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#26 2002-11-25 00:25:10

Shaun Barrett
Member
From: Cairns, Queensland, Australia
Registered: 2001-12-28
Posts: 2,843

Re: Canyon habitats - Cliff dwellings along covered cayons

Hi again, Josh!

    I was just re-reading Dr. Zubrin's "At Home in a Dome" section in his book, The Case For Mars. (It starts on page 177.)
    He describes a few different ways of tackling dome construction on Mars - and all but one involve the use of closed 'bubbles' of plastic. The odd one out is essentially a hemisphere of clear plastic with a skirt which is buried in the regolith, and possibly 'pegged' as well. This latter type is still presumed to be airtight, even though there is no floor in it except undisturbed Martian dirt! The trick is simply to hold the damned thing down by either burying the skirt and pegging (as Bob Zubrin suggests) or maybe by creating massive reinforced concrete footings, as we have discussed in other threads here over the past year.

    One of Bob's ideas is to dig a hemispherical hole, say, 50 metres across (25 metres deep), place a spherical 'balloon' of reinforced clear plastic in the hole, and then bring all the tailings in through the airlock and fill the sphere up to ground level again! The trouble with this idea is the enormous amount of material you have to dig out and push back in.
    A modification of this concept involves a hemisphere of clear plastic, again with a radius of curvature of 25 metres, attached to a section of a sphere with a radius twice as great. The section with twice the radius of curvature forms the bottom of the 'bubble' and is much shallower, requiring a correspondingly shallow excavation with a central depth of only 3.35 metres (instead of 25 metres). This way, the amount of soil moved is reduced from 260,000 tonnes to just 6,500 tonnes ... a hugely more manageable task!!

    If you could find an obliging crater of shallow depth and about the right diameter, you could perhaps save yourself some of the excavation work, and maybe use the crater walls as 'backfill' inside the dome. I think this is the kind of thing Byron is suggesting (? ) and it seems like a good idea.

    I was wondering about that first type of dome, though - the one which is simply a half buried sphere. I know there's a lot of soil to dig out (a hemispherical hole 25 metres deep), but what if you didn't put all that soil back inside at all? What if you made 6 or 7 floors of living area with a 10-metre-diameter central vertical shaft for elevators and for natural light. The roof of the topmost floor could be made level with the ground outside the dome, by covering it with a metre or two of soil for agriculture and radiation protection.
    This would make maximum use of the volume of the sphere for radiation-free living space, while also maximising the free and open space in the top half of the dome for farming and leisure purposes.
    I just haven't figured out what to do with the 260,000 tonnes of dirt outside the dome yet!!

                                          ???


The word 'aerobics' came about when the gym instructors got together and said: If we're going to charge $10 an hour, we can't call it Jumping Up and Down.   - Rita Rudner

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#27 2002-11-25 01:03:38

Josh Cryer
Administrator
Registered: 2001-09-29
Posts: 3,830

Re: Canyon habitats - Cliff dwellings along covered cayons

Hmm, so all along the truely feasible design for a dome has been a bubble. I used to joke with my brother about bubbles on Mars, but I was confident we could build a true dome (saving materials and work), but I guess I was wrong for the most part. The pressures involved are amazing!

:-\

I totally agree with the idea of not really filling a bubble in with regolith. That volume would obviously provide a perfect place for living quarters. And a crater would obviously be the best place to put a bubble dome, since it's alreay partially carved out.

The volume of living space underground within a bubble would be huge though. For a 50 meter dome, you would have some 30 thousand cubic meters of room to put stuff in (if I did the math right). Quite a huge living area. All of which can probably be used in some way.


Some useful links while MER are active. Offical site NASA TV JPL MER2004 Text feed
--------
The amount of solar radiation reaching the surface of the earth totals some 3.9 million exajoules a year.

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#28 2002-11-25 02:07:16

Shaun Barrett
Member
From: Cairns, Queensland, Australia
Registered: 2001-12-28
Posts: 2,843

Re: Canyon habitats - Cliff dwellings along covered cayons

Yeah, that 30,000 cu.m. living space is just too good to waste!

    I'm rapidly coming around to the idea that, at least in the early stages of colonisation, and for domes with diameters up to about 50 metres, a full plastic sphere is probably the easiest way to go.
    It eliminates all the problems associated with trying to mix and pour concrete for massive footings, since there's no net force with spheres. And you can import a ready-made 'bubble' from Earth, and an earth-mover (or should that be mars-mover?! ).
    I'm not sure about supports for floors and the flooring material itself, though. Would we have to import that from Earth, too, or could we manufacture aluminium or iron beams from Martian regolith?

    But, once we start talking about domes hundreds of metres in diameter, I think we'll have to go back to the type of hemispherical dome and massive concrete foundations we've talked about elsewhere.

    God I wish they'd stop procrastinating and get on with this stuff!! I'd love to see it started before I drop dead!

                                         ???


The word 'aerobics' came about when the gym instructors got together and said: If we're going to charge $10 an hour, we can't call it Jumping Up and Down.   - Rita Rudner

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#29 2002-11-25 06:53:27

Byron
Member
From: Florida, USA
Registered: 2002-05-16
Posts: 844

Re: Canyon habitats - Cliff dwellings along covered cayons

I'd have to agree with the idea of complete spheres as well...I think that if suitable craters could be found, plastic spheres up to 100m in diameter would work very well, as you wouldn't have to remove nearly as much regolith as you would for a complete half-sphere.  Also, the sphere wouldn't have to be sited all the way down to the half-way mark...provided there's enough ground support, I would say they could put about 2/3's of the complete sphere above ground..and in this case, it may be possible to set the thing into a small crater with very little excavation of the regolith at all - just a "collar" of dirt around the base of it to hold it firmly in place.

As for manufacturing floor and other interior supports, I think producing aluminium on Mars would be easy enough...you just have to have a source of plentiful energy.  Remember, the .38 gee will certainly make things much easier in terms of construction...thin and flimsy will be the way to go on Mars...lol.

Shaun..I fully agree with you in that they just need to get on with it...now!   smile

B

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#30 2002-11-25 17:21:32

dicktice
Member
From: Nova Scotia, Canada
Registered: 2002-11-01
Posts: 1,764

Re: Canyon habitats - Cliff dwellings along covered cayons

But...would, where craters are, be where we would wish to establish the first colony...with respect to all the obvious: water, minerals, atmospheric pressure, shelter from winds, access to eg. launch rails (my own "hobby horse") up the sides of Tharsis volcanos, etc. As my real estate agent keeps telling me: location, location, location!

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#31 2002-11-26 13:57:10

dickbill
Member
Registered: 2002-09-28
Posts: 749

Re: Canyon habitats - Cliff dwellings along covered cayons

Austin said:
"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."

Great idea that you have !

That's the point Austin, since the local conditions do not allow to make a bubble of glass with the martian sand, maybe the concept of enclosed bio-hemisphere has to be reconsidered.
I said before that Martians will have to "reinvent the wheel" in a certain sense. They will have to use artisanal techniques that we consider as primitive, but's that the only way to really expand the initial colony, in my opinion. The only things from earth that the martians should depend on, is the tools and the high technology electronic etc, not the raw infrastructure.

A biosphere is a modern concept, why not to consider pyramids or cubes instead ?  could it be possible to use clean martian sand to make thick FLAT panels of glass, possibly reinforced, and assemble those panels on a pyramidal metallic framework, or alternativelly, just sealed those panels with a silicon glue just like the glass panels used make a water tank aquarium ? then put the 500 mb pressure inside.

Use also local stones to make houses. Think primitive.

In Quebec, the first year, the frenchs colons were surprised by the harsh winter and cold temperatures (Montreal is at the same latitude that Bordeau, so they probably expected a similar climate). They relied to much of stocks food, cloths,etc imported from France. All of them from that first colony died if I remember well. That was a disaster. The second year, collaboration with the indians (as opposed to extermination, as most people would think) better planning and use of local ressources allowed the colony to survive. 
This shows that a first colony is very fragile and need redondency to have chance to survive and most importantly, usage of local ressources as much as possible.

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#32 2019-10-27 19:15:46

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 17,360

Re: Canyon habitats - Cliff dwellings along covered cayons

What a wonderful old topic....

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