Quote from: Ludus on 10/13/2016 07:11 am I'd have to think that insulating the face of the ice from the settlement's air temperature isn't that killer an issue. A settlement with reactors and waste heat anyway could keep a huge volume at a very comfortable temperature. Reactors could be located in the rock a short distance away.Keeping the habitats warm is not what I am concerned about. Dumping waste heat while making sure the ice won't melt is the engineering challenge IMO. That would require the ice surface to be exposed and temperatures well below freezing. People do enjoy winter temperatures and snow and ice. Though some caves may be isolated and kept warm so plants can grow. Technical solutions to dissipate low temperature heat energy would be complex and may be prone to failure. Better to have a naturally stable system.Having some green to walk throug is nice to have. But light for plants would introduce a lot of heat that needs to be dissipated. I am not thinking of growing much food there but plants that need little light as a public park. Plants like ferns and philodendron. Plus a few separately lighted spots for plants that grow fruit like strawberries.
I'd have to think that insulating the face of the ice from the settlement's air temperature isn't that killer an issue. A settlement with reactors and waste heat anyway could keep a huge volume at a very comfortable temperature. Reactors could be located in the rock a short distance away.
If you want a naturally stable system you can also live in, nothing on Mars will do... Seriously, you will have to manage your temperatures (by cooling or heating) just as your atmosphere and everything else. This is true for spacecraft, for space stations as the ISS and also will be the case on Mars. Dissipating heat isn't easier in surface structures than in caves in rock or ice. In fact ice at -50°C allows dumping quite a lot of heat into it without the ice melting, making this easier than on the surface where you have to use radiators to get rid of it just like at the ISS.
Quote from: uhuznaa on 10/13/2016 09:36 amIf you want a naturally stable system you can also live in, nothing on Mars will do... Seriously, you will have to manage your temperatures (by cooling or heating) just as your atmosphere and everything else. This is true for spacecraft, for space stations as the ISS and also will be the case on Mars. Dissipating heat isn't easier in surface structures than in caves in rock or ice. In fact ice at -50°C allows dumping quite a lot of heat into it without the ice melting, making this easier than on the surface where you have to use radiators to get rid of it just like at the ISS. Yes, of course it will need heating. But with energy consumption inside the living quarters and good isolation not much.What I mean with naturally stable is the heat flow from habitat to ice being in a range where you don't need technical intervention to keep the temperature outside the habitat and within the ice cave in a practical range. As that cave would have pressure and breathable atmosphere you can vent excess heat by opening the window like you do on earth. Just size habitat size and total energy consumption and size of the ice cave so you don't need active cooling for the cave.
Opening the window will be a bad idea though, losing precious oxygen and nitrogen would be bad.
Its major industrial products are caustic soda and chlorine, and is used in many industrial processes including the manufacture of polyvinyl chloride, plastics, paper pulp and many other products. Of the annual global production of around two hundred million tonnes of salt, only about 6% is used for human consumption.
Let's see how much salt would be in a large body of water. If it is from precipitation, virtually none. If it is an ancient ocean it may be more. But the oceans of earth have accumulated their salt content over billions of years from rivers. The liquid oceans of Mars did not exist that long at all. I expect that it would still even pass as drinking water, except for possible poisonous ingredients.
Quote from: uhuznaa on 10/13/2016 11:08 amOpening the window will be a bad idea though, losing precious oxygen and nitrogen would be bad.The whole cave would be pressurized. And soon, if not immediately, filled with breathable air. There will be plenty of it available from fuel ISRU. Oxygen because the engines run fuel rich and the production is stochiometric. Nitrogen or a breathable mix of oxygen and argon are just a byproduct of extracting the CO2 for the Sabatier process.
Yes, the atmosphere being 96% CO2, 2% nitrogen and 2% argon (roughly) means you will accumulate quite a bit of both. Still, to replenish your internal atmosphere you will have to store them in high pressure vessels. In the long run you'll have reserves, but for quite a while having a nice atmosphere in your habitats will be too precious to vent them. Also nitrogen is important for plants, you'll tend to not waste it.
90 percent of the glacier-cave talk here sounds like it's been lifted strait from the Zygote settlement of the Mars Trilogy. The notion that a cave itself can be a pressure vessel is deeply flawed, the rock that a glacier sits on can easily be fractured and allow air to escape, as the habitat air is warm it can cause sub-surface melting, likewise the interior air in the cave would have to be kept away from the ice roof to prevent all the issues I described earlier. The net effect is that your going to need to have a full top and bottom pressure envelope inside the cave, it can be thin because it dose not need protection from micrometeorites as it would exposed on the surface but the cave is really not doing anything that a architectural dome and a few meters of regolith couldn't do, and it has disadvantages too, susceptibility to creep over time, difficulty in dumping waste heat as have been mentioned, inability to use skylights or any other top-down access to the habitat area. Probably most important is that it requires that you not perform simple surface mining of the same glacier body that your living in so as to avoid damaging your own habitat.Construction on the surface with arches, vaults, columns and other compression load bearing structures can provide the necessary radiation protection without any of these issues. The same thin membrane pressure vessels inflated inside these protected spaces will be necessary but this is unavoidable and a wash. Also note that some posters have erroneously claimed that a single massive pressure vessels is more efficient then many small ones, this is a common error in thinking that the pressure vessel mass scales only with surface area, in actuality it scales with volume due to a large vessel needing a thicker wall. Given the inherent danger, I would say death-trap-ishness, in a single pressure vessel the interconnecting of many individual pressure vessels is certainly the way to go.Note that a livable habitat is going to consist of a LOT more mass in equipment, life-support and otherwise beyond the pressure vessel, even a pressure vessel made 100 percent from local materials will need nearly the same amount of vital equipment to shipped in. This is the flaw in most space-cadet style housing solutions, they pretend that they are making log cabins in which just walls and roof are all that's needed and that they are saving 90 percent of the shipment mass from Earth.
Also a few feet of regolith on top won't help much against an atmospheric pressure of 10 tons per square meter trying to push things apart from the inside. You'd need to pile 10 tons of regolith per square meter on top of your building to counter the atmospheric pressure inside. Regolith has a density of about 1.5 g/cm^3, so in Mars' gravity this would be a layer of 20 meters (about 65 feet) thick. Only if you would add even more on top your structure will start to come into compression and you'll start to need arches, columns etc. Until then it is under tension and will try hard to explode from the inside.
Quote from: uhuznaa on 10/13/2016 11:03 pmYes, the atmosphere being 96% CO2, 2% nitrogen and 2% argon (roughly) means you will accumulate quite a bit of both. Still, to replenish your internal atmosphere you will have to store them in high pressure vessels. In the long run you'll have reserves, but for quite a while having a nice atmosphere in your habitats will be too precious to vent them. Also nitrogen is important for plants, you'll tend to not waste it.It seems we have a misunderstanding. I am not suggesting wasting anything. We have a large habitat with breathable air. We have a house that is not pressurized by itself because it does not need to be. Opening the window exchanges air with the larger cave which is closed. Nothing is wasted unless you see pressurizing a large cave with breathable air is waste.
OK, so a big buffer of pressurized volume to dump excess heat into. I would guess just dumping into a more remote part of the glacier with water loops and heating the ice there a bit would be easier, but on the other hand you will be carving out bigger and bigger caves all the time anyway.