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#76 2019-12-19 15:58:59

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,322

Re: Greenhouses

We have alot to learn about farming mars and while we know we are in a chamber to grow food as we will need to know more.

9 Strategies for Self-Sufficient Living

Skills to Work on Before You Begin Homesteading

10 Rules for Starting a Successful Farm Business

So you want to start a farm in time as we will need more than plants to eat.

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#77 2020-01-05 19:46:51

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,322

Re: Greenhouses

Martian habitats: molehills or glass houses?

MH_LigneCompleteOrange.jpg

This is the mars to come for sure once we can make the glass and framing....

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#78 2020-01-08 21:04:48

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,322

Re: Greenhouses

Lots of good information in this Farming and the geography of nutrient production for human use: a transdisciplinary analysis

The variety of crops and of livestock as well as fish biomes but not how much land or energy for each are required. Lest we forget we have hugh biomes of forest and oceans with which we would not live with as well.

So data from FOOD, LAND, POPULATION and the U.S. ECONOMY

At least 1.2 acres per person is required in order to maintain current American plus Currently the 400 gallons of oil equivalents expended to feed each American ...

Its actually more when we include the other resources which make these other food possible along with the breathable air and materials we take for granted.

Lets call it 2 acres and that converts to 8093.71 m^2 for just 1 person....or 90 meters on a side...
https://www.metric-conversions.org/area … meters.htm

So now what is the energy that we need for solar light...
Goggling mars greenhouse floor thermal insulation  for heat lose calculations reference materials
Will read more tomorrow for these links

https://www.greenhousemag.com/article/t … heat-loss/

Conductive heat loss = SA x U x TD
Infiltration heat loss = 0.02 x V x C x TD

http://www.marshome.org/files2/Hublitz2.pdf
ENGINEERING CONCEPTS FOR INFLATABLE MARS SURFACE GREENHOUSES

https://farm-energy.extension.org/wp-co … tation.pdf
Greenhouse Energy Efficiency (Heating)

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#79 2020-01-08 23:31:45

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,322

Re: Greenhouses

https://www.vcalc.com/calculator/?uuid= … 764e2038f2
The Greenhouse Calculator provides useful equations and data for people who work with greenhouses and high-tunnels.  This includes basics for greenhouse construction and heating, for mulching and coverage with straw and for greenhouse planters.



https://www.cedengineering.com/userfile … ciples.pdf
Heat Loss Calculations and Principles

http://citeseerx.ist.psu.edu/viewdoc/do … 1&type=pdf
Engineering concepts for inflatable Mars surface greenhouses

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#80 2020-01-26 17:24:08

SpaceNut
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From: New Hampshire
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Posts: 18,322

Re: Greenhouses

This article is not really about the crops that can be grown but the conditions which must be controlled.

Scaling of Greenhouse Crop Production During Nuclear Winter

Meaning low levels of light energy to grow with.

This study designs a method for scaling up crop production in low-tech greenhouses to contribute to global food sustainability during global catastrophic conditions. Constructing low-tech greenhouses would obviate growing crops using more expensive and energy intensive artificial light. To significantly contribute to world-wide food demand, these greenhouses must be constructed quickly, cost-effectively, and in extreme quantity.

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#81 2020-02-10 17:55:22

SpaceNut
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Re: Greenhouses

Calliban wrote:

I am impressed by Casey Handmer's work.

https://caseyhandmer.wordpress.com/2019 … ver-rated/

His idea of a ETFE blanket, anchored to the ground with cables, is a very good one.

https://caseyhandmer.files.wordpress.co … 213244.png

I ran a few calcs to look into what sort of material requirements this would entail.  I assume that tensile cables will be made from basalt fibre, which is 20 times more energy efficient than steel on a MJ/MPa.m basis.  I assume that the pressure in the habitat in 0.4bar and that the ceiling height in 30m.  The tensile strength of basalt fibre is 3GPa and I assume a working stress of 1GPa.  There would be one cable for every 10m2 of roof.  The internal pressure must be balasted by 10t/m2 of soil and rock to balance internal pressure.  So each cable must be anchored to at least 100t of rock.  So it will need to be tied to an anchor at least 10m beneath the surface.  The density of basalt is 2.7t/m3.  For each m2 of land, some 1.6litres of fibre must be used, weighing 4.32kg.  Each kg of basalt fibre requires 5kWh of electricity.  So, each m2 of land requires 21.6kWh of electricity to render it habitable.

How much land could we produce each year, if our basalt fibre plant is powered by a 1GWe nuclear reactor?  The reactor will produce 7.89billion kWh per year, assuming 90% capacity factor.  So that's 365km2, or 141 square miles.  Of course, the ETFE manufacture will consume a lot of power too.  But if basalt fibre can be used to reinforce it, only a very thin layer will be needed.

So assuming we can scale basalt fibre and ETFE manufacture quickly; a Mars colony could paraterraform country size areas of the Martian surface within a few decades, using a standard size nuclear power reactor.

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#82 2020-02-14 16:17:10

tahanson43206
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Registered: 2018-04-27
Posts: 2,177

Re: Greenhouses

This is for SpaceNut re Correct Topic for (possible) new discussion ...

The recent and ongoing discussion of the idea of creating a greenhouse that would be inflated to Earth normal pressure (ie, 14.7 psi) with Martian atmosphere included citations you provided that showed design of a research greenhouse that was itself enclosed in a dome to simulate the Martian atmosphere.

After thinking about the text inside the citation(s) for a while, I've retained a concern expressed by the authors, that in ANY system with gas pressure inside a container that is itself enclosed by a lower pressure environment, there WILL be leaks.  The authors cited numerous examples of leak sites.

This led me to consider what might be a mechanism for reducing leak losses on Mars (or other locations away from Earth) by adapting the tool used by the researchers but with a twist.

Let us imagine a thin walled habitat for humans, such as an airplane cabin, or the ISS, come to think of it.  Humans have become adapted to spending time in such structures, as they have to spending time in ships at sea, and especially submarines, which Calliban brought up in a recent post.

Inside the cabin the atmosphere would be optimized for humans, just as it is reported to be on the ISS.

Unlike with airplanes, but much more like with submarines, the atmosphere in an off-Earth structure would be a closed system and carefully managed by automation to maintain optimum conditions for the occupants.

Outside the cabin, the default would be whatever the off-Earth environment provides, all the way from vacuum on the Moon, through the relatively benign atmosphere of Mars, through the deadly environments at selected other locations.

I am proposing an alternative, based upon the greenhouse research.  The human habitat would be inside a larger structure containing a gas or mixture of gases which would be maintained at the same pressure as is maintained inside the human habitat.  There would be little incentive for molecules to migrate from the human habitat to the enclosure or vice versa.  Migration might occur, but it would be much less in volume that would be the case if there were a large pressure difference between the inside of the habitat and the exterior.

The gas chosen for the pressure buffer might be chosen from the external environment when practical, or it might be supplied from another resource if necessary.

In any case, leakage that would occur would be between the buffer and the external environment, instead of from the human habitat.

So the question for you is ... (assuming you want to see this topic explored) ... where would you want to put it?

Related to that is ... has this come up before?   The forum has a pattern of re-inventing the wheel as each new member joins.

I'd like to try to avoid that in this case.

(th)

Last edited by tahanson43206 (2020-02-14 16:18:22)

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#83 2020-02-14 16:36:06

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,322

Re: Greenhouses

Leaks for the ISS are tested for long before its sent up to space with that we can have meteorite hits that can cause little to much damaged depending oin the size, hardness and velocity of what might strike the modules. Its the unexpected strikes that would make any modules as you said with a greater pressure inside than versus what is outside.
Now on the greenhouse I was starting with what we know about the earths atmospher of which with science studies do show that we can be fine at a lower pressure for what we breath and so on. I was attempting to show how much air from mars would need to be processed in order to fill the greenhouse up to the levels to which we desire for Mars.
With that said what is the values for that lessor pressure air gas content that will allow for both men and plant to thrive.

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#84 2020-02-14 17:48:50

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,322

Re: Greenhouses

Air Pressure and Volume: Boyle's Law. Boyle's Law defines the relationship between a gas volume and its pressure.

The lowest atmospheric pressure humans can breathe in, with a pure oxygen supply on hand, is roughly around 12.2 percent sea level air pressure or 121.7 millibars, the pressure found at 49,000 feet.

https://sciencing.com/minimum-oxygen-co … 15546.html
http://www.nwohs.com/Oxygen%20Regulator … s%20II.pdf

16% oxygen was at altitude 7500 ft. 2286 m

Spacesuits for the space shuttle era are pressurized at 4.3 pounds per square inch (psi), but because the gas in the suit is 100 percent oxygen instead of 20 percent, the person in a spacesuit actually has more oxygen to breathe than is available at an altitude of 10,000 feet or even at sea level without the spacesuit. The Apollo LM cabin pressure was 3.5 psi.

https://en.wikipedia.org/wiki/Space_suit

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#85 2020-02-14 19:59:43

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,322

Re: Greenhouses

http://wordpress.mrreid.org/2014/08/01/ … elevation/

https://www.engineeringtoolbox.com/air- … d_212.html

As elevation rises the density for a cubic meter drops as to why we have trouble breathing at altitude.

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#86 2020-02-14 21:19:55

tahanson43206
Member
Registered: 2018-04-27
Posts: 2,177

Re: Greenhouses

For SpaceNut re #83

Your statement about ISS leaks caught my eye, so I went looking for some "real world" reports. 

Here is a discussion from StackExchange from 2014 ...

https://space.stackexchange.com/questio … -atm-conta

@DaveNay -- The ISS has leaks. The mechanisms used to remove CO2 from the breathing atmosphere concentrate CO2 and vent that concentrated gas to space. The vented gas is not pure CO2; it still contains some oxygen and nitrogen. The joints between modules leak breathing atmosphere. The tiny little gaps around windows leak breathing atmosphere. Oxygen is easily replaced; simply electrolyze some water and vent the hydrogen to space. Nitrogen? That's not so easy. It needs to be hauled up to the ISS as compressed nitrogen gas. Most Soyuz launches carry nitrogen to the ISS as part of their manifest. – David Hammen Oct 25 '14 at 14:01

The researchers who reported on the test greenhouse discussed in another topic recently asserted that "all systems with compressed gases leak" or words to that effect.  It would appear to make sense to plan for leakage, while at the same time doing everything possible to prevent it.

(th)

Last edited by tahanson43206 (2020-02-14 21:22:18)

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#87 2020-02-15 08:34:49

SpaceNut
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Registered: 2004-07-22
Posts: 18,322

Re: Greenhouses

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#88 2020-03-12 19:19:31

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,322

Re: Greenhouses

How to Build a Pit Greenhouse on Your Homestead

016-083-01.gif


Some types of plant shelter are simple and easily understood; a shade or windbreak screen, an arbor or even a cold frame are rational structures requiring minimum knowledge to construct and manage. A greenhouse is something more than a sun trap and a light trap for the benefit of plant growth; it's complexity lies in the fact that plant forcing, itself, is a highly complicated affair. In a greenhouse there exists a so-called trinity of plant ecology, which necessitates a balance between light (heat), moving air, and controlled humidity. Temperature, first of all, affects plant growth because it directly influences such internal processes as photosynthesis (food manufacture). Plant growth also requires respiration — which is energy generated by the breaking down of foods manufactured by the plant.

Tomatoes, for instance, require an optimal daytime temperature of 80 to 90 degrees Fahrenheit, nighttime 65 degrees F. The optimal daytime humidity was found to be 50 to 80%, nighttime 95%.


Here, you’ll find our best ideas and plans for DIY cold frames, greenhouses, hoop houses, low tunnels, cloches and other tools that can keep the harvests coming throughout fall and beyond.

Build an Earth-Sheltered, Energy-Efficient Greenhouse; Triple the length of your growing season with this simple, energy-efficient greenhouse design.

Ninety frost-free days here in the mountains of Idaho close to the Canadian border are not enough to raise most vegetable crops succumbed to frost in early September. Most plants will not grow in temperatures lower than 40 degrees; so, on a 30-degree day I was destroying the cozy, sun-baked 50- or 60-degree environment, shocking the small starts..

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