Author Topic: Envisioning Amazing Martian Habitats  (Read 88923 times)

Offline john smith 19

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Re: Envisioning Amazing Martian Habitats
« Reply #1120 on: 03/12/2017 04:20 PM »
Concrete will be tricky on mars, no limestone.

It could be marscrete. A material made from local resources, not limestone. It needs less energy to produce, too.The material is even better than normal concrete except it is not very resistant to water. Not a concern on Mars.


This stuff sounds like a real winner for Mars. Multiple potential raw materials (at least some already confirmed on Mars, hopefully the ideal source will be as well). Minimal water usage. Substantially less energy and physical properties as good as (or maybe a bit better) than conventional Portland cement. Sticks to almost anything so good for air sealing caves as well.

It's water stability may be a slight issue. Obvious ideas would be to make it the external structural shell for a pressure tight internal membrane (so all the rest of the regolith can be scooped on top of it. Or the surface can be sealed with some kind of watertight  coating (essentially high tech paint).

Energy wise this sounds like it would be a much better idea to do focused solar rather than the trouble of PV arrays to electricity to heat.

It sounds like you could build hardware on a viable scale for Mars that could really do this, provided you can land somewhere near the necessary supplies of raw materials.

[EDIT I'll note this is V 0.1 technology, hence the large proportion of trapped air. On Mars I would not expect this to be a major issue, with a near vacuum available at the opening of a tap to the outside, if the use of a vibrator is not enough ]
« Last Edit: 03/12/2017 04:38 PM by john smith 19 »
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline Paul451

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Re: Envisioning Amazing Martian Habitats
« Reply #1121 on: 03/13/2017 03:22 AM »
Energy wise this sounds like it would be a much better idea to do focused solar rather than the trouble of PV arrays to electricity to heat.

Atmospheric dust scatters sunlight amazingly well. Even on a bright clear day on Mars, you can lose 30% of direct light. Concentrator-mirrors can't work with scattered light, but solar panels are barely affected. Additionally, solar panels produce general purpose electricity (obviously), which can be diverted to any use, especially in an emergency. Solar furnaces will be single-purpose dedicated systems, nearly worthless for backing up other systems.

So, IMO, even with the loss of efficiency with solar PV, the net benefits vastly outweigh the costs.

Offline john smith 19

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Re: Envisioning Amazing Martian Habitats
« Reply #1122 on: 03/14/2017 10:21 PM »
Energy wise this sounds like it would be a much better idea to do focused solar rather than the trouble of PV arrays to electricity to heat.

Atmospheric dust scatters sunlight amazingly well. Even on a bright clear day on Mars, you can lose 30% of direct light. Concentrator-mirrors can't work with scattered light, but solar panels are barely affected. Additionally, solar panels produce general purpose electricity (obviously), which can be diverted to any use, especially in an emergency. Solar furnaces will be single-purpose dedicated systems, nearly worthless for backing up other systems.

So, IMO, even with the loss of efficiency with solar PV, the net benefits vastly outweigh the costs.
The trouble with any sort of bulk material processing (and if people are serious about mass settlement that's what's needed) is they are going to need a lot of raw heat energy.

Multi junction PV's can give 46% efficiency but IIRC they use (focusing) concentrators anyway. OTOH thin film systems have hit 20%+, although less in complete modules. However either ends up dumping the rest as heat. On Mars this should be quite valuable but it won't be anywhere near the temperatures needed to process minerals.

BTW a focused system may lose 30% due to dust scattering. That leaves 70% as usable energy. The reduced gravity also implies you can build large reflector structures with less material to give the same stiffness as Earth.

My instinct is you will need a PV power array but also some focused heat system for multiple materials processing tasks. This is the simplest way to harvest energy from the environment. It has a good TRL and it's much easier (in principal) to build out than PV arrays (excluding possibly thin film types).
In complexity terms it would be this, then biogas then geothermal, then PV, with nuclear a long way down the road.

It's only when you start digging into this stuff you realize how convenient a really large supply of coal or a hydroelectric dam is.  :(
« Last Edit: 03/14/2017 10:25 PM by john smith 19 »
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline ThereIWas3

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Re: Envisioning Amazing Martian Habitats
« Reply #1123 on: 03/14/2017 10:24 PM »
Do high-temp solar furnace processing on Phobos?
"If you want to build a ship, don’t drum up people to collect wood and don’t assign them tasks and work, but rather teach them to long for the endless immensity of the sea" - Antoine de Saint-Exupéry

Offline MickQ

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Re: Envisioning Amazing Martian Habitats
« Reply #1124 on: 03/16/2017 07:47 AM »
Do high-temp solar furnace processing on Phobos?

I see a problem there.  Isn't Phobos tidally locked to Mars ?  At the speed it orbits at you would have a hard time keeping anything focused.

Offline Oersted

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Re: Envisioning Amazing Martian Habitats
« Reply #1125 on: 03/16/2017 10:54 AM »
Hmm, photovoltaics deployed on the surface of Mars will most probably be less complex than a system that involves flying back and forth between Phobos and the Martian surface.

Roll-out thin-film PV sheets (tied down to the Martin surface so they won't lift off when a cleaning dustdevil passes) are basically maintenance-free and highly dependable. I am quite sure they will provide the energy needed on Mars.

Offline john smith 19

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Re: Envisioning Amazing Martian Habitats
« Reply #1126 on: 03/16/2017 01:37 PM »
Hmm, photovoltaics deployed on the surface of Mars will most probably be less complex than a system that involves flying back and forth between Phobos and the Martian surface.
True.
Quote from: Oersted
Roll-out thin-film PV sheets (tied down to the Martin surface so they won't lift off when a cleaning dustdevil passes) are basically maintenance-free and highly dependable. I am quite sure they will provide the energy needed on Mars.
I wouldn't bet on that. Roughly speaking Sunlight at Mars surface is about 59% of Earth at SL. Lab scale thin films have hit 20% efficiency and should be available by the time of a landing but that gives you about 120W/m^2 of surface, rather than the close to 200W/m^2 you can expect at the Earths surface.

That might be fine for electricity use but will cause trouble once you get into "bulk" energy use, like driving rock breaking, rock moving and materials processing. Some of those are just better suited to having the heat generated directly and applied to the problem.

For radiation shielding the best habitats are likely to be either underground or in a cliff face.

However that does not necessarily mean they have to cramped and/or badly lit.  :(
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline Oersted

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Re: Envisioning Amazing Martian Habitats
« Reply #1127 on: 03/16/2017 02:44 PM »
Thanks for your reply, John. However, I don't understand what the problem is. If you need more electricity for energy-intensive construction work you would just lay out more PV film, wouldn't you? It is not as if they lack real estate on the surface. Or is there a problem with having a lot of PV sheets generating electricity without "tapping it off"? Sorry, I just don't know.

I totally agree that tunneling is the way to go for the initial habitats and internal space. That has been quite conclusively proven in this thread, I think, and Musk seems to have arrived at the same conclusion it seems, given his new-found interest in the subject.

Offline john smith 19

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Re: Envisioning Amazing Martian Habitats
« Reply #1128 on: 03/16/2017 09:06 PM »
Thanks for your reply, John. However, I don't understand what the problem is. If you need more electricity for energy-intensive construction work you would just lay out more PV film, wouldn't you? It is not as if they lack real estate on the surface. Or is there a problem with having a lot of PV sheets generating electricity without "tapping it off"? Sorry, I just don't know.
Electricity is useful for some things and the substantial losses (roughly speaking Mars surface at Noon will give you 12% what the same 20% efficient thin film array would give you at the Earth's surface) IOW throw away 88% of the available sunlight from Earth orbit.

In contrast using solar concentrators (imagine or non imaging) may lose 30% due to dust scatter. That leaves 70% as available energy that can be used to process materials.

One conversion process leaves you leaves you with <20% of your input power (at Mars orbit, which is 41% down on Earth). The other leaves you with 70% as concentrated sunlight.  Neither works after sun down and bulk power storage remains difficult.

In general when it comes to bulk mfg people tend to avoid electricity as a heat source unless there are issues with purity (such as chip mfg) or the most efficient method is electro chemical (for Aluminum smelting). They prefer to work with direct combustion of either a fuel or the raw materials themselves. Without coal or coke you're left with biogas, solar PV or solar thermal.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline biosehnsucht

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Re: Envisioning Amazing Martian Habitats
« Reply #1129 on: 03/17/2017 09:52 PM »
Why not both? Mirrors to concentrate more sunlight into panels?

Online Chris_Pi

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Re: Envisioning Amazing Martian Habitats
« Reply #1130 on: 03/18/2017 03:28 AM »
Why not both? Mirrors to concentrate more sunlight into panels?

Scattering from dust/haze in the atmosphere. The panels themselves don't care what direction the light comes in from but reflectors do. If a large percentage of the light delivered to the panels comes off the reflectors there's a huge drop in power output whenever the weather isn't clear.

Works wonderfully when it does work but a lots of panels approach does better in less than ideal conditions. And anything needing lots of power is probably going to work better with a smaller but less variable supply.

Offline Paul451

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Re: Envisioning Amazing Martian Habitats
« Reply #1131 on: 03/18/2017 08:08 AM »
In contrast using solar concentrators (imagine or non imaging) may lose 30% due to dust scatter. That leaves 70% as available energy that can be used to process materials.

That 70% is best case, on clear mid-summer days at noon, during low-storm years. It's generally much worse. The MER rovers have seen numbers under 2%. (Oppy under 0.5%.) Concentrator-reflectors are a bad idea on Mars.

For example: At Opportunity's site, transmissivity hasn't gotten above 60% for the last 11 months. And is currently at around 20% direct light.

The efficiency of concentrator reflectors directly correlates with focused sunlight, hence will correlate directly with transmissivity. Can an industrial process even operate if it's receiving 20% of it's rated heat? I mean work at all, there will surely be a minimum before the process doesn't work. Boltzmann's law and all that.

PV panels are happy with indirect sky glow. Oppy's solar panels are currently (with ~20% direct transmission) at 2/3rds of the capacity they were 11 months ago (with~60% direct transmission), with roughly similar levels of dust on the PV-array. PV arrays are more consistent and reliable. And during really bad times, you can turn off the heavy-industry production and divert that extra PV acreage to essential services. It's just electricity through wires. You can't do that with concentrator reflectors, they are site-specific, hence task specific.
« Last Edit: 03/18/2017 08:25 AM by Paul451 »

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