Author Topic: Scaling Agriculture on Mars  (Read 233943 times)

Offline Paul451

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Re: Scaling Agriculture on Mars
« Reply #1200 on: 04/17/2018 02:14 AM »
They may not need real insulation with the thin martian atmosphere.

As I mentioned above (and has been mentioned many times before), Mars' atmosphere is thick enough for convection cooling to dominate over radiation emission.



Since we have so many people interested in the subject has anyone actually tried to live on potatoes for a year?

Yes, apparently it's an effective way to lose weight. So... not the best diet for survival.

But there have been rural European cultures where potatoes were the primary source of calories, augmented by small amounts of meat for protein.



if we use just artificial light then considering the efficiency of the solar cell and transmission we need 4 times the area of the greenhouse to have the same light as what is outside the greenhouse

So? There's a huge difference in the complexity and maintenance demands of simply laying extra solar arrays vs building a thin-membrane pressure vessel that can allow undiminished Mars sunlight from multiple angles (time-of-day/time-of-year) and be sufficiently insulated against heat loss without reducing light transmission and/or building a separate heat-pump system of sufficient scale. Simplistic area comparisons are irrelevant.

Additionally, bespoke systems for greenhouses on Mars are worthless for anything else. Uniquely complex systems that serve no other role, can be diverted to no other purpose. OTOH, artificially lit hydroponic grow modules merely means more of the power system you already have (power which can be diverted in emergencies), and merely more pressure vessels of a type you already use for every other form of habitation.

If you want to scale anything on Mars, you want to avoid unique systems and focus on commonality and modularity. For any task, it will be better to have ten copies of one system than five unique systems of the same scale that do the same job slightly more efficiently.

Offline speedevil

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Re: Scaling Agriculture on Mars
« Reply #1201 on: 04/17/2018 03:14 AM »
The same MIT study using NASA growth model that used more standard crops, calculated that MarsOne would need to use closer to 240 m2 of growth  space per person. Much as I don't like repeating myself ad nauseum, ESA MELiSSA's 9 crops are in my opinion the best choice for a crop model.
Growing under 3kW electricity into good LEDs of continuous light, 39m^2, was adequate to make enough calories using only potatos per astronaut.
This is of course a minimum.
25m^2, if you use 5kW.

( references here)

In order to provide 3kW, constantly, we need of the order of one ton of solar + batteries, or about $20/day, based on $150/kg to Mars,and a 20 year system life.



Offline guckyfan

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Re: Scaling Agriculture on Mars
« Reply #1202 on: 04/17/2018 05:15 AM »
They may not need real insulation with the thin martian atmosphere.

As I mentioned above (and has been mentioned many times before), Mars' atmosphere is thick enough for convection cooling to dominate over radiation emission.

What are you trying to say? That greenhouses are not efficient in retaining heat? Even here on Earth with the dense atmosphere and wind even single pane glass houses are very efficient in retaining heat. It can only be better on Mars.

Additionally, bespoke systems for greenhouses on Mars are worthless for anything else. Uniquely complex systems that serve no other role, can be diverted to no other purpose. OTOH, artificially lit hydroponic grow modules merely means more of the power system you already have (power which can be diverted in emergencies), and merely more pressure vessels of a type you already use for every other form of habitation.

If you want to scale anything on Mars, you want to avoid unique systems and focus on commonality and modularity. For any task, it will be better to have ten copies of one system than five unique systems of the same scale that do the same job slightly more efficiently.

Again, what are you trying to say? It is not efficient to make a dedicated design for greenhouses for growing plants? Should they use the same design as for habitats for commonality?

Online Robotbeat

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Re: Scaling Agriculture on Mars
« Reply #1203 on: 04/17/2018 02:11 PM »
They may not need real insulation with the thin martian atmosphere.

As I mentioned above (and has been mentioned many times before), Mars' atmosphere is thick enough for convection cooling to dominate over radiation emission.

What are you trying to say? That greenhouses are not efficient in retaining heat? Even here on Earth with the dense atmosphere and wind even single pane glass houses are very efficient in retaining heat. It can only be better on Mars.

Additionally, bespoke systems for greenhouses on Mars are worthless for anything else. Uniquely complex systems that serve no other role, can be diverted to no other purpose. OTOH, artificially lit hydroponic grow modules merely means more of the power system you already have (power which can be diverted in emergencies), and merely more pressure vessels of a type you already use for every other form of habitation.

If you want to scale anything on Mars, you want to avoid unique systems and focus on commonality and modularity. For any task, it will be better to have ten copies of one system than five unique systems of the same scale that do the same job slightly more efficiently.

Again, what are you trying to say? It is not efficient to make a dedicated design for greenhouses for growing plants? Should they use the same design as for habitats for commonality?

Greenhouses in cold climates have to be heated in the winter. This is a legitimate challenge for Martian night.
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Offline guckyfan

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Re: Scaling Agriculture on Mars
« Reply #1204 on: 04/17/2018 03:22 PM »
Greenhouses in cold climates have to be heated in the winter. This is a legitimate challenge for Martian night.

Yes. But a big part of that are the short days during winter. Also atmosphere on earth does more cooling than on Mars. I agree that likely some heating will be required.

Online docmordrid

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Re: Scaling Agriculture on Mars
« Reply #1205 on: 05/31/2018 09:57 AM »
PhysOrg article about the benefit of probiotics for vegetable growth on Moon/Mars, in space. Increases productivity.

Link....
DM

Offline johnfwhitesell

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Re: Scaling Agriculture on Mars
« Reply #1206 on: 05/31/2018 12:22 PM »
if we use just artificial light then considering the efficiency of the solar cell and transmission we need 4 times the area of the greenhouse to have the same light as what is outside the greenhouse

Plants dont absorb the entire natural light spectrum.  Right off the bat that is a factor of two efficiency for LED.  Plants cant be titled towards the sun.  With sunlight you need gaps between the plants and to wait for them to sprout so most of the time you are shining light on dirt.  Probably a lot less then a factor of 4 and solar might even need less space altogether.

But then there are numerous advantages besides the area.  It's much easier to put solar panels outside then to build a greenhouse.  If you farm vertically, you can put your farms underground which makes construction easier.  Hydroponics need 99% less water then conventional farming.  With hydroponics you dont need to remove toxins from soil, you just need water.  Those toxins are a double concern because they represent and unknown that you have to equip yourself against before you have boots on the ground.

Offline Paul451

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Re: Scaling Agriculture on Mars
« Reply #1207 on: 06/01/2018 01:04 AM »
They may not need real insulation with the thin martian atmosphere.
As I mentioned above (and has been mentioned many times before), Mars' atmosphere is thick enough for convection cooling to dominate over radiation emission.
What are you trying to say? That greenhouses are not efficient in retaining heat? Even here on Earth with the dense atmosphere and wind even single pane glass houses are very efficient in retaining heat. It can only be better on Mars.
Greenhouses in cold climates have to be heated in the winter. This is a legitimate challenge for Martian night.

Don't forget, the sunlight is already half the Earth equivalent, and the atmosphere is vastly colder at night.

Additionally, bespoke systems for greenhouses on Mars are worthless for anything else. Uniquely complex systems that serve no other role, can be diverted to no other purpose. OTOH, artificially lit hydroponic grow modules merely means more of the power system you already have (power which can be diverted in emergencies), and merely more pressure vessels of a type you already use for every other form of habitation.
Again, what are you trying to say? It is not efficient to make a dedicated design for greenhouses for growing plants? Should they use the same design as for habitats for commonality?

It's not just the module itself, it's every other subsystem that people have come up with to try to get around the problems created by using exposed greenhouses. (Tracking-mirrors, insulating covers, heat-pumps, etc.) Complex systems that exist for no other purpose, with no commonality of parts/engineering with any other necessary system. Whereas the only real issue when using artificially lighting is the requirement for power, which shares every part with the power system used for everything else (especially propellant production.) It also means, as I said, that you have an effective "free" backup for your power system during low-power conditions (dust-storms, maintenance, sudden failures.)

And on that subject...



Plants cant be titled towards the sun.

Well, plants tilt themselves towards the sun. But I assume you are referring to having sun-tracking systems on the solar panels. In which case, again I say no. You are creating a unique, high-mainenance system that serves no other purpose. Better to just throw out more solar panels, more storage.

Plants dont absorb the entire natural light spectrum.  Right off the bat that is a factor of two efficiency for LED.

AIUI, yellow actually reduces the ability of some plants to use higher levels of light. Using tuned frequencies allows you to increase their rate of growth or maximum yield beyond natural levels.

so most of the time you are shining light on dirt.

Whether you are using natural-light greenhouses or artificially lit grow-chambers doesn't alter you choice of farming methods. Greenhouses happily grow sprouts in smaller specialised areas and then space them out as they grow. Likewise, most commercial hydroponics is done in natural-light greenhouses.

Offline johnfwhitesell

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Re: Scaling Agriculture on Mars
« Reply #1208 on: 06/01/2018 08:02 PM »
But I assume you are referring to having sun-tracking systems on the solar panels.

You assume wrong.

Static solar panels are placed at an angle so that on average they face as much towards the sun as possible.  Plants do not have a flat surface pointed towards the sun.

Quote
so most of the time you are shining light on dirt.

Whether you are using natural-light greenhouses or artificially lit grow-chambers doesn't alter you choice of farming methods. Greenhouses happily grow sprouts in smaller specialised areas and then space them out as they grow. Likewise, most commercial hydroponics is done in natural-light greenhouses.

Yes most greenhouses aren't LED.  However we were talking about LED greenhouses.  And that does change the farming methods.  Did you see the link I provided?

Offline Paul451

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Re: Scaling Agriculture on Mars
« Reply #1209 on: 06/02/2018 02:50 AM »
Plants do not have a flat surface pointed towards the sun.

I believe they are called leaves.

so most of the time you are shining light on dirt.
Whether you are using natural-light greenhouses or artificially lit grow-chambers doesn't alter you choice of farming methods. Greenhouses happily grow sprouts in smaller specialised areas and then space them out as they grow. Likewise, most commercial hydroponics is done in natural-light greenhouses.
Yes most greenhouses aren't LED.  However we were talking about LED greenhouses.  And that does change the farming methods.  Did you see the link I provided?

As I said, hydroponics can be done in a natural light greenhouse as well, the advantages of hydroponics has nothing to do with the difference between using natural vs artificial lighting. (And in practice, almost all commercial hydroponics is done in naturally-lit greenhouses. Likewise, commercial greenhouses routinely move plants to optimise area-coverage.)

The method of farming doesn't have any influence over whether you use natural sunlight, or pure LED, or LED-boosting of natural sunlight. Arguing for hydroponics doesn't argue for artificial lighting.

Offline AegeanBlue

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Re: Scaling Agriculture on Mars
« Reply #1210 on: 06/03/2018 06:38 AM »
Mars equator has more or less the same solar illumination with the Netherlands on a cloudy day. Most days in the Netherlands are cloudy, yet they use clear greenhouses with supplementary artificial illumination rather than all sorts of complexity of panes and the like. I do not know if we can make a pressure vessel with the structural transmissivity of a typical earth greenhouse, but if the ISS Cupola is any guide I would say yes. Now a typical greenhouse in Greece has 4 times the heating requirements of a house of the same size because exactly it is not well insulated compared to a home. Then again BY DEFINITION a greenhouse requires heating, otherwise it is a cold covered facility. Plants do not only use the part of the EM spectrum that chlorophyll absorbs, they also use other parts of the EM spectrum especially when dealing with photoperiodism. I am not sure if a facility in darkness illuminated only by LEDs that cut off rather than earth surface solar spectrum can provide a sufficiently diverse species of plants for a nutritious meal. Some plants simply require a whole spectrum to go through their entire cycle, though apparently pulses of 10^-5 Hz are sufficient rather than constant illumination, at least as far as I remember. We plant with space in between plants in order to avoid crowding, plant do not react too well to being too close to others of their own species. This is why we also illuminate the soil. Now crowding depends on the plant stage, hence the plants get moved around in greenhouses in order to optimize efficiency.

Offline sghill

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Re: Scaling Agriculture on Mars
« Reply #1211 on: 06/14/2018 02:23 PM »
Additionally, bespoke systems for greenhouses on Mars are worthless for anything else. Uniquely complex systems that serve no other role, can be diverted to no other purpose. OTOH, artificially lit hydroponic grow modules merely means more of the power system you already have (power which can be diverted in emergencies), and merely more pressure vessels of a type you already use for every other form of habitation.

If you want to scale anything on Mars, you want to avoid unique systems and focus on commonality and modularity. For any task, it will be better to have ten copies of one system than five unique systems of the same scale that do the same job slightly more efficiently.

Yes yes yes. A thousand times yes! Redundancy, simplicity and commonality will be the drivers of scale.

As I said, hydroponics can be done in a natural light greenhouse as well, the advantages of hydroponics has nothing to do with the difference between using natural vs artificial lighting. (And in practice, almost all commercial hydroponics is done in naturally-lit greenhouses. Likewise, commercial greenhouses routinely move plants to optimise area-coverage.)

The method of farming doesn't have any influence over whether you use natural sunlight, or pure LED, or LED-boosting of natural sunlight. Arguing for hydroponics doesn't argue for artificial lighting.

Paul is correct here. I don't know why there was any discussion otherwise.  I grow lettuce and tomatoes all the time outside with a hydroponics system I have setup on wheeled grow-tables. It's great for reducing the electricity costs of lighting, while also extending my growing season. I'm in north Florida, and I wheel the tables inside on cold or freezing nights in the winter, and then back outside during the day if the temps get above 65.

On Mars, you'd want the sun to be the primary greenhouse lighting system, and LED's to augment that system for safety against dust storm blackouts and to achieve longer growing periods (16-20 hour daily grow periods).

However, back to Paul's point that if it's easier to use LED's because you don't have to engineer a transparent pressure vessel solution, you do that instead. As Paul points out. The power is already there.

« Last Edit: 06/14/2018 02:31 PM by sghill »
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Offline johnfwhitesell

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Re: Scaling Agriculture on Mars
« Reply #1212 on: 06/14/2018 03:15 PM »
Guys, if this is absurd to you:
"I typically go for walks outside without a spacesuit so I guess all the people on Mars will do the same."

Then this should be absurd to you:
"All the greenhouses on Earth use natural light so natural light is the thing they should use on Mars."

Offline sghill

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Re: Scaling Agriculture on Mars
« Reply #1213 on: 06/15/2018 07:21 PM »
Guys, if this is absurd to you:
"I typically go for walks outside without a spacesuit so I guess all the people on Mars will do the same."

Then this should be absurd to you:
"All the greenhouses on Earth use natural light so natural light is the thing they should use on Mars."

No one is saying that.
Bring the thunder!

Offline colbourne

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Re: Scaling Agriculture on Mars
« Reply #1214 on: 06/26/2018 04:22 AM »
As an alternative to LEDs for use in underground or badly lit areas , we can also consider the use of steerable mirrors.
These would be easier to produce on Mars than LEDs + solar panels.

Offline speedevil

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Re: Scaling Agriculture on Mars
« Reply #1215 on: 06/26/2018 10:35 AM »
As an alternative to LEDs for use in underground or badly lit areas , we can also consider the use of steerable mirrors.
These would be easier to produce on Mars than LEDs + solar panels.
On Earth, the use of this can bellimited due to clouds.
On Mars, you have very little time when clouds re significant, and may be able to write off crops in this situation, if otherwise it makes your system more efficient.
If, for example, you can find a suitable shallow depression, place your mirrors in it, and the garden on a crater wall, you can easily illuminate any window with many suns radiance.

I question how useful this is, given PV is considerably less constrained and less precision is required to install it - even assuming directly lit - perhaps with simple mirrors to slightly increase input light - is not an option.

Offline AegeanBlue

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Re: Scaling Agriculture on Mars
« Reply #1216 on: 07/30/2018 06:15 PM »
What will humans eat on Mars:

https://www.inverse.com/article/47474-what-will-humans-eat-on-mars-after-civilization

I am not a great fan of methods that assume an entire high tech biotechnology lab to bear fruition

Offline Paul451

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Re: Scaling Agriculture on Mars
« Reply #1217 on: 07/31/2018 02:13 AM »
Colbourne, speedevil:

Re: Using mirrors on Mars.

Dust in the Martian atmosphere scatters direct sunlight, and indirect light can't be focused. On average, over the Martian year, only 50% of direct sunlight reaches the ground, the rest is scattered. However, at that level you still get nearly the same overall illumination on the ground as full sun, so systems that can handle indirect light, such as modern PV (or plants, for that matter), can still operate at high efficiency.

Hence using mirrors to increase sunlight will fail long, long before PV production declines significantly.

Taking an extreme case: The Opportunity rover's final readings were more than Tau=10, ie, 99.998...% of direct sunlight blocked, but at that time was still producing 7% of the power as before the storm (when the sky was actually unusually clear, less than 50% blocked). Rough calc: 0.00035% of direct sunlight before/after, 7.5% of the power, hence 200 times more than mirrors would be achieving under the same conditions.

And you can't make up for it by throwing in 200 times more mirrors. You are area limited. Every mirror must have a clear line to the sun, and a clear line to the greenhouse. Add too many and they will self-shadow. You can, however, add 15 times more solar PV, just stick it wherever suits you and the panels/film.

Going further, fixed mirrors are obviously nearly worthless, you will need sun-tracking which adds mass and complexity (more things to go wrong.) Sun-tracking solar panels are nice, but it would be more effective to just bring more rolls of thin-film solar cells for the same mass and spread them out on a suitably angled berm or hanging from slightly elevated wires.

And, of course, a purely electric lighting system running off solar is also plug'n'play compatible with a local nuclear reactor, once you get one.
« Last Edit: 07/31/2018 02:24 AM by Paul451 »

Online Robotbeat

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Re: Scaling Agriculture on Mars
« Reply #1218 on: 07/31/2018 03:29 AM »
Fixed mirrors aren't at all worthless if you just want to increase the light levels by like 30% or so on average.
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Offline colbourne

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Re: Scaling Agriculture on Mars
« Reply #1219 on: 07/31/2018 05:14 AM »
Mirrors also have the advantage over solar panels and leds, of being much simpler to construct on Mars, making Mars less dependent on Earth.

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