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#26 2017-04-27 12:43:43

louis
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From: UK
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Posts: 5,872

Re: Air. Shelter. Water. Food.

Mars will be the perfect proving ground for solar power satellites which can beam power to the surface.

Oldfart1939 wrote:

Louis-

I'm actually more concerned with having fail-safe energy production as an insurance policy for the return to Earth portion of the mission(s). There have been many times when the planet has been subjected to dust storms lasting nearly an Earth year, and it would be fatal to rely on just solar power to keep everything running--especially any artificially lighted greenhouses. I really don't see this as an either-or situation, but as I've stated earlier, will require both technologies. As a somewhat more aesthetic issue: I consider both solar farms and wind farms as massive eyesores. I'd really like to preserve the Martian landscape for viewing. Structures with solar panel roofs? No problem from me. Nearby the base for small solar setups? Again, no problem. Covering the landscape with acres and acres of solar panels? No thanks.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#27 2017-04-27 13:38:37

elderflower
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Re: Air. Shelter. Water. Food.

It would, Louis, except for the cost of installing them in synchronous Mars orbit.

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#28 2017-04-27 17:20:20

Oldfart1939
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Re: Air. Shelter. Water. Food.

Not to mention that isn't a mature enough technology to rely upon.

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#29 2017-04-27 17:41:43

louis
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From: UK
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Posts: 5,872

Re: Air. Shelter. Water. Food.

I'm not suggesting it is but it is definitely a viable technology:

http://spectrum.ieee.org/green-tech/sol … solar-farm

Much better prospects than hot fusion.

From a standing start we won't get humans to Mars for another ten years and we won't need major energy input until ten years after that.
SPS could be viable by then.


Oldfart1939 wrote:

Not to mention that isn't a mature enough technology to rely upon.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#30 2017-04-27 18:50:47

SpaceNut
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Re: Air. Shelter. Water. Food.

While beam or microwave focused power has promise as well as other for mars it does come at an expense that early developement of mars makes it so that we are delayed from going so it will need to wait just as fusion will.
I would look at reuse of materials from RTG's for any sort of nuclear reactor in it early stages once we build or send a core unit for making it possible. Sure early reactor will be small but sending the much larger unit will allow for a built on mars assembly to happen to happen from recycling and supplementing from what mars has to offer.

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#31 2017-04-28 07:52:27

Oldfart1939
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Re: Air. Shelter. Water. Food.

SpaceNut-
The RTGs all depend upon Plutonium. If we're really looking forward, a switch needs made to Thorium based reactors which are intrinsically a lot safer, since the wastes are not nearly as hazardous to handle, store, and dispose of. Additionally, there's a lot of Thorium available here on Earth--far more abundant than Uranium.

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#32 2017-04-28 10:55:47

Terraformer
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Re: Air. Shelter. Water. Food.

Energy wise, how much energy are we talking about? A lot of energy is used to transport people from place to place, here on Terra - on Mars, we're not going to be having people commuting for a couple of hours by car every day. We also won't be manufacturing throwaway items, so that energy won't be wasted. On the other hand, we'll need power for heating and life support, including artificially balancing the ecosystem (it's a garden, not a biosphere).

I'm with the use of ambient light to grow crops, whether that be using greenhouses or by piping the energy in to underground chambers. Though it has the disadvantage that dust storms would interfere with the gardening - if you want to avoid that, you'll need nuclear power and LED lighting. Can we store excess oxygen to last us through the storms? People need ~0.7kg per day, so it should be doable for any habitat that's storing hundreds of tonnes of LOX for propellent...


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#33 2017-04-28 11:22:00

louis
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Re: Air. Shelter. Water. Food.

Methane is an alternative to nuclear power during dust storms. It should be remembered that dust storms do not reduce PV to zero.

Terraformer wrote:

Energy wise, how much energy are we talking about? A lot of energy is used to transport people from place to place, here on Terra - on Mars, we're not going to be having people commuting for a couple of hours by car every day. We also won't be manufacturing throwaway items, so that energy won't be wasted. On the other hand, we'll need power for heating and life support, including artificially balancing the ecosystem (it's a garden, not a biosphere).

I'm with the use of ambient light to grow crops, whether that be using greenhouses or by piping the energy in to underground chambers. Though it has the disadvantage that dust storms would interfere with the gardening - if you want to avoid that, you'll need nuclear power and LED lighting. Can we store excess oxygen to last us through the storms? People need ~0.7kg per day, so it should be doable for any habitat that's storing hundreds of tonnes of LOX for propellent...


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#34 2017-04-28 11:58:51

Terraformer
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Re: Air. Shelter. Water. Food.

You might use methane to provide power during dust storms, but you certainly won't use it to power LED lighting for agriculture. Not when you can just store food. There's also little point in using PV powered LEDs if you can use ambient light, because of conversion losses.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#35 2017-04-29 00:55:32

RobertDyck
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Re: Air. Shelter. Water. Food.

Terraformer wrote:

Can we store excess oxygen to last us through the storms?

A semi-permeable membrane is used on Earth to produce nitrogen. The membrane allows "fast" gasses to pass through the membrane, nitrogen does not. "Fast" gasses include O2, CO2, water. However, some nitrogen gets through as well. I read the "membrane method" is used by SCUBA divers, it can produce 40% O2. Earth's atmosphere has 20.9% O2. That's far from perfect, but one way to produce oxygen. You could then use a regenerable sorbent to remove CO2. Then store the rest? I wonder if multiple passes could remove more nitrogen, producing oxygen that's far more enriched. Pure oxygen is separated by cryogenic freezing. Oxygen liquefies at a different temperature than N2, CO2, or argon, neon, krypton, xenon. Cryogenic separation is energy intensive, a semi-permeable requires significant pressure but power for the pump is significantly less than a refrigeration system necessary for cryo-separation. That's why it's used by automotive service garages that sell nitrogen for tires. To produce nitrogen, compressed air is dried before putting in through the membrane. Water could clog the membrane.

So yes, you could store oxygen.

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#36 2017-04-29 02:56:40

louis
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Re: Air. Shelter. Water. Food.

I would agree that under a PV power system approach there would not be much point in producing storeable food during dust storms. As you say, easier to store a food surplus at times of plenty. We might continued production of salad vegetables though. However, everything should be failsafe in the early colony.  I would favour building up a huge methane power surplus asap to ensure we can continue at full power with agriculture if necessary.

I think we need to be careful about dust storms though before we frighten ourselves. They are not that common; parts of Mars are less affected by them; and you still get some power even during a storm (I have seen 10% mentioned as a minimum but I don't think in reality the Rover on Mars have often dipped below 20% of expected).

There is a lot of point in using LEDs because you can have any number of tray layers over the same area.  With a buried hab you could within a ceiling height of 2.5 metres easily have up to 5 tray layers growing various food plants...maybe average about 3. So your farm hab structure is (a) much smaller for the same output (b) much simpler to build (because you can use cut and cover rather than constructing large domes) and (c) much more dependable.

Terraformer wrote:

You might use methane to provide power during dust storms, but you certainly won't use it to power LED lighting for agriculture. Not when you can just store food. There's also little point in using PV powered LEDs if you can use ambient light, because of conversion losses.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#37 2017-04-29 03:09:40

louis
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Re: Air. Shelter. Water. Food.

A rather nice vid showing a DIY solar array plus 12 Kwe steam generator. I am impressed at how compact the generator is.


https://www.youtube.com/watch?v=jTvAL7ty53M

Presumably on Mars we might get about half that - so 6Kwe - with a similar set up. Of course we would likely need to incorporate a condenser unit, to preserve water.

However, there is nothing inherently undoable about such a set up. Most of the parts could be produced on Mars at an early stage with the help of 3D printer machines.

Solar powered steam engines would be perfect for industrial processes like methane production, oxygen production, purification of ores, basalt melting and steel production.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#38 2017-04-29 03:24:19

RobertDyck
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Re: Air. Shelter. Water. Food.

The best space solar cells available today convert 30.7% of sunlight to electricity Beginning-Of-Life, 26.7% End-Of-Life. LEDs are very efficient, but they aren't perfect either. So using PV to generate electricity, then LEDs to illuminate plants, is very inefficient. Far better to use natural light.

During a dust storm, you will have to illuminate plants until harvest. Then just don't re-plant annuals. However, perennials and trees will have to be illuminated. You don't want a tree that takes 3 Earth years before first harvest and several more years to achieve peak production to die with the first dust storm.

And you can store oxygen, but it would be safer to use chemical/mechanical life support during a dust storm. Such as the system currently on ISS. It requires power, but that means power for industrial production will be shut down in favour of life support.

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#39 2017-04-29 04:37:55

louis
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Re: Air. Shelter. Water. Food.

How much energy - and more importantly people hours - are required to put together a surface glass dome? You need to cover probably at least 10,000 sq. metres (probably more since the dome will to some extent restrict light entry) to provide enough energy for one person.  The equivalent area covered by an artificially lit hab (in a simple cut and cover construction) would be as low as 2,000 sq. metres, depending on what you grow.

As long as you have plenty of water stored, and methane as well, then you should be able to replenish your stocks of oxygen. 

RobertDyck wrote:

The best space solar cells available today convert 30.7% of sunlight to electricity Beginning-Of-Life, 26.7% End-Of-Life. LEDs are very efficient, but they aren't perfect either. So using PV to generate electricity, then LEDs to illuminate plants, is very inefficient. Far better to use natural light.

During a dust storm, you will have to illuminate plants until harvest. Then just don't re-plant annuals. However, perennials and trees will have to be illuminated. You don't want a tree that takes 3 Earth years before first harvest and several more years to achieve peak production to die with the first dust storm.

And you can store oxygen, but it would be safer to use chemical/mechanical life support during a dust storm. Such as the system currently on ISS. It requires power, but that means power for industrial production will be shut down in favour of life support.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#40 2017-04-29 08:45:18

Oldfart1939
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Re: Air. Shelter. Water. Food.

We seem to have an energy "Catch 22" situation here. In order to have Methane produced, we need either (a) lots of H2 generated from the electrolysis of water in order to subsequently manufacture it, or we can used the energy to (b) contribute towards artificial lighting. Given the postulated size of the Solar Array, there will NOT be enough energy generated to do all things together, and at the same time. Burning Methane to produce steam and subsequently  electricity also requires Oxygen. This system is energetically getting out of control. Solar only operates at 30% efficiency for half a Sol. Dr. Zubrin has done the calculations in Entering Space, which serves to illustrate the need for Nuclear Power, no matter how badly some want Solar Panel (PV) technology to succeed. We really don't have immediately available the numbers of KWe needed to (1) electrolyze water for both H2 and O2, (2) energy required by the Sabatier reactor for Methane production, and (3) energy required for all heating, cooking, lighting, etc., for Mars base, all competing with (4)  greenhouse lighting. Initially, storage of "excess methane," that over and above that needed for ascent vehicle use, will be either strictly limited or non-existent. Oxygen is also facing the same limitation. No how badly some others here wish it otherwise, the initial missions will absolutely require Nuclear Power.  To do otherwise will put all the lives at risk, and flirt with abject mission failure. I just cannot comprehend trying to bring radical Green environmental policies to Mars--grasping at straws in order to do so. I will, however, agree that having an alternative power supply "on hand" is also essential; once we get through the initial stages of settlement, we can add the Methane/Oxygen powered steam plant for emergency backup.

The other kicker is how much more equipment will need to be brought to Mars from Earth in order to have artificial greenhouse lighting? LED bulbs, and lots of wire, junction boxes, wire nuts, fight fixtures/bases don't grow on yet-to-be-planted Martian trees!

My main argument here is not whether or not to be "Green," but how to stay alive should we get a 7 month dust storm.

My apologies to Louis, and I want to reassure him that I'm simply viewing the Mars world through my Physical Chemist eyeballs, and NOT attacking him personally. I simply am viewing the entire Mars base colony as a Thermodynamic System; energy in, energy consumed, energy stored. It's just that inefficient systems cannot be utilized in order to just fit Green Energy plans.

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#41 2017-04-29 11:47:17

Terraformer
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Re: Air. Shelter. Water. Food.

I've suggested before that we use an RTG system based on Strontium-90. As pure metal it produces ~0.5 W/g (beta decay, so easy enough to shield), as Strontium Titanate about half that, and with a half-life of ~30 years there's plenty of time to get new energy source going. The Russians use it a lot for their RTGs, but I don't know much about the particular designs. But it doesn't seem all that implausible to get a system that can produce, say, 25 kWe/tonne, and as far as shipping mass to Mars goes, with the amounts we're talking about sending for the most basic mission, 10 tonnes for the power supply isn't much at all...


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#42 2017-04-29 13:56:54

louis
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Posts: 5,872

Re: Air. Shelter. Water. Food.

No, I don't accept your assumptions.

The MIT paper suggests that we can get 100KWe average with an array of 25,000 sq. metres (158 x 158 metres).

We know we can get about 45 kgs water per sol in summer from an 885 Kg atmospheric extractor for 15 Kwe constant (that's 9 tonnes over 200 days). 

It takes 3.67 KwH to split one litre/kg of water.

So, let's say it would take 165.15 KwHs persol to process the  45Kgs persol of water produced, which is about 6.8 Kwe constant. So that would require an array of about 1700 sq. metres (41x 41 metres).

Combined with the atmospheric water extractor that's 21.8 Kwe constant that would require an array of 5434 sq, metres (73 x 73 metres).

I think we could land and set up an array robotically that produced enough power. 

Yes there are other things we would need to do before the crew arrived, e.g. making methane by combing hydrogen and carbon, derived from CO2 but we don't necessarily have to do everything simultaneously and the work can be undertaken over an extended pre-landing period, maybe 4 years (two summers, about 400 days). 

So, for Mission One, which is the most difficult Mission, a lot can be done before humans land.

I don't envisage there being a huge food production element to Mission One. We would probably want to have a modest salad vegetable production facility going.  I found a citation (not a very sympathetic one) that suggests it takes 24000 calories (= 27 KWhs) to grow a head of lettuce in an indoor farm. I doubt we'd want more than 2 heads of lettuce (or equivalent salad produce) persol for a community of six. So I would suggest we run with that, which would mean expending about 2.2 KwE constant to indoor farming on Mission One. I guess with temperature and atmosphere generation/control it might be more...let's say 3.5 KwE max.

I think we could afford that out of a 100 Kw budget on Mars.

https://energyfarms.wordpress.com/2010/ … cal-farms/

Once the humans land as part of Mission One they will be bringing with them plenty more energy resources. As part of something in the  the order of a 60-80 tonne sort of mission, I would expect at least a tonne of chemical batteries to be landed. By the time the humans get there we should have tonnes of methane available. One tonne of LNG on Earth produces 14000 KWhs of energy which converts to about 6300 KwHes, or enough for 63 days for a colony of 6 using 100 KwEs per sol. I appreciate we need something like double or more of the mass of methane as oxygen to burn it on Mars. But even so, I think that when humans land on Mars they can have a huge energy surplus available to them without using any nuclear power.

That said, I think it prudent to bring along some small RTGs as further back up.

PV panelling is straightforward to set up and requires minimal maintenance once laid out. It is highly flexible. I really think it is the right way to go on Mars. I am not saying nuclear power will be a disaster. But you'll need at least two main reactors and it will be an untried technology in terms of Mars. If you rely solely on two nuclear reactors you will have a very static and non-dynamic mission. But if you want to have your cake and eat it: produce methane and also take PV then, any mass advantage will soon disappear.


Oldfart1939 wrote:

We seem to have an energy "Catch 22" situation here. In order to have Methane produced, we need either (a) lots of H2 generated from the electrolysis of water in order to subsequently manufacture it, or we can used the energy to (b) contribute towards artificial lighting. Given the postulated size of the Solar Array, there will NOT be enough energy generated to do all things together, and at the same time. Burning Methane to produce steam and subsequently  electricity also requires Oxygen. This system is energetically getting out of control. Solar only operates at 30% efficiency for half a Sol. Dr. Zubrin has done the calculations in Entering Space, which serves to illustrate the need for Nuclear Power, no matter how badly some want Solar Panel (PV) technology to succeed. We really don't have immediately available the numbers of KWe needed to (1) electrolyze water for both H2 and O2, (2) energy required by the Sabatier reactor for Methane production, and (3) energy required for all heating, cooking, lighting, etc., for Mars base, all competing with (4)  greenhouse lighting. Initially, storage of "excess methane," that over and above that needed for ascent vehicle use, will be either strictly limited or non-existent. Oxygen is also facing the same limitation. No how badly some others here wish it otherwise, the initial missions will absolutely require Nuclear Power.  To do otherwise will put all the lives at risk, and flirt with abject mission failure. I just cannot comprehend trying to bring radical Green environmental policies to Mars--grasping at straws in order to do so. I will, however, agree that having an alternative power supply "on hand" is also essential; once we get through the initial stages of settlement, we can add the Methane/Oxygen powered steam plant for emergency backup.

The other kicker is how much more equipment will need to be brought to Mars from Earth in order to have artificial greenhouse lighting? LED bulbs, and lots of wire, junction boxes, wire nuts, fight fixtures/bases don't grow on yet-to-be-planted Martian trees!

My main argument here is not whether or not to be "Green," but how to stay alive should we get a 7 month dust storm.

My apologies to Louis, and I want to reassure him that I'm simply viewing the Mars world through my Physical Chemist eyeballs, and NOT attacking him personally. I simply am viewing the entire Mars base colony as a Thermodynamic System; energy in, energy consumed, energy stored. It's just that inefficient systems cannot be utilized in order to just fit Green Energy plans.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#43 2017-04-29 16:04:44

SpaceNut
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Re: Air. Shelter. Water. Food.

Loius the link from utube is for this http://www.greenpowerscience.com/ which seems to be a DIY type of site for those that want to make rather than buy an item. There are lots of these kind of sites out there and they could play an important part in mars.

One thing that mars will need are people able to create something from what they have as we will not be able to wait for it to be sent from earth.

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#44 2017-04-29 18:15:15

Oldfart1939
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Re: Air. Shelter. Water. Food.

OK, Louis-

The energy balance is OK as far as it goes. At this juncture we haven't located any readily available water, and you made NO allowance for extraction/production of necessary water for electrolysis, which is substantial. There is also nothing in the works as far as I can tell towards development of the necessary robotics for building your massive solar grid. There is also no mention of the liquefaction energy required for Methane storage, nor any explanation of where the cryogenic storage tanks are coming from.

It' s our "job" on these threads to be the "hole-pokers" in various theories/architectures, then refine out something that will actually supply the needs of the colonists/advance base/whatever.

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#45 2017-04-29 18:33:18

louis
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Re: Air. Shelter. Water. Food.

Oldfart - I am referencing atmospheric extraction of water vapour.  The details I give are from a bona fide study. So as long as you are in the northern equatorial zone those figures are OK.

You are quite right to point the importance of storage depletion etc. Something I would like to work on is how far you can just store a lot of stuff like oxygen and methane as clathrates or in plastic bags on the surface of Mars...or maybe buried a metre under the surface. 

I have no fear of detail! lol

I will go back to the MIT study. They had no problem with automated roll out - I think if you have anything on a roll, then "roll out" is not that complicated from an automated point of view. As I understand it, they look to lay down kevlar weights every so often. Again not a problem robotically. They were not specific on this point but if you are laying ultra lightweight PV over a rugged surface then presumably it is not bad in terms of a fairly consistent PV input over the course of a sol as the panelling will be facing in different directions.

Oldfart1939 wrote:

OK, Louis-

The energy balance is OK as far as it goes. At this juncture we haven't located any readily available water, and you made NO allowance for extraction/production of necessary water for electrolysis, which is substantial. There is also nothing in the works as far as I can tell towards development of the necessary robotics for building your massive solar grid. There is also no mention of the liquefaction energy required for Methane storage, nor any explanation of where the cryogenic storage tanks are coming from.

It' s our "job" on these threads to be the "hole-pokers" in various theories/architectures, then refine out something that will actually supply the needs of the colonists/advance base/whatever.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#46 2017-04-29 19:48:15

SpaceNut
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Re: Air. Shelter. Water. Food.

The storage problem is not all that as you just landed plenty of cargo ships and all of the oxydizer/ fuel tanks are empty to reuse as we see fit to do. all that is needed are some means to alter the connections to them for the new sources of what will fill them, possibly a pump to move liquids and chillers to cool the gasses which will fill the others.

The roll out solar cells that lay on the ground will in time be covered with dust and will need to be rolled up to allow for man to do this as it can not be done while its laying on the uneven ground surfaces of mars let alone be space appart for man to go between rows to wipe them off.

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#47 2017-05-01 11:38:11

Dook
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Re: Air. Shelter. Water. Food.

You can't pressurize a dome.  If you attempt to pressurize it, even to as little as 2 psi, the dome will be lifted out of the ground and you will lose all your pressure.  If you can't pressurize a dome you can't have liquid water, it will be all vapor.  The only thing a dome can be used for is to provide daytime heat. 

You could build a large sphere with regolith filling in the bottom but the pressure applied to every panel (If there were 550 panels 8 sq ft ea) would be 2,300 lbs at just 2 psi.  It's possible but  I think using the same material to build a buried habitat would be better since the weight of the regolith on top would balance the internal pressure.  And the regolith would provide radiation shielding.

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#48 2017-05-01 13:06:45

RobertDyck
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Re: Air. Shelter. Water. Food.

Dook wrote:

You can't pressurize a dome.  If you attempt to pressurize it, even to as little as 2 psi, the dome will be lifted out of the ground and you will lose all your pressure.

Inflatable greenhouse design comes from "Case For Mars" studies, published before the founding of the Mars Society. It called for a polymer film, held down with straps attached to large pegs pounded into the ground. Think of an event tent on Earth, which uses pieces of rebar as tent pegs. The ribs of the rebar help hold it in the ground. An inflatable greenhouse on Mars would use the same.

Are you talking about a dome with no floor? Just counting on Mars ground to keep air in? That can be anchored. It would require a foundation where the dome meets the ground. If you're talking about a dome shape, then the foundation will be a ring. It will have to be deep enough and heavy enough that air pressure cannot lift it. I say "deep" because a foundation is integrated to the "earth" (soil and rocks) so that attempting to lift it not only requires lifting the foundation itself, but all the soil and rocks bound to it. Then you have to ensure all that has greater weight than the upward force of air pressure under the dome, plus a safety factor. And if it starts to move, soil and rocks could come lose, reducing the weight bound to the foundation, so a safety factor has be enough that it won't pull out.

But even with all that, I worry that pressurized air would form a channel through loose soil. That channel would be a leak, allowing air to vent out. You need something more substantial than loose soil to hold pressure. At minimum dig down to bedrock or permafrost. Ideal is some sort of "floor", something we know is air tight and can be sealed to the edges of the dome. You could pile regolith or soil on top of the floor, creating the illusion of a dome sitting on ground.

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#49 2017-05-01 16:08:22

Dook
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Re: Air. Shelter. Water. Food.

RobertDyck wrote:
Dook wrote:

You can't pressurize a dome.  If you attempt to pressurize it, even to as little as 2 psi, the dome will be lifted out of the ground and you will lose all your pressure.

Inflatable greenhouse design comes from "Case For Mars" studies, published before the founding of the Mars Society. It called for a polymer film, held down with straps attached to large pegs pounded into the ground. Think of an event tent on Earth, which uses pieces of rebar as tent pegs. The ribs of the rebar help hold it in the ground. An inflatable greenhouse on Mars would use the same.

Are you talking about a dome with no floor? Just counting on Mars ground to keep air in? That can be anchored. It would require a foundation where the dome meets the ground. If you're talking about a dome shape, then the foundation will be a ring. It will have to be deep enough and heavy enough that air pressure cannot lift it. I say "deep" because a foundation is integrated to the "earth" (soil and rocks) so that attempting to lift it not only requires lifting the foundation itself, but all the soil and rocks bound to it. Then you have to ensure all that has greater weight than the upward force of air pressure under the dome, plus a safety factor. And if it starts to move, soil and rocks could come lose, reducing the weight bound to the foundation, so a safety factor has be enough that it won't pull out.

But even with all that, I worry that pressurized air would form a channel through loose soil. That channel would be a leak, allowing air to vent out. You need something more substantial than loose soil to hold pressure. At minimum dig down to bedrock or permafrost. Ideal is some sort of "floor", something we know is air tight and can be sealed to the edges of the dome. You could pile regolith or soil on top of the floor, creating the illusion of a dome sitting on ground.

How are you going to get the hold down pegs through the permafrost? 

An inflatable sphere filled with regolith would work for a while and you wouldn't need any hold down straps if the floor was filled with regolith but an inflatable would have a life expectancy of about a year or two and when it fails it would kill all the plants and any crew that happened to be inside when it goes. 

Inflatables are not durable enough for a settlement to depend on.  Food is life support.  It can't fail every year or two, it has to be built to last.     

Am I talking about a dome with no floor?  Yes, a plastic panel dome with a floor of Martian regolith would not be able to be pressurized, but it could be built over a buried habitat to provide heat. 

The foundation would have to be heavy enough that air pressure cannot lift it?  Okay, at 2 psi air pressure that is 1.2 million pounds of uplifting force on a 100 foot dome.  Mars atmospheric pressure would be about 60,000 pounds of down force on the dome so you would need a foundation weighing 1.1 million pounds.  Where are you going to get a 1.1 million pound foundation from on Mars?

Pressurized air would form a channel through the loose soil and leak out?  If the dome were pressurized to 2 psi it would not be enough to blow out the regolith.  A few feet of regolith would be piled up against the outer bottom of the greenhouse but there would likely be some small leakage of air.

Last edited by Dook (2017-05-01 16:09:00)

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#50 2017-05-01 16:12:28

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,729

Re: Air. Shelter. Water. Food.

http://www.biodomes.eu/

Something like this would work

domehouse.jpg

RobertDyck as described this type anchored to concrete ring

glass-geodesic-dome-22.jpg

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