New Mars Forums

Building buildings on Mars is very,  very different from building buildings on Earth.  Precisely because Martian buildings must be strongly pressurized to be habitable,  and Earthly buildings are entirely free of this requirement.  Pressurization means your structures must resist high tension and/or high bending.  Bending involves high tension,  too. 

Our masonry materials (cemented bricks and stones,  concrete) have good compressive strength,  but lousy to vanishing tensile strength.  The partial (PARTIAL !!!) exception is reinforced concrete.  The steel rebar in reinforced concrete carries the tensile loads,  but ONLY because the Young's Modulus of steel is much higher than the Young's Modulus of the concrete matrix.  That means you cannot use other materials of lower modulus than steel as your substitute rebar.

You can load the rebar to the point where the concrete cracks,  but no further.  Once cracked,  the concrete's compressive strength degrades,  sometimes is lost completely.  On Mars,  if you lose building pressurization,  the compressive strength is required to prevent collapse under its own weight,  lower gravity notwithstanding.  Lose compressive strength because you cracked the concrete matrix,  and the building falls.  The rebar WILL NOT prevent that.

These concrete and cement structures really are porous.  They will not be airtight without an appropriate coating on the inside.  If you crack them,  you tear that coating.  Just something else to consider.

Also,  consider the cold soak temperature effects we see on Mars that we don't even see at South Pole Station (coldest ever seen ~-115 F = ~ -82 C).  Mars has -130 F or colder,  quite commonly.  It can get to -200 F in some places.  I don't know what effect that might have on the concrete matrix,  or other masonry,  but it is catastrophic on the usual mild carbon steel we use for rebar.  It becomes as brittle and fragile as a glass window pane. 

Your rebar will have to be 304 stainless,  304L if you intend to weld it (and most rebar is welded).  That is a high-nickel steel that does not heat treat,  although it cold-works very hard very quickly.  It is NOT magnetic,  so that means of material handling gets ruled out. 

Just more food for thought. 

Bear in mind that these masonry and concrete materials (and the related soil mechanics for foundations) were not the focus of my aerospace education,  nor of the strength of materials classes that I had in college as an aerospace student.  I learned most of this on the job working in one or another aspect of civil engineering.

GW

Spacenut:

Many of us had side effects similar to yours,  myself included,  after the second Moderna shot.  Not the first,  but the second had me feeling poor for about 36 hours.  No lasting effects. 

GW

The Angry Astronaut has a good analysis of the NASA decision to fund SpaceX lunar lander.

Scott Manley does too, and as does Marcus House.

The SpaceX renders show 3 meter diameter pads on the landing legs (4 legs). as well

louis,

Are you aware of steel reinforcing bars (rebar) in concrete? The reason is concrete has great compressile strength, but very weak in tension. That means if you attempt to crush it, or sit a great weight on it, concrete will resist. But if you pull it, concrete will break easily. Bending involves compressing on one side, tension on the other. Steel has good tensile strength, so holds concrete together. But it can crack. To prevent cracks, you can prestress. That means the steel rebar or steel cables embedded in the concrete are put in tension. So attempting to pull will fight against that tension.

Bruce Mackenzie suggested brick. His idea was a brick structure using Roman technology: arches. Air pressure inside would blow the brick apart. To prevent that, Mars dirt is piled on top with more weight per unit area than air pressure inside. So there's still net compression, no tension. That has several issues. Air pressure pushes in all directions, including sideways from walls. This requires a the dirt to extend a significant distance from the walls. You will need a door of some sort to get in. The tunnel to the door will not have tens of feet of dirt pressing against it; in fact the door frame will have none. So any tunnel piercing the hill or dirt pile must be made of something with tensile strength. That means it can't be brick or concrete. Notice the Mars Homestead has a two story atrium with vaulted ceiling, made of brick. But that structure is will inside the hill. Apartments have a window, so apartments must be made of something else. Rover garage, entrance airlock, tunnel to surface structure such as greenhouses; all are made of something else. Options are steel, aluminum alloy, or fibreglass.

The other issue with brick is making it air tight. Pressure finds any way out that it can. A crack or small opening in the mortar will cause air pressure to leak into surrounding Mars dirt. That will result in a small tunnel to the surface. To prevent that, you have to spray the inside of the brick with a polymer sealant.

Notice I didn't include concrete. Because concrete doesn't have anywhere near the tensile strength. Rebar will hold it together, but any crack will form a pressure leak. Basically concrete has the same problems as brick. Mars Homestead did use concrete, but it requires rebar, and concrete was used to hold up the weight of Mars dirt over fibreglass tunnels. That way fibreglass shell outer surface can be accessed for repair, and doesn't have to withstand the dirt overburden. But don't expect concrete to be air tight.
http://www.marshome.org/images2/albums/ … age014.jpg

So far we have wondered all over power creation and from the many sources that could be but are not to much help for the total topic of creating a settlement design which we know is not a one time building process. That it takes many building steps plus temporary structures to allow for the build while occupying those for the final build is completed. Once the finish home is made all of the temporary construction is recycled and saved for other projects to come as the city grows outward.

The power we need will also be temporary with steps taken to achieve the final systems no fail design. This will be the methods for all that we need for mars as the equipment and people to make things happen to grow so with the need for all of this to transition through temporary states as we build to a sustainable settlement.

For Louis re #3

Thank you for your interesting (to me for sure) contribution to this new topic!

Your suggestion for a slogan reminded me immediately of a song "premiered" in one of the videos saved in YouTube for the 2020 Mars Convention.  The refrain included the words "to Mars" ... I'll try to find the actual video and add it to this post...

However, in the process of looking for ** that ** video, I found ** this ** video from August 2020 ...

https://www.marssociety.org/videos/halfway-to-mars/

Apparently it was inspired by Elon Musk's publicity stunt (to which you referred...)

Halfway to Mars
August 9th, 2020
Permalink
Mars Society releases new song celebrating mankind's recent achievements in space In light of recent achievements in space and our continued efforts as a species to get humans on to the surface of the red planet, the Mars Society is thrilled to release an inspiring new song that celebrates the work of the pioneers of Mars and hopes to inspire us to strive even harder. The idea for the song came up, three months into the covid-19 lockdown, when Opera singer Oscar Castellino in a chat with British artist Linda Shanson in London realized that they could be halfway to Mars, if their home that they were confined to was a spaceship. The journey to Mars did not seem so difficult after all!

Regarding the slogan ... I like it, but the vast majority of people who are likely to earn incomes in careers related to Mars are ** not ** going there.

Like the suppliers to the gold miners in the American Gold Rush, the ** real ** economic winners are going to be all those individuals and companies (and indirectly governments) who support the many expeditions that will be occurring.

A slogan for ** those ** people would (probably) be phrased slightly differently.

In any case, thanks again for giving this new topic a boost!

(th)

For Louis ... re Post #7

In the modern world we are careful about contact with very primitive tribes. We know that contact can be lethal both physically and culturally for such tribes and so we try to limit it.  There is a tribe in the Andaman Islands which India knows all about but basically leaves to their own devices having only very limited contact with them. India could easily move in and occupy the islands but, purely out of ethical considerations, they don't.

The island you mentioned above was in the (global) news not too long ago, when a white Evangelical youth decided to row himself onto the beach of the island. The natives put the individual to death.

There were observers, but knowing the prohibitions, they kept their distance.

***
I like the discussion here, and particularly your consideration of a superior set of beings hinting at presence but otherwise leaving us alone.

Many science fiction writers have speculated about advanced technology civilizations keeping an eye on us.  I don't remember any that I have read who posit the sort of curious glimpses that we have been observing for many decades, perhaps centuries, and perhaps even millennia.

There's a cable TV channel that exploits interest in these ideas with far out speculation on a regular basis.  I've met at least one person who is credulous enough to tune in and absorb some of that entertainment as "real".

(th)

Musk states that SN 15 will fly next week.

Not one of my favorite links about SpaceX: https://www.youtube.com/watch?v=qdH-VulltHI

Some kind of super advanced drone aircraft perhaps?  Nothing made of meat, human or not, could survive the sort of high g's that the movement of these craft would exert.  I think we are dealing here with robots.  But are they human artifacts or non-human?  One theory that I heard floated back in the 90s was that UFOs were robotic craft built by human beings in the future and sent back in time to gather archaeological information.  It is about as plausible as any other explanation that I have heard, though admittedly far fetched.

You guys go on and on. Here's a question: how are you going to smelt steel? I have proposed the Direct Reduced Iron Method. It uses less heat. Requires grinding ore to fines, uses carbon monoxide and hydrogen to convert oxide ores to pure iron. Carbon from carbon monoxide is dissolved into the iron. Using pure CO requires less energy, but results in far too much carbon in the steel. Metal with that much carbon is brittle. Removing the carbon requires heating the metal to completely melt it, and bubbling oxygen through to burn off carbon. If you mix hydrogen with CO for the first step, that hydrogen also binds with oxygen from the ore, converting ore to metal. Result is steam, which doesn't dissolve in steel. Hydrogen takes longer and requires more energy to make, but if you get the balance right then the final product won't have too much carbon. Although this works at lower temperature, it still requires between 800°C and 1,200°C; usually between 900°C and 1,000°C. This method requires high grade ore with very few impurities, basically pure iron oxide such as hematite concretions. Iron produced this way still has to be processed further to eliminate final impurities to become steel.

So how are you going to produce that much heat? Enough to heat literally tonnes of ore to well over +900°C? One advantage of this method is temperature is hot but low enough that a nuclear reactor can directly produce the heat without melting the reactor. Any conversion of heat from a reactor to electricity, then electricity back to heat, is very inefficient. It's far more efficient to directly use the heat. Temperatures for the Direct Reduced Iron Method is below the melting temperature of steel. You could use exotic materials for the reactor such as nickel/chrome allow to withstand higher temperature, but the point is to use the heat directly.

So again, if you want to go solar, how are you going to smelt steel?

In places where labor is nearly free, prices can be 2 cents per kWh.  The electricity prices per kWh, as paid by the rate payer, are NOT 2 cents in Germany.  They're at least triple what Americans pay.

No amount of government-sponsored market manipulation can change how much actual energy can be extracted from a kilo of Uranium or a liter of liquid hydrocarbon fuel or a square meter of solar panel erected in the sunniest locales on Earth for a given period of time.

The Chinese can and did (to weaken or eliminate overseas competition) sell steel below what it actually cost to produce their steel, in terms of raw energy input, but that doesn't mean such a practice is sustainable into perpetuity.  The Chinese will run out of money (energy) long before market demand is satisfied.  The moment they achieved their market share objective by cornering the market, they dramatically increased their prices to triple what they were before.  Of course it was all driven by greed, but they also had to increase prices in order to recoup their losses, in order to remain solvent.  After their stunt, other companies formed to domestically produce or recycle steel at lower prices using more efficient production processes, so that set a new market cap on how much the Chinese could charge for steel without driving their customers towards their new competitors.  The entire concept behind "economy" has always been devising the most efficient organization and employment of capital / labor / resources for delivering a good or service that paying customers actually want to buy.

In a market that isn't being manipulated by governments or corporations run amok, then prices (economization) will determine that if every other steel maker can produce steel for 2kWh/kg, but one particular company's production process is consuming 20kWh/kg, then that company or their current steel production process dies a natural death by being priced out of competition with all the other steel makers.  In that way, capital / labor / resources (one of them being energy) is conserved for other more productive uses.  That is how a normally functioning economy not being manipulated by governments works.  It also drives innovation to continually improve upon what was done previously, in order to deliver the same or substantially similar product for less energy and ultimately money.

If it takes 2 to 8 years for energy payback on a square meter of solar panels, here on Earth, then 18 to 12 years of energy output can be devoted to any other purpose.  If the energy production technology will be sustained into the future, then an additional 2 to 8 years of energy production payback will be devoted to producing new solar panels to sustain the output of solar power.  Mars receives half, 43% actually, as much solar radiation, so the panels used there either have to be twice as efficient or their energy payback time period doubles.

If it takes closer to 8 years than 2 years to achieve energy payback, but the panels degrade and produce less power over time, then we run into an ultimately unsolvable problem of energy payback duration being longer than the period of time that the solar panels can continue producing energy in a practical way.

The solar panel "game" is a very clever market manipulation that says, "Short term investment money is cheap right now, so we're going to take advantage of that fact by producing a product we know will be replaced in 20 years, and then 20 years from now when money is more expensive, the customer simply has to pay more money to continue receiving electricity."  There is, of course, a serious problem with that strategy.  It relies upon the availability of cheap investment money and government-sponsored market manipulation.  If the governments or the rate paying customers stop playing that game, then the jig is up, and suddenly energy becomes a lot more expensive and scarce.  We can see how well that strategy worked, longer-term, from the example of Germany, where electricity rates paid by their rate payers or 3 to 4 times higher than they are in the US.  People can always economize on energy usage, but only to a point.  After that point, it's just deprivation in service to ideology.  All of the money that could have been used for other useful purposes was and is tied up in producing enough energy to meet demand.  In France, there were / are riots over their government's market manipulations, and unrest is growing elsewhere as well.

Anyway, it takes very contorted ideologically-motivated thinking to refuse to acknowledge how a 100-to-1 energy payback is better than a 10-to-1 or 5-to-1 energy payback.  If wind and solar truly were producing abundant and cheap energy, then the prices for every other good or service using wind and solar energy should be falling, but they're not.  This is just the latest of an endless series of manipulative schemes to extract more and more money from a captive market that needs energy, little different than the market manipulations of OPEC or other special interests.