Construction technology for Mars?

tahanson43206 · 2019-12-17 07:41:10

For Calliban re #124

Thank you for collecting and posting this summary!

For those who are new to the forum, Calliban can go back to edit the post to add more related information as time passes.

The purpose of THIS post is to try to insure Calliban's contribution is easy to find:

SearchTerm:EmbodiedEnergyMars
SearchTerm:EnergyEmbodiedMars

(th)

GW Johnson · 2019-12-17 09:25:48

Basic strength and embodied energy are important, but there is more to consider than just them. For one, there is stiffness. For another there is vulnerability to impact damage.

Stiffness is related to geometry and to a material property called Young's modulus. Foundations need to be stiff in order to spread the load out over a larger area of the stuff below. Concrete made with steel rebar will be a lot stiffer than concrete made with not-steel rebar. That's because steel has such a high Young's modulus compared to most other not-steel materials. And that's a fact, Jack.

This stiffness issue is why carbon-epoxy composites are preferred over the others like glass-polyester or vinyl ester composites. Yet those others resist impact damage far better than carbon-epoxy. This has to do with the area under the effective stress-strain curve to failure. With a short plastic strain capability on that curve for carbon-epoxy, the energy under the curve is lower; further, physically, the damage is usually hidden from the eye, an extreme danger for a load-bearing structure. That is why I dislike (extremely) using carbon-epoxy for primary load-bearing flight structures in aircraft.

There is also the under-appreciated issue of connections between greatly-differing materials: such as between composites and metallic structures. Get that wrong, and your structure is a lot weaker than you think it is. Guaranteed failure mode. See on my "exrocketman" site an article titled "Commentary on Composite-Metal Joints" dated 13 June 2015, for some tested insights into how to do that job correctly.

Structural design is a lot more complicated than most folks think.

GW

Last edited by GW Johnson (2019-12-17 09:28:05)

kbd512 · 2019-12-17 11:49:26

If we're trying to provide radiation protection, then all the experimental data on GCR says we need about 2 meters of regolith overhead to provide an Earth sea level radiation environment. Apart from nuclear reactor containment buildings and bunkers, we don't build anything else with 2 meters thick walls. None of those things have been built with a significant premium on labor, equipment, or resources. All of those things are built on bedrock, which is ultimately what's supporting the incredible weight of the structure on top of it.

Whatever it is that we're trying to build, if humans are living out their entire lives inside of it then it's essentially a fallout shelter. We don't build fallout shelters above ground here on Earth and I would question the notion that it'd be any easier to do that on Mars.

If it's not that, then what else is it that we want to build that would require a steel reinforced concrete foundation?

Since we've yet to figure out where we're sourcing the construction materials from and have yet to set foot on the surface of the planet, do we have an imminent requirement for structures that are so heavy that simply digging down to bedrock won't be sufficient to support the weight?

If it turns out that we can't source the materials required to make concrete, or can't make it without substantial precursor technology to control the temperature and pressure at the work site, then no matter how infinitely preferable it may be to some other technology, we're either going to devise an alternative or the structure won't be built.

SpaceNut · 2019-12-17 13:52:13

The final structure for long term would need the full thickness and be below ground but what if the surface is the means to to being able to build with less materials while being sheltered? Change how we build using what we can. There is plenty of materials to make use of from cargo BFR as its not going back.

The ship outer plate materials could be used to make it so that you have an inside shell for the regolith to be add to around it. Then add more on the inside to make up the dimensions required if required. Take the nose off from a bfr and use that as the arched top structure to build up the regolith over it.

Insulated Concrete Forms Foundations
ICFs provide durability and insulation for below-grade walls. Constructing ICF foundations involves dry-stacking expanded polystyrene foam panels, or interlocking hollow extruded polystyrene foam, to a foundation's length. The forms are reinforced and braced.

https://www.foxblocks.com/blog/icf-vs-poured-concrete

https://buildblock.com/how-to-build-an- … undations/

https://www.homedepot.com/p/SmartBlock- … /203012853

tahanson43206 · 2019-12-17 19:50:10

The article at the link below describes maintenance activities at Thule Air Force Base in Greenland. The author mentions the need to keep buildings above the ground, as reported by RobertDyck earlier in the forum. One recent activity that might be of interest is destruction of older buildings which were scattered across the terrain, and construction of new ones to improve heating efficiency.

https://www.yahoo.com/news/us-army-engi … 17923.html

(th)

Yggdrasil · 2020-01-25 12:57:37

While not an engineer, it's always been surprising to me that so many/most design concepts for Mars habitats fail to take the challenges seriously – materials, pressure, construction methods required, etc – and it's refreshing to see such a well-informed discussion. Thank you all for sharing your expertise and thoughts!

I found this post on Casey Handmer's blog about using a thin, flexible tensile membrane supported by its own pressure to pressurize large areas for habitation and manufacturing very interesting, as it addresses many of the problems you've been discussing in this thread, and also addresses the need for large amounts of space to create an industrial base, which is seldom discussed:

https://caseyhandmer.wordpress.com/2019 … ver-rated/

Do you think this concept holds up? Any thoughts?

Last edited by Yggdrasil (2020-01-25 18:02:27)

SpaceNut · 2020-01-25 14:40:54

Welcome to NewMars Yggdrasil, the posting of links will change.

I think part of that is they are not considering building at all and that what they came in is the only home they will ever know. So depending on the size of the can you came in as well as to how many crew members you are sharing it with, one could go nuts after a period of time.

Of course as other have indicate energy efficiency is a must for not only heat lose but for all other functions requiring it as mars has a starting deficit when compared to earth.

tahanson43206 · 2020-01-25 15:32:05

For Yggdrasil re Post #131

Thank you for your interesting post, and for the link to a site which I have not seen before.

Here is the link you should now be able to create: https://caseyhandmer.wordpress.com/2019 … ver-rated/

***
We seem to receive a great number of registrations, but very few folks try to post anything, and of those, the vast majority are spam sales agents of one kind or another. Thank you for your contribution, and I hope you will help in future as you have done on this occasion.

Edit: I am back from reading as far as:

How does redundancy work?

So far I'm finding this gent's offering to be well worth my time.

For Yggdrasil ... To set off text in quotes as I have done above, you can use commands from a subset of html, whose name I have already forgotten.

In this case, start with [ q u o t e ] and finish with [ / q u o t e ]

Of course, you'll remove the spaces I have inserted to show you the syntax.

(th)

Last edited by tahanson43206 (2020-01-25 15:48:22)

louis · 2020-01-25 17:40:39

I thought the article was excellent - very grounded and not dodging any important issues.

The case made against domes was strong.

The proposed solution for habitation is interesting. I suggested something similar on this site a few years ago. I was wondering whether we could create a pressurised environment (but low pressure) using that sort of material simply resting on supports with the edges sealed by many tons of regolith. My thought was we could create an area where people could walk for long distances in something more like an "outdoors" experience; this could be a Mars atmosphere environment, with people using respirators to breathe.

One issue I would have with Casey Handmer's proposed solution is that he seems to accept you have to build habitations within the space created. So it's hardly a resource-effective solution from that point of view.

Personally I favour (a) cut and cover habs (b) covered gorges, (c) inflatables and (d) bolt together, quick assembly units.

I disagreed with some statements:

"That said, the surface of Mars is next level in terms of its sheer hostility to life. It’s a pitiless frozen vacuum. The Earth’s south pole in the middle of winter is closer to a beach in Hawaii than the nicest place on Mars on the nicest day of the year. "

Summer temperatures during the hours of light are frequently well above zero on Mars up to about 20 degrees celsius. Also, Mars has no hurricanes, major tornadoes, strong winds, big earthquakes,exploding volcanoes, tsunamis, floods (well except in a few places perhaps), deluges, snow (a few flakes perhaps) or hailstones. In many ways it is a benign environment.

"...the Mars city will need teams of specialists to replicate every part of the modern industrial stack, from raw material extraction and processing through to advanced lithography, and everything in between. This process is enormously labor intensive, requiring on the order of 100 million humans on Earth. "

I think the figure of 100 million may be valid for Earth - but that is serving a world population of 7 billion. The UK has 470,000 hospital doctors and nurses for a population nearing 70 million. So about 1 in 150. For a population of 100,000 on Mars the equivalent would be around 660 (of whom about 200 would be doctors). That would provide a reasonable spread of surgical expertise. Perhaps the settlement could not undertake some procedures, such as complicated transplants, but that would not affect the settlement's ability to thrive. But of course in the UK, there is a high proportion of unhealthy people. The same will not likely apply on Mars.

Some techniques - I would suggest advanced lithography might be one of them, along with paper manufacture - will not be required at all on Mars. Also, expertise does not need to cover so much ground on Mars as on Earth. On Earth we need experts in a wide range of energy systems e.g. hydro, coal, gas, wind, solar, nuclear etc. On Mars we might need experts only in solar energy and methane to have a workable energy industry. That sort of shortening of range could be the pattern across various industries.

JUST TO ADD (edit): Earlier saw a YT video on the Apollo project mentioning that at its peak Apollo was employing 400,000 people. How many people are Space X employing for their Mars colonisation programme? I'd guess less than 5,000.

Yggdrasil wrote:

While not an engineer, it's always been surprising to me that so many/most design concepts for Mars habitats fail to take the challenges seriously – materials, pressure, construction methods required, etc – and it's refreshing to see such a well-informed discussion. Thank you all for sharing your expertise and thoughts!
I found this post on Casey Handmer's blog about using a thin, flexible tensile membrane supported by its own pressure to pressurize large areas for habitation and manufacturing very interesting, as it addresses many of the problems you've been discussing in this thread, and also addresses the need for large amounts of space to create an industrial base, which is seldom discussed:
I'm not allowed to post links, but if you google
2019/11/28/domes-are-very-over-rated/
it'll be the top search result.
Do you think this concept holds up? Any thoughts?

Last edited by louis (2020-01-25 20:54:15)

Calliban · 2020-01-26 11:34:48

tahanson43206 wrote:

For Yggdrasil re Post #131
Thank you for your interesting post, and for the link to a site which I have not seen before.
Here is the link you should now be able to create: https://caseyhandmer.wordpress.com/2019 … ver-rated/
***
We seem to receive a great number of registrations, but very few folks try to post anything, and of those, the vast majority are spam sales agents of one kind or another. Thank you for your contribution, and I hope you will help in future as you have done on this occasion.
Edit: I am back from reading as far as:
How does redundancy work?
So far I'm finding this gent's offering to be well worth my time.
For Yggdrasil ... To set off text in quotes as I have done above, you can use commands from a subset of html, whose name I have already forgotten.
In this case, start with [ q u o t e ] and finish with [ / q u o t e ]
Of course, you'll remove the spaces I have inserted to show you the syntax.
(th)

I just read the article.
https://caseyhandmer.wordpress.com/2019 … ver-rated/

It is quite convincing. To summarise, the author recommends deploying large horizontal fibre-reinforced ETFE (Ethylene tetrafluoroethylene) sheets across the surface of Mars. These are regularly anchored to the ground using tensile steel cables. The structure can be thought of as a transparent tensile tent.
https://en.wikipedia.org/wiki/ETFE

The author does not believe underground living is the way to go, because digging out living space is both labour and energy intensive. They also make it difficult to allow natural light into habitats. He cites this as a reason that it has not been widely deployed on Earth.

A thoughts on the ETFE approach:

1. Tensile stresses tend to force polymers into curved shapes. So a EFTE tent would have the appearance of a mattress. There would be dust accumulation in depressions. Static charge may become a problem that would encourage dust accumulation across the transparency.

2. We have discussed in the past just how energy intensive plastics would be on Mars. Producing methane from H2O and CO2 is only about 5-8% efficient in terms of captured energy. So producing a single kg of EFTE, would require somewhere in the region of 1GJ primary energy.

3. It is unclear which fibres would be used to reinforce the EFTE or what their embodied energy would be. How much fibre-reinforced EFTE would be needed to produce an acre of land?

4. Fire would be a significant risk in any pressurised habitat. It would appear to be worse in a habitat with a plastic roof. Presumably, we would need an inbuilt watermist type system to protect the roof in the event of fire.

Last edited by Calliban (2020-01-26 11:36:57)

tahanson43206 · 2020-01-26 13:10:30

For Calliban re #135 ...

Nice to see your review of the plastic roof proposal, and comments pro and con.

I was taken by the author's mention of the elevation the roof could achieve if the steel cables are relied upon to hold against internal pressure due to their own weight. That is an interesting thought, even though the author admitted it was a bit on the speculative side.

To your point about dust collecting in the nadir of the junctions ...

Potentially that could be turned into a benefit, if the locations are tapped periodically. I'm unsure of the potential value of the collected dust, but since Ma Nature is hard at work filtering material for humans to think about, perhaps there is value I'm just not aware of.

I scanned the article at this link but did not pull out a clear analysis of Martian dust: https://en.wikipedia.org/wiki/Martian_soil

One possibility ** might ** be that the dust is lower in perchlorates than the non-airborne regolith, but that is (of course) only a speculation at this point.

However, if there is some useful differentiation provided by the airborne phase of transport of material, the nadir of the nodes would be a good place to collect it.

Edit: One thing seems clear ... the airborne differentiation process will provide finer material to work with than would be the case if a shovel were used to put material into a hopper.

(th)

Last edited by tahanson43206 (2020-01-26 13:12:22)

SpaceNut · 2020-01-26 16:02:27

ETFE (Ethylene tetrafluoroethylene) is one of the favorites that RobertDyck has proposed for Greenhouse use as it can tolerate the martian temperatures and high UV levels. In one of the topics I had proposed a pizza like foldable container with a layer of aerogel and a second pizza container to form a multi traingle panel that would be used tyo make a geodesic dome.

louis · 2020-01-26 18:40:26

Casey Handmer places a lot of emphasis on steel in creating a self-sufficient industrial infrastructure on Mars.

I'd like to put the case for use of basalt:

https://beyondmaterials.com.au/2018/06/ … -concrete/

https://www.made-in-china.com/products- … Slabs.html

http://www.gly.uga.edu/railsback/BS/BS-Loa.html

https://www.tikamoon.co.uk/art-nobu-bas … UEQAvD_BwE

Basalt can be used in a huge variety of ways.

Basalt slabs could be used as lining for habs on Mars (floor, walls and ceilings) - particularly useful I would suggest for cut and cover type of construction.

Lava stone bricks can be used in construction.

Basalt rods can be used to reinforce concrete.

Basalt fibres can be used in the creation of fibre glass.

Basalt slabs can be used as hygienic surfaces in the kitchen and bathroom.

Basalt can be used for wash hand basins, sinks, bowls and various utensils.

Lava rocks are more often than not very impermeable to water. Gas impermeability seems to vary as far as I can make out. Whether they could be made suitable for sealing pressurised environments is an interesting question...I would think there could be applications which would seal the nano holes through which gas can escape.

Anyway, basalt is a versatile material that is readily available on the Martian surface. I am sure it makes sense to use it to its full potential.

kbd512 · 2020-01-26 19:10:57

Louis,

Well, for once we agree on something. Casey Handmer either doesn't have a realistic answer to or profoundly underestimates the difficulty of making useful quantities of structural quality steels with consistent mechanical properties, as compared to basalt fibers, which would require less energy and equipment to process into useful construction materials in the quantities required to support a sizable colony.

louis · 2020-01-26 19:35:40

Yay! One should always celebrate agreement!

kbd512 wrote:

Louis,
Well, for once we agree on something. Casey Handmer either doesn't have a realistic answer to or profoundly underestimates the difficulty of making useful quantities of structural quality steels with consistent mechanical properties, as compared to basalt fibers, which would require less energy and equipment to process into useful construction materials in the quantities required to support a sizable colony.

louis · 2020-01-26 19:37:18

I think thick basalt slabs could be used as structural elements in construction, but I need to investigate that a bit more.

Terraformer · 2020-01-27 06:27:13

Another thing that has to be borne in mind is, buildings perform a multitude of functions, and not all of them have to be done by a single layer. We could have, for example, an unpressurised greenhouse that exists to filter UV and provide a warmer environment. Inside that, there could be a low-pressure farm hab, which provides food and oxygen, and filters water. Inside that, a pressurised hab for people to live in.

Calliban · 2020-01-27 18:46:42

Would agree with Louis on the use of basalt as a structural material. In terms of melting it into fibres designed to take tensile loads, it would appear to be a much better option than steel.

The limited information I can find puts the melting point of basalt at 1500C and latent heat of melting of 840kj/kg, assumingsimilar qualities to glass. Let's take specific heat to be 1KJ/KgK. To melt 1kg of basalt would take 2.3MJ if perfectly efficient. That is about a tenth the energy cost of virgin steel.
https://www.researchgate.net/post/What_ … _rock_wool

But basalt has about one third of the density of steel and about 4-8 times its tensile strength. So, building a tensile structure using basalt ropes, would consume less than 1% of the energy needed to make it from steel. What's more, because basalt is an ionic substance, it can be melted in an electric induction furnace with very little heat loss. It therefore makes little sense using steel to make tensile members. Basalt fibres should be far more cost effective.
https://www.build-on-prince.com/basalt-fiber.html

For cut and fill underground habitats, basalt can be cast into beams and columns simply by pouring it into steel moulds. It could be reinforced using higher melting point fibres. Alternatively, it could be cast into arches for entirely compressive elements. It would appear to be relatively easy to assemble a cast basalt form work within a crater or other depression and then bulldoze a few metres of overburden over the top of it. Hexagonal blocks could be assembled into free standing domes, which could either be covered with overburden or placed under tension using basalt fibres.

For tent like structures, basalt could be woven into nets, supporting transparent polymer membranes. Given the relatively high energy cost of polymers, the most energy efficient solution involves short spans in the netting, supporting a relatively thin polymer sheet.

It is easy to imagine cast basalt becoming the most important structural material on Mars.

Last edited by Calliban (2020-01-27 19:05:41)

louis · 2020-01-27 19:11:26

Thanks for that summary Calliban - very helpful.

Sounds to me like developing a multi-application basalt industry should be a priority for the early settlement.

Calliban wrote:

Would agree with Louis on the use of basalt as a structural material. In terms of melting it into fibres designed to take tensile loads, it would appear to be a much better option than steel.
The limited information I can find puts the melting point of basalt at 1500C and latent heat of melting of 840kj/kg, assumingsimilar qualities to glass. Let's take specific heat to be 1KJ/KgK. To melt 1kg of basalt would take 2.3MJ if perfectly efficient. That is about a tenth the energy cost of virgin steel.
https://www.researchgate.net/post/What_ … _rock_wool
But basalt has about one third of the density of steel and about 4-8 times its tensile strength. So, building a tensile structure using basalt ropes, would consume less than 1% of the energy needed to make it from steel. What's more, because basalt is an ionic substance, it can be melted in an electric induction furnace with very little heat loss. It therefore makes little sense using steel to make tensile members. Basalt fibres should be far more cost effective.
https://www.build-on-prince.com/basalt-fiber.html
For cut and fill underground habitats, basalt can be cast into beams and columns simply by pouring it into steel moulds. It could be reinforced using higher melting point fibres. Alternatively, it could be cast into arches for entirely compressive elements. It would appear to be relatively easy to assemble a cast basalt form work within a crater or other depression and then bulldoze a few metres of overburden over the top of it. Hexagonal blocks could be assembled into free standing domes, which could either be covered with overburden or placed under tension using basalt fibres.
For tent like structures, basalt could be woven into nets, supporting transparent polymer membranes. Given the relatively high energy cost of polymers, the most energy efficient solution involves short spans in the netting, supporting a relatively thin polymer sheet.
It is easy to imagine cast basalt becoming the most important structural material on Mars.

SpaceNut · 2020-01-27 19:36:36

Here are some more of those project and technologies just waiting in the wings to use
http://canada.marssociety.org/winnipeg/materials.html

Calliban · 2020-01-27 19:49:53

One the materials mentioned on the Mars Society webpage is plastics, which it is noted, can be produced using CO2 and H2. The problem here is that even on Earth plastics typically have high embodied energy: 50-100MJ/kg. But we are fortunate, in having huge feedstock of fossil fuels on earth that we don't really have to pay much for. The only cost is the cost of extracting them from the ground.

On another thread, it was established that the chemical reaction steps converting CO2 and H2 into methane and oxygen, were 5-8% efficient. About 1/5th of the mass of the bipropellant is methane. Assuming that methane is used as the starting material for plastics, and has a heat of combustion of about 50MJ/kg, then manufacturing it from CO2 and H2 would require an energy investment of 600-1000MJ/kg. Compare that to measly 3MJ/kg energy cost of cast basalt or the 30MJ/kg energy cost of steel and you begin to get the scale of the problem..

Finding a natural source of methane, or any concentrated organic material on Mars, would be a huge asset to any plastics industry on Mars. Along with water supply, it may turn out to be a key siting criteria. If you want to make steel, it is also a useful reducing agent.

Last edited by Calliban (2020-01-27 19:53:14)

SpaceNut · 2020-01-27 20:12:24

The ethane outputs from the sabetier can be altered with different initial inputs and temperatures so as to make others which can go direct into making of the plastics.

Terraformer · 2020-01-28 06:10:04

Oooh. 4 Vesta apparently has basalt. Perhaps a good construction material for space habitats? Though around Terra, you could just get it from Luna - the energy cost of mining and launching it is a lot less than the energy cost of polymers, even if you had water and CO2 for free in orbit.

I'm quite relieved to hear that plastics will be quite rare once we no longer have cheap oil. They're good, but so overused.

Yggdrasil · 2020-01-29 12:33:10

Thank you all for the welcoming comments – having lurked here for many years, I really appreciate being able to contribute to a constructive discussion. I've emailed Casey Handmer to invite him to join the discussion, and I hope he does. I would be very interested in hearing what he thinks of e.g. using basalt instead of steel, and the challenges of producing the necessary quantities of plastics.

Speaking of constructive thinking about solutions for establishing a sustainable human presence on Mars, there's a new book coming out that looks to be interesting – I hope these solutions are realistic, and take the challenges discussed here into account:

https://www.marssociety.org/news/2020/0 … RO7FQJqVKM

By the way, referring to the earlier discussion about the challenges of how low Martian temperatures can affect the structural integrity of materials such as steel, do you see any potential problems for e.g. the outer layers of Starship when used as an interim habitat, as has been suggested by SpaceX?

louis · 2020-01-29 19:01:41

I am sure the content of the book's great but the graphics!!! We need to move away from the 80s red dust vibe! It's horrible!!

Let's use more real colour. Let's picture people more as they would be on Mars ie in pressurised environments, indoors or in vehicles, not undertaking hazardous EVAs.

Yggdrasil wrote:

Thank you all for the welcoming comments – having lurked here for many years, I really appreciate being able to contribute to a constructive discussion. I've emailed Casey Handmer to invite him to join the discussion, and I hope he does. I would be very interested in hearing what he thinks of e.g. using basalt instead of steel, and the challenges of producing the necessary quantities of plastics.
Speaking of constructive thinking about solutions for establishing a sustainable human presence on Mars, there's a new book coming out that looks to be interesting – I hope these solutions are realistic, and take the challenges discussed here into account:
https://www.marssociety.org/news/2020/0 … RO7FQJqVKM
By the way, referring to the earlier discussion about the challenges of how low Martian temperatures can affect the structural integrity of materials such as steel, do you see any potential problems for e.g. the outer layers of Starship when used as an interim habitat, as has been suggested by SpaceX?

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