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A UV protection coating can be applied to the dome material (like sunglasses) to help reflect UV rays. Another idea I had was to have a dome inside a dome and fill the gap between with ozone but the inside of the center dome would probably get too hot.
To help lessen the temperature extremes inside the dome we could install a large water bladder with an open top. Water resists rapid temperature change. The water will slowly absorb heat during the day and cold at night.
Also if we insulate the bottom of the dome, fill it with treated regolith (mars soil) and install soil heaters (tubes that warm air is pumped through?) then I don't think it would be a problem.
Aluminum tubes could also be placed into the mars soil to pump out water that sinks to the bottom of the dome during irrigation.
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Interesting that keeping greenhouses cool may actually be a problem. Piling up more dirt around them, say half way up the sides of a cylinder-shapped greenhouse, might help a little.
As RobertDyck has investigated, UV-blocking coatings are already used in high-end windows here on Earth, on a plastic substrate no less, with essentially 100% optical transparency.
Another option would be to use an IR-reflective coating, which is also available I am sure, to cool things off a bit. Forget putting water tanks in the greenhouse, just put piles of rocks on the floor to help moderate the temperature, since they have a much higher specific heat then water does and need no maintenance.
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Plan B to cool greenhouses would be to circulate hydroponic irrigation water through a heat exchanger outside the greenhouse that would dump the excess heat into the air or the ground more efficently then the plastic walls would.
I also wonder if water could be naturally circulated against the floor or roof of the greenhouse through some passive means to avoid the need for seperate machinery or power.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Difficult to tell if it will be neccesary to dump heat at all, this is not the usual thing one thinks about when planning a habitable area within an environment with an average temperature of -50°C.
Clever designs will call for a balance between average heat production and the size of heated areas in the base. More heat only means a larger habitable zone in the end, with daily fluctuations stored in surrounding rocks and released during night.
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Despite it's cold temperature, the rarified atmosphere probably acts as fairly effective insulation. So heat dispation may be a \n issue for a green house/hot house.
He who refuses to do arithmetic is doomed to talk nonsense.
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I like the idea of using the ground as a heat sink. It wouldn’t need to be built directly under the greenhouse if the soil was unsuitable for heating. The heat sink could perhaps increase the efficiency of the nuclear reactor and act as a backup power source if needed. It could also provide waste heat if needed during the martin night.
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If the plan is to vent excess heat into surrounding regolith (far enough away not to melt any high water content regolith under your hab) might the temperature differential be sufficient to run Sterling cycle engines?
It seems to me that a sealed system is essential with coolant running through a closed system in any event.
Give someone a sufficient [b][i]why[/i][/b] and they can endure just about any [b][i]how[/i][/b]
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Short answer: no, the coolant won't be hot enough to have a large enough temperature differential to operate a heat engine able to produce enough energy to be worth the trouble of developing/sending/building it.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Toilet paper? You think that's what's keeping us from colonizing mars?
I guess if you just ignore the facts then everything seems so easy. A child's view of the world.
So what if your first 100 colonists suffocate from lack of oxygen in less than a year and the next 100 die of starvation because plants just don't grow very well in mars regolith because it completely lacks any organic nutrients.
It's the price you pay to achieve Star Trek.
A small successful group will lead to colonization much more quickly than a large one that struggles to survive.
If you are really serious about this then solve the problems in my previous post, not to mention the many more problems-like cost.
How about this, tackle just one of them. How are you going to provide oxygen for your 100 colonists?
My point was not that a lack of ambient toilet paper will prevent a Mars colony from being feasible. My point was that there are a plethora of everyday items that we take for granted to such an extent that it's difficult to realize just how many items are required for everyday life at the standards of most developed countries. I don't doubt that the early western settlers got by with less equipment, but in many ways they had far more than Martian colonists can ever hope to have readily availible to them. American settlers had 100 kilometers of plentiful, sheilding, life-giving atmosphere over their heads, Martians will have no such luxury. Obtaining water was as simple as bringing a bucket to the local stream or well and filling up. On Mars, the same task will be far more difficult and more labor intensive. Martian colonists will be forced to live their entire lives either within the confines of a pressurized hab or inside a space suit. There will be no going outside for fresh air, cool dips in a river, and not much in the way of privacy. Human factors, while an issue, is by no means a showstopper for a two-year jaunt on the red planet, it is perhaps one of the biggest problems with colonizing the planet, however.
No public or governmnet in the world will tolerate a colonization effort that leaves the first hundred participants dead, that should be obvious. Had Apollo 13 not turned out as well as it did, it probably would have been the end of the program. As it happened, the final three Apollo missions were cancelled in large part because of the debacle. Failure quite literally is not an option. To tell you the truth, most people honestly could not care less about whether or not we achieve Star Trek, within their lifetimes or not. The vast majority of the general public is far more interested in what the price of gas will be in a year and when they can expect US troops to leave Iraq. These people, normal people, would be shocked at a program that kills so many of its colonists, and would start to wonder why it's being done in the first place. After not finding a satisfactory reason, they promptly withdraw their support. Overestimating the public's support of space exploration and development is a surefire way to kill any hopes of advancing either cause.
If anyone is ignoring the facts here, it's not me. I want to see a permanent, sustainable colony on the red planet as badly as all of you, I'm not just playing flame-weilding troll. There are serious, show-stopping issues that currently exist that have to be solved before colonization of Mars will become feasible. A two-way mission that brings 4-6 people to the surface of Mars for a year and a half and then returns to Earth will need all the resources needed to maintain human life in deep space for about three years, plus the ability to manufacture fuel for the return trip in-situ. A one-way colony mission will require every single resource needed to support humans permanently in deep space, or the ability to manufacture such resources on Mars. That will be far more difficult. Think about it: a simple sample-and-return mission can afford not to close all the life support gaps. They can bring frozen food and simply dump waste overboard to simplify things. A permanent colony will need to have every single loop in the life support problem closed. Oxygen, carbon dioxide, food, waste, water, it all needs to cycle around just as it does on Earth, but with zero help from the planet. That is simply not going to be feasilbe for the first mission.
Even under ideal circumstances, I'm afraid I disagree with the notion that a one-way mission would be better. One of the biggest selling points of a manned Mars mission is that it would allow scientists to study hand-picked pristine-quality Mars rocks with the best scientific equipment the Milky Way has to offer. If the rocks stay on Mars, what's the point? A huge chunk of the mission's value is lost. Overall, I stand by my vote; two-way missions first, later followed by permanent colonists. I guaruntee you that's how it will be accomplished.
A mind is like a parachute- it works best when open.
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The problem with going first for science is that like the Apollo missions, they can be discontinued very easy.
Building something gives use a much greater emotional attachment. And once its done theres almost no limit to the science we can do. And sending people with the equipment to carve out a permenent existance opens up the possibility they they may feel no great need to come home, esspecially considering that NASA won't send them twice.
"Yes, I was going to give this astronaut selection my best shot, I was determined when the NASA proctologist looked up my ass, he would see pipes so dazzling he would ask the nurse to get his sunglasses."
---Shuttle Astronaut Mike Mullane
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If the plan is to vent excess heat into surrounding regolith (far enough away not to melt any high water content regolith under your hab) might the temperature differential be sufficient to run Sterling cycle engines?
It seems to me that a sealed system is essential with coolant running through a closed system in any event.
After thinking about this more you wouldn't want to use your heat sink as a thermal storage reservoir. The heat sink would probably want the pipes to run close to the surface and be spaced far apart while the thermal reservoir would want the pipes to run deep into the ground and are spaced close together. Another though is we probably wouldn't want to waste a lot of water on a cooling system. I suspect that the working fluid for both power generation and cooling may be be liquid CO2.
The CO2 is stored under enough pressure to put it into a liquid state. It is pumped passed either the nuclear reactor or the greenhouse and the expanding gas drives a turbine. The expanding gas is then stored in a condenser and once it liquefies at night time it is then pumped back into the storage tank. Perhaps there is enough temperature difference between day and night to drive a power cycle based on expanding and contracting CO2. Anyone know the day and night time temperatures on mars. Time to dig out some thermodynamics books.
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If anyone is ignoring the facts here, it's not me. I want to see a permanent, sustainable colony on the red planet as badly as all of you, I'm not just playing flame-weilding troll. There are serious, show-stopping issues that currently exist that have to be solved before colonization of Mars will become feasible. A two-way mission that brings 4-6 people to the surface of Mars for a year and a half and then returns to Earth will need all the resources needed to maintain human life in deep space for about three years, plus the ability to manufacture fuel for the return trip in-situ. A one-way colony mission will require every single resource needed to support humans permanently in deep space, or the ability to manufacture such resources on Mars. That will be far more difficult. Think about it: a simple sample-and-return mission can afford not to close all the life support gaps. They can bring frozen food and simply dump waste overboard to simplify things. A permanent colony will need to have every single loop in the life support problem closed. Oxygen, carbon dioxide, food, waste, water, it all needs to cycle around just as it does on Earth, but with zero help from the planet. That is simply not going to be feasilbe for the first mission.
Financial efficiency restricts a supply everything from earth to the first ten colonists.-The survey teams.
A permanent colony will need to have every single loop in the life support problem closed. Oxygen, carbon dioxide, food, waste, water, it all needs to cycle around just as it does on Earth, but with zero help from the planet. That is simply not going to be feasilbe for the first mission.
At twenty billion a year per person, for colonization support, two hundred billion dollars a year is your absolute limit in population support. There is no possibility of supporting continuously beyond that level of colonization for earth nations.
Considering that the return for earth is scientific samples that pretty much brings this down to the Nation of Mars pursuing self colonization.
The only method open to reduce the expense of colonization below the 20 billion billion is to terraform first until there is an ecosystem of food available across the entire surface of Mars and while that is "in the works" devote our time to developing Space transfer systems capable of moving millions every year.
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RobS has some uses for waste heat in his (scientifically rather sound) novel
-pump it down, and use it as an 'accumulator' Some kind of heat-battery, handy when duststorms etc lower your energylevels (if you go solar)
-use it to keep a *large* body of H2O liquid, for fish. In essence a big, outside(!) pond, upperlayer is Ice, with a tarp above it to insulate it from outside.
A permanent colony will need to have every single loop in the life support problem closed. Oxygen, carbon dioxide, food, waste, water, it all needs to cycle around just as it does on Earth, but with zero help from the planet.
Why with zero help from the planet? Apollo-style missions do that, two days, not worth to drag ISRU hardware with you, but months-long Mars missions are another story.
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My point was not that a lack of ambient toilet paper will prevent a Mars colony from being feasible.
Mad Grad: My post was in response to Ryke's joking about toilet paper being an essential item. I agree with you 100%. Going to mars to colonize on the first trip is insane and likely will just lead to many unnecessary deaths.
I see 100 years worth of landings, site surveys, pressurized rover exploration, a small scientific colony on planet, more exploration, digging, testing greenhouses, regolith sampling...only when we know it's even possible would we begin to attempt terraforming and I doubt there would be any significant human presence on mars until there is at least liquid surface water and a sufficient pressure in the atmosphere.
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-A mobile machine to extract water from martian regolith
Why not land near a known source of water ice (or an underground deposit if Mars Express finds them), such as in that crater closer to the poles. If underground ice or liquid water deposits are found they could bring some sort of drill. I imagine said drill would be mightily hard to get to Mars.
-A 100% efficient human waste recycling machine
Land near a source of water that isn't going to run out in the timeframe they are looking at. Keep an 1 year supply of backup water at all times.
-Long lasting, safe, lightweight power source (2 nuclear power sources with solar backup may be enough)
With 2 nuclear power sources might as well include a 2nd backup Solar array, even if was launched on the 2nd mission or a resupply mission.
-Some way to make/grow food on planet
I think we have the technology to do this, obviously some R&D would be needed but on a large budget it's definatly possible.
-Much better machines to get Oxygen from CO2
What is holding back this technology? lack of researchers?
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Well of COURSE sending people one-way first thing would be silly, there are a variety of variables that we need to know and work out first, and it will probobly take boots-on-the-ground to find and prepare a suitable site.
If were honest with ourselves about opening a colony that has no real quantifiable material bennefit to the home planet, which would probobly become a seperate soverign state, and there was still enough support (either public taxes or private investment) then I don't think it would take 100 years to get started... fifty or sixty at least, but not a hundred.
100% closed-loop recycling is almost impossible nor is it nessesarry: oxygen, carbon, hydrogen, and a little nitrogen all exsist in quantity on Mars and are accessable, albeit with a little difficulty. CO2-to-O2 conversion for instance is a pretty energy intensive process right now, so the watts-per-colonist required is probobly too high, hence the need for more efficent methods.
Nitrogen can be refined from liquified Martian air or decomposed nitrate salts if we find any, and if we are stingy with it there should be enough. There is plenty of water to be had if you drill for it, though you might have to transport it a ways. Carbon dioxide will be abundant, and there are synthetic and biological ways of capturing/converting it into useful forms.
Back to the greenhouse waste heat question, the problem is all about temperature, that heat energy carried by a coolant will only be transferred efficently to a heat sink at a substantially lower temperature. Since the greenhouse coolant will probobly be no warmer then bath water, therefore you can't heat up a big pile of Martian rocks to a very high temperature, so you can't pump/store much heat energy into them.
Using liquid CO2 for a phase-transition coolant is probobly practical for small/medium scale machinery (like carrying waste heat from the nuke or to/from the chemical plant), but due to the pressure and toxticity of warm liquified CO2 I don't think it would be a good coolant for greenhouses or any "indoor" application. If there is a leak, you are going to have big problems, and maintaining that pressure safely would be too much trouble. When you build your base next to an ice flow or frozen lake a few miles wide, you can spend a little for coolant.
An outdoor "pond" is a cute idea, but how are you going to harvest anything out of it? Plus there will be pretty serious energy loss to the soil, which is quite cold year-round. I would also worry what would happen if the warm coolant flow were interrupted. Making plastic domes will be pretty cheap and easy once the method is perfected, and putting bodies of water indoors for growing fish would probobly be far easier... And when we're talking about the colonists spending the rest of their lives indoors or in a suit, any excuse to add habitable volume - particularly with living things in it against the backdrop of a dead world - is a good one. Cooped up kids would love it, hide-and-seek between vats or scaring the poor fish.
Using the temperature differential between Martian day and night to use CO2 expansion/contraction for power is a clever idea, but its not going to work very well. The problem isn't the temperature, its the thermal conductivity of the environment. In order for the CO2 to cool at night the heat absorbed in the day, it would have to dump this heat somehow, which will not be practical on any large scale. Since your options are the atmosphere which is too thin to conduct much heat, or the cold ground which doesn't conduct that well either, there isn't much of a very good way to do this.
For every watt of electrical power you get, I am sure you would have to dump alot more into the environment, which will require an impractically large cooling system. You could improve the situation by using solar energy to heat CO2 directly with a solar/thermal heat sink, but why bother? Just build thin-film bulk photovoltaic arrays and ship them from Earth in bulk, eventually converting to indigenous ones. Amorphous gallium arsenide or advanced photovoltaic polymers would be thin, light, and easy to make huge areas of.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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We are not exactly going to have one greenhouse are we. If we have a group of them then the likehood is that we will need different operating tempatures for the different plant types we grow. There is also the likehood that for purely morale reasons we might create a garden dome just for people to be able to walk into and see greenery.
With this in mind we can use a cooling system and pump to move heated liguid to warm the greenhouses that need more heating and cool the ones that dont. If we use the idea of a large tank reservoir that is sealed we can pump heat into it and have for all intents a large fish farm.
We will only need such a complicated cooling system if we do insulate the greenhouses and domes to the point of little heat loss during the night. But we can use the problem we create as a solution to other issues we have and hopefully reduce the power we need to have to divert from the Nuclear power plant that is essential to any base or colony plan we have.
As RobertDyck has investigated, UV-blocking coatings are already used in high-end windows here on Earth, on a plastic substrate no less, with essentially 100% optical transparency
Interesting but most Uv protection coatings on windows only reduces the amount of Uv that penetrates. Mars though has not atmospheric protection at all and as such the most dangerous bands of Uv light will have unlike on the Earth free access to the surface. The best Uv protection I have found from a lot of googling and asking glass companies is to stop all but 8% of the Uv light and this begins to make the glass very dark. Add the increased protection needed to strengthen the plastic and the extra Uv protection it is likely that Mars greenhouses will have rather dark windows
Chan eil mi aig a bheil ùidh ann an gleidheadh an status quo; Tha mi airson cur às e.
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Interesting thought of going to stay but that requires lots of work to use insitu resources and the proper planning of what equipment as well as supplies to bring.
The solution to which is being explored by the Mars society homestead group.
The Homestead Project: Making a Mars Settlement a Reality
Building upon concepts and designs from the past several decades,
the Mars HomesteadTM Project, the main project of the Mars FoundationTM,
seeks to develop a unified plan for building the first habitat on Mars by exploiting local materials. The ultimate goal of the project is to build a growing, permanent settlement beyond the Earth, thus allowing civilization to spread beyond the limits of our small planet.
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I'm just guessing but there might be mirrors that don't reflect UV light, maybe something like a prism that breaks up the light into spectral colours. We could use these exclusively to light up greenhouses rather than bothering with UV blocking windows if they can't be made any better.
A one way mission would be possible from the day any mission to Mars is doable at all. Returning the crew after a minimum of two years of being isolated from any resupply is not easier than sending a resupply capsule after this time.
But I'm realistic enough to know that the first one will be a return mission if it is done by a government space agency, which I'm not 100% sure about after seeing this fuel tank debacle, it's definately not going to happen in this style.
Anyway I wouldn't support a one way mission without the option to return at the next window and would leave it up for the crew to decide if they want to stay.
Even for a two way mission, there will have to be a couple of long duration missions to the Moon before to test out as much of te equipment as possible with a fast emergency return option.
For the waste heat don't forget that the base temperature of Mars is some 60K lower than that on Earth, so you still have a temperature difference of about 100K, and this closer to absolute zero than on Earth making it more efficient for the same difference.
Anyway this is just wild guessing without doing some basic calculations.
GCN, you're right with not using pressurized CO2 within the base, maybe it would be good to add heat exchangers and a second water loop for habitable parts of the base, if it doesn't decrease efficiency too much.
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I'm just guessing but there might be mirrors that don't reflect UV light, maybe something like a prism that breaks up the light into spectral colours. We could use these exclusively to light up greenhouses rather than bothering with UV blocking windows if they can't be made any better.
Problem with refraction is that one of the important colours of light that plants need is the colour blue which has a wavelength about 475nms so would probably be blocked by this method. We will just have to accept that the best method of farming on Mars is to use artificial lighting to grow plants to support the poor light Mars gets. Still not a surmountable problem as long as we have the energy.
Chan eil mi aig a bheil ùidh ann an gleidheadh an status quo; Tha mi airson cur às e.
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We are not exactly going to have one greenhouse are we. If we have a group of them then the likehood is that we will need different operating tempatures for the different plant types we grow. There is also the likehood that for purely morale reasons we might create a garden dome just for people to be able to walk into and see greenery.
With this in mind we can use a cooling system and pump to move heated liguid to warm the greenhouses that need more heating and cool the ones that dont. If we use the idea of a large tank reservoir that is sealed we can pump heat into it and have for all intents a large fish farm.
We will only need such a complicated cooling system if we do insulate the greenhouses and domes to the point of little heat loss during the night. But we can use the problem we create as a solution to other issues we have and hopefully reduce the power we need to have to divert from the Nuclear power plant that is essential to any base or colony plan we have.
As RobertDyck has investigated, UV-blocking coatings are already used in high-end windows here on Earth, on a plastic substrate no less, with essentially 100% optical transparency
Interesting but most Uv protection coatings on windows only reduces the amount of Uv that penetrates. Mars though has not atmospheric protection at all and as such the most dangerous bands of Uv light will have unlike on the Earth free access to the surface. The best Uv protection I have found from a lot of googling and asking glass companies is to stop all but 8% of the Uv light and this begins to make the glass very dark. Add the increased protection needed to strengthen the plastic and the extra Uv protection it is likely that Mars greenhouses will have rather dark windows
Just shifting the heat around between greenhouses growing different crops won't work, that is like shifting water between different compartments of a ship full of holes. The problem must be aproached from the whole pressurized volume of the colony, that the total amount of heat energy it absorbs from the sun or is pumped in by nuclear/solar sources must be balenced by the amount of energy that is lost, or else you get a net buildup of heat. If the total heat absorbed by the colony exceeds that lost, then it doesn't matter where you move the excess heat to, somewhere in the colony will become too hot and the heat transport system will not be able to cope. Remember, heat only travels from hot to cold (without phase change anyway), so eventually the "hot" greenhouse will get just as hot as the coolant from the other "cold" greenhouses, and no more heat can be dumped into it. Simply because it has a fish pond in it doesn't change the fact that you must balence the heat in versus heat out.
Of course, the equation won't be the same for the entire day, that even though the greenhouses may get too hot during the day, they may also get too cold during the night. In this case, having a "pond" or fish tanks or something as a heat sink would be useful, that you could circulate warm water into it during the day, and warm water out of it during the Martian night. There may still be too much heat though, but it would go a long way to helping. You would also have the ease of only having to heat/cool one body of water with mechanical means.
I also reject this notion that a UV/IR selective coating for plastic greenhouses would make them "too dark" or something, you don't give the chemists enough credit... I do think that such a coating would be pretty easy to develop, as coatings that work nearly as well as we need for greenhouses are already used in high-end windows. If they aren't good enough, I am sure we could do better with a little research. You might be confused also, that the coating in windows is most often applied to a plastic sheet, which is then sandwiched between the glass.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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We are not exactly going to have one greenhouse are we. If we have a group of them then the likehood is that we will need different operating tempatures for the different plant types we grow. There is also the likehood that for purely morale reasons we might create a garden dome just for people to be able to walk into and see greenery.
With this in mind we can use a cooling system and pump to move heated liguid to warm the greenhouses that need more heating and cool the ones that dont. If we use the idea of a large tank reservoir that is sealed we can pump heat into it and have for all intents a large fish farm.
We will only need such a complicated cooling system if we do insulate the greenhouses and domes to the point of little heat loss during the night. But we can use the problem we create as a solution to other issues we have and hopefully reduce the power we need to have to divert from the Nuclear power plant that is essential to any base or colony plan we have.
As RobertDyck has investigated, UV-blocking coatings are already used in high-end windows here on Earth, on a plastic substrate no less, with essentially 100% optical transparency
Interesting but most Uv protection coatings on windows only reduces the amount of Uv that penetrates. Mars though has not atmospheric protection at all and as such the most dangerous bands of Uv light will have unlike on the Earth free access to the surface. The best Uv protection I have found from a lot of googling and asking glass companies is to stop all but 8% of the Uv light and this begins to make the glass very dark. Add the increased protection needed to strengthen the plastic and the extra Uv protection it is likely that Mars greenhouses will have rather dark windows
Just shifting the heat around between greenhouses growing different crops won't work, that is like shifting water between different compartments of a ship full of holes. The problem must be aproached from the whole pressurized volume of the colony, that the total amount of heat energy it absorbs from the sun or is pumped in by nuclear/solar sources must be balenced by the amount of energy that is lost, or else you get a net buildup of heat. If the total heat absorbed by the colony exceeds that lost, then it doesn't matter where you move the excess heat to, somewhere in the colony will become too hot and the heat transport system will not be able to cope. Remember, heat only travels from hot to cold (without phase change anyway), so eventually the "hot" greenhouse will get just as hot as the coolant from the other "cold" greenhouses, and no more heat can be dumped into it. Simply because it has a fish pond in it doesn't change the fact that you must balence the heat in versus heat out.
Of course, the equation won't be the same for the entire day, that even though the greenhouses may get too hot during the day, they may also get too cold during the night. In this case, having a "pond" or fish tanks or something as a heat sink would be useful, that you could circulate warm water into it during the day, and warm water out of it during the Martian night. There may still be too much heat though, but it would go a long way to helping. You would also have the ease of only having to heat/cool one body of water with mechanical means.
I also reject this notion that a UV/IR selective coating for plastic greenhouses would make them "too dark" or something, you don't give the chemists enough credit... I do think that such a coating would be pretty easy to develop, as coatings that work nearly as well as we need for greenhouses are already used in high-end windows. If they aren't good enough, I am sure we could do better with a little research. You might be confused also, that the coating in windows is most often applied to a plastic sheet, which is then sandwiched between the glass.
Fortunatly we can automate the process by pumping the hot water to a series of loops outside to cool the mixture if we find it is getting too hot. Especially if they have a high surface area and we can use these only if we truly need too. Hopefully the insulation we use will mean that heat loss from the colony is small at night.
I certainly hope that a Uv protection for greenhouses has been done but as stated with a lot of googling and asking people who deal with the glass industry I have still to find anyone who has such a coating that does not reduce the visible light spectrum. It does not mean it does not exist just I have not found it yet. You will also see in my post that it is the plastic that is sunblocked and I have even mentioned it still glass is the cheapest stuff we use even when toughened enough to protect a greenhouse on mars. It will be glass we use there as it will reasonably easy to make more as long as we have silicates and if we have to create a thick anti Uv layer it is that layer that makes the glass more opaque.
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My idea is to intentionally let heat escape from the greenhouses at night, and to activly heat them with warm water from the fish/seaweed vats/ponds. This way, you may be able to get rid of heat stored from the day that was collected to keep the greenhouse cool, thus balencing the heat flux of the colony by simply differing when you do your cooling. Retractable reflectors/insulators will still be nessesarry probobly, to maximize the light the plants get, which would cover the greenhouse at night if it gets too cold anyway or if the coolant is interrupted.
Glass? Greenhouses won't be made from glass, thats for sure. We have carbon, we have oxygen, and we have hydrogen, which with a little chemistry yeilds you polymers. Make them out of inflatable plastic, which you could make in vast quantities instead of glass much more easily. No worries about explosive shattering or support structure either. The obvious choice.
Talk to RobertDyck, who is a member of the MarsHomestead project, who has been investigating just this sort of thing and I do believe that he found such a coating/plastic combination that would do the job.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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We are not exactly going to have one greenhouse are we. If we have a group of them then the likehood is that we will need different operating tempatures for the different plant types we grow. There is also the likehood that for purely morale reasons we might create a garden dome just for people to be able to walk into and see greenery.
Hmm...We could have one greenhouse inside the next at increasing airpressures so they will never rip. We could do the same for Mars Domes.
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No, because if we wanted to use air-pressure supported inflatable greenhouses, then you would need higher and higher internal pressure for the inner envelopes. It wouldn't solve the thermal control problem either. The solution to avoid ripping is just to make them strong enough that a serious tear is unlikly, and make them in small enough segments that you can afford to lose some.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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There has been some discussion about how much power it would take to heat or cool a Martian greenhouse. I have done a simple model on this page:
http://www.newmars.com/wiki/index.php/M … _The_Walls
If this model is not convincing I'll work on a more complex model. Examples:
http://www.newmars.com/wiki/index.php/T … greenhouse
I think though it provides a good baseline. It assumes the Martian air can keep the outside wall near the temperature of the Martian air and that all loses are due to conduction through the walls of the half cylinder greenhouse. The conclusion is that if the walls are made of mylar and 2 cm thick then the greenhouse will receive the same power from the sun as it gives off in heat. If the walls are 4 cm thick the greenhouse will absorb twice the power from the sun as it gives off in heat. If it gets too hot, why not open a window. Well you couldn't open a window but if you had a second greenhouse with walls 1 cm thick then if you opened the doors between the two greenhouses the net exchange in heat would be equal to the heat absorbed by the sun.
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