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In Warlords Europa is a semi-independent world who's surface is dominated by ice mining companies or colonies dug into the ice, but below the ice thrives the "Hanging Cities" affectionately named Atlantis.

I'm my head the city would look like a massive dome built encasing the opening to a mile diameter long borehole to the surface (which is installed with a thick steel casing and a large elevator). The dome itself would be supported by what would look like a series of large metal roots.

Would it be feasible to build a dome that is gripping the roof of the ice on Europa (with supports drilled into the ice of course)? Or is this idea just too crazy to work?

Note: The dome needs to support the weight of a decent sized city. Also the ability to look out of the dome (probably through projections on the inside of the dome) is a necessary feature.

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    $\begingroup$ sure it would be easy, Europa's gravity is less than our moon. $\endgroup$
    – Kilisi
    Commented Jul 26, 2018 at 13:29
  • $\begingroup$ @Giter last time I checked there is no air. $\endgroup$
    – Celestial Dragon Emperor
    Commented Jul 26, 2018 at 13:38
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    $\begingroup$ I was coerced to write this and I don't know why: "All those worlds are yours. DO NOT ATTEMPT TO COLONIZE EUROPA. Sincerely, Monolith." $\endgroup$
    – Thorsten S.
    Commented Jul 26, 2018 at 14:43

4 Answers 4

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It depends just how thick the ice crust actually is. If the estimates are correct and it's 10 miles or more thick, if you put anchor bolts right through it, then you could hang anything you wanted off them. That's without even taking into account the fact that:

  1. Atlantis is going to weigh almost nothing, Europa has a fraction of Earth's gravity.

  2. There will also be a buoyancy effect from the ocean that the city is "hanging" down into, you may have more trouble with damage from the water squeezing the city up into the ice crust than anything else.

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    $\begingroup$ Beat me to this. The bouncy effect could be varied by the size of the dome and the amount of water it displaced, and any ballast tanks incorporated in to the design. It might actually be more feasible to consider the city a submarine docking to fixed points on the icy "crust" and move from place to place as needed or desired. $\endgroup$
    – Thucydides
    Commented Jul 26, 2018 at 13:38
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    $\begingroup$ @CelestialDragonEmperor You could cut a grove where the top of the walls would meet the ice and use a gas cushion shock damper to separate the city from the crust. You'll need something to base isolate the walls given the gravitational flexing Europa does during it's orbit. $\endgroup$
    – Ash
    Commented Jul 26, 2018 at 13:49
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    $\begingroup$ You'd probably also build multiple domes. One dome is a single point of failure, you wouldn't build a city you wanted to keep under a single point of failure. $\endgroup$
    – Racheet
    Commented Jul 26, 2018 at 15:37
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    $\begingroup$ @Racheet Not if you were thinking sensibly no but never under-estimate human stupidity. $\endgroup$
    – Ash
    Commented Jul 26, 2018 at 15:38
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    $\begingroup$ @MikeNichols The gas cushion could solve the issue of gradual plastic deformation of the ice, since the pressure of the gas shouldn't be very high and the buoyancy pressure of the city could be widely distributed over hundreds of square miles of ice surface. $\endgroup$
    – Ash
    Commented Jul 29, 2018 at 15:02
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It might not be a good idea over long times. It's correct that ice has great rigidity and strength, but

under steady pressure it behaves as a plastic (mouldable) body. In contrast, when put under sudden compression or tension, it will break or shear apart.

Therefore if your city only rely on ice for stability and positioning you will be disappointed when the plastic flow will start moving it.

The fastest glaciers move at about 40 meters per day. It take even less than that to crumble down a building.

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    $\begingroup$ lol if you live in that city, you may be more than disappointed $\endgroup$
    – Spike0xff
    Commented Jul 26, 2018 at 14:42
  • $\begingroup$ curious to know why the downvote $\endgroup$
    – L.Dutch ♦
    Commented Jul 26, 2018 at 14:46
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    $\begingroup$ @L.Dutch I am interested in that, too. Some people seem to have weird reasons for their votes. And too often people don't bother to say why they downvote or flag something. Sadly. $\endgroup$
    – ArtificialSoul
    Commented Jul 26, 2018 at 14:59
  • $\begingroup$ Would this plastic behavior work fast enough to be an issue? I am thinking it would be so slow as to be negligible. Kind of like how glass has a similar property, and the glass in windows is constantly "flowing," yet we have windows hundreds of years old which are still usable. $\endgroup$
    – Loduwijk
    Commented Jul 26, 2018 at 17:28
  • $\begingroup$ @Aaron, ice plasticity is what makes glaciers move $\endgroup$
    – L.Dutch ♦
    Commented Jul 26, 2018 at 20:44
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Yes, it would be possible

From this we can roughly see the max stress for ice is about 9MPa. Steel for example withstand about 400 MPa (strongly depending on what steel you use). if I am interpreting the graphs correctly.
So steel is easily better for this, but that only aside.

But what you have to take into account is that europas gravity is more than 7 times lower than earths. So the strain you would put on the ice would be significantly less than it would be here on earth.

Also it is not hanging in air, but in water. Water itself is about as heavy as the ice and would carry some of the weight to.

While I am not a mechanical engineer and couldn't design a facility hanging from the ice, I am convinced it is possible to built something that would.

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    $\begingroup$ You have interpreted the graph correctly but without taking into account that fact that the temperatures are too high, steel in Europa's climate is likely to be very brittle. $\endgroup$
    – Ash
    Commented Jul 26, 2018 at 13:41
  • $\begingroup$ @Ash Might be. I have no background knowledge about very low temperature ice. I think it still might be possible since the strain you put on the ice is very low compared to what it would be if you had a free-hanging ice structure in air on earth. $\endgroup$
    – ArtificialSoul
    Commented Jul 26, 2018 at 14:41
  • $\begingroup$ Yeah I don't know about the ice at those temperatures, I've heard terms like "rock hard" but that's not really useful, I just know that steel starts to get very brittle once the temperature drops below zero. $\endgroup$
    – Ash
    Commented Jul 26, 2018 at 14:47
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    $\begingroup$ I'm just saying steel may not be better than ice in those conditions I'm not making any judgement about how good the the ice actually is though, I have no useful data in that regard. $\endgroup$
    – Ash
    Commented Jul 26, 2018 at 15:00
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    $\begingroup$ Yeah down at 110 Kelvin a lot of what we think we know about everyday materials simply isn't so anymore. $\endgroup$
    – Ash
    Commented Jul 26, 2018 at 15:04
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Yes. Under the ice is a subterranean ocean. You can make your dome out of ice and due to buoyancy it will float. Attach the reverse dome to the ice above - now you have an enclosed space. Similar to an igloo, you would have to re-ice the dome but that actually strengthens it.

Inside the dome, you would anchor the buildings to the ice sheet above so that the dome does not have to support their weight. Connect the buildings with skybridges.

You can either drain the dome and fill it with air or make the buildings air tight and leave the water. If you leave the dome filled with water, the buoyancy will reduce the weight that hangs on the ice sheet and allow you to build taller (or I guess in this case deeper) buildings.

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