Author Topic: Elon Musk: glass geodesic domes  (Read 96582 times)

Online meekGee

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Re: Elon Musk: glass geodesic domes
« Reply #380 on: 01/20/2019 01:03 pm »
Or, work the Sprung on making pressurized domes. The overall design will be different, but the devil's in the details and they have a lot of real-life experience.

Yes, Sprung, capital-S, the company, might have the skills to design a pressure vessel suitable for Mars. But it won't be based on the "sprung" spans, little-s, that their existing buildings are based around. The second sentence was the point I was trying to make.

People have a tendency to point at a picture of pretty much any novel Earth-structure and shout "on Mars!" But it's meaningless if you don't look at how that structure works on Earth, look at the problem it's trying to solve, and ask whether that's at all related to the completely different requirements you need on Mars. There's nothing about Sprung's self-supporting buildings, or geodesic domes to bring it back to the topic, or domes in general, that makes them suitable for Mars just because they vaguely resemble the sci-fi images we all know and love.

Does Sprung (the company) have the engineering skills to design a Mars-hab? Maybe. Does their experience with building clever compressive structures on Earth give them any more insight that any other company with structural engineering experience on Earth? No.
Again, the overall geometry is not applicable.  But that's only a small portion of their know-how.

Lightweight durable skins, connecting such skins to rigid members in a way that's compatible with being deployed outdoors, the beam structure itself, the logistics of transport and deployment - all very applicable if they have the passion to go there.
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Offline spacenut

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Re: Elon Musk: glass geodesic domes
« Reply #381 on: 01/20/2019 03:28 pm »
What would it take to be able to manufacture glass on Mars to avoid transporting from earth?  Natural gas (Methane) for melting the silicone can be made for rocket fuel and maybe some used to manufacture glass.  Can it be made like safety glass on car windshields on Mars?  Making the glass panels small and double pane to interlock in a geodesic dome or tunnel would allow for easier repair without depressurizing the habitat. 

Online Jcc

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Re: Elon Musk: glass geodesic domes
« Reply #382 on: 01/20/2019 05:46 pm »
What would it take to be able to manufacture glass on Mars to avoid transporting from earth?  Natural gas (Methane) for melting the silicone can be made for rocket fuel and maybe some used to manufacture glass.  Can it be made like safety glass on car windshields on Mars?  Making the glass panels small and double pane to interlock in a geodesic dome or tunnel would allow for easier repair without depressurizing the habitat.

For applications that require a large amount of heat, how about direct solar thermal:
https://en.m.wikipedia.org/wiki/Ivanpah_Solar_Power_Facility

(Applications like glass making, iron refining, etc.)
« Last Edit: 01/20/2019 05:47 pm by Jcc »

Offline spacenut

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Re: Elon Musk: glass geodesic domes
« Reply #383 on: 01/20/2019 05:59 pm »
Electric melting of glass is not efficient, electric heat is not efficient in general, at least on earth.  A gas furnace can melt glass easier, unless solar can be concentrated directy on the silicone, or directly on iron, aluminum etc and can get hot enough.  The plant you referenced got the water to 550 C.  Pretty hot, but silicone melts at 1,400 C, while aluminum is 660 C.  Can a reflective solar plant on Mars get as hot as it does on earth?

Offline AC in NC

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Re: Elon Musk: glass geodesic domes
« Reply #384 on: 01/20/2019 06:16 pm »
ISTM that challenges are:

Clean raw material:   http://planete-mars.com/a-mars-colony-a-tentative-technical-analysis/14/

Quote
Glass and ceramics
Mars clays should enable the manufacture of ceramics, while silica, ubiquitous, will allow producing glass. One problem though: the Martian silica will be obtained from a sand rich in Fe2O3 iron oxide (hematite) that we must get rid of if we want to get a good optical quality glass. This can be done by reducing Fe2O3 with carbon monoxide and segregating the iron thus obtained. From glass, we can also manufacture glass fiber, useful for elaborating composites.

Energy:  https://www.lowtechmagazine.com/what-is-the-embodied-energy-of-materials.html

Quote
Energy to Produce Glass per KG(from sand, etc): 18-35 MJ (5 to 9.7 KWhrs)

Online Jcc

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Re: Elon Musk: glass geodesic domes
« Reply #385 on: 01/20/2019 06:56 pm »
Electric melting of glass is not efficient, electric heat is not efficient in general, at least on earth.  A gas furnace can melt glass easier, unless solar can be concentrated directy on the silicone, or directly on iron, aluminum etc and can get hot enough.  The plant you referenced got the water to 550 C.  Pretty hot, but silicone melts at 1,400 C, while aluminum is 660 C.  Can a reflective solar plant on Mars get as hot as it does on earth?

There's this:

But mainly I was thinking of using direct solar to "preheat" the materials to bring them closer to the temperature needed and reducing the amount of electric or combustion heating.

Online RonM

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Re: Elon Musk: glass geodesic domes
« Reply #386 on: 01/20/2019 08:20 pm »
Electric melting of glass is not efficient, electric heat is not efficient in general, at least on earth.  A gas furnace can melt glass easier, unless solar can be concentrated directy on the silicone, or directly on iron, aluminum etc and can get hot enough.  The plant you referenced got the water to 550 C.  Pretty hot, but silicone melts at 1,400 C, while aluminum is 660 C.  Can a reflective solar plant on Mars get as hot as it does on earth?

Industrial solar furnace would work. Focused properly, they can easily melt glass. But an industrial solar furnace would use a lot of large mirrors, especially on Mars. Look at the size of the example on Wikipedia.

https://en.wikipedia.org/wiki/Solar_furnace

Offline Slarty1080

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Re: Elon Musk: glass geodesic domes
« Reply #387 on: 01/20/2019 08:28 pm »
Electric melting of glass is not efficient, electric heat is not efficient in general, at least on earth.  A gas furnace can melt glass easier, unless solar can be concentrated directy on the silicone, or directly on iron, aluminum etc and can get hot enough.  The plant you referenced got the water to 550 C.  Pretty hot, but silicone melts at 1,400 C, while aluminum is 660 C.  Can a reflective solar plant on Mars get as hot as it does on earth?
I think you mean silica (silicon dioxide)
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Offline nacnud

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Re: Elon Musk: glass geodesic domes
« Reply #388 on: 01/20/2019 09:14 pm »
A light furnace can heat things as hot as the thing that emits the light, which in this case is the surface of the sun, so 3500C.
« Last Edit: 01/20/2019 09:15 pm by nacnud »

Online RobLynn

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Re: Elon Musk: glass geodesic domes
« Reply #389 on: 01/20/2019 09:54 pm »
A light furnace can heat things as hot as the thing that emits the light, which in this case is the surface of the sun, so 3500C.

Could probably find a lot of uses for a big Martian mirror field placed on a steep equator-facing hill side.

Could be redirected for occasional high-power localised needs like baking soil for volatiles, or rovers so that they didn't need such large batteries or panels themselves.  Could melt areas of the surface to create smooth roadways or landing pads or to provide primary energy input to materials and chemical processing.

And the rest of the time could be used for enhancing green-house operation.
The glass is neither half full nor half empty, it's just twice as big as it needs to be.

Online Jcc

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Re: Elon Musk: glass geodesic domes
« Reply #390 on: 01/20/2019 11:18 pm »
Also melting of ice in the soil and steam disillusion of brine to pure water.

Which you can drink while living in glass geodesic domes (back on topic).

Offline Paul451

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Re: Elon Musk: glass geodesic domes
« Reply #391 on: 01/20/2019 11:45 pm »
Making glass from raw materials is a complex process, requiring enough chemicals and purification steps, many which will need to be different enough on Mars, that picking a heat-source will be the smallest issue to solve.

Offline lamontagne

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Re: Elon Musk: glass geodesic domes
« Reply #392 on: 01/21/2019 03:00 am »
Electric melting of glass is not efficient, electric heat is not efficient in general, at least on earth.  A gas furnace can melt glass easier, unless solar can be concentrated directy on the silicone, or directly on iron, aluminum etc and can get hot enough.  The plant you referenced got the water to 550 C.  Pretty hot, but silicone melts at 1,400 C, while aluminum is 660 C.  Can a reflective solar plant on Mars get as hot as it does on earth?
Got to disagree on this:
http://ietd.iipnetwork.org/content/electric-melting
Electric furnaces are much more logical on Mars than gas fed ones, since the gas on MArs comes from electricity in the first place.

Offline Lampyridae

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Re: Elon Musk: glass geodesic domes
« Reply #393 on: 01/21/2019 12:12 pm »
Making glass from raw materials is a complex process, requiring enough chemicals and purification steps, many which will need to be different enough on Mars, that picking a heat-source will be the smallest issue to solve.

Glass can be pure silica, ie fused quartz but that is harder to deal with than the soda-lime glass windows are normally made out of (~25% additives by wt). I expect they would be more like bottle glass due to condensation and lifetime issues (the additives are water soluble and degrades over time). And as you mentioned there are many steps in getting even to powdered silica feedstock.

It'll probably use a flotation glass method (liquid glass on liquid metal bed), and here the gravity may even help because normally molten glass spreads until it's 6mm thick. We may find the gravity lets it settle at 1.8mm thick. Now just that statement alone shows just how much work is ahead. The first manned expedition would probably have a bunch of little mining, refining and manufacturing experiments just to see how everything works on Mars, along with little prototypes of structures.

The domes themselves need not be spheres. In addition to flattened spheres, you can also subtract dome sections from domes. By doing this, you sacrifice the internal volume but keep the surface area constant, reducing stress on the dome's surface.
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Online CuddlyRocket

Re: Elon Musk: glass geodesic domes
« Reply #394 on: 01/21/2019 06:20 pm »
Electric melting of glass is not efficient, electric heat is not efficient in general, at least on earth.  A gas furnace can melt glass easier, unless solar can be concentrated directy on the silicone, or directly on iron, aluminum etc and can get hot enough.  The plant you referenced got the water to 550 C.  Pretty hot, but silicone melts at 1,400 C, while aluminum is 660 C.  Can a reflective solar plant on Mars get as hot as it does on earth?

I think you mean silica (silicon dioxide)

He certainly didn't mean silicone! :)

Offline Paul451

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Re: Elon Musk: glass geodesic domes
« Reply #395 on: 01/22/2019 06:01 am »
Making glass from raw materials is a complex process, requiring enough chemicals and purification steps, many which will need to be different enough on Mars, that picking a heat-source will be the smallest issue to solve.
Glass can be pure silica,

Except even high quality sand is not pure silica.

Getting from sand to silica is a complex, chemical hungry process. With enough steps (remembering that you have to make everything else you use) that the step "heat the purified silica until it melts" is such a trivial step, it can be ignored or treated as solved in a thread like this one. It's everything else that needs to be fleshed out.

[edit: Oops, didn't see this sentence in your comment: "And as you mentioned there are many steps in getting even to powdered silica feedstock." D'oh.]

flotation glass method (liquid glass on liquid metal bed), and here the gravity may even help because normally molten glass spreads until it's 6mm thick. We may find the gravity lets it settle at 1.8mm thick.

What's the reasoning for the latter? I would assume the minimum thickness is a function of gravity and surface tension. Less gravity, the greater the effect of surface tension and so the thicker the glass panes (without further rolling/stretching.)
« Last Edit: 01/22/2019 11:18 pm by Paul451 »

Offline rarchimedes

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Re: Elon Musk: glass geodesic domes
« Reply #396 on: 01/22/2019 06:23 am »
Every once in a while, Elon spouts off on a subject without spending the time and brain cells to have control of the subject. Geodesics only work as compression structures. I suppose one could dump a geodesic dome, inverted, into a well or trench, but that would not be volumetrically efficient and would require anchoring to prevent unintended blowouts. In addition, such a negative structure would have difficulty providing the desired insolation. Without a fairly thick layer of water or other filter, illuminated surfaces would merely become sterile due to ionizing radiation. To work safely, mirrors or light tubes would be necessary. I would suggest that in the absence of a mitigating atmosphere to significantly protect from all but the lightest of objects, no atmosphere containing volume should be directly exposed to incoming objects, considering the risks of unpredictable loss of that atmosphere. That way, significant mass could be interposed, with mirrors to bring in light/heat. Since it seems unlikely that reasonable amounts of glass can be brought in or produced in the short to medium term, early habitats should be largely buried or installed in caves, with artificial lighting where light is needed. The most likely early, in situ solids to be produced on Mars are ceramics, then metals, with mirror coatings easily transported and applied. In some perfect world, the constituents of usable glass to be produced with a rational level of effort on Mars will jump up and make themselves available. Lacking that highly unlikely discovery, we need to proceed as I have noted here. The one absolute necessity for human survival on Mars is H2O and lots of it. The corollary to that is the amount of energy necessary to process that water. The only rational and dependable source of that energy is nuclear, as sufficient solar panels or concentrated solar for all needs seems more than a stretch. I would recommend a liquid metal/thorium reactor for the best longevity and safety. Such a reactor would not be pressurized and would be passively safe and could work beautifully in a vacuum or near vacuum environment. 

Offline rarchimedes

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Re: Elon Musk: glass geodesic domes
« Reply #397 on: 01/22/2019 06:45 am »
I missed a point. Yes, methane and oxygen can be probably separated/combined from the existing atmosphere and water in quantities sufficient for rocket fuel, but I doubt that sufficient can be obtained to make glass. It may even turn out that hydrolox is the only reasonably efficient rocket fuel. Any way you figure it, it will be quite a while before sufficient energy is available to make glass of reasonable quality for any purpose. Just off the top of my head, I suspect that thicknesses of frozen water will make the best windows for quite some time, as well as providing good radiation protection. We might want to take along some surface films to reduce deliquescence and/or evaporation.

Offline JamesH65

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Re: Elon Musk: glass geodesic domes
« Reply #398 on: 01/22/2019 11:56 am »
I missed a point. Yes, methane and oxygen can be probably separated/combined from the existing atmosphere and water in quantities sufficient for rocket fuel, but I doubt that sufficient can be obtained to make glass. It may even turn out that hydrolox is the only reasonably efficient rocket fuel. Any way you figure it, it will be quite a while before sufficient energy is available to make glass of reasonable quality for any purpose. Just off the top of my head, I suspect that thicknesses of frozen water will make the best windows for quite some time, as well as providing good radiation protection. We might want to take along some surface films to reduce deliquescence and/or evaporation.

You also missed paragraphs which would make your post a lot more readable.

Offline Lampyridae

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Re: Elon Musk: glass geodesic domes
« Reply #399 on: 01/22/2019 12:22 pm »
Making glass from raw materials is a complex process, requiring enough chemicals and purification steps, many which will need to be different enough on Mars, that picking a heat-source will be the smallest issue to solve.
Glass can be pure silica,

Except even high quality sand is not pure silica.

Getting from sand to silica is a complex, chemical hungry process. With enough steps (remembering that you have to make everything else you use) that the step "heat the purified silica until it melts" is such a trivial step, it can be ignored or treated as solved in a thread like this one. It's everything else that needs to be fleshed out.

Yeah, I'm not disagreeing with you... pretty much said the same thing. What I'm saying is that it's possible to make glass, the ancient Phoenicians did it, but it depends what kind of glass. Beads and jugs are a far cry even from the glass bricks of the 1800s used for natural lighting.

Quote
flotation glass method (liquid glass on liquid metal bed), and here the gravity may even help because normally molten glass spreads until it's 6mm thick. We may find the gravity lets it settle at 1.8mm thick.

What's the reasoning for the latter? I would assume the minimum thickness is a function of gravity and surface tension. Less gravity, the greater the effect of surface tension and so the thicker the glass panes (without further rolling/stretching.)

That would be my assumption, yes. Well, we don't have anything other than a theoretical grasp of how industrial processes would work in reduced gravity so it would be good to find out how this stuff actually works. Glass fibres grown (extruded?) in zero gravity can be extremely pure with minimal stresses, so perhaps glass made on Mars might be a bit stronger than the same glass made on Earth.
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