如果月球上没有大气层,您能否将卫星送入距月球仅100英尺高的轨道上? If there is no atmosphere on the moon, can you put a satellite to orbit it only as high as 100 feet from the moon?

【翻译自Quora】

@ Bill Otto Lived next to NASA Huntsville;became manned spaceflight SME 的回答

No.

At first it seems possible. Even NASA thought it would be feasible in the 1960s to orbit as low as 50 km. However, the moon does not have perfectly symmetric mass distribution (in fact it is quite “lumpy” with mass concentrations called “mascons”), so its gravity varies significantly around its surface. The Apollo astronauts actually placed two small satellites in low lunar orbits before NASA was aware of how lumpy the moon’s gravity was. One of these satellites crashed within days because of the uneven lunar gravity. The other survived because by chance it was in a stable orbit. (One of the four known “frozen” orbits.)

乍看似乎是可能的。 甚至1960年代的NASA也曾认为低至50公里的轨道运行是可行的。 但是,月球的质量分布并不完全对称(实际上,它的质量分布呈“块状”,称为“ mascons ”),因此月球的重力在其表面附近变化很大。 在美NASA意识到月球引力有多大之前,阿波罗宇航员正将两颗小型卫星放到月球低轨道上。 由于月球重力不均,这些卫星之一在几天之内坠毁。 另一个幸存下来是因为它偶然处于稳定的轨道上。 (四个已知的“冻结”轨道之一。)

100 feet above the highest point (I say highest point because you don’t want to hit a mountain or the rim of a big crater) on the moon does not leave enough margin for the gravity variations, and the satellite would dip too close to the moon and crash before even a few orbits were completed. It would be extremely difficult if not impossible to find an orbit that is quasi-stable at that altitude, and even then the slightest variation (perturbation) would drive it into chaos and a crash would occur. A satellite would probably need to be at least 50–100 km above the lunar surface before a stable orbit could be found.

月球上的最高点上方100英尺(我说最高点,是因为您不想撞到山顶或大陨石坑的边缘)没有足够的余量来承受重力变化,卫星将有可能离因为引力而离月球太近而坠毁,甚至可能都并没有飞完几次轨道。 要找到在该高度上准稳定的轨道,即使不是不可能,也将是极其困难的,就算找到了,最小的变化(扰动)也将使其陷入混乱,并坠毁。 在找到稳定轨道之前,卫星可能需要距离月球表面至少50-100 km。

If it were not for mascons, craters and mountains, 100 feet would still be an issue due to the tidal effect of Earth’s gravity, the effect of solar wind, and if your satellite is made of metal, the magnetic field of the Moon. The magnetic field also happens to be “lumpy” so you could easily dip 100 feet just due to the magnetic field variations. (A conductor moving through a magnetic field generates eddy currents within the conductor which in turn produce a force on the object within the magnetic field.)

如果没有 mascons ,陨石坑和山脉,但由于地球引力的潮汐效应,太阳风的影响以及如果您的卫星是由金属制成的,那么月球的磁场也会使100英尺成为一个问题。 磁场也恰好是“块状”的,因此由于磁场的变化,您很容易就可以下降100英尺。 (导体在磁场中移动会在导体内产生涡流,进而在磁场内对物体产生作用力。)

【评论区】

@ Stephen Malbon Contract software developer, .NET, SQL Server databases, C/C++/C#, VB,

The Apollo program placed exactly two (2) small satellites into lunar orbit. By pure blind luck the first one of these was very close to being in one of the “frozen” low lunar orbits and remained in orbit for nearly two years. The second happened to placed into almost the most unstable LLO and lasted 35 days. These satellites were deployed by Apollo 15 and 16 respectively.

阿波罗计划将两颗小型卫星放入了月球轨道。 但纯粹由于运气不佳,第一个非常接近处于“冻结”低月球轨道之一,并在轨道上停留了近两年。 第二个恰好放置在几乎最不稳定的LLO中,持续了35天。 这些卫星分别由阿波罗15号和16号部署。

答主:

Thanks, it was quite a while ago and I am not sure whether my memory is bad or whether the briefing I attended was already third hand information. Thank you for the correction. At any rate, we learned eventually that there are many unstable orbits and few “frozen” ones.

谢谢,已经有一段时间了,可能是我的记性不好,或者我看到的信息是第三手信息。 谢谢你的纠正。 无论如何,我们最终了解到,不稳定的轨道很多,“冻结”轨道很少。

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