We need a brainstorming session! - Bat around a few ideas.

Shaun Barrett · 2002-02-08 01:12:32

Excellent stuff CaptainRich, RobS, and Phobos .... so much food for thought!!
Given that surface conditions on Mars are effectively a vacuum, we are going to have trouble not only with the temperature but also with pressure. So I think the tented area will become a must. However, I'm not sure of the evaporation rate of moisture at, say, 15-20 degreec C under conditions of about 320 mbars. I suspect it will result in the concrete drying out way too fast, which apparently leads to a weaker structure.
Now we could always pump up the tent to a higher pressure; 1 bar would give us Earth conditions, which we're familiar with, and the problem would be solved.
But from what I can make out here, we're dealing with a necessarily portable "bubble" which can be moved along as each section of the building is completed (yes?). Even assuming we can get away with 320 mbars, which I very much doubt, that means a vertical pressure on the tent of at least 3.3 tonnes for every square metre of ground surface enclosed. Allowing for a bit of "elbow room" in which to work, it seems likely that an area of about 100 sq. metres at a time will need to be tented, which gives a vertical force of at least 330 tonnes!
It's one thing to talk about a permanent dome with massive footings to restrain it, but how are you going to hold down what is effectively a hot-air ballon with 330 tonnes of lift, using temporary anchoring devices?! And then blithely shift it along about 10 metres every few days?
As a matter of fact, I can see that this whole thing could become a bit of a "chicken and egg" conundrum for cementing or concreting of any sort on Mars. It seems you need strong footings (presumably of concrete) in order to anchor a tent or dome, but you need a fairly well-pressurised dome before you can mix and pour the concrete!!
I think Phobos is right when he/she suggests that a completely new system of building may have to be devised for Martian conditions.
A thought just occurred to me: What about bricks which interlock like a 3-D jigsaw puzzle with some sort of specially formulated epoxy sealer or glue between them? That way we get away from the water-based-material problem which is what's causing most of the trouble.
Any thoughts?
:0

RobS · 2002-02-08 13:59:00

I don't think you'd need 300 millibars or anything like that. If you did, you might as well oxygenate the air and lay the bricks in shirtsleeves. If you're pressurizing the construction site you probably need to pressurize big portions of it at a time, because of the difficulty of burying the plastic to hold the air in, unburying it to move the plastic, and having portions of the construction itself sticking out of the pressurized area and maybe allowing leakage of the air.

You could pressurize with compressed Martian air. I don't have my copy of the CRC here at home with me; it gives the vapor pressure of water for every degree or so. But for a temperature of 30C (which is warmer than you want) I think it is less than 100 mb or a tenth of an atmosphere.

So I suppose the first step is to excavate the area for construction and the second is to install a bubble over the area to retain solar heat and water. You also need to install an industrial airlock (big enough for trucks to drive through). Then you haul in your construction stuff and build the structure, then remove the dome. The last task may be complicated by permafrost and ice buildup between the dome and regolith, where warm, moist air escaped under pressure and lost its water. You may end up ripping the plastic off and leave some of it frozen in place.

Alternately, if you have enough water and you have forms made of sheet metal, you'd weld/solder airtight forms together and fill them with concrete or duricrete, possibly adding heat and CO2 to make the stuff set properly. Then you'd peel off the form in pieces, reassemble it, and pour another section. That might not need a dome at all. The forms could leak a little bit because the water trapped inside the concrete or duricrete mixture wouldn't escape that fast through a few small holes.But you could probably spray polyurethane on the seams of the forms to seal leaks first ("Great Stuff"; available at hardware stores, probably easy enough to make on Mars).

Yes, construction on Mars will be complicated. Concrete and duricrete could be labor intensive if all the workers have are wheelbarrows and rovers. Hauling ten-tonne mixers and sand sifters and lime roasters to Mars would be rather expensive.

-- RobS

Lil_vader · 2002-02-08 16:33:54

Two things:
One: Wouldn't the sudden presure change when you remove the form cause the concrete to explode?

Two: Couldn't we just find an area without so much dust and anchor directly to the bedrock?

CaptainRich · 2002-02-08 17:23:01

Here's my first rendering of the Courtyard landscape, without plants at this time. Also the spacesuit won't be needed at this point, but I don't have any non-spacesuited figures to use in the rendering!

CaptainRich · 2002-02-08 17:34:24

Two things:
One: Wouldn't the sudden presure change when you remove the form cause the concrete to explode?

Since the vault will not be pressurized until it is buried I don't think this will be a problem. Or did you mean something else?

Shaun Barrett · 2002-02-10 07:34:12

Very pleasant courtyard setting CaptainRich! You can landscape my yard any time; I love it! And the overall design of "New Underhill" looks good, too. I especially like the fact that it is extendable ... would the next phase be octagonal in shape?
I'm probably not visualising this construction-site tent clearly, RobS, and if I'm being obtuse I apologise in advance, but I'm still not comfortable with how to anchor this portable bubble. Even if we assume a modest 50 millibar "atmosphere" inside the tent, that's still over half a tonne per square metre of ground covered ... say 50 tonnes of lift for a relatively small work-area.
And I thought one of the advantages we were looking for was to get away from working in space-suits(?). Isn't it difficult to handle tools in pressurised gloves ... very tiring?
I'm not trying to be argumentative. It's just the anchoring and sealing of the pressurised enclosure that's got me worried. But I'm ready and willing to be persuaded that I'm worried for no reason!

CaptainRich · 2002-02-10 10:15:42

Nope, the next thing I'm working on is the "Trench" or "Arcade".

Here is my first rendering of it.

RobS · 2002-02-19 01:59:19

Thank you for your interesting questions. Yes, a temporary dome over a construction site would be a fair amount of work to erect. Yes, 50 millibars of pressure amounts to half a tonne per square meter, so a big dome would need a big skirt and a lot of tonnes of Martian rock and soil piled on top of the skirt to keep the dome in place. Furthermore, a pressure skirt under the construction site might be hard to install, so air will leak downward into the soil and escape the bubble. So probably pressurized forms into which concrete or duricrete is poured would be better. As someone noted, a big pressure change could burst the concrete, so one would be better off keeping the pressure in the forms as close to Mars normal as possible, and depressurizing only slowly.

-- RobS

Lil_vader · 2002-02-20 18:03:54

Again, couldn't we anchor directly to the bedrock? Granted, the floor would have to have an airtight lining, but the bedrock would provide a stable foundation that wouldn't have to be hauled several thousand miles.

Phobos · 2002-02-20 21:44:17

Nope, the next thing I'm working on is the "Trench" or "Arcade".
Here is my first rendering of it

You know, I'm beginning to like this idea of digging a big trench and putting a cover on it more and more. Talk about easy to build, you could dig a trench like that in no time, maybe cover the exposed soil inside with sheets of plastic or something, and voila, your home. You could also dig out a big square, or a circle, or anything. I think digging such a trench is a better idea than domes or vaults. No elaborate concrete walls to build, no worries about taking unexpected hot air balloon rides, etc.

CaptainRich · 2002-02-28 08:40:03

I've been having a few email discussions with Bruce MacKenzie concerning the Trench base. I'm going to have to rescale everything. And those vaults are a lot more complicated! Besides I made a little error in the original rendering, didn't anyone notice the little white dots under the frame? ???

Shaun Barrett · 2002-03-01 05:03:42

We're all anxious to be of any small help we can, but without being sure what you are trying to portray, we naturally have trouble spotting errors.
In any event, errors or not, we think what you're doing is excellent! I'm sure I speak for all of us in saying we love what you've shown us and look forward to more.
The very best of luck from us all!

Sagebrush · 2002-03-12 20:31:49

Just a thought... why not use high-altitude balloons to simulate a martian enviroment? I got to thinking about this when reading a National Geographic from a few years ago, it was about the history of ballooning. The military has used balloons to conduct high-altitude suit tests. One mission included the highest jump ever... from 102,000 feet. Took the guy 13 minutes to reach the ground, most of it free-falling.

Another thought...why would martian bases need to be on the ground? Why not floating in the atmosphere?

Austin Stanley · 2002-03-22 15:07:45

Well with all this manufacture of bricks (and even magnesium beams), underconsideration, the use of other construction materials should also be thought of, specificly steel. Certianly steal-beams could be used more effectivly in many places than bricks.

The real question becomes, how much more difficult would it be to creat steal beams, and compare that to the difficulty of manufacturing large quantities of brick.

RobS · 2002-03-23 02:07:25

We would need metallurgist to answer the question of the ease of making steel on Mars. But several things occur to me: (1) there should be a fair amount of meteoritic nickel-iron lying around, which can be picked up magnetically; and (2) methane/oxygen rocket fuel could be used to melt it and would even add the carbon needed to convert iron into steel. Modern blast furnaces use coal and air, but they have been using oxygen more and more, and there are probably blast furnace designs that use natural gas and air, which would be very close to the methane and oxygen system one would use on Mars. Of course, it would take a nuclear reactor many weeks or months to make the methane and oxygen needed to melt meteorites into iron, and you'd have to have a water source to replace the hydrogen lost unless you could capture all the exhaust gasses inside a VERY large dome. It may be easier to manufacture certain light-weight plastics first, or fiberglass.

--RobS

RobHazlewood · 2002-03-24 02:11:41

Why are domes all the craze?

To me the concept sounds expensive, vulnerable, dangerous (radiation).
The main advantage would be the psychological advantage of being able to see around.

Why not create a colony underground?

My reasons:
-safe from projectiles (although I can't imagine that being a huge problem)
-low radiation
-cost (remember it wouldn't cost as much on mars as on earth.. supports wouldn't need to be as strong due to lower gravity)
-expandibility - a large dome when filled would require the creation of a new dome for it to continue to grow

trees, etc could be planted inside for phsychological reasons. Perhaps the complex may extend to the side of a cliff face for views of outside with lower radiation being inflicted as a result.

I guess the main reasons I think the underground colony is worth looking at are the cost, radiation, expandibility.

What are the disadvantages to this approach?

Is it easy to create a material similar to concrete on mars?

thanks,
Rob

Shaun Barrett · 2002-03-25 06:04:28

Hi again, Rob! In reply to your question about concrete, I don't think anybody is entirely certain how to work with such materials under Martian conditions.
However, for an interesting exchange of opinions on this subject, see earlier posts in this topic.

Austin Stanley · 2002-03-25 19:57:14

Well, I'm certianly not a nuclear engineer or an expert in steel refining, but I'm sure nuclear power could be harnesed directly to help in refining steel.

A nuclear reactor could be used to greatly heat up concentrated martian air, in place of Coke which is typicaly used on Earth. Crushed steel-ore and limstone would be placed into the furnace where it would be heated, then tapped off into Steel beams. Most of the Carbon and other impurities necessary for steel would probably be present in great quantities in the Ore anyways, and would have to be refined out, not added in.

At least this is one semi-convential method (replacing nuclear heat for coke) which might work. I'm sure there are other possible methods (like electro-arc) which also could be engineered to work on the Martian surface.

The steel produced at the start would no doubt be low-quality. But since great amounts of it could potentialy be produced, and even low-quality steel would be MUCH stronger than brick, I think steel production on Mars has lots of potential.

RobHazlewood · 2002-03-26 21:44:15

I like Lil_vader's concept (using existing rock and just digging into it)

The ideas that have been suggested thus far sound VERY expensive to me. Just simple things like making bricks and laying them is a very slow, time consuming process.

Whoever works on this may be outside the hab for so long that they receive lethal ammount of radiation. Remember its the same radiation level as working outside the space station, and I know NASA wouldn't like to have its astronauts working long shifts outside the station for weeks on end. Why would mars be any different?

I feel that the moving "bubble" concept just sounds too bulky, thus expensive. Remember the materials required for this are going to have to be moved into orbit at a cost of around US$1000/pound (whatever a pound is.. i'm used to kilo's)

Look at how tunnels are created on earth (water, transport, etc). They consist of a huge drilling worm type device, which is probably quite feasible to have on mars. Only one, about the size of the hab would be required.
They drill through the rock, leaving a rough tunnel. Dangerous rocks are then removed, and where necessary, cemented.
Inside the tunnel, the rubbel from creating the tunnel (decent sized rocks) could be rearranged to create a living environment (ie stone age huts).

This would provide a crude living environment for the first permanent mars bases. The intention is that the whole tunnel could be pressureised, and slowly fabricated using techniques that would have to be developed on mars by method of trial and error.

Would pressurising the whole tunnel would create a problem with loss of oxygen due to escaping through cracks or getting absorbed by rocks.

Its crude, but I haven't heard another way to create sizeable living/working space for a reasonable cost.

-Rob

thunder · 2002-04-04 22:49:10

A lot of people seem to think of Mars as a small, distant Earth with a thin atmosphere and no biosphere. And by thinking like that, solutions are made that won't work well if at all.
When the word "dirt" or "soil" is used, it conjures images of the brown stuff underneath the grass in the back yard. But there hasn't been rainfall on Mars in a very long time. Think of how hard the ground gets on Earth when it hasn't rained in a month or so. Most of the land on Mars is going to be very hard as the wind blows the smaller stuff out and the larger stuff compacts. ANd that's where there is dirt at all. Dirt is mainly produced by numerous weathering factors, but the two biggest things needed to create dirt are living things (such as plants) and water.

Lil_vader · 2002-04-07 11:06:20

Think of how hard the ground gets on Earth when it hasn't rained in a month or so.

Ever been to Death Valley? It hasn't rained there for, oh, about 200 years, at least.

If Mars has enough wind, then there will be wind erosion, and the ground won't necessarily be rock-hard.

thunder · 2002-04-10 06:25:04

It hasn't rained in Death Valley in 200 years...It hasn't rained on Mars 200 millenia or longer. ANd wind erosion doesn't make the ground softer, it makes it harder. It picks up the lighter materials, leaving the heavier materials to get compacted down. And without water or living things to break down the rock, most of Mars will be exactly that, pure solid bedrock. The dust from the dust storms isn't going to be more than a few inches thick.

Shaun Barrett · 2002-04-11 17:46:08

I don't really want to get bogged down in a hypothetical discussion about the consistency of the Martian surface. I imagine it will vary enormously from one place to another anyhow.
The first data back from Odyssey, though, makes me think we'll be dealing largely with regolith hardened by permafrost. It will probably be as good as bedrock from a construction point of view in any event.

RobS · 2002-04-11 23:37:01

This information is from my planetary geology graduate student days, 1975-77, but probably is still more or less correct.

Both Vikings landed in areas where bedrock wasn't far below the surface; you can see outcrops of it. The bedrock was covered by loose rocks, gravel, sand, and dust, with scattered dust drifts. The regolith had caliche on top in spots; caliche is formed when water carries calcium carbonate, calcium sulphate, and salts to the surface and leaves them. They lightly cement the surface materials. The Viking arms had no difficulty digging through the caliche and found plenty of spots where they could dig ten centimeters (4 inches) or so.

The bedrock is extensively cracked because of cratering; the outer few hundred meters to few kilometers of Mars is considered a "megaregolith" of cracked bedrock, depending on age (the older areas are more cratered and have been "gardened" to a deeper level).

Basalt is a very tough material to tunnel through because it is so hard. Natural lava tubes can be seen in orbital photos because some parts of the roofs collapse and provide natural caves (though I once walked in a lava tube on the south side of Mt St Helens and can tell you it'd be a helluva lot of work to make one habitable because they're filled with heaps of sharp rock!). Tunnels in basalt would be full of cracks, but it would be easy to spray polyurethane on the walls to make them airtight.

-- RobS

ulthacalthing · 2002-07-28 04:48:23

>The first data back from Odyssey, though, makes me >think we'll be dealing largely with regolith hardened >by permafrost. It will probably be as good as bedrock >from a construction point of view in any event.

But Permafrost could be a problem, as it loses its strength, when it gets warm, as it will, because the isulation of the habitat can't be that strong.

Cheers

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