Material Choices for Mars

SpaceNut · 2016-12-08 22:35:03

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

The natural gas is then condensed into a liquid at close to atmospheric pressure by cooling it to approximately −162 °C (−260 °F); maximum transport pressure is set at around 25 kPa (4 psi). LNG typically contains more than 90 percent methane. It also contains small amounts of ethane, propane, butane, some heavier alkanes, and nitrogen.

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

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

The density of liquid propane at 25 °C (77 °F) is 0.493 g/cm3, which is equivalent to 4.11 pounds per U.S. liquid gallon or 493 kg/m3. Propane expands at 1.5% per 10 °F. Thus, liquid propane has a density of approximately 4.2 pounds per gallon (504 kg/m3) at 60 °F (15.6 °C).

http://inspectapedia.com/plumbing/Gas_Pressures.php

•LP gas pressure in the LP gas tank: 100-200 psi LP gas pressure
LP gas pressures inside a propane tank (before the LP tank regulator) can be much higher than at the gas appliance, anywhere between 100 and 200 psi, which explains why a pressure regulator is needed at the tank (dropping the supply pressure to the range given just above) and a second regulator is used at the appliance to regulate the pressure to the levels required by the appliance itself.

3015 · 2017-09-05 20:22:51

RodbertDyck, I know this is going way back in the history of a very old thread, but a couple years ago you did the math showing that PCTFE thickness would be very high for a 6mx12m greenhouse. This paper mentions a way around that by using pillowing to decrease the radius of curvature and therefore put less force on the bladder. The pressure force would instead be mostly on the restraints between pillows, which could have much greater tensile strength than PCTFE. This would allow the PCTFE film to be quite thin.

SpaceNut · 2017-09-05 21:07:44

The issue for a bladder or pillow approach is that the internal pressure within the structure is going to cause the shape of the outer wall of the pillow to bow outward as the inner wall is compressed since there is no counter pressure pushing on the outer wall.

Either the bladder seams will fail between pillows or it will lose structural shape. The figure 4 in the linked pdf shows the latice net that is used to anchor the inflateable structure to the ground would allow for the bladders or pillows to form in between the cords.

I have been looking at geodesic dome construction techiques using like a slice of pizza tray but shaped out of a thicker form of the material. If you want a double layer use a sandwich of aerogel in between them and make a common inner seam for the joint from one panel to the next. The double seam of the pair of traingular shapes and its adjacent seam wpuld be used to create the framing to make the structure strong.

3015 · 2017-09-05 21:30:24

The "pillows" will definitely bow outward, that's why they're used. Force on the wall of a pressure vessel is proportional to the radius of curvature, and the bowed out sections have low radii of curvature and therefore low forces on them. As long as the tethers are close together though I don't think it would change the shape of the vessel much. Or am I misunderstanding your argument?

I'm intrigued by your dome idea. Is aerogel transparent enough for such an idea to be used for a transparent enclosure?

SpaceNut · 2017-09-05 22:21:13

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

Make the triangles simular in shape to the flaps of the box but only in halves with the second half stuck inside with the flap still exposed to create the rib to rivet or bolt together.

RobertDyck · 2017-09-05 23:16:51

3015 wrote:

RodbertDyck, I know this is going way back in the history of a very old thread, but a couple years ago you did the math showing that PCTFE thickness would be very high for a 6mx12m greenhouse. This paper mentions a way around that by using pillowing to decrease the radius of curvature and therefore put less force on the bladder. The pressure force would instead be mostly on the restraints between pillows, which could have much greater tensile strength than PCTFE. This would allow the PCTFE film to be quite thin.

Good idea. We have kicked around the idea of reinforcing the film with thermally applied fibreglass gauze. That would form rip-stop as well as reinforcement. The manufacturer of PCTFE film offers that. An old painting by Robert Murray shows straps over the greenhouse. One purpose is to squish the shape: reduce ceiling height while increasing width. That requires hold-down straps. But to reduce tensile force on the film, each cell must be allowed to "pillow" out. If it's pulled taught then the film experiences all the force for the full structure. Hexagonal cells? You can buy Kevlar webbing straps. Curiosity rover parachute cords were Technora; also an aramid fibre. Technora withstands shock loads and fatigue better than Kevlar, and higher tensile strength. So webbing of that material? All aramid fibres are sensitive to UV, so would require UV protection coating.

Could you post a link to my post, where I did the math?

3015 · 2017-09-06 13:16:42

I like the fiberglass gauze idea. Some glass fibers have ridiculous tensile strengths, and glass is resistant to radiation and a wide range of temperatures.

I'm somewhat skeptical of the idea of squishing the shape of a greenhouse using tethers though, I worry the force on the tethers would be too much. For a hemispheric dome where all the anchors are pulling straight down, I think that the force trying to lift the dome upward is equal to the area under the dome multiplied by the pressure in it. The dome pictured above looks to be at least 6mx12m, if we assume that and a low pressure of 20 kPa, then the force the anchors would have to counter would be 72 m^2 * 20 kPa = 1.44 MN. If there were 36 tethers spaced around the dome at 1 m intervals, each would have to bear 40 kN, which on Mars is the force exerted by 40/3.7=10.8 tons. Is that a level of force that we could manage by drilling anchors into rock? I don't know but it seems like a huge amount.

You did the math on greenhouse thickness in page 1 of this thread in posts #11 and #18. I haven't checked the math but your results are in the ballpark of math I have done for cylindrical greenhouses.

NearryPayob · 2017-09-07 12:41:48

Comparing microstructures in Mars rocks with microstructures in Earth rocks is like comparing clouds with faces? Do you really think so?

SpaceNut · 2017-09-07 16:04:10

only when ignoring that life comes from the same process no mater where we find it and that size is a matter of where it starts as gravity plays a big part in the chemistry of what will happen with that priordial soup.

Not to get the topic to far off topic but Discovery of boron on Mars adds to evidence for habitability and its also another element for making insitu solar cells and other items as well.

RobertDyck · 2017-09-07 17:24:37

I thought Opportunity already discovered Borate. That's boron oxide, which can bond to various minerals. Borate acts as a catalyst to form ribose sugar, one of the components of RNA.

SpaceNut · 2017-09-07 20:22:55

Yes made a post a long time ago 2017-01-02

SpaceNut wrote:

Was reminded of last months Boron find...NASA’s Curiosity Discovers Boron On Mars
But found an earlier news story about Mars Clay Harbored Boron, Key Element For Life, Meteorite Study Suggests

SpaceNut · 2018-12-05 21:21:28

RobertDyck wrote:

Another useful technology for Mars is rock wool. Same insulation as fibreglass but non-flammable, and perhaps more importantly easy to make. It's made by melting rock and extruding. No binder, the hot rock fibres stick together before they cool.
Comfort Batt

SpaceNut · 2019-08-10 12:30:52

very important step for mars insitu use

SpaceNut · 2020-09-06 13:43:57

3D printing in concrete

tahanson43206 wrote:

The article at the link below shows a 3D Printed house in Belgium. The roof and windows were supplied as add-ons, as well as a steel stairway to reach the second floor.
I would assume the second floor was supplied as an add-on as well.
https://www.businessinsider.com/kamp-c- … ium-2020-8
(th)

Or using a material with simular consistency.

https://www.brusselstimes.com/news/busi … /undefined

as you noted what would we use for flooring
this-3d-concrete-printer-just-printed-this-two-story-house-on-site-7.jpg?w=800&h=449

tahanson43206 · 2020-09-28 09:39:15

Void, it is time for this topic from 2017 to return to view ...

From the most recent Sunday edition of the local news outlet, here is a bit of text that potentially sets the stage for a re-thinking of ideas for construction on Mars ...

Buildings rise high with wood
Keith Schneider
The New York Times
SPOKANE, Wash. — Although it
was established in 1873 near some of
North America’s most productive for-
ests, Spokane has rarely focused on
new timber products in construction.
But that is starting to change.
In the city’s downtown, Eastern
Washington University has moved
into the Catalyst Building, a 5-story,
150,000-square-foot structure, the first
tall wood office building in Washington
state. Sunshine pours through the $40
million building’s large windows and
bathes the wood beams and laminated
wood floor and ceiling panels.

Carbon is readily available at Mars.

kbd512 has explored the potential of this material in numerous posts in the forum.

The lower gravity of Mars, and the need to withstand compression loads of rooftop regolith and tension loads of Mars habitat pressure will lead to interesting opportunities and challenges for architects.

(th)

SpaceNut · 2020-09-28 17:46:51

I think wood structure with seal and mass to hold it in place could be used in time.

Calliban · 2020-09-30 08:00:25

As with everywhere else, the correct choice of material will be the one that meets a functional requirement for the minimum possible cost. This isn't an easy thing to determine, because it will be governed by all sorts of logistical considerations, such as the cost of equipment needed to make it, its maintenance costs and of course its mass and the cost of importing it from Earth.

But one can perhaps obtain a crude estimate of the relative cost of a material on Mars, by working out the energy cost of producing it.
https://en.m.wikipedia.org/wiki/Embodied_energy

Iron and plain carbon steel, have embodied energy of about 30MJ/kg here on Earth. On Mars, we will be reducing iron ore using electrolytic hydrogen, with heating probably provided using an electric furnace. Given the efficiency of electrolysis, let's say Martian plain carbon steel would have an embodied energy 10% greater, or 33MJ/kg - say 250GJ/m3. You really need a round the clock power source for steel production, as the electric furnace linings do not like the temperature gradients associated with heating up and cooling down.

Glass production has embodied energy of 15MJ/kg, say 37.5GJ/m3. Glass production involves heating a mixture of oxides to melting point, having first removed iron oxide contaminants by reducing them and removing them with a magnetic, or simply finding a clean feedstock. I don't see why embodied energy would be dramatically greater on Mars, although of course, we won't necessarily have the same feedstock as we do on Earth.

The problem with plastics, is that before we can make them, we must first manufacture the monomers from carbon dioxide, water and other compounds like chlorine and fluorine. The monomer for polyethylene, the simplest polymer, is ethylene, C2H4. A while back, I estimated the efficiency of the production of methane and oxygen from Martian CO2 and water and it came out between 5-8%. The heat of combustion of methane is 50MJ/kg. So 5-8% efficiency, suggests that the embodied energy of Martian methane is 625-1000MJ/kg. If ethylene has a similar embodied energy to methane, then the energy cost of plastics on Mars will be upwards of 1000GJ/m3, with higher values for complex polymers requiring more reaction steps.

Concrete has embodied energy about 1MJ/kg - 2GJ/m3. Martian soil is rich in gypsum, so concrete may be readily producable on Mars. The water content has its own embodied energy of about 1MJ/kg on Mars, as we need to melt ice at temperatures as low as -60C and pump it out of the ground. So let's say 2MJ/kg - 4GJ/m3 for Martian concrete.

Adobe and rammed soil based materials could be very cheap, as we would be mixing Martian fines with water and baking them in a mould. About 90% of the water can be recovered. Embodied energy about 100KJ/kg - 0.2GJ/m3, assuming about 10% water by volume and an equivalent amount of energy for drying the brick, say. For baked (fused) house bricks, say 3MJ/litre, or 3GJ/m3. Of course, a hole in the ground or simple berms of unprocessed regolith could be even cheaper. Stone is relatively energy cheap, but its irregularity may make it labour intensive.

Based on this crude investigation, I will hazard the following. Glass and steel will be moderately cheap on Mars. Adobe and other soil based materials, very cheap. Excavated volumes, even cheaper. Native stone, cheap. Concrete: cheap.
Plastics, very expensive. In terms of building, I would expect to see excavated tunnels, and regolith ballasted adobe and cast mud structures, as the most desirable option in situations where we don't need natural light for crop growth. For food growth, either steel framed glass panel structures, or subterranean greenhouses. In the second case, I would expect to see curved adobe and stone roof structures with adobe and stone supporting columns and steel framed glass panelled skylights. Internal pressure will be balanced by raw regolith and stone overlay. It is possible we would have mixed use structures, with growing areas directly under skylights, and living areas and manufacturing areas in the more shaded regions of the underground structure.

Non-pressurised structures within pressurised areas: expect to see natural stone, adobe, cob and other forms of dried mud, probably with barrel vault roof space, especially in multistorey structures. Interior furniture and fittings will be adobe, stone and dried mud, including tables, sitting areas, kitchen surfaces, workbenches and beds, etc. Earth houses of North Africa probably give a good idea of what Martian buildings will look like. Some concrete will be used as well, but without rain or ground water, mud based architecture will work well on Mars.

In short: lots of underground spaces. Lots of natural stone, lots of adobe and dried mud; lots of heaped regolith berms where appropriate and some concrete. Some steel and glass. Very little plastic. All this assumes that real costs tally with energy costs.

Last edited by Calliban (2020-09-30 08:10:58)

tahanson43206 · 2020-09-30 09:52:35

For Calliban re #67

Nice Summary! SearchTerm:MaterialsSummary Mars insitu

SearchTerm:SummaryMaterials Mars insitu with energy investment estimates

SearchTerm:EmbodiedEnergy Mars estimates

(th)

Calliban · 2020-09-30 14:30:17

Expanding on post 67, perhaps a better comparison would be to look at how much tensile or compressive strength a MJ of energy would buy you, if you invested it in different materials on Mars. If will update my previous analysis to reflect this and see if it changes the results.
_________________________________________

I have run the numbers and have come up with some results. Starting with tensile materials:

Carbon steel: embodied energy = 250GJ/m3; typical yield strength = 500MPa. Energy per unit strength = 500MJ/MN.
Aluminium alloy: embodied energy = 194.4GJ/m3; typical yield strength = 400MPa. Energy per unit strength = 486MJ/MN.
Polyethylene: embodied energy on Mars = 1000GJ/m3; typical yield strength = 26.25MPa. Energy per unit strength = 38,100MJ/MN.
ETFE: embodied energy = 1700GJ/m3; typical yield strength = 43MPa. Energy per unit strength = 39,500MJ/MN.

Out of the tensile substances, steel and aluminium alloy easily outperform the polymers. Aluminium alloys have fatigue life issues, that would make steel preferable for structural applications. Things that might make plastics more favourable would be the discovery of concentrated methane or other fossil organics on Mars. Biomass grown in greenhouses or algae, could be used to produce monomer feedstock in a way that bypasses the need for so much electrical energy. But it would clearly be challenging for polymers to rival steel in terms of embodied energy.

Compressive substances:

Concrete: embodied energy = 2.0GJ/m3; typical crush strength = 40MPa. Energy per unit strength = 50MJ/MN.
Glass: embodied energy = 37.5GJ/m3; typical crush strength = 1000MPa. Energy per unit strength = 37.5MJ/MN.
Natural basalt: embodied energy = 0.1GJ/m3; typical crush strength = 200MPa. Energy per unit strength = 0.5MJ/MN.
Compressed soil brick: embodied energy = 0.1GJ/m3; typical crush strength = 2-10MPa. Energy per unit strength = 10-50MJ/MN.
Adobe: embodied energy = 0.2GJ/m3; typical crush strength = 2MPa. Energy per unit strength = 100MJ/MN.

Compressive materials like concrete provide much more strength per unit energy than do tensile materials. This is why masonry is used overwhelmingly as a structural material here on Earth. To produce pressurised masonry structures on Mars, overburden is needed to counteract internal pressure. Martian soil is highly basic and contains a higher concentration of gypsum than would typically be found on Earth. So it should make an effective binding agent. Natural stone is a very energy efficient material, because the only energy expended is that involved in gathering it. So my guess is that natural stone walls and pillers with cement binder, will be a popular building material. To let light in, we could use light tunnels with convex concrete caps with glass inclusions on the inside, holding back internal pressure and transferring load to thecoverburden.

Martian adobe may well be more efficient than I have calculated here, due to its gypsum content. It would make sense in situations where only low strength is needed and concrete shells would be too thin to be stable. Small structures may work better if Adobe is used.

Last edited by Calliban (2020-09-30 17:58:05)

Terraformer · 2020-10-03 03:30:18

How does basalt fibre compare? I know it has to be melted, but so does steel.

SpaceNut · 2020-10-03 17:35:23

Energy burden to process to a finished good is part of the selection but it's got to fit the building requirement. The the additional energy border comes from the gathering or mining plus refining to get a given level of the selection ready to process.

Terraformer · 2020-10-04 13:12:17

A previous study estimates the energy required for basalt fibre production to be around 5 kWh/kg in an electric furnace, whilst the energy required to produce steel is around 14 kWh/kg

From A mechanical and environmental assessment and comparison of basalt fibre reinforced polymer (BFRP) rebar and steel rebar in concrete beams

That is in comparison to rebar though? But as far as i can tell, basalt has a significantly higher yield strength than steel wire as well. So it sounds like it should perform far better from an energy perspective.

tahanson43206 · 2020-10-04 14:55:20

For Calliban and Terraformer re basalt as a material ...

Is it possible (feasible) to use basalt fiber as a wrapping material for RobertDyck's Large Ship habitat rim?

While the habitat is likely to be shipped up from Earth in parts and assembled on orbit, it seems to me that wrapping the entire Rim with basalt thread might greatly increase its ability to withstand the stress of constant rotation at 3 RPM, combined with the equally constant movement of mass inside the structure. It seems to me that any joint that is not flexible is going to fail.

The habitat is going to be subject to temperature extremes in space, in addition to the stresses of mass movement.

An enclosing ring of basalt thread might help to increase the service lifetime of the system, and (theoretically) it could be supplied from the Moon or a convenient asteroid at less expense than shipping from Earth.

(th)

Calliban · 2020-10-14 05:28:13

Interesting reference on the use of basalt fibre as rebar.
https://www.sciencedirect.com/science/a … 021730022X

Basalt fibre has embodied energy 18MJ/kg; tensile strength of 3GPa and density of 2670kg/m3. That is 16MJ/MN. Per unit strength, basalt fibre is about 30 times less energy intensive than steel. The material is also very abundant.

The main thing driving cost appears to be the rhodium bushes, through which the molten material is drawn into fibre. These wear out and need to be periodically recast. We would either need the capability to do this on Mars or they would need to be shipped back to Earth for reworking. Either way, basalt fibre looks like the most economically favourable tensile material on Mars.

tahanson43206 · 2020-10-14 06:56:12

For Calliban re #74

Thanks for continuing to investiate basalt as a material for Mars (or Earth where feasible). I appreciate your adding details about embodied energy, which you have brought to the forum.

Would you be willing to post more about the rhodium bushes? They would appear to be essential for manufacture of thread, but they are also a dependency for a Mars operation.

Per Google:

Search Results
Web results
Is There A Fortune To Be Made On Mars? - Forbeswww.forbes.com › sites › quora › 2016/09/26 › is-ther...
Sep 26, 2016 — Mars may have concentrated mineral ores, with much greater ... gold, palladium, iridium, rubidium, platinum, rhodium, europium, etc.

That ** may ** catches my eye.

Here are some Google snippets that hint at how folks on Earth are working with rhodium ...

CN101570393A - Single male tab platinum rhodium bushing ...patents.google.com › patent
The invention discloses a single male tab platinum rhodium bushing for glass fiber ... The bushing has a groove-shaped container structure, and comprises a ...
Bushings for Glass Fiber Production 3D Printed in Platinum ...3dprint.com › bushings-for-glass-fiber-production-3d-pri...
May 15, 2020 — Bushings for Glass Fiber Production 3D Printed in Platinum-Rhodium by ... A 3D-printed tip plate made from platinum-rhodium alloy.
Rhodium Alloys - an overview | ScienceDirect Topicswww.sciencedirect.com › topics › materials-science › rho...
5. Sketch of the formation of a glass fiber and a bushing tip. ... Platinum–rhodium alloys in the form of wires woven into screens or gauzes are catalysts for the ...

(th)

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#51 2016-12-08 22:35:03

Re: Material Choices for Mars

#52 2017-09-05 20:22:51

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#53 2017-09-05 21:07:44

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#54 2017-09-05 21:30:24

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#56 2017-09-05 23:16:51

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#57 2017-09-06 13:16:42

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#58 2017-09-07 12:41:48

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#59 2017-09-07 16:04:10

Re: Material Choices for Mars

#60 2017-09-07 17:24:37

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#61 2017-09-07 20:22:55

Re: Material Choices for Mars

#62 2018-12-05 21:21:28

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#63 2019-08-10 12:30:52

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#64 2020-09-06 13:43:57

Re: Material Choices for Mars

#65 2020-09-28 09:39:15

Re: Material Choices for Mars

#66 2020-09-28 17:46:51

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#67 2020-09-30 08:00:25

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#68 2020-09-30 09:52:35

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#69 2020-09-30 14:30:17

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#70 2020-10-03 03:30:18

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#71 2020-10-03 17:35:23

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#72 2020-10-04 13:12:17

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#73 2020-10-04 14:55:20

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