Author Topic: Envisioning Amazing Martian Habitats  (Read 316937 times)

Online Tulse

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Re: Envisioning Amazing Martian Habitats
« Reply #1800 on: 02/13/2019 06:35 pm »
The problems might be greatly reduced if a thick layer of clear ice was formed on top of a flat clear plastic ceiling and the air pressure increased underneath it to support it.
Exactly my thought as well -- since water will be part of the ISRU production anyway, why not use it structurally as well?  It has to be easier to make clear ice than glass.

Offline lamontagne

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Re: Envisioning Amazing Martian Habitats
« Reply #1801 on: 02/13/2019 08:35 pm »
The problems might be greatly reduced if a thick layer of clear ice was formed on top of a flat clear plastic ceiling and the air pressure increased underneath it to support it.
Exactly my thought as well -- since water will be part of the ISRU production anyway, why not use it structurally as well?  It has to be easier to make clear ice than glass.

It gets complicated fast.  Your ice musn't melt, yet it's just a plastic pane away from the hot base.
The ice is going to get dusty.  If these dust grains get a bit hot they will melt into the ice and damage it.
Ice is ridiculously weak structurally and breaks easily under impact.  It might be interesting to go with translucent ice, but again there is a serious risk of overheating the ice.  In summer, after all, certain areas of MArs can get fairly hot.
Ice is not very expensive but the cost of thick ice quickly gets out of hand.  See the joined table.  Glass is 14 times more expensive than ice to manufacture on Mars, plastics are 15 times more expensive than glass.  After all, to make plastic on Mars you need to electrolyse water, or to manage to build Algae farms and do extensive treatment to the biomass.

So if your ice is more than 30 cm thick, compared to small glass panes, it will be more expensive.  And you really need about 20m of ice to offset the pressure of a base at 1 atmosphere. 1 atmosphere is 10 tonnes per m2 of pressure, and as water on Mars weighs only 500 kg per m3...  even at reduced pressures it's ridiculously thick.
It's not impossible, just not, IMHO, a cost effective first solution, or even a first century of occupation solution.  For huge domes it might be applicable.

BTW the table is a compendium of various sources about the intrinsic energy costs of materials.  It a trending way of evaluating construction methods.   The values are far from certain, but give a good idea.  The energy cost if to amortize solar panels on Mars over 20 years with 500$ per kg transportation costs.  Optimistic might be a polite description.
« Last Edit: 02/14/2019 12:55 am by lamontagne »

Offline Slarty1080

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Re: Envisioning Amazing Martian Habitats
« Reply #1802 on: 02/13/2019 08:54 pm »
You're probably right for the early habitats, but later on it might have some appeal. I doubt that many of the early habitats would count as amazing in any case. If the upper surface is covered with a thin plastic layer it should be possible to keep the dust out. It would also provide radiation and meteorite protection. Multiple layers of glazing would help insulate the ice from the warm interior.
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Offline Rocket Surgeon

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Re: Envisioning Amazing Martian Habitats
« Reply #1803 on: 02/13/2019 10:13 pm »
The problems might be greatly reduced if a thick layer of clear ice was formed on top of a flat clear plastic ceiling and the air pressure increased underneath it to support it.
Exactly my thought as well -- since water will be part of the ISRU production anyway, why not use it structurally as well?  It has to be easier to make clear ice than glass.

It gets complicated fast.  Your ice musn't melt, yet it's just a plastic pane away from the hot base.
The ice is going to get dusty.  If these dust grains get a bit hot they will melt into the ice and damage it.
Ice is ridiculously weak structurally and breaks easily under impact.  It might be interesting to go with translucent ice, but again there is a serious risk of overheating the ice.  In summer, after all, certain areas of MArs can get fairly hot.
Ice is not very expensive but the cost of thick ice quickly gets out of hand.  See the joined table.  Glass is 14 times more expensive than glass to manufacture on Mars, plastics are 15 times more expensive than glass.  After all, to make plastic on Mars you need to electrolyse water, or to manage to build Algae farms and do extensive treatment to the biomass.

So if your ice is more than 30 cm thick, compared to small glass panes, it will be more expensive.  And you really need about 20m of ice to offset the pressure of a base at 1 atmosphere. 1 atmosphere is 10 tonnes per m2 of pressure, and as water on Mars weighs only 500 kg per m3...  even at reduced pressures it's ridiculously thick.
It's not impossible, just not, IMHO, a cost effective first solution, or even a first century of occupation solution.  For huge domes it might be applicable.

BTW the table is a compendium of various sources about the intrinsic energy costs of materials.  It a trending way of evaluating construction methods.   The values are far from certain, but give a good idea.  The energy cost if to amortize solar panels on Mars over 20 years with 500$ per kg transportation costs.  Optimistic might be a polite description.

Given gravity on Mars is 38% of that on Earth, it'd need to be closer to 27m of water for 1 atmosphere.

Also bare in mind that "clear" ice is about as see-through as water. 27m of water is going to absorb light, making the problem with darkness on Mars even worse... and remember you need to some how build up 27 meters which is basically a 9 storey building, either as a giant tank while the water freezes or lifted into place as specially made 'clear' blocks of ice... and remember that 27 meters doesn't include your living space, so you'd almost certainly have to go higher, or dig deeper.
 
And to be honest, 27,000kg of water per m2 is going to have much better uses on Mars.

Offline RobLynn

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Re: Envisioning Amazing Martian Habitats
« Reply #1804 on: 02/14/2019 12:02 am »
Pretty sure that the basic element of habitat construction on Mars is going to be huge flat stainless steel balloons, laid on slightly dished and flattened ground and then buried under ~10m of dirt before being inflated to create large circular lenticular habitats.  Add a layer of dirt internally to protect floor from damage.
-Lowest manufactured or imported materials input - maybe only a couple of 100 tonnes per hectare.
-Huge internal space to meet psychological need for wide open spaces/vistas and space needed for growing food.
-Good radiation protection and thermal insulation (in fact might even need radiators for cooling).

If someone with a fortune of (say) $20 billion put it into such a habitat then could probably build something on the order of 1km diameter with 50-100million m≥ volume to support several thousand inhabitants using $1000/kg imported stainless steel, and all within 20 years of now.
The glass is neither half full nor half empty, it's just twice as big as it needs to be.

Offline lamontagne

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Re: Envisioning Amazing Martian Habitats
« Reply #1805 on: 02/14/2019 12:50 am »
Pretty sure that the basic element of habitat construction on Mars is going to be huge flat stainless steel balloons, laid on slightly dished and flattened ground and then buried under ~10m of dirt before being inflated to create large circular lenticular habitats.  Add a layer of dirt internally to protect floor from damage.
-Lowest manufactured or imported materials input - maybe only a couple of 100 tonnes per hectare.
-Huge internal space to meet psychological need for wide open spaces/vistas and space needed for growing food.
-Good radiation protection and thermal insulation (in fact might even need radiators for cooling).

If someone with a fortune of (say) $20 billion put it into such a habitat then could probably build something on the order of 1km diameter with 50-100million m≥ volume to support several thousand inhabitants using $1000/kg imported stainless steel, and all within 20 years of now.
Pressure supported domes are great, until they aren't pressurized anymore. 
Add to this a few tonnes of radiation protection regolith, or ice, per m2, and that become a very dangerous situation indeed.

I agree that probably all colonies will need active cooling.  There's just too much loss when the system go down if they are not properly insulated.  If there is no input, then you need a way to lower your output.  And active cooling can be stopped, not passive cooling.

I've added a calculation for a 1 km stainless steel dome, not pressure balanced.  I find it would need to be about 10 cm thick, and mass about 3 to 4 million tonnes when you include the floor.  At 1000$ per kg that's 2 000 billion dollars.  Plus the metal.
It's a simple calculation but I may be wrong.  Feel free to check.


Offline livingjw

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Re: Envisioning Amazing Martian Habitats
« Reply #1806 on: 02/14/2019 01:30 am »
So, you are saying that if it loses its air, it collapses? If it loses it air, I don't think the people inside will care.

Offline lamontagne

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Re: Envisioning Amazing Martian Habitats
« Reply #1807 on: 02/14/2019 01:42 am »
So, you are saying that if it loses its air, it collapses? If it loses it air, I don't think the people inside will care.
Well yes, if there are tonnes of ice or regolith on it to stop radiation.  Depends if it's a gentle collapse or a catastrophic break.  Stainless steel should be more forgiving than ice, in any case. 
As in any building you hope it is built so that you can detect signs of failure and get out before it collapses.  Limit state design.

Offline Eylrid

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Re: Envisioning Amazing Martian Habitats
« Reply #1808 on: 02/14/2019 01:46 am »
If it rapidly depressurizes the people inside will be dead whether it collapses or not.

Offline lamontagne

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Re: Envisioning Amazing Martian Habitats
« Reply #1809 on: 02/14/2019 01:50 am »
If it rapidly depressurizes the people inside will be dead whether it collapses or not.
A well designed dome will not collapse rapidly.  It will collapse gracefully.  Or else it is not a well designed dome.
You need an incredibly large hole in a km wide dome to make it collapse quickly. And one of the virtues of steel is its toughness, that makes large failures unlikely.
Not that I think the dome is a good idea.  I'm a tunnel person, with, at most, little domes to gladden the hearts of peppy colonists :-)
« Last Edit: 02/14/2019 01:51 am by lamontagne »

Offline Lampyridae

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Re: Envisioning Amazing Martian Habitats
« Reply #1810 on: 02/14/2019 07:49 am »
Even for very low ovalities they find strains go up practically 50 times.

At certain locations, yes, but that's kind of a internal shear of the pressure vessel material between inside and outside. Elliptical tank heads are used everywhere. Usually they are overdesigned relative to the cylindrical section anyway because it's a pain to make it a different thickness.

Additonal stress is kinda a good thing for tanks because a tank with two hemispherical heads will experience differential strain at the dome joins... wehen pressurised the cylinder wants to expand more than the domes so you need to account for that with a kind of elbow or just make thick walls and welds.

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Offline Paul451

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Re: Envisioning Amazing Martian Habitats
« Reply #1811 on: 02/14/2019 09:11 am »
So, you are saying that if it loses its air, it collapses? If it loses it air, I don't think the people inside will care.

Sure, but if they get to safety during the pressure loss, afterwards they'll want to be able to repair it by simply fixing the hole and repressurising it, not having to replace the entire structure and everything that is crushed under it. So being able to self-support seems a reasonable minimum requirement.

Offline rsdavis9

Re: Envisioning Amazing Martian Habitats
« Reply #1812 on: 02/14/2019 08:27 pm »
So, you are saying that if it loses its air, it collapses? If it loses it air, I don't think the people inside will care.

Sure, but if they get to safety during the pressure loss, afterwards they'll want to be able to repair it by simply fixing the hole and repressurising it, not having to replace the entire structure and everything that is crushed under it. So being able to self-support seems a reasonable minimum requirement.

Large columns of rock put in place when dome is inflated?

Rock cutting should be a basic skill on mars. Might even be better than concrete because the raw materials are cutting cables, diamond saws, torches. All light compared to the materials of concrete. sand(silica) limestone, lots of heat.

So what do people think about cut rock versus poured cement? It seems like cut rock has a lot of advantages?
Native weight instead of imported.
Lower energy to manufacture.

I know in New England we would rather uses cut rock(granite) for curb stones, lighthouses(well not anymore), breakwaters, boat moorings, etc.

With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
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Offline Oersted

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Re: Envisioning Amazing Martian Habitats
« Reply #1813 on: 02/14/2019 08:33 pm »
The whole dome idea is looking less and less feasible. Won't be a big loss either: glass domes never were a big hit on Earth, why should they be on Mars. Nice panoramic flat glass windows sure, domes.... well. Seems a bit complicated.

rsdavis9, absolutely agree with you: building with slabs cut out of rock makes a lot of sense. I especially love the interlocking stone courses of lighthouses such as Bell rock: https://www.gracesguide.co.uk/images/4/49/JD_Bell_Rock4.jpg

That would make a lot of sense on Mars, to create guaranteed stable and airtight structures.
« Last Edit: 02/14/2019 08:37 pm by Oersted »

Offline RobLynn

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Re: Envisioning Amazing Martian Habitats
« Reply #1814 on: 02/14/2019 09:05 pm »
So, you are saying that if it loses its air, it collapses? If it loses it air, I don't think the people inside will care.

I imagine that one of first jobs after inflation would be to make a flat topped basement floor, living, work and industrial space over entire dome area out of a cheap rock based materials (martian masonry) to allow people to escape and move around to do repairs to the thin membrane in the case of a loss of pressure.  Everything above that layer to be easily collapsible.

Or maybe emergency bouncy-castle type air bag mushrooms that can be inflated rapidly in case of loss of pressure to support entire roof.

Or maybe cover dome in vast array of hexagonal water tanks that can be drained quickly to a reservoir to remove the weight.
The glass is neither half full nor half empty, it's just twice as big as it needs to be.

Offline Slarty1080

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Re: Envisioning Amazing Martian Habitats
« Reply #1815 on: 02/14/2019 09:36 pm »
The problems might be greatly reduced if a thick layer of clear ice was formed on top of a flat clear plastic ceiling and the air pressure increased underneath it to support it.
Exactly my thought as well -- since water will be part of the ISRU production anyway, why not use it structurally as well?  It has to be easier to make clear ice than glass.

It gets complicated fast.  Your ice musn't melt, yet it's just a plastic pane away from the hot base.
The ice is going to get dusty.  If these dust grains get a bit hot they will melt into the ice and damage it.
Ice is ridiculously weak structurally and breaks easily under impact.  It might be interesting to go with translucent ice, but again there is a serious risk of overheating the ice.  In summer, after all, certain areas of MArs can get fairly hot.
Ice is not very expensive but the cost of thick ice quickly gets out of hand.  See the joined table.  Glass is 14 times more expensive than glass to manufacture on Mars, plastics are 15 times more expensive than glass.  After all, to make plastic on Mars you need to electrolyse water, or to manage to build Algae farms and do extensive treatment to the biomass.

So if your ice is more than 30 cm thick, compared to small glass panes, it will be more expensive.  And you really need about 20m of ice to offset the pressure of a base at 1 atmosphere. 1 atmosphere is 10 tonnes per m2 of pressure, and as water on Mars weighs only 500 kg per m3...  even at reduced pressures it's ridiculously thick.
It's not impossible, just not, IMHO, a cost effective first solution, or even a first century of occupation solution.  For huge domes it might be applicable.

BTW the table is a compendium of various sources about the intrinsic energy costs of materials.  It a trending way of evaluating construction methods.   The values are far from certain, but give a good idea.  The energy cost if to amortize solar panels on Mars over 20 years with 500$ per kg transportation costs.  Optimistic might be a polite description.

Given gravity on Mars is 38% of that on Earth, it'd need to be closer to 27m of water for 1 atmosphere.

Also bare in mind that "clear" ice is about as see-through as water. 27m of water is going to absorb light, making the problem with darkness on Mars even worse... and remember you need to some how build up 27 meters which is basically a 9 storey building, either as a giant tank while the water freezes or lifted into place as specially made 'clear' blocks of ice... and remember that 27 meters doesn't include your living space, so you'd almost certainly have to go higher, or dig deeper.
 
And to be honest, 27,000kg of water per m2 is going to have much better uses on Mars.

Yes all true, but thatís worse case. It may not be desirable to have 1 atmosphere of pressure and the ice does not have to carry the entire pressure on its own as I imagine a significant steel structure would still be needed. Even a few metres of ice would help as a radiation shield and aid in the strength of the structure.
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Offline MickQ

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Re: Envisioning Amazing Martian Habitats
« Reply #1816 on: 02/15/2019 12:32 am »
Inflate your dome underneath a rigid spider web of steel bands.  Once in the right position, attach the dome material to the steel with some form of adhesive overstraps glued to the material on either side of a steel member.
This should allow some slight movement due to pressure variations but prevent a full collapse in the case of pressure loss.

Over the top of the steel frame goes multiple layers of clear poly something or other to act as mmod and radiation protection.  Seal the bottom layer/s to the dome material to give an air gap for insulation purposes. When the top gets too dusty just replace the top layer with a fresh, clean one.

Offline Paul451

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Re: Envisioning Amazing Martian Habitats
« Reply #1817 on: 02/15/2019 08:39 am »
to act as mmod and radiation protection.

You don't need MMOD protection on Mars. Micrometeors can't reach the ground, only larger ones.

Inflate your dome

Domes are the wrong shape for a pressure vessel.

Offline Semmel

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Re: Envisioning Amazing Martian Habitats
« Reply #1818 on: 02/15/2019 09:46 am »
How about:
Use curved glass plates that follow the outward curvature, but cover it on the outside with thin wire mesh. These are mounted to beams just as shown before. The trick of the wire mesh on the outside of the windows is, that they take all the tensile forces that the glass cant resist. It would look ugle up close but if you are a few meters away, the mesh would hardly be visible.

Offline Robotbeat

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Re: Envisioning Amazing Martian Habitats
« Reply #1819 on: 02/15/2019 10:44 am »
to act as mmod and radiation protection.

You don't need MMOD protection on Mars. Micrometeors can't reach the ground, only larger ones.

Inflate your dome

Domes are the wrong shape for a pressure vessel.
Wrong on the second part. In fact, if you have only radial reinforcement, a dome (of a specific type) is the ideal shape for a pressure vessel.
« Last Edit: 02/15/2019 10:44 am by Robotbeat »
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