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The year is 2030. The US has set up a moon base with about 2,000 people. The base can theoretically survive indefinitely, growing its own food and 3D-printing supplies, but in practice it needs trade with earth to get critical resources like lithium (no asteroid mining, yet).

This colony decides to declare independence in a way that they come out looking like the "good guys" (the US government, which they already didn't like, refused to let them give humanitarian aid to an "enemy" base, and tried to arrest them when they did anyways). The US military decides that it needs to reconquer the base within a year or two, or the American people will demand peace. Public support for the war is already lukewarm at best. Until this point, no space weapon systems have been built (though some may have been designed in secret).

My question is, how would the US go about re-conquering the lunar-colony?

Constraints:

  • Technology is very close to present day. The war will end after 2 years at most, so there isn't much time to develop any radically new techs.
  • Both sides are flying a mostly-reusable BFR-style rocket, which will cost the US military about 50 million per launch. The number of launches will be limited at first, unless they scale up production.
  • China also has a moon base, on the south pole (the rebellious base is in a crater near the north pole). Chinese launch capabilities are more limited, but they could possibly supply the rebels with resources and equipment, if they can transport it long distances across the lunar surface. Russia and India are also willing to help the rebels, but they would need to hard-land payloads near the base, limiting their effectiveness.
  • The rebels have about 6 BFRs, 3D printing capacity, and the ability to produce rocket fuel from water ice. They are also extremely technically adept (they're basically all brilliant engineers), and will be working on counter-measures.
  • The moon base is one large structure that's mostly buried under ground. There are airlocks all over the place, and several large doors leading to the surface. The landing-pad is a few km away, and they travel back and forth in souped-up lunar rovers. These rovers can, theoretically, travel all the way to the moon's south pole, but only if they bring tons of solar panels to recharge along the way.
  • The colony is powered by a massive solar array that surrounds part of it.
  • Both sides start the conflict hoping to inflict as few casualties as possible. Politically, the US would rather give up the moon-base than see it fully destroyed. The rebels, meanwhile, will never even consider attacking civilians on Earth, although they will go after military targets if they feel they have to. Their support for the war is also lukewarm at best.

The two plans that come to mind are to either try to blockade Chinese resupply missions (though I'm not sure if the US has the ability to hit a convoy of lunar rovers), or to give spacesuits to a bunch of marines and have them storm the base Starship Troopers-style (though this seems incredibly dangerous and would result in high casualties). Neither of these plans seems great, so I'm curious to hear your thoughts?

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    $\begingroup$ This seems a very energy-intensive colony (you need a lot of electricity to spit water into hydrogen and oxygen). $\endgroup$ – RonJohn Mar 31 '18 at 4:51
  • $\begingroup$ @RonJohn Good point! I didn't think of that. Taking out their power source would probably be a really effective plan! Thanks! $\endgroup$ – Bert Haddad Mar 31 '18 at 6:02
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    $\begingroup$ Have you ever read "The Moon is a Harsh Mistress"? $\endgroup$ – pojo-guy Apr 1 '18 at 3:03
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The United States isn't going to allow the rebels freedom because of the consideration noted by StephenG: the rebels are on the top of a gravity well. A moonbase in rebellion is a deadly threat to the United States and her allies (and I'm going to suggest the Russians, Chinese and any other Great or even medium power isn't going to be very keen on this idea either) because they can launch large rocks on ballistic trajectories to crash onto Earthly targets with relative ease. This is, in fact, the plot driver behind Robert A Heinlein's "The Moon is a Harsh Mistress"

enter image description here

What the AOR looks like

Now while the Moon may be in an advantageous position in terms of gravity, the Earth is backed by the industrial resources of an entire planet and the manpower resources of 8 billion people, so even the most brilliant of Lunar engineers is going to be at the wrong end of things. For every brilliant Lunar engineer, there are tens of thousands of brilliant Earth engineers working at R&D establishments, and millions of ordinary engineers working in production facilities, backed by tens of millions of workers and hundreds of billions of dollars of financial resources. The Lunar colonists are still going to be boiling elements out of rock to get any resources they need....

While the US is likely going to use its diplomatic resources first, the most likely outcome is the leadership of the colony will receive a polite note from the United Nations suggesting they reconsider their position WRT US governance....or else.

In the mean time, since this is 2030, US Space Command is busy as well. A flurry of activity is happening at launch facilities across the United States and around the world. The President, following the example of the 45th POTUS, makes a multitude of contradictory posts on social media, allows an old personal relationship to dominate the news and continues "refilling the swamp", making the news follow these stories while the Secretary of Defense and the Secretary of State burn the phone lines. Finally, in an insanely choreographed performance, spaceships are launched from multiple pads at Cape Canaveral, Vandenberg AFB, Baikonur, Jiuquan Satellite Launch Centre, Satish Dhawan Space Centre, Palmachim Air Force Base, Tanegashima Space Centre and the Guiana Space Centre, demonstrating that the Lunar Rebels are going to face the wrath of the entire planet (even if many of the spacecraft are unable to reach the moon in this launch phase).

Hidden among the various launches are a pair of S-37D's (now in service, the "X" moniker has been dropped), quickly setting course to the Moon.

enter image description here

X-37b, the predecessor to the S-37d

On board, each spaceship has a brace of powerful non nuclear EMP weapons. If the ships don't receive orders by a specified time, they will release the EMP devices and blast the solar cell arrays and any surface power transmission lines. The concentrated energy will destroy the solar cell arrays and the transmission lines will pump high transient voltage spikes into the colony, damaging computer equipment and electronic devices, as well as any spacecraft or equipment parked on the lunar surface.

enter image description here

Explosively driven EMP generator

Faced with this display of power, the rebels should consider surrendering right away, and await the arrival of the US Marshals to take them into custody, while US Space Command personnel move to occupy the administrative and managerial positions.

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  • $\begingroup$ A single BFR armed with a nuclear warhead, landing alongside the Moon base would have the same threat potential. What worries me is if the rebels refuse to surrender. Using the EMPs will kill everybody on the Moon base due to the consequences of total power failure. A very difficult stand-off. I don't know how to resolve it, do you? Otherwise your proposal is an excellent solution. $\endgroup$ – a4android Apr 1 '18 at 4:11
  • $\begingroup$ The Americans would never allow the rebels the chance to "drop rocks" on the United States, so disabling the power supply negates any attempts by the rebels to threaten the Earth. If Space Command were to send some BFR's with security forces, US Marshals and engineering troops to retake the base after the EMP strike, they could conceivably rescue everyone when the rebels are unable to defend themselves (win-win for the Americans, they get their base back and don't look like monsters for killing the rebels). $\endgroup$ – Thucydides Apr 1 '18 at 6:24
  • $\begingroup$ The obvious response is to make a few dozen little rc rockets, put them all in orbit, an if anything launches from earth, aim for a collision. $\endgroup$ – Donald Hobson Apr 1 '18 at 11:05
  • $\begingroup$ @DonaldHobson rc rockets?? What is "rc"? Not everybody speaks or writes that dialect of abbreviations. Kindly explicate. $\endgroup$ – a4android Apr 2 '18 at 2:32
  • $\begingroup$ Remember the disparity between the resources the Earth can muster and those of the Moonbase? If there are indications that the rebels have some sort of Surface to Space capabilities, the US will launch more attack vehicles, decoys and so on to overwhelm the defence. Suppression of Enemy Air Defense (SEAD) has been practiced since WWII, so the Space Force can adapt almost a century of experience to the space environment. The Rebels can put up a limited defence, but I doubt they have the capabilities to muster an indefinite defence. $\endgroup$ – Thucydides Apr 2 '18 at 5:16
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The rebels have about 6 BFRs, 3D printing capacity, and the ability to produce rocket fuel from water ice. They are also extremely technically adept (they're basically all brilliant engineers), and will be working on counter-measures.

My question is, how would the US go about re-conquering the lunar-colony?

The US Military would not.

Why ? Gravity.

In simple terms the "rebels" have the ability to create an effectively arbitrary number of rocket powered rocks (and I mean large rocks) to hurl at any point on Earth they want.

They can wipe out large chunks of the surface.

They can do this because the Moon's gravity is a fraction of Earth's and it also lacks an atmosphere.

It's essentially down hill most of the way for the object coming from the Moon. And conversely it's mostly uphill for the object coming from Earth. They have the high ground, and it's fabulous high ground.

For them to send a rocket powered rock to Earth, that will become a large and deadly meteor, is a relatively low energy task. They've got the fuel (Oxygen and Hydrogen) and they'd got rocks, so no problem making rudimentary rocket that do the deadly work.

They'll quite simply use this threat as a weapon of last resort. Try and take us over and we'll kill you all. Simple. This policy has a name : it's called MAD.

So there is, ultimately, no "win" scenario for the US military.

They can draw, but it's a draw where e.g. every large metropolitan area of the US is a wasteland.

It's not really possible for the Moon rebels to win, but they'd gain superpower status politically because being able to kill everyone is a pretty big stick diplomatically.

Short version : shoot the generals who want to attack the moon before the idiots doe something stupid and get everyone killed.

Now an early first strike might prevent the rebels from preparing this (very obvious) deterrent. However the rebels also have another advantage - the Chinese. The Chinese would be looking on thinking "If the US succeeds in taking that base back, they might get greedy and try it with ours.". Diplomatically they'll scream bloody murder and everyone's missiles will start going to alert status "far too high".

And even if the rebels can't get the Chinese to back them willingly, they can immediately threaten to launch every rocket they have against the Chinese base if they are attacked.

Now the correct way to deal with this is, of course, diplomacy.

The two plans that come to mind are to either try to blockade Chinese resupply missions (though I'm not sure if the US has the ability to hit a convoy of lunar rovers),

World War 3 as it's also known. Unless you know a reason the Chinese would let you do this, it's an exceptionally dangerous move that could rapidly escalate into WW3. What exactly would you expect the Chinese response be to the first dead Chinese national ?

Lousy plan.

or to give spacesuits to a bunch of marines and have them storm the base Starship Troopers-style (though this seems incredibly dangerous and would result in high casualties).

In theory you can storm any base and take it.

In practice you loose most or all of your people doing it.

This is almost a certainty when you factor in the nature of the base - all corridors and choke points. It's kill zone heaven for the defenders. For example - put a few containers of Hydrogen and Oxygen in every corridor and blow them when someone enters the corridor (by remote control) - result : Crispy Fried Marine.

Makes D-Day at Omaha beach look inviting. Think "Charge Of The Light Brigade" or "Pickett's Charge". That level of suicidal planning.

To take the base would probably mean killing every single person in it. There's no easy way to take such a base. You have to fight for very corridor, every room. Even if you did win, you'd look like the Nazis doing it. This has no happy ending, unless you don't like Marines because the casualty rate would be insanely high.

So not an option, IMO.

The best option : negotiate. Do a deal. Suck it up and make a face saving deal that "looks* like they stay with the US (so they become a new State). Something like that. Maybe they become a US protectorate or some such nonsense. Maybe they'd be OK with that if the cash flow was right.

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  • $\begingroup$ Very good points! Although ethically the rebels would rather lose the war than destroy any major cities (though military bases might be OK). Their whole reason for revolting was that the US government was stopping them from delivering humanitarian aid to an "enemy" base. Editing the question now to make that last part clear. $\endgroup$ – Bert Haddad Mar 31 '18 at 8:42
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    $\begingroup$ I'll give that some thought, although it strikes me that, whatever people's intentions when they start a rebellion, the end result is usually a lot of bloodshed, as people on both sides get very, very bloodyminded. $\endgroup$ – StephenG Mar 31 '18 at 9:19
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    $\begingroup$ You could recognize Taiwan as a part of China. Then China would probably stop. $\endgroup$ – Hazard Mar 31 '18 at 12:28
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    $\begingroup$ This is not MAD. MAD is where both sides can destroy each other. So far, all you've established is that given time, the moon colony could destroy their Earth attackers. There's no mutual in your assured destruction. To get MAD, they would first have to build the weapons. Then they'd have to be balanced by Earth weapons. $\endgroup$ – Brythan Mar 31 '18 at 13:41
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    $\begingroup$ If the rebels have about 6 rockets, they can devastate about 6 targets on Earth. Then it will be impossible for a colony of only 2,000 people to build any more large rockets. The USA obviously has a number of large rockets that deliver large payloads to the Moon since it has built a large moon base, and only needs to get one tiny rocket with one lightweight atomic bomb to the moon base for total destruction of the moon base. Starting a war of extermination by throwing rocks at the USA is not a good idea. $\endgroup$ – M. A. Golding Mar 31 '18 at 17:57
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There may one or more (but not many) power junctions on the surface for easy routing of the solar grid power into the base. Hit those with missiles. My guess is that the fuel costs more energy to produce than it provides. You have simultaneously accomplished several things:

  • Incentivized NOT launching rockets (because the colony may need that fuel to survive)
  • Relocated some portion of defenders to a known locations (the generators - I assume you have a map of the base)
  • Threatened the food supply (how long can those plants last without power)

You could stop there. I'm not certain how often that has worked. It might cause the rebels to reconsider, but it may just harden them. I'd like to see statistics on how often cutting the power alone leads to a peaceful surrender.

You could follow up with a blockade ring around one or both colonies to keep foreign supplies out.

Or you could follow up immediately with Marines at multiple airlocks in a shock & awe style attack coordinated to begin when the lights go out to take maximum advantage of the gap before backup generators are on-line.

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They would arrange a terrible accident that suddenly wiped out all colonists but left the infrastructure in place (preferably but not necessary).

Boohoo, everyone one is very sad but space is a dangerous place. I'm sure the brave colonists would want us to carry on their brave mission so we're sending up new colonists to carry on the mission.

If you can make it look like an accident and declare all the colonists brave heroes, you'll come out smelling like roses.

The colonists would know this and would try for fail safes so arranged accidents couldn't happen without exposing it.

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The weakest link in this setup is the solar arrays. If they are on the visible side of the Moon, they can be damaged from Earth, or LEO, based lasers, and the lunar colony would have no way to protect them.

It is a little more difficult to attack them, if they are on the far side of the Moon, but still they are the most vulnerable. Shooting lots of small projectiles, like grapeshot, from a distance, would do a great damage. They would be almost invisible, and arrive at the Moon like small meteorites, because there is no atmosphere to slow them down.

Neither of these measures would kill many people, they are well protected underground, but the shortage of energy would force the colony to negotiate. Then the US can offer to install a nuclear power plant on the Moon, regain the support of the people both on the Earth and on the Moon and make a lasting peace. By controlling the energy source, and not allowing the colony to rebuild their large size solar arrays, they can remain firmly in control until the colony grows large enough to build its own nuclear reactor.

According to ESA the natural flux of meteorite in space near Earth is "5.10-6 impact craters of 100 microns or greater per m2 per second (some 160 per year on 1 square metre) on HST solar arrays." It is less than a gram per m2 per year, yet those solar panels needs to be replaced regularily. On the surface of the Moon it would be a little higher, due to the gravity of the Moon, and the normal lifetime of the solar panels would be even shorter. But by intentional bombardment the flux could be raised much higher, and would speed up the aging of the solar panels considerably. The continuous bombardment would also make repair or replacement almost impossible.

The colony cannot retaliate with similar weapons. Although they can launch anything easily, their projectiles would either burn up in Earth's atmosphere, or would be big enough to intercept, long before impact.

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Earth could launch a series of missiles at the moon-base.

The first set are nuclear reactors capable of supplying power required by moon base if their solar farm stopped working. The reactors are controlled from Earth and rigged with self-destruct mechanisms if tampered with

The second set of missiles are paint balls and target the solar arrays, rendering them inoperable until cleaned.

But, not only is the moon a harsh mistress, she’s a fridged one, too. Without heating, ventilation and waste processing, the 2000 lunar colonists will die in a few days unless they accept the Earther’s terms and can hook up the nuclear reactors to their power grid.

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  • $\begingroup$ what prevents the colonists from going out and cleaning the solar arrays? $\endgroup$ – Tom Jul 31 at 8:58
  • $\begingroup$ There are only 2000 colonists and the area of the arrays is most likely very large. In a vacuum, paints cure quickly are hard to remove and solar cells are very delicate since they have fine traces of metal on their surface. If those are damaged the cells are impaired or ruined. I don't think they'd have time, plus the cells can be painted again. $\endgroup$ – EDL Jul 31 at 15:10

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