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here is the other newmars thread: Possible natural radiation shielding on Mars
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RobertDyck said: Skin-tight spandex suit with leather boots? Black leather with spike heels? Oops! This is for Mars.
Well, imagine how fashionable it will be running around in your spandex underwear when you are inside! While a funny thought, it does encourage population increase! There's some motivation there to get on with developing the techniques and infrastructure to thrive, not just survive.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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All the more reason for the mod's to move and merge posts/topic to keep discussion on target....As I once did do years ago....
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Well earth seems to have a bit of defences for when the sun kicks up a storm....
Earth raises a plasma shield to battle solar storms
Earth can raise shields to protect itself against solar storms. For the first time, satellites and ground-based detectors have watched as the planet sends out a tendril of plasma to fight off blasts of charged solar matter. The discovery confirms a long-standing theory about Earth's magnetic surroundings and offers us a way to keep track of the planet's defences.
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Well earth seems to have a bit of defences for when the sun kicks up a storm....
Earth raises a plasma shield to battle solar storms
Earth can raise shields to protect itself against solar storms. For the first time, satellites and ground-based detectors have watched as the planet sends out a tendril of plasma to fight off blasts of charged solar matter. The discovery confirms a long-standing theory about Earth's magnetic surroundings and offers us a way to keep track of the planet's defences.
If i've understood correctly, it's some kind of natural feedback: douring solar storms magnetic reconnection broke Earth magnetosphere and solar protons hit high atmpsphere. Ionized plasma formed in high atmosphere enflates again Earth magnetic field, reforming a new magnetosphere that counteract solar wind pressure and deflect incoming solar particles.
There is another very interest work by Robert Winglee, about Earth magnetosphere: in the model proposed, Earth magnetic tail shields the Moon from cosmic ray for almost seven days a month: so it's possible to plan manned moon mission in these safe periods.
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For bases off Earth (moon, Mars, etc), it's my understanding that about a meter or two of rocks and dirt over your head makes a pretty good shield against anything the sun can throw, and cuts down on cosmic ray threats, too.
All we need is a concrete substitute that works in vacuum and in intense cold, yet doesn't go away in the heat. Then ordinary construction of a dugout "house" becomes possible with the space equivalent of a front end loader.
You use gravity to offset internal pressurization forces, and line the thing with a multi-layer inflatable to hold the air.
Concrete substitutes could be developed down here and final-demonstration-tested at ISS. Makes you wonder why that hasn't been tried in all these years, doesn't it? Any outfit serious about going to Mars and/or back-to-the-moon should have been doing things like this.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Bruce Mackenzie has advocated Roman arches for Mars, supported by the weight of regolith overburden. Others, including Bruce, have argued for Mars concrete. NASA did a study of Mars regolith simulate + water. Not as strong as portland cement, but very simple. One reason it works on Mars is pressure is above the triple point. The Moon has no water, and vacuum. So forget concrete on the Moon.
There are cold weather concrete formulae on Earth. Used in Canada in winter. Actually, I caused a little trouble with this. One guy gave a presentation at the 2005 Mars Society convention in Chicago. He argued for concrete. My question was how he would deal with nitrogen? Because concrete on Earth uses tiny bubbles of air to provide nitrogen, necessary for conrete to set. Too few bubbles and it wont set properly. Too many bubbles will aglomerate creating voids. Earth has 1 atmosphere pressure with 78% N2, while Mars where we would want to build has about 7 millibars with 2.7% N2.
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In construction work here, temporary bracing and facilities are normal operating procedure. For construction "out there", it should be the same notion, just different details. The problem is water in vacuum with a lot of materials, so temporarily enclose that item in an inflatable at low pressure, just high enough to stop the boiloff. That would be 6 mbar of water vapor alone, in a bubble over water being used at 0 C. You could make "icecrete" on the moon or Mars or even an asteroid that way.
The nitrogen problem rules out Earthly cold-weather concrete techniques, as you say. But for structures that will stay cold and be protected from ice sublimation, "icecrete" is a real possibility, and very simple. It's not atmospheric pressure that prevents sublimation, it's water vapor partial pressure in the atmosphere that prevents sublimation. That's the kicker.
But, we already know buried ice seems to be stable on Mars, and maybe the moon. So, buried "icecrete" foundations look like a real application. And, we do need a solution to the concrete problem. This sort of thing can be researched in simulation chambers down here, and demonstrated to some extent in LEO, or even on the moon. These are activities that already should be going on, if we really intend to send men to Mars or back to the moon and create bases. They are not, and that disturbs me.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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There have been papers proposing basalt structures on the moon. Basically, you have to heat up the basalt rubble regolith and melt it into bricks, or pour it into molds and microwave it. For Mars, Zubrin mentions "open ground" domes. You hold them down by driving pilings into the regolith and inject steam through them to freeze them into place. To prevent the air pressure from leaking downward and out, you add water and install a water table and ice table underneath the surface. Something like that might work near the lunar north and south poles if the ground has disseminated ice in it.
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When Mars Pathfinder was current, I had the idea of creating a high-precision Mars regolith simulant. Not just Hawaiian volcanic ash, but very precise match of minerals found on Mars. I thought we sent enough probes to Mars, so read everything I could find that was published. It was too vague, so I contacted primary investigators of instruments on Sojourner. I discovered the data was not as definitive as I thought. I found a CIPW analysis of data from the APXS instrument on Sojourner, but it was also vague. I learned what a CIPW analysis is, and tried to do one myself. I had difficulty getting the numbers to balance. Hydrogen data was missing. So I contacted primary investigators for that instrument; learned the Proton mode just didn't work. Oops. Tried to do the analysis with available data, including hydrogen data from orbiters, but the numbers just didn't balance. When I talked to Dr. Carol Stoker at a Mars Society convention, she suggested I contact the guy who did the CIPW analysis for NASA. So I did. He said he also had difficulty getting it to balance, so gave up. He gave me his spreadsheet. I noticed an error; he started with the assumption that all minerals were igneous. Oops. Ok, so I continued my approach with my spreadsheet, but added a few refinements from his spreadsheet. That helped, but still couldn't get the numbers to balance. The proton mode was supposed to measure light elements. You could get data for light elements like carbon and oxygen from alpha or X-ray modes, but they're intended for medium and heavy elements. For light elements they aren't as precise. Data for light elements just isn't precise enough, and there's no hydrogen data at all. Without a direct measurement of hydrogen there's no way to determine clay vs feldspar. There's a big difference between clay and feldspar.
So my little project got stalled. Spirit and Opportunity were launched so soon after Pathfinder that they didn't have enough time to fix the proton mode. So same problem. They do have a mini-TES, but that didn't give the precision I was hoping for. Then I learned the Canadian Space Agency took responsibility for the APXS instrument on Mars Science Laboratory, now called Curiosity. So I contacted them, and asked them to ensure the proton mode was fixed. Planetary scientists said they knew nothing about this. They never got back to me. Eventually I was able to meet the director for planetary exploration. He said flatly "No". He refused to fix the proton mode. Damn! So Curiosity still has the same data problem. They improved precision for the alpha and X-ray modes, but there's still no measurement of hydrogen.
I had expected the regolith simulant I was going to formulate would be used for concrete experiments, ISRU experiments, as well as greenhouse experiments. But alas, no go. I'm not a geologist, just trying to do something significant to get us to Mars. GW Johnson: does that help?
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Wow, that's some history. More than I understand, being a mechanical engineer, not a geologist or instrumentation scientist. Odd, how no one ever fixed a known problem, isn't it? The emperor runs around naked in a lot of organizations, and no one ever tells him.
I'd suspect that no two locales on Mars have the same regolith, myself. There's many, not one. At least, that's the way it is here. The dry salty dirts we've seen might resemble a sample from the Atacama desert, or maybe the lake bed in Death Valley. Not-so-salty dried up lake and stream beds might resemble something from the Owens Valley near China Lake. There's got to be lots of volcanic stuff resembling the lava flow terrains in New Mexico. Do any of those ideas have any merit?
I'd think there's sandstone-like rocks on Mars, not unlike the red-rock sandstones of places like Monument Valley, although perhaps a different mineral species than straight silica. What seems to be missing so far is anything resembling limestones. I was surprised and pleased when they announced they'd found clays. Although your proton-mode problem description could cast doubts on that.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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TES and THEMIS data clearly indicates clay. But I was hoping for measurements of specific samples, not just planetary or regional averages. Quantitative measurements. One problem Spirit and Opportunity had was finding minerals identified from orbit. The orbiters get a regional average, so they may get the data a little wrong. One mineral that is high in this, and another that is low, results in the orbiter thinking it found a third that is the average of the two. But yea, geologists report they are seeing a lot of variation from site to site.
Still, I think it's way cool that I could talk to scientists, all with a Ph.D. in geology, and do so as if I'm an equal. Talking to world leading researchers in the field is a great way to learn. I learned a lot about geochemistry. Little old me, a computer programmer who wanted to be an aerospace engineer.
Last edited by RobertDyck (2014-03-09 10:38:42)
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Good news for mini-magnetosphere: Ruth Bamford's team of Rutherford Appleton Laboratory has found that the model used by Robert Winglee is incorrect, because it is based only on ion gyroradius ( http://en.wikipedia.org/wiki/Larmor_radius ), giving on order of magnitude overstimate power compsuntion (almost 100 KW according to Winglee http://earthweb.ess.washington.edu/space...elding.pdf ) for GCR deflection.
According to RAL's model, wich is based on electron gyroradius, 10-20 KW may be enough to create a weaker magnetic field, that can deflect electrons creating a charged separation in the bow shock region of the mini-mag, resulting a strong electrostatic gradient that deflect GCR.
http://www.nextworldweb.co.uk/wp-content...iation.pdf
Last edited by Quaoar (2014-03-09 10:17:30)
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But you need a means to conduct the charge that creates the umbrella of protection and mars does not have the moisture in the air to make it happen or free ions that make up the van allen belts that allows for the charge to make up the shield.
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But you need a means to conduct the charge that creates the umbrella of protection and mars does not have the moisture in the air to make it happen or free ions that make up the van allen belts that allows for the charge to make up the shield.
Mini-mag is only for space travel, where the charged particles interact with the solenoid field: it seems not possible to use it on the surface of a planet with atmosphere like Mars. There, the best thing to do is using local water or regolith to screen the habitat.
Last edited by Quaoar (2014-03-10 02:52:09)
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All we need to build domiciles on Mars, the moon, or the larger asteroids is a cold/vacuum substitute for concrete, and a substitute for tempered glass. That and a vacuum-operable front end loader.
The building is a core with a cap, resembling a mushroom in shape. It sits on a suitable foundation, and is ballasted above with regolith (that is also the radiation shield) to contain internal atmosphere pressures. You "hang" a transparency as a series of columns and panes, all around the perimeter of the mushroom cap. I have such a concept documented as "Aboveground Mars Houses", dated 1-26-13, and posted at http://exrocketman.blogspot.com. This is a concept whose maximum scaled size is limited by strength of materials and the square-cube law effect.
The other is the aquaculture pond habitat, which is an ice-covered pond, in turn buried under regolith to prevent ice sublimation. The overburden weight pressing on the water provides water pressures such that a pressure suit is not required to swim around, only thermal insulation (wet suit or dry suit). You put light and heat under the water to do photosynthetic aquaculture. This concept is not limited by strength-of-materials / square-cube law effects. How many square miles do you want? I documented this concept in "Aquaculture Habitat Lake for Mars", dated 3-18-12, same "exrocketman" site.
Both concepts offer about the same technical difficulty as burying habitation structures, or finding and adapting caves. Both concepts offer far more flexibility as to base location. I kind of doubt the aquaculture lake could be made to work very well in really low-gravity environments. I ran the numbers for Mars, but not the moon. Might work on the moon, probably not on a really low-gravity place like Vesta.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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The other is the aquaculture pond habitat, which is an ice-covered pond, in turn buried under regolith to prevent ice sublimation. The overburden weight pressing on the water provides water pressures such that a pressure suit is not required to swim around, only thermal insulation (wet suit or dry suit). You put light and heat under the water to do photosynthetic aquaculture. This concept is not limited by strength-of-materials / square-cube law effects. How many square miles do you want? I documented this concept in "Aquaculture Habitat Lake for Mars", dated 3-18-12, same "exrocketman" site.
GW
I suggest you to farm giant gourami ( http://en.wikipedia.org/wiki/Giant_gourami ) and/or catfishies: both are herbivore fish that are very easy to farm and can be feeded with the wastes of cereals and legumes from the greenhouse.
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For buried foundations, there is "icecrete". It stays cold down there, and the overburden prevents ice sublimation.
All you need is a sieve-bottomed bucket on your front end loader to extract the right gravel from the regolith (you'll need two sieve inserts for lower and upper limits on gravel size). Then a spinning barrel tumbler to round the sharp edges off the gravel. You'll need the rock dust equivalent of sand (two more sieve inserts for your front end loader bucket). And you'll need water. Your spinning barrel tumbler can double as the mixer.
Build closed (self-pressurizing) forms that can hold 5-10 mbar pressure (water vapor atmosphere over the unfrozen icecrete as you pour it, and over the fresh-poured icecrete as it freezes). Then bury the foundation before it sublimates. You're pouring the same kind of "mud" into the same kind of hole there, as we do here when we pour concrete here.
So, what do we use for concrete out on the surface and in the sun? In a non-oxidizing atmosphere without any nitrogen, whose pressure is a first cousin to hard vacuum?
GW
Last edited by GW Johnson (2014-03-13 08:22:42)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Mars appears to have a lot of caliche. When the regolith gets wetted (as it does every few million years when the tilt of mars's axis gets very extreme and the poles get more sun than the equator, so the equator gets snow and ice) the water perculating through the regolith causes salts to accumulate on the surface, cementing the surface materials together. You can take the caliche, crush it, add water, and it will set again, making duricrete. It is not as strong as concrete, but apparently it isn't bad.
They are also finding calcium sulphate (gypsum; plaster of Paris) and calcium carbonate (limestone; cement) on the Martian surface. If there are deposits (which is possible; there were water bodies in the past) they can be mined. I assume in my science fiction novel about exploring Mars that buildings inside pressurized shells or enclosures are built out of sheet rock on metal frames, as is standard practice here on earth.
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Mars appears to have a lot of caliche. When the regolith gets wetted (as it does every few million years when the tilt of mars's axis gets very extreme and the poles get more sun than the equator, so the equator gets snow and ice) the water perculating through the regolith causes salts to accumulate on the surface, cementing the surface materials together. You can take the caliche, crush it, add water, and it will set again, making duricrete. It is not as strong as concrete, but apparently it isn't bad.
Can it be reinforced with steel rebar or glass or basaltic fiber producted locally from regolith sands?
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It would not be difficoult to performe some tests, mixing duricrete and fiberglass, or duricrete and sawdust, or duricrete and iron mosquito net.
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Caliche? On Mars? Are you serious? I have heard nothing about that.
Caliche is a dirty, low-grade limestone from sea-bottom sediments. It's usually a white rock without much structural integrity, and it's usually fractured. It is very hard to dig holes in. Ground finely, that's road base "lime". Calcium carbonate limestone with a lot of other crap polluting it.
If there's really limestones on Mars, then some version of cement is possible. The process here is to grind it up, then heat it. It is energy-intensive to do both jobs.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Mars surface dirt includes both calcite (calcium carbonate) and dolomite (calcium magnesium carbonate). These are the minerals of limestone. It's not a separate limestone deposit, at least haven't found one so far, just mixed with soil.
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