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#26 2017-09-13 17:53:14

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 10,527

Re: Trees

Related topic Material Choices for Mars as GW is suggesting when considering a greenhouse structure. robust enough for mars as the likelyhood of finding a flat rockless location to put the structure up on is questionable but not impossible.

Even with a sandy location the floor still needs to be able to not be penetrated by downward pressure as caused by people working to grow food within the structure but yet able to support the tray mass of soil and plants within the structure.

Post #52 or so we started to talk about construction techniques that might be applied to the creation of a greenhouse structure on mars.

Here on Earth we can get away with the use of materials such as on this page http://www.domerama.com/coverings/polycarbonate-panels/ to make a dome for use but on earth we are not presurizing them and there is no need for a sealed flooring system. Mars is not that case for how we might build.

I sort of like the thought of a corregated panel material.
polycarbonate_layers.jpg
But that would mean a framing stucture to place the panels into.
poly_h_channel_installation.jpg

Favored materials are http://www.nationwideplastics.net/high- … tics/pctfe for use

This calculate is for a 2 V 2vtp1.gif

https://www.ziptiedomes.com/geodesic-do … ulator.htm

while this one is for 3 V top down view 3v_oct_top.png or from the side 3v_58_kruschke_assembly1.jpg

http://www.domerama.com/calculators/3v- … alculator/

Triangle shape images of them for a dome


People and tree within a dome structure size comparison table
GeoDome-Size-Chart-Domerama.com_.png

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#27 2017-09-14 00:55:49

Oldfart1939
Member
Registered: 2016-11-26
Posts: 941

Re: Trees

In order to accommodate ANY realistic form of agriculture, we're going to need a source of motive power and lifting/digging capacity. In an earlier thread or threads, we discussed having a skid-steer/front loader type vehicle in one of the early cargo loads to Mars. Virtually every machinery company builds these but have somehow all captured the name of "Bobcat."
I for one, am strongly in favor of the hillside structure proposed by Robert, which if properly aligned w/r the sun track, allows maximum solar gain and illumination for the growing crops. As a secondary feature it can be built high enough to allow trees to flourish inside.
I also support the rigid structure as mentioned by GW, since protection from micrometeorites is essential, and polycarbonate plastic can certainly provide that. The third consideration is weight of structure versus having an integral floor to hold it down on the surface instead of being levitated away by internal pressures.
To SpaceNut: maybe we need to have a new thread here--one which attempts to unify all these concepts that growing trees has elicited? I may start something a bit later after completing the proposed organization mentally.

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#28 2017-09-14 08:04:46

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 4,993
Website

Re: Trees

Oldfart1939 wrote:

skid-steer/front loader type vehicle ... Virtually every machinery company builds these but have somehow all captured the name of "Bobcat."

A company that builds large vehicles used the brand name "Cat". That name is a contraction of the word "Caterpillar", derived from their first vehicles that used tracks. Now Cat produces a lot of wheel vehicles. When I hear that name, I think of this one...
C830064?$cc-s$

Then another company built a small skid-steer loader. Because it's small, they gave it the name "Bobcat". They also produce compact track loaders and mini track loaders, but wheeled skid-steer loaders became very popular.
bobcat-skid-steer-loader-family-nav_pf_list.jpg

Ironically, the first dozers and loaders were about the size of a Bobcat. They scaled up for highway construction during World War 2. Of course the compact ones from the 1920s were a lot smaller than the monsters of the steam era. Even in the 1960s they didn't have a safety cage, just a seat at the back. Today the brand name Bobcat has become synonymous with compact loaders like the brand name "Kleenex" with facial tissue or "Aspirin" for ASA. However, it is a brand name, other manufacturers don't use that name.

Anyway, I suggest a compact track loader for Mars. Wheeled vehicles work better on hard ground, such as paved streets. But tracks work better on loose soil and for hill climbing.
bobcat-t595-trailering-t6k1552-16j1-fc-promo_ci_horizontal_small.jpg

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#29 2017-09-14 09:48:19

Oldfart1939
Member
Registered: 2016-11-26
Posts: 941

Re: Trees

Robert-

I agree that the tracked vehicles are probably more suitable for the Mars application, but they also need to increase the width of the tracks to handle the loose and sandy regolith we're anticipating. Having a look at the vehicle in your picture, I can also see that the operator could possibly work w/o having a space suit style helmet on while operating the unit. That would indeed be another "plus."

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#30 2017-09-14 14:49:43

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 2,692
Website

Re: Trees

Let us assume for the sake of argument that (1) somebody has developed an electric,  tracked backhoe machine of fairly large size and lift capacity,  (2) somebody has developed a concrete substitute that can poured into forms and cured at ambient Martian conditions,  and (3) that glass or plexiglass panels usable for pressure window panes exist in some standardized form. 

Let us assume these things plus steel rebar are all shipped to Mars along with whatever else establishes the first permanently-occupied station. 

Then you can build shirt-sleeve buildings with bounced solar lighting during the day,  that also provide radiation protection and great resistance to meteor hits,  wind-blown debris,  or bumbling humans.  These are mushroom-shaped objects with a clear ring wall around the periphery under the cap.  Simple polished aluminum or stainless sheets can bounce the light. 

These can be habitations or greenhouses.  Or whatever you need.  Dead weight contains the air pressure.  We already know how to engineer slabs with grade beams,  that's the roof panel,  I just put the grade beams on top.  The walls and columns are just compressive masonry. Bury with sand to cast the roof panel,  then dig out when cured.  Pile dirt on top,  then pressurize when the caulk around the window panels has cured. 

I posted long ago how to do this over at "exrocketman".  It was the article titled "Aboveground Mars Houses",  dated 1-26-2013.  This should be at least as easy as building a house here out of cinderblocks.  That site is http://exrocketman.blogspot.com.  There is a by date navigation tool on the left.  Click on 2013,  then on January.  It's the first thing "up" in that month of that year.

Key:  you don't have to have a nearby hillside for this to work.  You can build this on an excruciatingly-flat plain if need be.  In other words,  you can build it anywhere,  there are no site restrictions.

We need the concrete and the electric Bobcat,  plus a big lander to bring them and the rebar down.  None of this presumes any ISRU beyond using local dirt and rocks,  and ice for the water.  Nor does it presume any ISPP.  But your job gets easier if those things actually work as advertised.  Point is,  it works anyway,  even if those ISRU and ISPP things don't.  And they might not!  You MUST allow for that!

Suspenders-and-belt,  armored codpiece.  That's the ticket!

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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#31 2017-09-14 20:40:17

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 10,527

Re: Trees

Trees are easily brought from earth as sapplings but the issue for mars is time to growth to allow for the fruit of that tree to become available for consumption is the really issue for man as we can not really waiting for food to grow if we are relying on it.
Continued thoughts for size of the greenhouse to be able to handle the full grown tree in the other topic.

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#32 2017-09-14 22:27:56

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 4,993
Website

Re: Trees

I have argued before that life support must be robust. This is a planet without breathable atmosphere, so life support redundancy is critical. An ambient light greenhouse is the only life support system that works during complete power failure. And the surface of Mars has half the radiation of ISS, and plants are more robust vs radiation than humans. All this means you do *NOT* bury a greenhouse underground. No mushroom head, or anything else. Living quarters for a science mission will be a tuna can with sandbags on the roof. Living quarters for a permanent hab will have much more regolith, at least 2.4 metre depth. One purpose for building into a hillside is you don't have to lift the regolith; just push down from the hill onto the pressure roof. The Mars Homestead Project came up with an atrium built into the hill, with Sun-tracking solar collector reflecting light into a light pipe. That light pipe ended with a diffuser in the ceiling of the atrium. That brings natural light inside, but it's way to little light for agriculture. The plan was some plants in the atrium, including some fruit trees, but don't expect the trees to produce a lot. Indoor plants are for aesthetics.

Wind-blown debris is not much. Mars atmosphere is very low density, it can't carry much. But I've posted before the hardness of minerals found on Mars vs glass. Tempered glass is all you need to ensure dust storms do not cause any crazing.

Vehicles? Robert Zubrin argued for methane/LOX engine vehicles, so it can use the same fuel as the ERV. The ISPP facility for the ERV can be used to produce vehicle fuel once ERV tanks are full. However, if you want an all-electric vehicle, this guy converted a Bobcat to full electric. Click image for YouTube video. Two videos, same guys. 72-volt AC motor, lithium-ion batteries.
hqdefault.jpg?sqp=-oaymwEXCPYBEIoBSFryq4qpAwkIARUAAIhCGAE=&rs=AOn4CLDyZxtbhId4jhC29htLMkCbvJLRLg hqdefault.jpg?sqp=-oaymwEXCPYBEIoBSFryq4qpAwkIARUAAIhCGAE=&rs=AOn4CLA3nF479_fFcPmXPQ_TzhNXljcljg

Don't bring rebar from Earth. Use all in-situ resources for construction. Hematite concretions are perfect iron ore, can be smelted with the direct reduced iron method. That method requires both carbon monoxide (CO) and hydrogen (H2), between 800°C and 1200°C and 1 atmosphere pressure. We could go over all the steps to make rebar, but the point is ISRU.

Concrete is very useful. Getting it to set in Mars atmosphere is an issue. That needs to be worked out.

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#33 2017-09-15 01:12:46

Oldfart1939
Member
Registered: 2016-11-26
Posts: 941

Re: Trees

Robert-

What was the operating time of these Bobcats operating with Lithium Ion batteries? Any idea of the charging time? If it could operate at full load for > 1 hour, that would be useful, especially if the recharge time were short. I have an E-Go battery powered lawnmower which can run at full load for nearly an hour with a recharge time of ~ 30 minutes, so it is actually a useful tool. I also have a Ryobi weed trimmer with decent operation time between recharges. Maybe the new Graphene batteries will do better?

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#34 2017-09-15 04:47:57

elderflower
Member
Registered: 2016-06-19
Posts: 521

Re: Trees

Rebar, like so many steel products such as joists and columns, is made by rolling. It will be a very long time before there is a rolling mill on Mars.
Pure iron or nickel can be deposited from carbonyl vapours and this offers means of making large items such as iron rods, but the resulting pure iron deposit is quite soft. I suppose it could be then roughened and case hardened for use as effective reinforcement, but we are still faced with industry on a considerable scale.
A concrete dome needs no reinforcement once it is complete, provided that the outward thrust can be resisted in the foundations. Hadrian's concrete Pantheon dome is still standing in Rome after nearly two thousand years.

Last edited by elderflower (2017-09-15 04:52:17)

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#35 2017-09-15 15:45:32

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 10,527

Re: Trees

There are other fuels to make use of for making insitu rebar that comes to mind one being the left over fuels from the landers, another is insitu magnesium and CO2 and I am sure there are others.

For concrete setting up use the same methods used in the cold weather repairs done of over passes or bridges here in NH which is a simple plastic tent that is heated.

In either case I think we are talking about Trees are we not....

To which we would need to solve transport and growth rates to maturity in order to make them useable as quick as we can for consumption.

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#36 2017-09-15 15:47:39

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 2,692
Website

Re: Trees

In my mushroom building concept,  the columns have to be pre-loaded in compression so as to take bending when the building is pressurized.  I rather doubt the deadload of the regolith-covered roof is enough compressive pre-load,  particularly once the building is pressurized.  A real civil engineer could figure this "for sure".  I am not one of those.  So I cannot.

That means these columns absolutely must be pre-stressed with threaded steel rods through their length,  tightened to torque with big nuts and spreader washers on each end.  No different than a concrete bridge beam.  But the proper steel parts are required,  and these aren't just rebar.  Although that is necessary too,  such as for shear stirrups.  As well as in the roof slab with its grade beams as longitudinal bars and shear stirrups.  And the foundations with their grade beams. 

This kind of thing simply isn't a possible ISRU item until somebody starts building steel mills of whatever form they finally take on Mars.  I'm sorry,  for the first generation or two,  these things just have to get shipped from Earth.  To dream otherwise is just that: dreaming,  not a proper plan.

Longer term,  once the form of a steel mill on Mars finally "gels" and becomes a reality,  the pace of construction increases,  because of locally made materials.  But you simply cannot do everything in just the first several missions!  To expect otherwise is both unreasonable and quite naive. 

Sorry,  that emperor has no clothes!  Naked as a peeled egg!

GW

Last edited by GW Johnson (2017-09-15 15:51:20)


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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#37 2017-09-15 20:28:39

RobertDyck
Member
From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 4,993
Website

Re: Trees

Boot-strapping requires starting small. A rolling mill does not have the be the size of a full-scale industrial operation. It can be smaller. A tuna-can hab will never have anything like that, but you can build moderate. And let's be blunt, you will never send bulk heavy construction material to Mars. You have to send small items, then use that to construct moderate facilities, then use that to build industry.

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#38 2017-09-16 06:12:24

elderflower
Member
Registered: 2016-06-19
Posts: 521

Re: Trees

I do think it will be a long time before there are trees in Mars greenhouses. If large plants with structural properties are needed, Bamboo is probably the answer. For fruits we can grow bushes and dwarf trees in a modest greenhouse. Either will produce oxygen, but all plants we would contemplate will do that. Paper can be produced from ruminant faeces and probably those of rabbits as well.
Life without maple syrup is slightly diminished, but the pioneers will get by.

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