Optimal size for domes and other structures

[Nuke]

the last season of for all mankind hit the nail on the head with that one. eventually you end up with a black market, and attempts to clamp down on it will result in a lot of violence. you are better off just letting people do their free trade in the open.  make it possible to purchase space on your earth-mars shipments. some space will be reserved for this (you would of course need to pay for its share of the launch costs) so long as it doesnt endager the base or life support or some basic safety requirements, it should be allowed. if people are killing each other over vodka and beef jerky you have a problem.

[kerbiloid]

Taking the mentioned N'York City as a test subject
https://en.wikipedia.org/wiki/New_York_City

Area = 1200 km2 (incl. land 780 km2)
Population = 9 mln
Elevation = 0..120 m.

Let's make it multi-layered, taking the former WTC-1/2's 400 m as the proven possible rectangular building height.

Let the habitats be two-layered, 2x2.3 = 4.5 m height + 0.5 m between the storeys.
I.e. one floor = 5 m.

400 / 5 = 80 floors.

Let's take that currently it's about 5 storeys in a building (from 1 to 100).

I.e. the land area can occupy ~15 smaller area, about 50 km2, or 8 km in diameter.

Then you can reach the closest edge of the city and join the nature in an hour by feet, or in several minutes by a rented electric car.

Spoiler

 

[farmerben]

Pavonis Mons having a crater 47km across and 5km deep could support 15 million luxury cliff dwellings (5m tallx 10m wide).  Meanwhile with our standard agricultural dome is 100 m2.   So that's up to 70 million dome units in the caldera of alone.   With extremely intensive layered vertical farming, you can probably feed one average human on 100 m2.  So the floor of the caldera could potentially feed 70 million people.  The balconies add 10% to growing space, but realistically we use more than that of the caldera space for non agriculture.  

A few mining boomtowns may spring up on Mars if we find rich veins of ore.  And the asteroid miners will purchase food from Mars in preference to Earth if they can for potentially 10% of the haulage costs.  Yet it makes little sense to develop agriculture elsewhere besides Pavonis Mons, since it is the best natural spaceport on Mars being equitorial high altitude and close to valles marineris.  You will still require vast amounts of nuclear energy.  The layout for primary logistics and communications are obviously hub and spoke.  

[AckSed]

Vertical farming? This lets me bring up the BioPod, a proposal for a self-contained greenhouse that can work on Earth, in orbit or on Luna or Mars. Flashy site aside, this is a legitimate effort that's been steadily developed since at least 2018.

Spoiler

 

[Pthigrivi]

 

13 hours ago, Nuke said:

really i think its a matter of putting a starship on its side

I think it's basically this. Despite their sci-fi cache domes just aren't a good form for offworld construction. There's a reason you don't see them often here, and thats because they come with a deep mismatch between usable volume and manufacture and assembly complexity. You're much better off with arched linear vaults that can be mass produced and dropped into place. Thats not even the real problem though. The real issue is that you're building in an environment with little or no manufacturing base and a long and expensive supply chain. The enclosure system is the least of your worries. By far the most complex task is the manufacture, assembly, and testing of the hab interiors--seals, plumbing, electrical, temperature and humidity control, furnishings and equipment, etc. Producing all of this from scratch on site is a LONG way off, easily 100 years or more. It takes millions of people here on earth to produce all of these things from scratch. Now of course over time a colony will be building up an industrial base thats heavily supplied from earth, but before you can even mostly construct and furnished hab modules you need hundreds of small factories processing materials and components. The other really important factor is testing. When your life depends on everything working you don't want to wing it on site. You want to fully run each module through its paces before it ships. So for all of time it takes to build up this capacity locally your best bet is going to be fully pre-fab environments, which pretty much means your form factor is a cylinder with the diameter and length equal to your largest orbital stage rocket. If we pretend thats Starship Block 3 we're talking 9m x 25m (maybe). 

The next biggest consideration is radiation. The shell of the prefab modules will have some resistance but that comes with a mass cost. You could be much more efficient by burying them in regolith. The simplest way to accomplish that would be dig a ditch, drop the hab module in, run the regolith through a grinder and bury the module in coarse gravel and riprap. You might want a few modules that are designed to be exposed with windows just to keep people sane but I wouldn't bother for agriculture. Plants are also susceptible to genetic damage from radiation. Just send small nuclear reactors and grow everything with LEDs and hydroponics. Concrete and steel enclosures might be important later for industrial plants, maintenance hangers, equipment storage, etc. but even producing basics like concrete, aluminum and steel at scale will take quite some time to establish.

Edited December 18, 2024 by Pthigrivi

[AckSed]

5 minutes ago, Pthigrivi said:

The simplest way to accomplish that would be dig a ditch, drop the hab module in, run the regolith through a grinder and bury the module in coarse gravel and riprap. You might want a few modules that are designed to be exposed with windows just to keep people sane but I wouldn't bother for agriculture.

Efficient, yes. Nice to live in? Hmm. One design I saw for a Mars hab was to, essentially, have a sod regolith roof atop a bungalow, and use mirrors to reflect sunlight into the interior. It'd need sturdy construction and maybe cleaning of the mirrors after a dust storm, but if you're making and shaping steel and glass and plastic on-site (and we could and should) it's no hardship to build tough. We have robots that brush dust off solar panels on desert solar farms, so those could be adapted for the mirrors.

[tater]

20 hours ago, magnemoe said:

The thing who stuck me was no balcony, here in Norway all city blocks have them, exception is the old ones downtown and this is Norway where you will use it for 1/3 of the year. My block is 50 years old and it had them enlarged. Looking at modern cruise ships I say this is an trend. 

In that concept design, it's just a sheet of glass, but I would imagine that were something like that to actually be constructed, there would be balconies.

Surface radiation on Mars is ~41X that on the surface of the Earth (0.7 mSv/day vs 0.017 mSv/day on Earth), so outside time on such a balcony or just wandering in a dome would probably have to be limited.

[darthgently]

4 minutes ago, tater said:

In that concept design, it's just a sheet of glass, but I would imagine that were something like that to actually be constructed, there would be balconies.

Surface radiation on Mars is ~41X that on the surface of the Earth (0.7 mSv/day vs 0.017 mSv/day on Earth), so outside time on such a balcony or just wandering in a dome would probably have to be limited.

Glasses-in balconies with glass-water-glass sandwich panes.  I can’t get the water sandwich thing out of my head now

[magnemoe]

8 minutes ago, tater said:

In that concept design, it's just a sheet of glass, but I would imagine that were something like that to actually be constructed, there would be balconies.

Surface radiation on Mars is ~41X that on the surface of the Earth (0.7 mSv/day vs 0.017 mSv/day on Earth), so outside time on such a balcony or just wandering in a dome would probably have to be limited.

How much would the dome realistic reduce it with, 
And in that case its not viable I say, outside of stuff like restaurants could do it here you could use much heavier domes as they are much smaller, more the size of the above tent. 

[tater]

I made this doodle years ago:

Regolith in orange. The blue line is line of sight—notice there is no sky visible from inside at least unless right up against window closer tothe floor, perhaps (I'd make it possible, just not where you'd spend huge amounts of time).

The covering on the roof is sufficient for at least Earth normal radiation inside (if the dose rate inside could drop below that of Earth, then total annual dose might allow for more outside time (EVA or under a dome) with the same ave annual rate of someone on Earth.

The idea is to have habitats on a crater bottom, or at least facing a terrain feature such that each hab can have large, open views outside of martian terrain. I have that sort of view from some of my east windows—my house is bermed into the hillside, and clerestory windows just a few inches above the uphill ground face the mountain, at certain distances from the windows you seem like you're looking up at a sloped yard from a basement (though getting closer you can see the almost 11k ft peak behind us).

Images:

Spoiler

Nothing but yard (with deer) in foreground, background is mountainside)

Getting to the right spots close to windows (leaves of the top of the same scrub oak the deer are passing at bottom):

 

For sun-facing directions, the windows could open on greenhouse space (likely actual windows in case of a greenhouse pressure failure).

The idea here is to "borrow" regolith within LOS  outside instead of burying the whole hab.

Edited December 18, 2024 by tater

[darthgently]

Apparently it would take 1 to 2 meters of water or ice to reduce Mars surface radiation levels to those of Earth.  With certain soluble additives it might be reduced to a meter.  Darn thick still.   But since water needs to be stored anyway why not store it in a way that allows light into the dungeon?

I’m not as enthusiastic about the dome though unless the 2m thickness is crystal clear ice with no liquid or vapor and supports itself mostly igloo style with perhaps assisting internal columns

 

Edited December 18, 2024 by darthgently

[farmerben]

8 minutes ago, darthgently said:

Apparently it would take 1 to 2 meters of water or ice to reduce Mars surface radiation levels to those of Earth.  With certain soluble additives it might be reduced to a meter.  Darn thick still.   But since water needs to be stored anyway why not store it in a way that allows light into the dungeon?

I’m not as enthusiastic about the dome though unless the 2m thickness is crystal clear ice with no liquid or vapor and supports itself mostly igloo style with perhaps assisting internal columns

 

More like 10m

[darthgently]

7 minutes ago, farmerben said:

More like 10m

Where does this number come from?

[Pthigrivi]

24 minutes ago, AckSed said:

Efficient, yes. Nice to live in? Hmm. One design I saw for a Mars hab was to, essentially, have a sod regolith roof atop a bungalow, and use mirrors to reflect sunlight into the interior. It'd need sturdy construction and maybe cleaning of the mirrors after a dust storm, but if you're making and shaping steel and glass and plastic on-site (and we could and should) it's no hardship to build tough. We have robots that brush dust off solar panels on desert solar farms, so those could be adapted for the mirrors.

Yeah I mean maybe eventually, but its hard to overstate just how much mass goes into industrial equipment. I mean imagine the mass of equipment that goes into a bauxite mine or a cement factory, and then multiply that against every basic material that you need. Even producing a few basic materals in modest quantities will take decades of work and tens if not hundreds of thousands of tons of equipment that all needs to be delivered from earth first. 

Ideally everything you do off-world is going to be as simple to assemble and as easy to maintain as possible. Everything is about mass and labor. The cost of adding more equipment and crew is just so high and compounding that you want everyone being incredibly efficient with their time. Robots that are wiping off reflectors are then not doing something more productive like wiping off solar panels. What you really have to think about is the total mass of equipment and people and life support for those people needed to produce glass or mirrors on site vs the mass cost of something like this that could be produced, integrated, and tested on earth:

 

[farmerben]

15 minutes ago, darthgently said:

Where does this number come from?

1 atm of pressure is increased every time you dive 33ft under water.

[darthgently]

7 minutes ago, farmerben said:

1 atm of pressure is increased every time you dive 33ft under water.

Radiation and cosmic ray shielding is what I was referring to.

Your methodology is interesting

Edited December 18, 2024 by darthgently

[farmerben]

Bulldozing dust along the sides of a rectangular vaulted arch is a very good method.  A good conveyor belt could deposit dust on top of a structure without crash loading it as much as a bulldozer would.  

Digging is not as easy as we wish it might be.  The best first base is to find lava tubes and work on just sealing them.  

When you want to dig into solid rock, which you will, its best to start at the base of a cliff and dig in, much easier than going down first.

3 minutes ago, darthgently said:

Radiation and cosmic ray shielding is what I was referring to.

Your methodology is interesting

It works out about the same because water is mostly oxygen, and oxygen has basically the same shielding as nitrogen.  When you get to discuss the shielding or rock vs metal, the simple mass comparison might not be sufficient.  

[darthgently]

10 minutes ago, farmerben said:

Bulldozing dust along the sides of a rectangular vaulted arch is a very good method.  A good conveyor belt could deposit dust on top of a structure without crash loading it as much as a bulldozer would.  

Digging is not as easy as we wish it might be.  The best first base is to find lava tubes and work on just sealing them.  

When you want to dig into solid rock, which you will, its best to start at the base of a cliff and dig in, much easier than going down first.

It works out about the same because water is mostly oxygen, and oxygen has basically the same shielding as nitrogen.  When you get to discuss the shielding or rock vs metal, the simple mass comparison might not be sufficient.  

Ok.  I’m seeing 1 to 2 meters liquid water here and there on the net to get exposure levels at Mars surface same as Earth surface.  Will keep exploring

 The 1 to 2 m may not be accounting for high energy cosmics.  Will adjust my search parameters 

Edited December 18, 2024 by darthgently

[AckSed]

Hang on, could we use hesco bag construction? Very quick, very simple, flat-packed cubical fibreglass bags made to be filled with dirt to construct walls. Combine it with locally-quarried stone beams and pillars, or a composite inner frame, plus an inflatable pressure vessel inside, more overfill on the top, and you have a home.

More whimsically, I'm imagining triple-glazed windows inset into the sides that double as 1 metre-thick water tanks.

[darthgently]

13 minutes ago, farmerben said:

Bulldozing dust along the sides of a rectangular vaulted arch is a very good method.  A good conveyor belt could deposit dust on top of a structure without crash loading it as much as a bulldozer would.  

Digging is not as easy as we wish it might be.  The best first base is to find lava tubes and work on just sealing them.  

When you want to dig into solid rock, which you will, its best to start at the base of a cliff and dig in, much easier than going down first.

It works out about the same because water is mostly oxygen, and oxygen has basically the same shielding as nitrogen.  When you get to discuss the shielding or rock vs metal, the simple mass comparison might not be sufficient.  

What bothers me about this approximation is it doesn’t appear to account for Mars atmosphere, thin as it may be, nor the earth’s magnetic field

[farmerben]

The danger of cosmic rays is much exaggerated.  Lots of people will average 2 hrs per day exposed to the full Martian surface and be totally fine.  Our beets and cabbages will grow in the 30 hour Martian day for their brief lives and not care at all about the higher dose of cosmic rays.

[Pthigrivi]

1 hour ago, farmerben said:

The danger of cosmic rays is much exaggerated.  Lots of people will average 2 hrs per day exposed to the full Martian surface and be totally fine.  Our beets and cabbages will grow in the 30 hour Martian day for their brief lives and not care at all about the higher dose of cosmic rays.

True, if you're planning on shipping all of your seeds from earth and aren't worried about self-sustained propagation I don't think there's too much worry about the plants themselves. They're probably all specifically engineered GMOs anyway. You're still going to need to supplement with LEDs and probably grow them in racks to maximize output. Mass wise I'd just use inflatable plastic and let the maintenance crews work in shielded suits. A gantry with pressurized air could blow the dust off easy enough. 

Edited December 18, 2024 by Pthigrivi

[tater]

I think it's worth the effort (for an actual colony, not just a base) to make at least some agricultural spaces such that they are places people can walk through. If deep, overhanging eaves with real martian views are part of the design language (you're on Mars, so look at Mars!), then planted spaces need not be domes at all. They can be interior spaces, with a system of heliostats to direct sunlight inside. These could in fact be dome shaped, but would be entirely shielded, and while some could be designed for the most efficient possible agricultural use, others could be set up as mixed functional and entertainment spaces—like the large conservatories at Kew, for example

The sky was gray enough when that pic was taken in June that it might as well have been reflected sunlight through a diffuser. BTW, it was actually pretty chilly outside (in June!) but it was quite hot in the Palm House (above image). This sort of system has the added benefit that sunlight can be concentrated.

Inside a crater, the heliostats can be on the crater rim, reflecting light to multiple locations on the crater floor since they have direct LOS. Light pipes (like Solatube skylights) can take in light from an area larger than their nominal collection area in this way, and have Earth level daytime lighting inside. Ie: a 1 m² solatube has a 4 m² heliostat pointing at it.

In some similar thread years ago here I posted about those same fake skylights ( @Pthigrivi). Definitely a way to go, and deep buried habs can have screens as windows—fed by real time camera views.

Edited December 18, 2024 by tater

[Pthigrivi]

Hmm there's also some interesting information in this article suggesting that for certain architectures exceeding certain shield thresholds  actually ends up increasing radiation dose for inhabitants. Thats because of the way galactic cosmic rays interact with different materials producing a cascade of secondary particles which propagate into the habitable space. Of course this is based on spacecraft bombarded from all sides and for a relatively short period (4y) compared to colonization but it gives some helpful benchmarks. They recommend shield thickness in the 30 g/cm^2 range, which if my math is right translates to 11cm thickness for aluminum, 4cm for steel, and 30cm for water. They also point out that this secondary particle effect is worse for materials with higher atomic numbers so if bulk isn't a design consideration you're better off with materials like aluminum, water, or silicon oxide (regolith). 

My feeling remains that for long term habitation on the surface you really want to deal not just with GCR and SEP but also with the secondary particles. I've seen some estimates suggesting 2-3m of regolith being sufficient. The advantage here is just abundance. Water is going to be a really precious commodity, making up just 2% of marsian regolith and even less on most of the moon. There are of course areas where concentrations are higher and even pure ice here and there but it seems like an incredibly precious resource and you'd want to devote almost all of it to agriculture and critical chemical processes. 

Looking back I think @tater's doodle is really pretty smart because you're only really being bombarded by cosmic radiation from the horizon up. All you really need are deep overhangs that shield you from the sky. Reflected light from the surface is fine. This could be accomplished by using natural terrain or even just mounding up berms. 

Edit: Did a quick sketch including a Starship diameter prefab hab module. Seems like maybe a bit of fuss for an omelette but it reduces cosmic ray exposure to about 1%, about the same as on earth at sea level. Plus you can look outside while you're making breakfast. 

Edited December 19, 2024 by Pthigrivi

[Nuke]

i can imagine a system where you bore out a vertical shaft in rock, and cap it with a prefab dome, sealed with concrete or whatever and an inner coating to make it air tight. you deploy some prefab metal decks and walls to create compartments. you put your farms and water reclamation at the top, these provide shielding from what makes it through the dome. this also works on lower gravity worlds, except scaled up and using an internal conical centrifuge to supplement local gravity.