Canyon habitats - Cliff dwellings along covered cayons

dicktice · 2002-11-18 20:30:43

By anchoring a translucent roof above a suitable canyon tributary, and constructing cantilevered living quarters along the sides, many advantages over a domed structure, as a follow-on habitat, might be obtained. With a "droop" to the canyon floor at either end to seal the ends, webbed netting (in the manner of gas balloons on Earth) the roof-envelope could be restrained from blow-outs by means of diagonal guy-wires anchored to "hard points" at the ends of struts driven into the canyon sides.
Warmth trapped from sunlight would then permit liquid water to be collected in lakes (eventually streams) along the canyon floor as atmospheric pressure buids up. Cantilevered-balcony cliff dwellings above the canyon floor would avoid flooding within the habitat, as well as provide an "instant" water-world lifestyle, greatly in advance of possible terraforming.
Post-occupation tunnelling into the cliffsides, would give easy access to potential below-surface mineral and water resources, provide expanding living space and protection from meteorites, solar flares, UV and cosmic radiation.
As for electrical power: Vertical wind-tunnels using Martian atmosphere in stretches of unpressurized tributary, with multistage turbo-electric generators at their bases, driven by the flow of solar-heated Martian "air" from beneath low transparent roofs, with guy-wires from high canyon tributary sides to stay the kilometre-high "chimneys."
With enough area-coverage surrounding the base(s), the accumulated warmth could be sufficient even to supply electricity during nighttime. East-west canyon alignment would of course be advisable, and alternative (eg. fuel-cell) power during sandstorms provided for.

Shaun Barrett · 2002-11-19 01:35:33

Dicktice, the idea of roofing over a canyon or valley is potentially a great idea. I like it!

But your phrase, "suspending transluscent roofs over ... ", seems to imply that the 'tent' will be hanging from the cliff tops.
As we've established in other threads, even a tent containing an atmosphere of only 500 millibars pressure, in present conditions on Mars, will have to resist an outward force of 5.17 tonnes per square metre of its area. Assuming a modest valley enclosure with dimensions of, say, 500m by 50m, the tent will be pushing upwards with a force of nearly 130,000 tonnes.

I'm not trying to say the idea isn't feasible. All I'm saying is we'll need to choose our valleys carefully and/or secure the tent very carefully into good, solid bedrock!

If these problems can be successfully overcome, I can visualise the most glorious settlements in beautiful craggy canyons - with living quarters built into the walls of the cliffs and boasting views over the stream meandering along the canyon floor! Magnificent!!
Along with large transparent domes, I think tented canyons will be among the most attractive and desirable places on Mars to live.
And maybe the engineering will be found to be easier than that required for domes, too! I hope we'll be finding out one day.

Josh Cryer · 2002-11-19 01:53:12

Hey Shaun, where are you getting your numbers? I think Zubrin had some numbers about domes, but I don't recall him actually saying how he came to those numbers. A good paper does the math so that people can see how you came to those conclusions.

HeloTeacher · 2002-11-19 09:14:08

This is a similar idea to that proposed by Marshall Savage in his book 'The Millenial Project'.

He proposed using transparent overhead covers for naturl depressions, specificaly small craters, and using water as the ballast to counteract the upward air pressure. The idea itself is an elegant design solution but gets a little held up in the search for adequate water. A good source of water would help the problem. I'm not sure if other problems with the design have been discovered, some of his ideas have met with much less than successful practice.

Bill White · 2002-11-19 10:57:50

As we've established in other threads, even a tent containing an atmosphere of only 500 millibars pressure, in present conditions on Mars, will have to resist an outward force of 5.17 tonnes per square metre of its area. Assuming a modest valley enclosure with dimensions of, say, 500m by 50m, the tent will be pushing upwards with a force of nearly 130,000 tonnes.

Add a superstructure of alloy tubes across the valley - like the poles of a large tent - and securely attach the roof material to that framework. The strength of the poles will help hold the roof up and the weight of the poles will help hold the roof down.

Engineer the roof by using water ballast along the edges (trapping the roof perimeter under water tanks or other stored materials) - attaching the roof fabric to a alloy tube superstructure (which give support and adds weight) - filling layers in the fabric sandwich with a clear liquid which is allowed to freeze (to add weight and insulation).

A liquid/frozen layer within a fabric sandwich might also be engineered to have self-sealing properties in the event of a minor leak.

Also, given that refraction will occur as sunlight passes through water ice, settlers can inhabit a valley often filled with countless tiny rainbows. [Some] or [Most] or [All] of the cliff dwellings should be designed to be vacuum tight all by themselves to provide redundancy in the event of a leak.

How wide of a valley do you propose we look for?

AltToWar · 2002-11-19 14:24:36

most of the benefits could be had by keeping the air pressure just at the levels needed for plant life.

Shaun Barrett · 2002-11-19 19:38:07

My apologies, Josh!
Here I am, the first person to complain about acronyms with no explanation, the first person to whinge about IT posts with no explanation, and off I go with numerical claims I fail to explain myself!!
Sorry!

Earth's atmospheric pressure at sea-level has been measured in various units as:-
1000 millibars
760mm Hg (Mercury)
14.7lbs/sq.in.
1013.25 hectopascals

For all my praise and glorification of the metric system, I still find the 14.7lbs/sq.in. measurement the easiest to remember and the most evocative of the weight of Earth's atmosphere! To me, it's a measurement you can almost feel!! Anyway ... enough of the BS !

A 500 millibar atmosphere under your canyon tent on Mars (i.e. half an Earth atmosphere), must exert an upward pressure on the material of the tent of 7.35lbs/sq.in.
There are almost exactly 1550 square inches in a square metre. So each sq.m of the tent must hold down a force of 11,392.5lbs ... or 5,169kgs ... which is 5.17 tonnes (to two decimal places).

[I confess I have assumed the Martian atmosphere to be negligible, which is not strictly true. In fact, it will push downwards with a force of about 62kgs for every square metre of tent.
So my figure of 5.17 tonnes per sq.m should really be 5.11 tonnes (to two dec. places again). This doesn't materially affect the outcome, though.]

I plucked the dimensions of the tent out of thin air! I could imagine a vast tent, many kilometres long and spanning a canyon 2 or 3 kilometres wide. But I thought I'd be conservative and choose a quite modest little canyon to illustrate my point.
50 metres by 500 metres (ignoring the sealing material at each end) gives us an area of 25,000sq.m
25,000sq.m multiplied by 5.17 tonnes/sq.m gives us 129,250 tonnes of upward force.
If we allow for the Martian atmosphere's weight, we still get a net upward pressure of 127,750 tonnes. All I was trying to do was to point out that such forces will require enormously strong footings for the tent.

Byron · 2002-11-20 06:23:21

[Some] or [Most] or [All] of the cliff dwellings should be designed to be vacuum tight all by themselves to provide redundancy in the event of a leak.

Considering how costly it would be build the tent superstructure in the first place, I doubt that individual dwellings be made "pressure proof." I envision that underground "air vaults" would be constructed throughout the community that could be used in case of an emergency...and the residents would be trained to make emergency evacuations within a certain time period, like 90 seconds or whatever.

B

Number04 · 2002-11-20 10:38:45

I think a "tent" would be a bad choice for a first settlement. It would be possible after smaller colonies have been established. This would allow for exploration teams to look at different canyons and rock formations.

Shaun Barrett · 2002-11-21 01:24:06

I've just read your revised post, Dicktice. Looking good! - Especially the "diagonal guy-wires" to add extra strength, which is a great idea.

And it certainly is enormous fun to 'brainstorm at this stage, before the "experts" catch on and take over! ' !!
I've had a ball here at New Mars discussing domes, ditches, dirigibles, and dwellings!

Josh Cryer · 2002-11-21 06:01:44

Hmm, thanks for the numbers Shaun. I think the solution to the problem of tying the tent down is fairly simple, though. All you would need to do is basically tie the bottom to itself, exploiting the air pressure to reenforce the overall dome, rather than using the ground itself to take care of it. The magic of geometry can let us do very cool things.

I've drawn a [very] crude idea of what I'm getting at:

Basically what we'd be doing, is we'd be pulling the dome inwards upon itself as its weight pushes down. We wouldn't necessarily have to have the whole floor covered in tent, of course. Just around the edges for several meters inwards (that's right! inwards! not down, underground, the whole dome would rest on a sleeve of itself). The weight of the air pressure alone should keep the air in!

Can this work with covered canyons / craters? Most definitely, only you would have way more tension wires along the canyon walls, acting as the whole of the bubble does.

Also, we wouldn't necessarily need material that's unbelievably strong. We could simply just layer a few tents within each other (connected with billions of superstrong fibers), and equalize the pressure over the whole volume. The outer volumes would have less air, and the inner volumes would have more. Not only would this prove to be a very good insulator, it would strengthen the overall dome (though I admit, there's one drawback; less sunlight).

Shaun Barrett · 2002-11-21 06:24:02

Hi Josh!

I think I must be misunderstanding your idea because, if it were as I understand it to be, the dome would lift off and deflate as fast as you raised the internal pressure (? ).

Am I right that there's no floor in your dome? ... Or what?

:0

Byron · 2002-11-21 06:57:03

Also, we wouldn't necessarily need material that's unbelievably strong. We could simply just layer a few tents within each other (connected with billions of superstrong fibers), and equalize the pressure over the whole volume. The outer volumes would have less air, and the inner volumes would have more. Not only would this prove to be a very good insulator, it would strengthen the overall dome (though I admit, there's one drawback; less sunlight).

Josh, would it be remotely feasible to have a tent / dome such as you have described made of transparent material? What you're describing sounds like kevlar-type material, which I must admit would be quite effective as a dome material, but I just can't stand the thought of not being able to see the open sky...after all, the weather is sunny there most of the time...and I hate to ruin it by having an "artificial overcast" overhead!

Also, and I know this would be horribly expensive, but would it also be remotely possible to use twin layers of regular glass (sheathed in polythene-type material), and have a layer of water in between for radiation protection? Or just having the double (or triple) layers of glass by itself? As heavy as glass is, that would certainly take a good deal of the pressure off the dome itself...(any idea of how much a 10cm-thick square-meter section of 'aquarium' glass weighs?)

Just tossing out some ideas, as usual...

B

dicktice · 2002-11-22 09:54:27

As we've established in other threads, even a tent containing an atmosphere of only 500 millibars pressure, in present conditions on Mars, will have to resist an outward force of 5.17 tonnes per square metre of its area. Assuming a modest valley enclosure with dimensions of, say, 500m by 50m, the tent will be pushing upwards with a force of nearly 130,000 tonnes.
Add a superstructure of alloy tubes across the valley - like the poles of a large tent - and securely attach the roof material to that framework. The strength of the poles will help hold the roof up and the weight of the poles will help hold the roof down.
Engineer the roof by using water ballast along the edges (trapping the roof perimeter under water tanks or other stored materials) - attaching the roof fabric to a alloy tube superstructure (which give support and adds weight) - filling layers in the fabric sandwich with a clear liquid which is allowed to freeze (to add weight and insulation).
A liquid/frozen layer within a fabric sandwich might also be engineered to have self-sealing properties in the event of a minor leak.
Also, given that refraction will occur as sunlight passes through water ice, settlers can inhabit a valley often filled with countless tiny rainbows. [Some] or [Most] or [All] of the cliff dwellings should be designed to be vacuum tight all by themselves to provide redundancy in the event of a leak.
How wide of a valley do you propose we look for?

A kilometre span, at least, should be feasible on Mars, over kilometre-plus deep canyons. However, a water-jacket of any useful thickness wouldn't be sufficiently transparent to visible and infrared wavelengths to provide light and warmth--a cold, blue valley habitat would result.
The idea of covered canyons, which could be lengthened as required, might be a way of of "upstaging" terraforming, as another alternative to permit mass-habitation because the roofing-over tributary valleys, capable of supporting millions of folks, is do-able with with existing construction techniques. And it would provide us with diverting, day-to-day news we back on Earth could identify with--using remote interactive presence, as virtual pioneers, for example--instead of the ho-hum space news we are being offered at present.

Shaun Barrett · 2002-11-22 19:48:58

In common with transparent domes, we'd have to come up with a way to get the dust off.
Water jets wouldn't work for obvious reasons. And I suppose fans or vacuum cleaners would be too inefficient in such a thin atmosphere.
???

Sweeping might work, I suppose. Or could we use some form of static charge to levitate and maybe repel the dust from the tent/dome surface?

:0

Josh Cryer · 2002-11-23 01:23:18

Shaun, basically what I'm suggesting is that we use as much sleeve as we need to keep it from flying off into space or whatever. A dome would be much like a ballon full of air. Only it would be a whole lot heavier in comparasion.

I believe we could have a dome with a very large sleeve around it. This sleeve would come in a ways, perhaps covering 1/5th the area of the dome floor from within, around the edge. This sleeve would naturally be staked to the ground; not to keep the dome from simply jettisoning into space, but rather, to keep the floor from sliding outwards, leading to an eventual collaspe. These stakes would go down a meter or so, and would face away from the direction of pressure pushing outwards on the dome itself. Resisting the pressure would also be assisted by high tension wire.

Could this work? I'm not sure. I think with the volumes we're talking about, it definitely could. I suspect the weight of a multidome would be equal to that of the air pressure beneath it. The dome would sit upon the surface of Mars like a water droplet, it won't explode outward becuase the overall mass is equalized.

Which actually brings about a good point. We wouldn't necessarily need extremely strong subtances if we used a multidome, multivolume, design.

(To see what I'm imagining, think of those inflatable play-pens kids jump around in. Or a simple air mattress. Hundreds of chambers containing certain volumes of air.)

Also, with regard to your question about dust. I don't think it would be hard to imagine a composite transparent plastic that graces the inside and outside of the dome. One which things find a very hard time to stick to.

Byron, I'm not a huge fan of Kevlar, because it's not as transparent as we could have a dome be. I'm thinking we ought to be able to use a good mix between UHMWPE (ultra-high molecular weight polyethylene) and carbon fibers. We'd want to experiment until we found a good mix between strength and transparency. Polyethylene is the most common plastic on earth, it's in everything; so it's transparent.

I don't know about using water to deflect radiation, though. I've been reading a lot about passive shielding, and people seem to claim that it's not dooable. This is still up in the air, in my mind, though. It could be possible to pump water through the dome (that would certainly add to its mass enough to make it be that ?water droplet? I envisioned), but that water has to be heated, I believe, for it to be effective. Heat means energy, energy is costly, and water tends to be a coolent. If we were simply pump water into a fully inflated dome which was a good 80-100 degrees inside, the water would decrease temperature of the dome quite quickly.

Austin Stanley · 2002-11-23 03:33:21

I like this idea, however it strikes me that that the actual construction of the canyon habitat would be a great deal more difficult than that of a similar dome. You would need all kinds of cranes, cables, bridges, ect, ect.. on both sides of the canyon.

dicktice · 2002-11-23 14:46:33

This is a similar idea to that proposed by Marshall Savage in his book 'The Millenial Project'.
He proposed using transparent overhead covers for naturl depressions, specificaly small craters, and using water as the ballast to counteract the upward air pressure. The idea itself is an elegant design solution but gets a little held up in the search for adequate water. A good source of water would help the problem. I'm not sure if other problems with the design have been discovered, some of his ideas have met with much less than successful practice.

Comments and background material appreciated. Water/ice would filter out visible light and heat, so I would propose reinforced plastic, strengthened by (gas balloon-like) netting on top and by diagonal tension cables between the netting and canyon sides below.

dicktice · 2002-11-23 14:49:37

I like this idea, however it strikes me that that the actual construction of the canyon habitat would be a great deal more difficult than that of a similar dome. You would need all kinds of cranes, cables, bridges, ect, ect.. on both sides of the canyon.

Agreed, that roofing over canyons would be 2nd generation habitat construction...but with the water "discoveries" much more inspiring! Very welcome reaction(s).

Shaun Barrett · 2002-11-24 07:08:24

Hi Josh!
I've been thinking about your idea that a dome could be made to sit on the surface like a water droplet. I understand your concept, and it's a potentially elegant one, but I'm afraid a few 'back of the envelope' calculations show it won't work.

Let's assume we want a modest-sized dome of 100 metres diameter. Since weight is important in holding this dome down, let's maximise the amount of dome material by making its shape hemispherical. The area of this hemisphere (from 2 pi r^2) is 15,710 sq.m.

The area of ground under the dome (from pi r^2) is 7,855 sq.m.
The area of bare ground, in from the 'sleeve', is 4/5ths of that area, i.e. 6,284 sq.m. This is the area over which there is no force opposing the internal air pressure of the dome, except the weight of the dome materials themselves.

Having assumed a modest dome, lets assume a relatively low pressure (high oxygen concentration) atmosphere inside the dome of only 350 millibars. Such an atmosphere will exert a pressure equal to 3.57 tonnes per sq.m.
Therefore, the unopposed upward force on the dome is equal to 6,284 sq.m. multiplied by 3.57 tonnes per sq.m., or 22,434 tonnes - all of which must be resisted by the weight of the dome materials.

We know the total area of dome materials is 17,281 sq.m. (the area of the hemisphere plus the area of the 'sleeve' which is 1,571 sq.m.) Hence, each square metre must weigh 22,434/17,281 or 1.3 tonnes. (Excluding the weight of the high tension wires, which I assumed to be negligible.)

To get this figure of 1.3 tonnes for each square metre into perspective, we have only to consider the density of steel, which is about 7.85 tonnes/cubic metre.
To oppose the upward force of 22,434 tonnes, even if you made your dome out of steel, it would have to be 16.5 cms thick ... that's 6.5 inches!!

I think the only way to make your idea work is if you could produce an absolutely rigid and airtight floor for the dome. Then it would sit like a water droplet on the surface, with no net upward force.
But the tendency for the edge of the floor to curl upward would be enormous, and I don't know of any material strong enough to remain flat over an area of 7,855 sq.m. under those circumstances.
???

Byron · 2002-11-24 07:27:45

I was questioning the 'integrity' of Josh's proposal as well...sorry Josh!

I know this was discussed a while back, but I just wanted to clarify whether it was indeed possible to site a dome over a symetrically round crater, excavate the regolith in the crater floor to a depth of a few meters, line the ground with reinforced material like steel-lined Kevlar, put the regolith back in (and 'treat' so it would have the properties of Earth-like soil so plants could grow in it), and build the rest of the dome (which would be extending up from the under-floor material) out of transparent polyethylene plastics, which would cover the bowl-shaped crater.

Sure, the inhabitants would be living inside a bowl, but if it was large enough, you would still have reasonably long sight lines, and the tremendous pressure would be pressing down as well as up against the surface of the dome...so the whole thing would look like a partially squished beach ball with its bottom portion buried in the sand.

Would this sort of thing be practical? Or would there still be too much pressure being exerted along the perimeter of the dome where it comes out of the ground and arcs overhead (where it changes shape as well)?

B

Josh Cryer · 2002-11-24 08:29:14

Hmm, the crux of my idea would work, but the dome would be so thick it wouldn't really be useful.

I guess I let my science fiction side get away with myself too much there. I was thinking that if we had decreasing volumes of air the dome would be so heavy that it would hold itself down. The logic is sound, but this wouldn't happen until the dome was extremely huge and thick, though. My idea basically leads to many domes, one inside the other, each with increasing air pressure inside. It would probably be so thick sunlight couldn't make it through, heh.

What do you think about putting a dome within a cater, Shaun? Could the outside edges of the crater hold it in? It may ultimately prove necessary to create completely air tight bubbles.

I'm confident we have the materials to create a large inflatable superstructure, the problem is deploying it with earth-pressures. It would seemingly take many many tons of regolith and a crapload of tension wires to keep a non-airtight dome from collapsing. Zubrin's articles don't even talk about how he is managing to keep domes from collapsing, unless they're air tight and he just doesn't say so.

dickbill · 2002-11-24 13:20:49

Idea:
since Mars is full of silicates, why not to add a layer of Martian clean white sand of top of a hemispherical dome of material and then heat the sand layer layer until fusion occured, then removed the underjacent material to leave a pure bubble of crystal.

first point: I think when you are on Mars you should always keep trying to use local materials rather than imported material from earth.

second point: at the beginning at least, some primitive techniques could apply to Mars, such as the egyptian techniques to move and raise big stones into pyramids, but also more generally artisanal techniques that have been replaced on earth by industrial production. I prefer to build myself my small silicate dome/house (like a big igloo) with my own artisanal techniques and with local materials rather than to always depend of the next shipping of titanium/kevlar/nylon ultramodern fabrics send from Earth.

Austin Stanley · 2002-11-24 15:29:08

Idea:
since Mars is full of silicates, why not to add a layer of Martian clean white sand of top of a hemispherical dome of material and then heat the sand layer layer until fusion occured, then removed the underjacent material to leave a pure bubble of crystal.
first point: I think when you are on Mars you should always keep trying to use local materials rather than imported material from earth.
second point: at the beginning at least, some primitive techniques could apply to Mars, such as the egyptian techniques to move and raise big stones into pyramids, but also more generally artisanal techniques that have been replaced on earth by industrial production. I prefer to build myself my small silicate dome/house (like a big igloo) with my own artisanal techniques and with local materials rather than to always depend of the next shipping of titanium/kevlar/nylon ultramodern fabrics send from Earth.

A couple of problems with this idea.

#1. The glass would have to be extreamly thick to support the internal pressure of the dome. Glass does not have alot of tensile strength. There are various way's to augment it, but all make it more complicated to make, and some disrupt it's clarity.

#2. It would be vary hard to make glass in this manner, especialy in the thickness necessary. It would be difficult to cool, would warp in various manners, ect... all this would disrupt it's optical and strength properties, which are highly varriable for glass in any case.

But this idea could work very well for concrete or various plastics (as well as fiberglass which is somplace bettwen glass and plastic). But of course none of these are likely to be transparent either.

I agree with your secound point whole hartedly however, and I'm working on a paper that adress the potential for the production of various materials on mars.

dicktice · 2002-11-24 17:33:08

I like this idea, however it strikes me that that the actual construction of the canyon habitat would be a great deal more difficult than that of a similar dome. You would need all kinds of cranes, cables, bridges, ect, ect.. on both sides of the canyon.

Definitely a post-dome idea, but what an improvement,eh?

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Re: Canyon habitats - Cliff dwellings along covered cayons

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