In the harsh Outback of South Australia, some 850 kilometres north of Adelaide and 680 kilometres south of Alice Springs is an opal mining town called Coober Pedy. It is recognised as the largest producer of opal in the world with an estimated 70 percent of the worlds precious opal being mined in the opal fields here.
The town is known as the opal capital of the world because what are widely regarded as the most precious opals are mined here. The name Coober Pedy comes from the local Aboriginal term kupa piti, which means white man in a hole.
OK, I'll give this a shot.
possible to live there in prefab houses made in Adelaide, Sydney, or
elsewhere, with everything being imported from outside, this would be
too expensive. Also, everything would have to be made specifically
for the hot, barren environment.
Instead, the opal miners used the very bedrock of Coober Pedy to
manufacture their homes. They were using digging equipment anyway, so
they used it to dig out homes. They used the resources of the land to
form the structure of the house, and the wealth of the land (those
lovely opals) to afford furnishings and whatever has to be imported.
In addition to opal mining, Coober Pedy has a tourism industry. Not a
very big one, but the community is unusual enough to support a hotel,
several shops, and a restaurant or two.
Even traditional games, such as golf, can be enjoyed, though they have
to be modified (it's too hot to play during the day and there's no
grass, so they play at night with glow-in-the-dark golf balls and
carry a hunk of turf around with them).
The parallels to space habitation are obvious.
There is a small diference, they dont have to use rockets to import their stuff.
revisa mi Blog!: http://lacuevadellobo.blogspot.com/
Nor do they have to recycle air. Underground living is a great idea in a great many earth environments. Stable temps, low environmental impact, etc, but I don't see what that has to do with living in a zero g, hard vacuum, high radiation environmnet??? GAry 7
There is a small diference, they dont have to use rockets to import their stuff.
revisa mi Blog!: http://lacuevadellobo.blogspot.com/
There is a misunderstanding of what it means to use tunnels on any non
earth-like body. The key for any habitation is that it is a pressure
chamber. No pressure outside and some atmosphere equivalent inside.
Long snake like irregular forms will not work. All pressure chambers or
vacuum chambers need to minimize surface area (spheres, cylinders). A
tunnel will be be one hole big enough to contain a complete
structure/base/pressure chamber. It will be more like living in a sky
scrapper without windows. Might be horizontal instead of vertical but
the result is the same: total isolation from the surrounding material.
Erm, my point wasn't that the environments were similar,
but that the situations were similar.
far from the traditional sources of pretty much everything.
In both cases, people are making use of what the environment
provides, both to build their homes and to supply the wealth
to import what can't be made from materials on hand.
Wow, I took that posting for irrelevant spam, and removed the user. But it seemed to provoke some on-topic discussion. What say you? Unwelcome spam or not?
Mike Combs
Moderator
Erm, my point wasn't that the environments were similar,
but that the situations were similar.
In both cases, people are living in a hostile environment
far from the traditional sources of pretty much everything.
In both cases, people are making use of what the environment
provides, both to build their homes and to supply the wealth
to import what can't be made from materials on hand.
Because of the way Yahoo mail sorts the new mail, I read the last received first and had not got to the explanation of the letter until I'd already put in my 2 cents worth. Didn't realize he was relating underground housing to potential Lunar living spaces.
Gary 7
I wonder if the availability of 1350 watts/m^2 in space is sufficient for a parabolic reflector to melt its way thru rock, providing both a tunnel and sealing the surface of the tunnel rock for pressure containment? Such mirrors would be a great deal lighter than rock boring, mechanical equipment but at the same time, it would be limited to line of sight,ie, you could only melt the tunnel in a straight line. Still, that might be sufficient for a basic Lunar site.
> I wonder if the availability of 1350 watts/m^2 in space is sufficient for a parabolic reflector to melt its way thru rock, providing both a tunnel and sealing the > surface of the tunnel rock for pressure containment? Such mirrors would be a great deal lighter than rock boring, mechanical equipment but at the same time, it > would be limited to line of sight,i.e., you could only melt the tunnel in a straight line. Still, that might be sufficient for a basic Lunar site.
It would simply be a matter of what square footage of mirror is required, with what attendant concentration factor. Of course a problem would be that the beams from a parabolic mirror would converge and then diverge. Maybe additional (high-temperature!) optics might collimate the beam somewhat, but there would be limitations. It isn't like you could create a beam as collimated as from a laser. Might work better for boring into a despunasteroid than into the lunar surface. Maintaining the shape of the mirror would be easier in 0-G than in even the reduced lunar gravity. I bring that up because I think the mirror would have to be several football fields in area.
Mike Combs
I have also considered flat mirrors, electronically controlled to concentrate their light onto a small area. One could then have them spread out over a line several hundred meters long, tilted inward to focus their collection on a few meter^2 of rock. I recall that Mythbusters tried that with considerably fewer mirrors to ignite a wooden boat. Of course, they were under severe limitations of energy density, number of flat mirrors employed, atmospheric absorption, etc, but they did get the wood to start smoking. I thought several times the energy density, and an order of magnitude more mirrors might do the trick for making tunnels on Luna, plus you could continue for a full two weeks of Lunar day.
Structural integrity under 1/6th G. is a lot easier than under one G. and there is no wind to interfere with the mirrors but I agree that boring thru an asteroid would be more credible. Still, maybe some simple calculations might be in order, as in 1350 W/m^2, times, say, 10^3 m^2 collection area concentrated on a 10 m^2 area would yield 135 kw/m^2.If we used mirrors of 10 m^2 area, that would take 100 such mirrors. Would 135 kw/m^2 melt rock? That I do not know.
> If we used mirrors of 10 m^2 area, that would take 100 such mirrors. >Would 135 kw/m^2 melt rock? That I do not know. I had just remembered O'Neill saying that a concentrating mirror 1 football field in area could be used for smelting and metal working. But we don't just want to melt the rock, we want to actually vaporize it in order to remove it. So that's why I said several football fields. Regards,
Mike Combs
In Israel, they've managed to shove eight watts down a
single submillimetre optical fiber. So ten watts per
millimetre seems a reasonable thing to aim for.
area of one metre at the business end could be putting
out ten million watts, which is enough for just about
anything you're going to want to do. Indeed, I
suspect that such a cable would be too much, and that
a 25 cm * 25 cm (625 KW) cable would be more likely.
I imagine such a cable being carried on and trailing
out behind an unmanned vehicle which is (remotely)
driven up to a rock face, vaporizes an opening, and
then gradually makes its way into the ever-growing
tunnel (which can have as many curves and swerves as
you like).
Of course you still need those concentrating mirrors,
but maybe it's worth it, now that you can do more than
just aim them at a rock face.
I have used a 1 meter Fresnel lens to melt rock into lava, so sunlight can indeed be used for process heat. Whether you'd be able to vary the focal length in order to create a tunnel is a different question. I have read a short story (perhaps by Mike Combs?) in which a tunnel was dug to the center of an asteroid, and ice placed in the center, then the whole rock heated with concentrated sunlight until it became molten and the ice flashed into steam, making a huge pressure vessel from the ex-asteroid; similar processes might be used to tunnel through rock on the moon or Mars. Ed
I wonder if the availability of 1350 watts/m^2 in space is sufficient for a parabolic reflector to melt its way thru rock, providing both a tunnel and sealing the surface of the tunnel rock for pressure containment? Such mirrors would be a great deal lighter than rock boring, mechanical equipment but at the same time, it would be limited to line of sight,ie, you could only melt the tunnel in a straight line. Still, that might be sufficient for a basic Lunar site.
Gary 7
It is amazing how quickly fiber optics degrade when you focus sunlight down the bundle. All it takes is a little minor defect, either in your interface to the end of the fiber bundle or within the bundle itself, to cause the fiber to melt. That leads to a cascading failure, as a damaged fiber will melt adjacent fibers. About the only thing that can handle super-concentrated sunlight (more than 1000 sols, for instance) is sapphire, and sapphire fibers can get to be pretty darn expensive. Ed
In Israel, they've managed to shove eight watts down a
single submillimetre optical fiber. So ten watts per
millimetre seems a reasonable thing to aim for.
Now, this means that a bundle of fiber optics with an
area of one metre at the business end could be putting
out ten million watts, which is enough for just about
anything you're going to want to do. Indeed, I
suspect that such a cable would be too much, and that
a 25 cm * 25 cm (625 KW) cable would be more likely.
I imagine such a cable being carried on and trailing
out behind an unmanned vehicle which is (remotely)
driven up to a rock face, vaporizes an opening, and
then gradually makes its way into the ever-growing
tunnel (which can have as many curves and swerves as
you like).
Of course you still need those concentrating mirrors,
but maybe it's worth it, now that you can do more than
just aim them at a rock face.
Cool! I'm a big fan of sapphire.
(I think, wouldn't swear) use single fibers, instead
of bundles.
> I have read a short story (perhaps by Mike Combs?) in which a tunnel was > dug to the center of an asteroid, and ice placed in the center, then the whole > rock heated with concentrated sunlight until it became molten and the ice > flashed into steam, making a huge pressure vessel from the ex-asteroid; Yep, that was one of mine: "Miranda and the Space Pirates" http://writings.mike-combs.com/havnrock.htm But I pinched the idea from Jerry Pournelle, who I think might have gotten the idea from Dandridge Cole. I tried to throw in a tiny reference to Cole.
Mike Combs
Vaporizing the rock:No Need for that.
We only need to drill upward at about a one or two degree incline to allow melted rock to flow out of the tunnel. Start the tunnel a few meters above the ground and the melt would make a nice ramp to the entry, plus the slight incline of the tunnel would allow for construction of a false floor to provide for underfloor cable troughs, water piping and sewage lines, all necessary adjuncts for a long term living facility.
I try to go for the cheapest, simplest tech in such an endeavor, which is why I proposed the flat mirror heat source. I expect highly reflective Mylar, stretched over a light weight frame, could be shipped rolled up, like the old movie pull down screens we used to use for 8 mm film home projection screens in the '60s/'70s. Telescope clock driven mounts would allow the mirrors to accurately track the sun, maintaining their focus on the desired spot.