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#51 2017-06-01 06:50:12

Oldfart1939
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Registered: 2016-11-26
Posts: 1,800

Re: Designing the best greenhouse demonstrator for Mars

If we're going through the efforts to put anything underground, it should be human sleeping quarters. Based on the Martian Sol, this will automatically reduce the accumulated GCR exposure significantly. Based on the recently released GCR exposure data for the BEAM habitat on the ISS, the Bigelow structure doesn't do much for cosmic radiation attenuation.

Last edited by Oldfart1939 (2017-06-01 06:54:31)

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#52 2017-06-01 11:22:40

GW Johnson
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From: McGregor, Texas USA
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Posts: 3,768
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Re: Designing the best greenhouse demonstrator for Mars

Be careful interpreting radiation measurements from BEAM on ISS.  It was designed with a 6 inch hull thickness to be equivalent to an ISS module in terms of radiation protection.  B330 is the "deep space" module design,  with an 18-inch hull thickness.  It doesn't pack up as tightly,  but provides 3 times the shielding,  and even better micrometeroid protection. 

It's awfully hard to find specifics,  as Bigelow has removed a lot of construction specifics from its website recently.  But as near as I can tell,  these hulls are many multiple layers of Kevlar and Vectran,  within a white cloth cover,  and surrounding an internal bladder and restraint system.  The white cloth cover controls both sunlight and atomic oxygen exposure.  The Kevlar is basically the bulletproof vest,  and the Vectran is the same radiation shielding as Vectran garments for nuclear workers. 

Looks like a pretty smart design to me,  and 3 times BEAM's radiation shielding is what Bigelow proposes for use outside low Earth orbit.  He is basically waiting around for NASA to get comfortable with it,  and already has designs for spacecraft modules,  space stations away from Earth,  and surface habs for moon and Mars.  I saw some hints of my proposal:  dock some end-to-end and spin that baton for spin gravity.  Bigelow says adding floors to stand on is a "nothing" sort of problem to solve. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#53 2017-06-01 19:13:08

SpaceNut
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Posts: 17,875

Re: Designing the best greenhouse demonstrator for Mars

Some of the articles talk about creating shield via 3D printing of materials in various thickness to test with in the Beam unit.

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#54 2017-06-14 10:14:12

RobertDyck
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Re: Designing the best greenhouse demonstrator for Mars

Antius wrote:

Greenhouses at night are a different matter.  A greenhouse at a temperature of 288K (15C) will radiate heat into the Martian sky at a rate of 390W/m2.  It is doing that 24 hours per day.  During the day, it will gain an average of about 300W/m2 for the 12 hours that the sun is about the horizon.

Excellent! Actual numbers. Now how will that change with spectrally selective coating? NASA uses vacuum deposited gold, nickel, and silver oxide to block UV and control IR. That technology has been commercialized, sold under the brand name "low-e". Low-e coatings use only silver oxide, they don't need to block UV because Earth's atmosphere has the ozone layer. Transmittance with commercial coatings looks like this. Graph line 5 is spectrally selective low-e glazing.

hmm This may be backwards. Transmittance at 0.5 micrometer (500 nm, green) wavelength is about 85%. Transmittance just above 1.0 micrometers (1,000 nm) is about 10%. Transmittance above 2.0 µm rises to 40%, and about 2.3 µm to 47%. Warm objects like the floor emit long wave IR. Extremely hot objects like the sun emit short wave IR. This appears to have the net effect of keeping radiant heat out. We need to keep it in.
spectrally_selective.jpg

800px-Solar_spectrum_en.svg.png

BlackbodySpectrum_loglog_150dpi_en.png
The red line is roughly room temperature: 300°K = 26.85°C = 80.33°F.

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#55 2017-06-14 10:34:15

RobertDyck
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Re: Designing the best greenhouse demonstrator for Mars

A couple papers about spectrally selective coatings:
Spectrally selective coatings on glass: solar-control and low-emissivity coatings

Glazing and Coatings - BRIMEE
quoting the second paper

3.10.3.4.1 Doped metal oxides
Low-e coatings based on doped metal oxides comprise a host lattice (usually In2O3,SnO2, or ZnO) that is doped by metal or halide atoms. The most common representatives of this group of films are tin-doped indium oxide (In2O3:Sn, usually called ITO), fluorine-doped tin oxide (SnO2:F, usually called TFO), and gallium-doped zinc oxide (ZnO:Ga, usually called GZO). Doping is accomplished either by adding a higher-valence metal, by replacing some oxygen with fluorine, or by oxygen vacancies. The compounds mentioned above have wide enough band gaps to allow considerable transmission in the visible and doping is feasible to a level high enough to render the materials IR reflecting and electrically conducting. In doped metal oxides, the degree of doping determines the position of the transition wavelength (λΤ): the higher the doping, the more metal-like the films are and λΤ appears at lower wavelengths. However, in these films, doping cannot be brought to a sufficiently high level required for solar control, their λΤ usually lies in the near IR and, thus, doped metal oxide coatings are used mostly for thermal insulation. The main advantage of the doped metal oxides, compared to metal-based films, is the chemical and mechanical stability, which allows their use on glass surfaces exposed to ambient conditions. This is why these films are referred to as ‘hard coatings’.

The development of these materials has reached maturity, and numerous commercial products are available in the market for windows and other architectural applications. Most of these films are prepared by spray pyrolysis and their typical thickness is on the order of 10−1 μm. Typical properties of such coatings are as follows: Tlum ≈ 90%, Tsol ≈ 75%, ε ≈ 0.20.

Although doped metal oxide coatings are well established, intense research activity continues in the field. The research effort is directed toward the development of alternative host materials and dopants, as well as multiphase mixtures of known materials, in order to improve various properties of the coatings, such as electrical conductivity, optical transmission, hardness, and adherence. Some of the combinations reported in the literature are the following: ITO:ZnO, ITO:Ti, In2O3–ZnO (IZO), In2O3:Ti, In2O3:Mo, In2O3:Ga, In2O3:W, In2O3:Zr, In2O3:Nb, In2-2xMxSnxO3 with M being Zn or Cu, ZnO:(Al,F), ZnO:B, ZnO(Ga,B), Zn0.9Mg0.1O:Ga, and many others.

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#56 2017-07-06 19:10:02

SpaceNut
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Re: Designing the best greenhouse demonstrator for Mars

Well here is something that would aid an above ground greenhouse...
These Transparent, Solar Power-Generating Windows Are the World's First

Trying to make large buildings energy-neutral, companies are taking advantage of building windows' surface area to harvest solar energy.

So double pane design from image:
physee-powerwindows_1e89166aa030469aaffff065ff312e64.focal-600x300.jpeg

The windows have solar cells installed in the edges at a specific angle that allows the incoming solar light to be efficiently transformed into electricity. The windows could generate 8 to 10 watts of power, according to Grapperhaus.

"This enables the user to charge a phone per every square meter [11 square feet] two times a day,"

Ya not many cell phones on mars but its still power being generated for use....

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#57 2019-11-27 20:47:31

SpaceNut
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Re: Designing the best greenhouse demonstrator for Mars

This is a fact for any mars food growth as there is no open environment on mars which means we are in a protective area...Using controlled environment food production to solve food shortages
There needs to be a high degree of automation not only to the growth but for the prep to the shelf for the consumption of its bounty.

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#58 2019-11-27 20:57:26

louis
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From: UK
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Posts: 5,482

Re: Designing the best greenhouse demonstrator for Mars

This was what got Musk going - NASA's refusal to take his greenhouse demonstrator project seriously:"OK I'll build me my own rocket!"


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

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#59 2019-11-28 07:21:30

tahanson43206
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Registered: 2018-04-27
Posts: 1,891

Re: Designing the best greenhouse demonstrator for Mars

For SpaceNut ... the idea of a design competition is on my mind this morning, and I was interested to see that you have brought back a topic which explicitly includes the word design in the title.

Without going back to read the entire set of 58 posts, I am unable to know if any ** real ** design elements were offered by anyone.  I sure hope so.

This forum is a potential treasure trove of useful work plans for future Mars expedition planners, all of whom have access to this forum thanks to the Mars Society Open Information Sharing policy.

What someone could do, if they have the time and energy, and motivation, is to collect the wisdom and insights from the topic in a single post, organized to maximize the benefit to an individual with capital to invest in a greenhouse demonstrator.

(th)

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#60 2019-11-28 14:24:14

SpaceNut
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Re: Designing the best greenhouse demonstrator for Mars

The demonstrator lander has 2 choices for food growth at a minimum of which the real issue is square footage for what crop types, mass of the lander with its payload since we are only at a Red Dragon retro propulsion lander with 2 mT of what ever we would want to take within the small internal cubic demensions.

That said what are the ideal methods and the associated mass for either.

With power coming from an RTG or solar panels simular to the ATK fans of which 2 to 4 panels with comparible batteries. So what are we using for an amount of brought along water since this is not intended to be an insitu for these. Only that we can automate the growth to the greatest degree possible and have food without a hands on approach.

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#61 2019-11-30 22:19:11

SpaceNut
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Re: Designing the best greenhouse demonstrator for Mars

A good rule of thumb is to use a minimum of 50 watts of light per square foot of course plants thrive in full sun, but can adapt to partial shade Minimum sun – 5 hours.  Low-light plants should receive between 10 and 15 watts. So natural light of 430 w m^2 is plenty for mars to grow food with.

https://www.firsttheseedfoundation.org/ … -Light.pdf

Now a 60w light bulb that is LED for the colors that favor food growth will be about 8 to 10 watts to give the same range of lighting energy.

NASA designs an inflatable greenhouse for Mars

space_greenhouse_nasa_lunar_mars_university_arizona_2.0.jpg

The prototype modules, a long cylinder measuring 18 feet long and 7 feet in diameter, are designed to help create an artificial ecosystem with plants feeding off the carbon dioxide exhaled by astronauts and astronauts breathing in the oxygen from the plants

space_greenhouse_nasa_lunar_mars_university_arizona_1.jpg

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#62 2019-12-12 17:36:38

SpaceNut
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Re: Designing the best greenhouse demonstrator for Mars

Here is a twist on such a technology...but when it comes to mars we will want to make use of daily sunlight just as much as we will artificial.

Punching holes in opaque solar cells turns them transparent

opaque-solar-cell-compared-neutral-colored-transparent-solar-cell-hg.jpg

Existing transparent solar cells tend to have a reddish hue and lower efficiency, but by punching holes that are around 100 um in diameter (comparable in size to a human hair) on crystalline silicon wafers, it allows light through without coloring. The holes are then strategically spaced, so the human eye is unable to "see" the pattern. The best solar cells on the market have an efficiency of over 20 percent. The transparent neutral-colored solar cell that the research team developed demonstrated long-term stability with a high-power conversion efficiency of 12.2 percent. The next step for the team is to scale up the device to 25 cm2 (3.88 in2) and increase the efficiency to 15 percent. Furthermore, most windows are vertically placed, which causes light to hit the windows at a low angle. When hit by low angle light, the electrical current in conventional cells drops nearly 30 percent, while transparent solar cells reduce less than 4 percent--allowing it to utilize solar energy more efficiently.

http://dx.doi.org/10.1016/j.joule.2019.11.008
Research Report: "Neutral-Colored Transparent Crystalline Silicon Photovoltaics"

This makes it ideal for solar concentrated light to pass as well as to get the energy from the reflected light. This is a benefit to a natural lighted greenhouse as the panels now become part of the construction and not extra mass to supply energy.

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#63 2019-12-17 16:34:52

SpaceNut
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Re: Designing the best greenhouse demonstrator for Mars

http://bigidea.nianet.org/wp-content/up … -et-al.pdf
Low Pressure Greenhouse Concepts for Mars:
Atmospheric Composition

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#64 2019-12-17 19:02:22

tahanson43206
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Registered: 2018-04-27
Posts: 1,891

Re: Designing the best greenhouse demonstrator for Mars

For SpaceNut re #63

From the paper cited:

We need to determine by
experimentation the cost of maintaining particular
conditions, and what effect different conditions would
have on plant productivity.

That is what I am proposing.

All the test modules should be set up by professional contractors under the supervision of top tier academic research organizations.

The results should then be collected in a rigorous fashion and collated for delivery to a master database.

Out of a profusion of tests there should arise a clear picture of which plants would do best under what circumstances.

Clearly the optimum solution would be a set of plants which meet human needs and which grow happily in an all CO2 atmosphere, with the minimal number of trace gases needed to sustain healthy growth.

Touching some of the links you have gathered in the past day tells me that much of the needed research has been done, so the standards for a large scale mass research project would appear to be in place.

With appropriate management of the campaign, I am hoping members of the general public would be willing to fund modules in the $500 range for the education of family members as well as for the contribution to the Mars project, as well as for the contribution to the well being of the Earth population as a whole.

As a reminder of kbd512's idea which was the inspiration for the present initiative, the greenhouse would be operated at ** Earth normal ** pressure, NOT Mars normal pressure.  The advantage is that the human worker can visit the facility without a pressure change, and by donning only an oxygen/air mask instead of a full body suit of some kind.

(th)

Last edited by tahanson43206 (2019-12-17 19:02:59)

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#65 2019-12-17 20:19:26

SpaceNut
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Re: Designing the best greenhouse demonstrator for Mars

Chamber size and design for natural or LED needs mass delivery dimensioning to be able to say we can deliver the unit or not.

If it were me I would use a spent Dragon cargo unit size for early mars cargo and crew men to mars for initial testing size. Once the cargo is out and setup we can build the connecting tunnels to make this design work. Connect them to each other via a pressure tunnel so that we can go into all connected units which are growing food as indicated to reduce need for space suits.

So far a collection of gas levels and heat plus light intensities seem to change how the plants grow and behave for nutritional content.

The above link is a nasa project which as of yet has need seen the light of funding to go to mars...

We also know that we can do just fine in less air pressure as well for pure to mixed oxygen levels so in a chamber tunnel situation we may also have less pressure for the plant growth as well which will save on initial energy to fill the area to make it viable for a greenhouse with shirt sleeve access.

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#66 2019-12-18 12:49:46

tahanson43206
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Registered: 2018-04-27
Posts: 1,891

Re: Designing the best greenhouse demonstrator for Mars

For SpaceNut re #65 ...

Your comments in this post appear (to me at least) to open the door to another option, which may well have been discussed earlier in the forum archive.

The advance of robotic waldos is sufficient already to permit entirely robotic "workers" inside the greenhouse on Mars, which would completely eliminate the issue of trying to accommodate the human workers as well as the plants.

The gas mixture, gas pressure, gas temperature and lighting can ALL be optimized for the plants, and the human operators can work from comfort, just as military drone operators do today, or industrial truck operators in Australia. 

Air locks for movement of items into and out of the greenhouses would still be needed, but the volume could be much less than would be true if humans had to make the trip.  A "special" air lock for humans could be included in the design for emergencies.

(th)

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#67 2019-12-18 18:06:48

SpaceNut
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#68 2020-01-08 21:07:08

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 17,875

Re: Designing the best greenhouse demonstrator for Mars

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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#69 2020-01-09 18:25:25

SpaceNut
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Re: Designing the best greenhouse demonstrator for Mars

For a well insulated for lose of thermal heat, sealed from leaks of pressure and covered at night clear material it just meets the goal without enhancement from reflection if its stays warm enough inside.

I think long before we will build we will bring and the simplest to bring is the vehicle for crew and cargo to convert to the chamber for food growth. If we want natural light we bring a top hatch lense unit to allow for the light to concentrate from its shape and then to spread out once on the inward side of the hatch lense assembly.
Once that is done then use a space foam insulation of a roll of good fiber insulation to wrap the capsule or cargo landers hull on the outside before burying it then connect to power, water supplies and plant the crop.
.

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