A highly reflective sail provides a way to propel a spacecraft out of the solar system using solar radiation pressure. The closer the spacecraft is to the Sun when it starts its outward journey, the larger the radiation pressure and so the larger the final velocity. For a spacecraft starting on the Earth's orbit, closer proximity can be achieved via a retrograde impulse from a rocket engine. The sail is then deployed at the closest approach to the Sun. Employing the so-called Oberth effect, a second, prograde, impulse at closest approach will raise the final velocity further. Here, I investigate how a fixed total impulse ($\Delta v$) can best be distributed in this procedure to maximize the sail's velocity at infinity. Once $\Delta v$ exceeds a threshold that depends on the lightness number of the sail (a measure of its sun-induced acceleration), the best strategy is to use all of the $\Delta v$ in the retrograde impulse to dive as close as possible to the Sun. Below the threshold, the best strategy is to use all of the $\Delta v$ in the prograde impulse and thus not to dive at all. Although larger velocities can be achieved with multi-stage impulsive transfers, this study shows some interesting and perhaps counter-intuitive consequences of combining impulses with solar sails.

中文翻译：

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太阳潜水员：结合太阳帆与Oberth效应

高反射率的帆提供了一种利用太阳辐射压力将航天器从太阳系中推出的方法。航天器开始向外飞行时离太阳越近，辐射压力越大，因此最终速度越大。对于在地球轨道上启动的航天器，可以通过火箭发动机的逆行脉冲来实现更接近的接近。然后将帆展开到最接近太阳的位置。利用所谓的Oberth效应，以最接近的方式进行第二次渐进式脉冲，将进一步提高最终速度。在这里，我研究固定总脉冲数（$\Delta v$）最好在此过程中进行分配，以最大程度提高无穷远处的风速。一次$\Delta v$ 超过取决于帆的明度数的阈值（衡量其太阳加速度），最好的策略是使用所有 $\Delta v$在逆行的冲动下，潜水应尽可能靠近太阳。低于阈值，最好的策略是使用所有$\Delta v$在前进的冲动中，因此根本不潜水。尽管可以通过多级脉冲传输实现更大的速度，但这项研究表明，将脉冲与太阳帆结合起来会产生一些有趣的，甚至可能违反直觉的后果。