用无模型强化学习算法的有效性。特别是，迭代改进了以往文献中三角棱柱形和半圆柱形光箔图案的性能。为此，我们开发了一种光线追踪光学仿真，该仿真模拟了真空中照射折射图案的单位面积的太阳辐射压力和扭矩。同时，开发了一个数值优化器，以根据用户定义的适应度函数迭代改进模拟模式。根据其目的，模型针对切向航行的太阳辐射压力或指向太阳姿态下的自稳定校正扭矩或姿态范围进行了优化。优化器被证明能够显着提高光学元件的性能，特别是通过利用全内反射。在一个案例中，数值优化器被证明可以将分析优化的聚苯乙烯棱柱图案的最大切向辐射压力提高 58%。在另一个案例中，优化器将聚对苯二甲酸乙二醇酯光箔图案的峰值校正扭矩提高了 74%。