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When near the south pole of our Moon a permanent human community is established to search for and produce water in the permanently shadowed regions there, it would be nice to have some light from above !

Would it be possible to instal a framework of mirrors in space above such a human settlement so there would not have to be worked in constant darkness ?

Within the framework the mirrors could turn independent from each other and could function as solar sails as well to withstand the gravity of the Moon.

Of course, software would be needed to anticipate the constantly changing position of the framework by changing the angle of the different mirrors independently.

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    $\begingroup$ Theoretically, you could have a moon rotation synchronous satellite that reflects sunlight onto the moon's surface. Of course, mirrors can't reflect more light that they receive, so the total mirror surface area would have to be at least 10% as large as the village, probably more. $\endgroup$ – user7073 Nov 26 '19 at 15:43
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    $\begingroup$ So... you're proposing an object that floats above the surface, in a completely impossible orbit; or am I missing something here? If it's not in orbit, and it's "static" then it needs propulsion to counteract the moons gravity. You cannot have an orbit that "stays above the pole" 100% of the time. The whole statement "static in space" doesn't really make sense. $\endgroup$ – Magic Octopus Urn Nov 26 '19 at 16:32
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    $\begingroup$ Can you actually position a statite over the moon, though? $\endgroup$ – Starfish Prime Nov 26 '19 at 16:48
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    $\begingroup$ @starfishPrime Not over a pole while reflecting light to a specific position and maintaining attitude to counter-act gravity... Maybe the question should've been, "is a statite over the moon possible? What about over the poles?". I feel like that would've been more answerable than this is in its current state. This adds a bunch of extra layers of complexity to an already complex problem. $\endgroup$ – Magic Octopus Urn Nov 26 '19 at 16:48
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    $\begingroup$ Software wouldn't help the problem. You cannot get the delta-v you need, in the direction you need to counter-act gravity AND reflect the light back to a specific location on the surface in quantities that are needed for illumination at the poles. Especially seeing as this sail would need to be absolutely massive. $\endgroup$ – Magic Octopus Urn Nov 26 '19 at 17:05
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The answer is no, you cannot have a static satellite. It would require high delta-V continually thrusting the mirror upwards. Solar sails do not have high delta-V. But that is okay - if all you want is polar moonbase illumination, that problem is already solved:

  • Solution 1 -

Have a network of satellites with mirrors, and use them in turn as they pass near the poles - software could do this fairly easily.

  • Solution 2 -

Build mirrors on polar mountains - there are some that are continually in sunlight. This solves the entire problem at much lower cost, no fiddly orbits to worry about, and you could climb up and fix issues if there are problems.

  • Solution 3 -

Floodlights powered by solar panels, as suggested by Magic Octopus Urn

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  • $\begingroup$ Solution 3 - flood lights powered by solar energy. $\endgroup$ – Magic Octopus Urn Nov 26 '19 at 18:48
  • $\begingroup$ I like that @magic - I'll edit that in $\endgroup$ – Rory Alsop Nov 26 '19 at 19:14
  • $\begingroup$ @MagicOctopusUrn Taking Shoemaker as an example, isn't even the rim of this 51 km wide crater permanently shadowed ? Floodlights would be the best solution i think, but the electric cables could be very long. $\endgroup$ – Cornelisinspace Nov 26 '19 at 20:02
  • $\begingroup$ I don't think you're going to be illuminating a 51km diameter crater using any methodology. $\endgroup$ – Magic Octopus Urn Nov 26 '19 at 20:04
  • $\begingroup$ The disadvantage of Solution 2 is that in general , the mountains would be far from the moonbase, so the light from the mirror would be almost horizontal. $\endgroup$ – Cornelisinspace Nov 26 '19 at 20:06
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There isn't a problem with sunlight supply at the south pole. It's actually the opposite situation. One of the biggest attractions to the lunar south pole (after water) is the fact that there are areas there that are in almost constant sunlight. From the rim of Shackleton crater, the sun skims the horizon to a complete 360˚ as the lunar day progresses. It's quite feasible to have constant solar power for a polar settlement by placing cell arrays in the right places and linking them into a network.

If a base is deep into a crater (say to run an ice harvest operation) they could save on cable by beaming microwave power from the rim.

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