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I watched Independence Day: Resurgence the other day. In it, Earth's first line of defense is a lunar base (that gets blown up), followed by an orbital satellite network (that gets blown up).

Now, assuming a sufficiently advanced society that can construct large scale installations in orbit, would a lunar base be redundant?

A military base may be limited, as the moon's rotation is negligible and it will be in a "fixed" position, relative to the Earth, making it easy to bypass. For commercial usage, I see a similar issue with its positioning.

Prior to the ability to produce large scale facilities in orbit, a lunar base may prove useful, but afterwards, could it prove of any real use? (Aside from the tides and stabilizing the Earth's orbit)

EDIT: Could the base be salvageable? Could there still be a use for it, or should it just be stripped for materials?

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  • $\begingroup$ Hello. Someone flagged this as off-topic and I had a hard time deciding how to vote. I voted "leave open", but it would help if you would include one basic thing in your question: how exactly are you building a fictional world with this information? $\endgroup$ – Mołot Apr 18 '17 at 7:57
  • $\begingroup$ This isn't for anything specific, per se. Rather I think it helps as a discussion of a popular trope in sci-fi $\endgroup$ – RenegadePizzaGuy Apr 18 '17 at 8:02
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    $\begingroup$ You can change the question to this: after the birth of orbital space station and lunar base become obsolete, how could I repurpose this lunar base? This question is still salvageable if you put constraints and make the question more clear. $\endgroup$ – Vylix Apr 18 '17 at 8:12
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    $\begingroup$ Or "How can I justify a lunar base in a world where large scale orbital constructs are a reality?" I too find the discussion of the trope interesting, if only the question can be squeezed into the topic of WBSE" $\endgroup$ – Guran Apr 18 '17 at 8:54
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    $\begingroup$ Space exploration SE has loads of questions about lunar bases with a real wealth of information over there. If you wanted specifics of why different bits would be useful you can check out the answers to those like this question comparing the moon vs an orbital station. $\endgroup$ – Lio Elbammalf Apr 18 '17 at 12:28
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It's depends but YES.

Military reasons

Military usefulness depends on threats. If headquarter decided that

  • orbital base is hard to protect but easy to see
  • aliens could silently concetrate on backside of the Moon
  • one line of defence is not enough
  • we need outpost
  • etc etc

then they would want to build lunar base.

Economical reasons

  • for some reason use of intermediate base is better than direct transport to long-ranged orbital equipment (radiation issues, operation time, possibility to service manipulations)
  • mining ice or another resources at the Moon is cheaper than mining on Earth and then deliver to the orbit
  • Any satelite needs engines and navigation equips just for keep a stable orbit. On the Moon it's not an issue although there are other problems.
    • Communication hub on the moon is an option
    • but interstellar telescope is impossible (for now) because precise details couldn't survive landing
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  • $\begingroup$ would a lunar base be redundant? could it prove of any real use? Which one is yes ? $\endgroup$ – Vylix Apr 18 '17 at 7:48
  • $\begingroup$ @AdiNugroho We are talking about possibilities so both may happen. In real world there are many discussions and holywars about do we need lunar base?. Right now it's an open question $\endgroup$ – ADS Apr 18 '17 at 7:57
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Yes, base on the moon is useful.

Main commercial reason to have the moon base is the difference in cost lifting the matter from earth compared the same from the moon.

It is not only 12 times cheaper energy-wise if you use non-rocket launch systems but the complexity and costs(energy and labor) involved in building such non-rocket launch systems (mass drivers or anything you may wish) on the moon compared to any other body in solar system.

No, the base it not obsolete after the interplanetary infrastructure is established.
Moon is a big possible source of main construction materials which we use today

  • Iron, Aluminium, and others. The may lose their significance, but still, they are possible building materials, which can be used

The most importantly it's close to the Earth. Proximity to earth means fewer delta-v requirements for delivering the materials for any construction you would like to build near Earth or in Sun-Earth L1, L2 points, especially with mass drivers. And as long as there more people on Earth than in other places in space, demand for those constructions here will be more than in any other place, especially because building those constructions can be useful for Earth climate maintenance, energy supplies etc.

Generally speaking there no a lot of possible alternatives for the moon. Asteroids - water(hydrogen), nitrogen, carbon, construction materials. Venus - carbon. Jupiter and its moons - hydrogen, carbon, nitrogen construction materials. Mars - construction materials(con - atmosphere and genetically modified Martians dreaming about terraforming). Mercury - construction materials(small con - high delta-v requirements). So even with infrastructures on all those bodies, the significance of moon will be reduced, but not vanish.

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  • $\begingroup$ Note that is probably obvious: Lunar mass drivers can drop heavy projectiles on any target on Earth. Moon based energy weapons would control most economically important orbits around Earth and have huge advantage of being able to use the Moon as a heat sink for cooling over satellite weapons. $\endgroup$ – Ville Niemi Apr 18 '17 at 13:00
  • $\begingroup$ @VilleNiemi preferred to skip the weapon aspect as there are more interesting ways to conduct power than using the moon as one of such tools. However, a nice argument about heatsink. $\endgroup$ – MolbOrg Apr 18 '17 at 15:18
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These are some of the advantages of a moon base over an orbital base:

  1. Camouflage: You can attempt to hide a base on the moon, because the moon is pretty big, and people expect it to be there. An orbital base is more difficult to hide.
  2. Armor: The surface of the moon is covered in craters, due to constant bombardment by rocks and ice travelling at up to orbital speeds. An underground moon base could be protected from this bombardment - and also from most weaponry (if they come with planet busters, your station doesn't matter anyway). This will also help with protecting a crew from radiation.
  3. Gravity: On the moon you don't need artificial gravity to stop everything from floating around. This is quite neat, when it's a manned station. On the other hand, lower gravity and lack of athmosphere means you can launch small craft quickly and easily - something a planetary base cannot provide.
  4. Mass of the moon: Your station will likely have a mass lower than the moon. Using an orbital space station to fire rail guns at an adversary, would change it's orbit. You would be limited to smaller, recoilless weaponry in most cases. The moon is a convenient emplacement for your heavy interplanetary artillery.
  5. Less collateral damage: Any shot that would miss an orbital defense station, could hit the nearby planet or be drawn into its gravity well, making for potentially devastating collateral damage, even from an unsuccessful attack on a military installation. The moon is more likely to provide a buffer for destroyed craft and malfunctioning/misaimed weaponry, where it wouldn't impact a planet's fragile ecosystem.

So, unless your base is the size of an Imperial Death Star, you would do well to keep it under the surface of the moon. As an advance outpost, a base on Pluto or similar sized rim-planet would be pretty neat, but out there you wouldn't be able to rely on solar power as much (at least for day-to-day operations), as on the moon, so you'd need either another locally available power source, or ship fuel out there every so often.

My assumptions are of course only valid, if the moon in question is similar to the Earth's moon, and generally considerd inhabitable, with significantly lower gravity than a reasonably nearby planet. In a solar system with inhabited moons around a gas giant, you would probably want to have your defensive perimeter outside the planet's gravity well.

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Remember space is big and empty. And yes, I know you think you know what that means. You don't. Space is bigger than you think. The human brain is not built to conceptualize something as big and empty as space. In scifi movies, we often have images of ships dogfighting and basically acting as souped up WW-2 battles. That's unlikely. Unless you are talking about some kind of sneak attack, the battles will probably be waged from a pretty far distance. So even if the enemy attacks from the far side of Earth, whatever defenses the moon base might have would have plenty of time to get on an intercepting orbit.

Also don't forget about ammunition. Rock could easily be mined locally from the moon to create munitions, whereas the space station would have to have it transported from somewhere else.

Finally the moon has inertia. Depending on the enemy's orbit, whatever you are firing may need quite a bit of delta-v to intercept it. If you are using rockets, that's fine as long as you are ok with wasting a lot of fuel. But a moon base would allow you to build some sort of rail gun or other ballistic weapon to give it the bulk of the acceleration. The space station would not be able to do that without Newton's third law mucking up it's orbit after enough rounds.

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  • $\begingroup$ I see. The moon could act as a stable platform for heavy munitions, whereas a station may need to fire thrusters in the opposite direction its firing, just to maintain its position $\endgroup$ – RenegadePizzaGuy Apr 19 '17 at 6:53

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