Crops

tahanson43206 · 2021-02-03 11:13:34

Without intending to focus on any one person in this forum, there ** is ** a premise floating in this topic, that humans can live on a diet created entirely of artificial growing systems. This idea is attractive for a number of reasons, not least of which is the rapid progress of the human population on Earth toward 10 billion, and the present inability to feed the multitudes adequately as it is.

However, since the desired state of affairs has NEVER been demonstrated on Earth, it seems overly adventurous to place the lives of people who will be brave enough to migrate to Mars at risk by planning ONLY for such food supply methods.

This topic is well suited for introduction of references to ACTUAL demonstrations of artificial agriculture, and to ACTUAL nutritional data which compares artificially created food to naturally grown foods of the same type.

(th)

Calliban · 2021-02-03 11:35:34

tahanson43206 wrote:

Here is a report about plants that grow so rapidly they are a nuisance, but they are under consideration for use as a food source ...
https://www.yahoo.com/news/fastest-grow … 43347.html

Because duckweed grows so quickly, scientists think they could use that feature to grow food for a rapidly increasing global population. The plant itself is already eaten in parts of Southeast Asia, where it's known as khai-nam, which translates as "water eggs."
Originally published Tue, February 2, 2021, 8:49 AM
(th)

Good find Tahanson. Wolffia consists of 11 species of small floating plant, all of them apparently edible and highly nutritious.
https://en.m.wikipedia.org/wiki/Wolffia

They appear to measure no more than a few mm and grow very rapidly in nutrient rich water. This looks like another plant that we can grow in tubes on the Martian surface.

tahanson43206 · 2021-02-03 12:05:57

For Calliban re #577

Thank you for your post! I'm inspired to imagine a test of your concept for growing plants in transparent tubes on Mars.

By purest coincidence, I ran across a report on some building/construction projects planned for 2021 in various parts of the world recently. One of these is an ambitious refurbishment of an already existing (rather futuristic looking) facility in a northern climate. I ** think ** the country involved is Norway. The project plan includes building a greenhouse to feed (this seems ambitious to me) all 60 permanent staff at the research facility.

Your idea would be totally new to them, and they might be willing to give it a try during the part of the year when they have sunlight.

As I recall your idea, it was to bring the floating plant pods "indoors" during the night on Mars. I'm unsure how the conditions at the research station would compare. They would have to deal with precipitation that would not be a problem on Mars, but Mars settlers would have to deal with dust, which is not likely to be a problem in the Arctic circle on Earth.

Still, as a bottom line, they might be willing to consider adding a small version of your idea to their plans. The results would (presumably) become available to the public, and specifically to Mars Mission planners.

(th)

Calliban · 2021-02-03 14:17:04

tahanson43206 wrote:

For Calliban re #577
Thank you for your post! I'm inspired to imagine a test of your concept for growing plants in transparent tubes on Mars.
By purest coincidence, I ran across a report on some building/construction projects planned for 2021 in various parts of the world recently. One of these is an ambitious refurbishment of an already existing (rather futuristic looking) facility in a northern climate. I ** think ** the country involved is Norway. The project plan includes building a greenhouse to feed (this seems ambitious to me) all 60 permanent staff at the research facility.
Your idea would be totally new to them, and they might be willing to give it a try during the part of the year when they have sunlight.
As I recall your idea, it was to bring the floating plant pods "indoors" during the night on Mars. I'm unsure how the conditions at the research station would compare. They would have to deal with precipitation that would not be a problem on Mars, but Mars settlers would have to deal with dust, which is not likely to be a problem in the Arctic circle on Earth.
Still, as a bottom line, they might be willing to consider adding a small version of your idea to their plans. The results would (presumably) become available to the public, and specifically to Mars Mission planners.
(th)

No doubt the 'floating plant pots in tubes' idea could be built and made to work on Earth. But conditions in Norway are very different to those on Mars. On Earth, we do not have high background cosmic radiation that we need to escape from. We do not have large day-night temperature fluctuations. Our greenhouses don't need to be pressurised and are therefore much cheaper. We do have a dense atmosphere that tends to remove a lot of heat by convection and precipitation that removes heat by conduction. We can grow plants in non-pressurised cold frames and open them without exposing plants to vacuum.

Some possible advantages that may make this system useful on Earth: (1) transparent tubes are more compact that greenhouses and do not need to stand up to wind loadings; (2) Plants can be tended in a relatively small heated space, so no one has to brave the cold.

tahanson43206 · 2021-02-03 18:40:05

For Calliban re #579

Thank you for adding refinements to the floating tube idea, and for specifically considering the greenhouse project in Norway.

Please expand a bit on why you brought up radiation ... there may be a good reason, but I must have missed it.

Regarding day/night temperature fluctuations ... I guess that is a relative judgement .... in a desert climate, temperature swings can be dramatic.

However, the thin nature of Mars atmosphere would ( I would think ) reduce its ability to pull thermal energy out of objects, compared to sea level density of atmosphere on Earth.

However, in any case, in both cases the plant floaters would be safely ** inside ** for overnight storage in both locations, so I'm not able (at this point) to see how that makes a difference.

How much of an issue is atmospheric density inside the tubes? If we take RobertDyck's suggestions as a guide, the pressure on Mars would be half that of Earth, inside the tubes. Is that a problem? I suppose the answer depends upon the material you have chosen for the walls.

It might turn out that Solar flux in the Northern Latitudes is comparable to what is available at Mars.

In both environments, some energy would need to be expended on maintaining suitable growing temperatures for the plants you've chosen.

I'm pursuing this with you for the simple reason that without input of (unusual/surprising) ideas like yours, our conservative science friends are going to repeat whatever patterns they've learned. The only way (that I can see) to break memorized patterns like that is to try something new on Earth.

There may be some fatal flaw in your concept, but if there is, I sure can't see it. The way to find any such flaw is to find someone willing to try it. I've given you enough information so you should be able to find the team working on the refurbishment.

They may very well have the typical closed minds of the well trained scientist, but it can't hurt (that I can see) to ask.

(th)

SpaceNut · 2021-02-03 18:49:39

Human only for farming in radiation exposure in a greenhouse as plants are not effected...

Opening it to mars pressure while it would not kill the plants imediately they would not survive in long exposures.

tahanson43206 · 2021-02-03 19:01:50

For SpaceNut re #581

To clarify ... I ** think ** Calliban's tubes would be pressurized to 1/2 Earth, which is the recommended pressure for RobertDyck's Large Ship.

The question is whether the material from which Calliban would be making his tubes could withstand that pressure.

It will be interesting to see Calliban's reasons for thinking about radiation. Your answer in Post #581 may hint at the direction he will go.

(th)

SpaceNut · 2021-02-03 19:24:09

Yes small calliban tubes are on the large ship and surface with algea in them but not on the surface of mars as we need to be able to stand within the greenhouse to plant and harvest other foods where its soil or hydroponically grown.

RobertDyck · 2021-02-03 19:37:00

tahanson43206 wrote:

It will be interesting to see Calliban's reasons for thinking about radiation. Your answer in Post #581 may hint at the direction he will go.

This is a concern many people have raised. If you have a greenhouse with windows exposed to sunlight, you will have radiation. The windows will stop alpha and beta radiation. Spectrally selective coating will block UV-C and UV-B, and high frequency UV-A (close to UV-B). NASA's formula for spectrally selective coating is vacuum deposited thin layers of gold, nickel, and silver oxide. Only silver is oxidized. There isn't much X-ray in space, but the metal coating should block what little there is. The atmosphere of Mars blocks over 90% of heavy-ion galactic cosmic radiation (GCR). How much depends on altitude; at a high altitude location such as Meridiani Planum where Opportunity landed, it blocks 90%. At a low altitude location such as Elysium Planetia where Spirit landed, it blocks up to 98%. That leaves proton, light-ion and gamma. The atmosphere blocks about half of medium-ion. Total radiation is about half that of ISS. So I don't see this as a problem.

Ps. The types of radiation that get through are ideally blocked by Mars dirt.

tahanson43206 · 2021-02-03 19:56:19

For SpaceNut re topic (and specifically Calliban's tubes) ...

There is so much going on in this forum, it is easy to miss details ...

The Calliban growing tubes were designed NOT for people.

People would NOT be inside one of Calliban's tubes.

For one thing, they may be too small for a person, but I'll admit I don't recall Calliban providing dimensions.

The idea Calliban offered was to push trays of plants out from an underground cavern into tubes half filled with brine, so they would float out into the sunlight of Mars (such as it is). At night, the trays would be pulled back inside the shelter.

Humans would be inside the shelter at all times, protected from radiation by layers of rock and regolith.

In the context of the Norwegian research station, I see a possible opportunity to give Calliban's idea a bit of testing, if the Norwegians are willing to consider the idea. It seems to me that on Mars, and certainly in northern Norway, some heating of the brine would be required, to keep it from freezing.

The lowest freezing point obtainable for NaCl brine is −21.1 °C (−6.0 °F) at the concentration of 23.3% NaCl by weight.[4] This is called the eutectic point.

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

(th)

SpaceNut · 2021-02-03 20:15:28

So Calliban's tubes would probably be a foot in diameter or 2 ft tube is clear on the outer facing half while the other can be pitch black in color to absorb heat in the IR band more readily. The length of the tubes would need to be short enough to provide brine circulation from end to end. The outer half in contact with the regolith of the mars surface needs to be isulated from the cold of mars.

Growing trays would be a 3 to 4 inch for depth and would take on the salty brine in the tube as it evaportes most likely in droplets in the arch of the tube. The depth of the brine will be less tan the half way point of the tube to allow easy placement of the traysonto the floating surface. The trays would be linked to gether from one to the next so as to be able to ring them back in one at a time as well. The length of the tray and width can not be to long as they get heavy over time as the food grows in them.
Due to tray depth only a few types of food will be grown in the trays and hopefully they are fast growing. To increase solar rays one could place a reflective panel along its length to cause more energy to be made available for the crop to grow in.

The ends of the tube would have a sort of dome that covers the ends to provide protection to the one loading and unloading the tube each day. It would be covered with a regolith shield to lower radiation that one might recieve while placing the crops into the tube each day. One could extend the length of the tube to be able to house the tays inside the habitat space but that means a longer protection covering for that to happen and it would lower the radiation exposure oncfe more.

tahanson43206 · 2021-02-03 22:16:14

For SpaceNut re #586

Thanks for adding details to Calliban's vision ... I like the idea of coating the inside of the bottom of the tube with black material to absorb and retain any photons that reach it.

Something that I thought of after reading your post is that the top of the tube might be a plastic film stretched between the sides of the trough, and held aloft by the air pressure inside the tube.

Your addition of a design that would allow the plants to move in a circle is interesting as well. My mental picture of Calliban's idea was of straight tubes projecting out into a valley (for example) from the habitat dug into a hill side. The floats would be pushed out in the morning and pulled back by string at night.

Your concept would allow for circulation of the floats from morning until night, with the entire set of floats returning to the "barn" at night.

Since the floats have to be stored inside the "barn" at night, they could be illuminated by artificial lights if outside conditions made it necessary (on Mars the only conditions that might be a problem would be dust storms).

Your vision seems to have the ends of the tubes out of doors?

I interpreted Calliban's idea as having the end of the tube inside the shelter, and not out doors.

However, your design (as I understand it) is a bit different, in that the "barn" might be a mound of regolith over a tunnel for the plants to shelter over night.

Interesting how there are branches flowing from Calliban's original post in a variety of directions.

(th)

Calliban · 2021-02-04 13:16:57

Radiation dose measurements taken by Curiosity amount to 210uGy per day, or 0.08Gy per year.
https://www.nasa.gov/jpl/msl/mars-rover … 17600.html

I do not know if this figure accounts for the high RBE of heavy ion radiation. If it does, then 1 full year of exposure would increase future risk of fatal cancer by 0.4% and reduce average life expectancy by 0.1 years for a 30 year old adult. If the average gardener spends no more than 1000 hours per year in an above surface greenhouse, that might be a tolerable risk. However, if RBE is not accounted for and is high, effective dose could be much higher.

The answer to this question will dictate a lot of how we end up doing things on Mars. If effective doses from cosmic radiation is greater than about 100mSv (10REM) per year, then we should probably be planning for a subterranean existence. We would look towards methods of farming that minimise human exposure to surface conditions.

The use of tubes allows us to grow in natural light without people having to be exposed to the surface. The tubes are effectively small, pressurised polytunnels containing a brine solution. I would propose a composite material to achieve minimum cost design.

1. An outer film of PCTFE (it is tough and durable, but quite expensive).
2. Beneath which we would have a layer of UV absorbing compounds.
3. Beneath this a fine mesh of basalt fibres.
4. A thicker inner layer of high density polyethylene.

The polyethylene provides rigidity and a modest amount of strength. The basalt fibre mesh provides the bulk of strength. The outer PCTFE layer is abrasion resistant and UV resistant and keeps the anti-UV coating over the much cheaper, but less UV resistant PE.

For insulation of the lower surface, fine regolith could be used. Under Martian near vacuum conditions, its thermal conductivity is 0.1W/m.K (Rock wool = 0.04, ordinary soil ~1.0). So fine regolith, free from rocks and stones which would act as thermal bridges, is a good insulator.

I would envisage a tube that leaves a shielded facility, coils around about 1 acre of land (12,000m of pipe, some 30cm in diameter) and then reenters the facility. The plant pots could be stored in racks overnight. Feeding them additional sprectrally optimised PAR light using LEDs, whilst in the racks, would boost productivity. In far Northern locations like Korolev, this may turn out to be important if we wish to extend growing season into spring and autumn, as this location would be beneath freezing for much of the year and insolation levels would be low.

I would anticipate that plants would be grown in polyethylene tubs. These would be carefully weighted to ensure stability, whilst allowing a reasonable depth for roots. A tub 15cm deep, would allow 15cm of growth space above the pot.

Some plants will need greenhouses to grow. In many latitudes this may require substantial supplemental heating. I keep meaning to put together a spreadsheet calculation.

Last edited by Calliban (2021-02-04 14:18:16)

RobertDyck · 2021-02-04 14:27:05

Calliban wrote:

If effective doses from cosmic radiation is greater than about 100mSv (10REM) per year, then we should probably be planning for a subterranean existence. We would look towards methods of farming that minimise human exposure to surface conditions.

When I was part of the Mars Homestead Project, we did a calculation. The project designed a habitat built into the side of a hill, so roof was buried in dirt. Sides and back also buried, but front of the building had windows. Ensure the habitat had at least 2.43 metres (8 feet) of Mars dirt, deeper into the hill had more. This eliminated radiation exposure while inside. However, the greenhouse was built on the surface. Restricting time outdoors in a spacesuit to 40 hours per week, reduced radiation to 5 REM per year. A spacesuit would not be required in the greenhouse, but since there's no Mars dirt on the roof, time in the greenhouse is included in that 40 hours. Considering 40 hours is a work week, I don't see this as a problem.

BTW, the habitat was designed with a two story atrium, with vaulted ceilings to increase ceiling height that much further. The atrium was designed to be deep within the hillside, with a light pipe to provide sunlight to a diffuser at the apex of each vault. Potted plants in the atrium, so the atrium is shielded. But agriculture in the surface greenhouse.

US nuclear reactor workers are limited to 5 REM per year, so this works out to the same.

Calliban · 2021-02-07 15:36:02

Robert, did the dose estimate of 5 REM per year take into account the high RBE of heavy ion radiation? If it did, then you are correct and there probably isn't a problem with a 40 hour work week on the Martian surface. If it didn't, then 5 rads of absorbed energy will result in something like 100 REM effective tissue dose. Thats because the RBE of ion radiation is about 20.

RobertDyck · 2021-02-07 16:58:51

We started with reports by the MARIE instrument team, from Mars Odyssey. That report already took that into account. I wish I could link some of the images from the report, but here is the cosmic ray map.

At Elysium Planetia, specifically shore of the frozen pack ice, total radiation is 22 REM / year. A Mars solar day is 24 hours, 39 minutes, 35.244 seconds, so 40 hours per week is 1/0.2317248328 so radiation is 5.098 REM/year. Number of heavy ion hits per cell per year on the Martian surface: 0.1 during solar maximum, 0.2 during solar minimum. Again at this location, due to altitude. These papers assumed shielding by traditional spacecraft structures, such as aluminum alloy capsule. The paper has a separate table showing effects of shielding: water equivalent 5g/cm² and 10g/cm². A buried habitat has a lot more than that.

Papers:
RADIATION CLIMATE MAP FOR ANALYZING RISKS TO ASTRONAUTS ON THE MARS SURFACE FROM GALACTIC COSMIC RAYS
Premkumar B. Saganti, Francis A. Cucinotta, John W. Wilson, Lisa C. Simonsen, and Cary Zeitlin

MODEL PREDICTIONS AND VISUALIZATION OF THE PARTICLE FLUX ON THE SURFACE OF MARS
FRANCIS A. CUCINOTTA, PREMKUMAR B. SAGANTI, JOHN W. WILSON, and LISA C. SIMONSEN

RADIATION CLIMATE MAP FOR ANALYZING RISKS TO ASTRONAUTS ON THE MARS SURFACE FROM GALACTIC COSMIC RAYS
Premkumar B. Saganti, Francis A. Cucinotta, John W. Wilson, Lisa C. Simonsen, and Cary Zeitlin

VISUALIZATION OF PARTICLE FLUX IN THE HUMAN BODY ON THE SURFACE OF MARS
PREMKUMAR B. SAGANTI, FRANCIS A. CUCINOTTA, JOHN W. WILSON AND WALTER SCHIMMERLING

louis · 2021-02-07 19:18:21

Agrarian farmers on Earth don't have to spend much time out in the fields in a year. I'd be surprised if the average farmer was out in the fields from necessity for more than maybe 500 hours a year. Also, with robot tractors (a reality now) you could probably spend even more time inside a building if you wished.

You could probably organise farm domes so that the access ways for humans were shielded but I doubt that would be necessary. Crop monitoring and so on can be all be done by robots either operating automatically or by humans housed in a safe location.

One issue though: is there any danger to human health from plants absorbing radiation? I know this was an issue when the Dutch used to (maybe still do) irradiate foods to kill off bugs.

SpaceNut · 2021-02-07 19:22:05

Water shadow barriers above the tractor rider sounds about right to aid in lowering the levels and we could also produce a localized magnetic field as well from the power take of systems if we are using a chemical engine as we are talking about elsewhere.... Internal combustion engines for Mars

RobertDyck · 2021-02-07 20:53:53

If you have to hide indoors, then stay on Earth. On Mars you'll want to go outside. Don't be afraid. The greenhouse should be some place you can enjoy greenery and sunshine. But yea, we have a lot of automation these days. Beans are harvested by a special combine. Mars will have agricultural machines sized for greenhouses.

louis · 2021-02-08 05:46:59

Depends what you mean by indoors and outdoors.

One way or another I think we'll be wanting to limit exposure to incoming radiation so there will no doubt be recommended limits on surface work or work in farm domes exposed to incoming radiation.

If you are talking about being outside on the surface in the near vaccuum of Mars, then getting suited up in a traditional space suit will be a real pain - you could be spending maybe 3 hours getting in and out of your suit. We may be able to get that time down with MCP suits but even so I expect with safety procedures and checks you will probably have to spend an hour or more getting in and out of a suit.

I think people are more likely to get that sense of freedom and being out and about on Mars through driving small pressurised buggies.

RobertDyck wrote:

If you have to hide indoors, then stay on Earth. On Mars you'll want to go outside. Don't be afraid. The greenhouse should be some place you can enjoy greenery and sunshine. But yea, we have a lot of automation these days. Beans are harvested by a special combine. Mars will have agricultural machines sized for greenhouses.

tahanson43206 · 2021-02-08 08:41:13

For Louis re #595

There are some in this forum who are cavalier about the risks of radiation damage to human cells. One even went so far as to taunt prospective Mars settlers with the expression "if you don't want to deal with radiation, then don't go to Mars." (or words to that effect).

Children born on Mars will NOT have that option, even if it made any sense for those born on Earth, which would be true if the individuals signed the appropriate releases of responsibility, and clarified for all time that they are aware of the risks and willing to take them, and that they will provide for their medical care when they become ill, and will provide for the disposition of their remains.

Greenhouses for Aesthetic enjoyment seem like a good idea, and I expect there will be plenty of them, on the order of one per household.

However, industrial agriculture seems likely to me to have a future that looks a lot like Calliban's vision, of tubes through which rafts of growing plants make their way from heated cavern in the morning to heated cavern at night.

And ** those ** installations will be few in number and extent compared to the all-indoors LED lighted growing facilities.

One of the recent Mars Convention videos (#50) included an interesting (to me for sure) dome design and one of the domes was dedicated to a large agriculture plot that looked a ** lot ** like the watered circles that are common out West in the US on Earth.

Dr. Muhammad Akbar Hussain - City State Design Contest - 23rd Annual Mars Society Convention

(th)

Calliban · 2021-02-08 11:00:45

From the link that Robert provided, the accrued dose from cosmic rays is dominated by protons, with an RBE of 1.1. Heavier ions have 100,000-1million times lower fluency. Even factoring in a factor 20-50 higher RBE, their dose effect is small. So it can be assumed that accrued dose for cosmic rays is roughly proportional to absorbed energy flux, much like gamma rays. This makes their impact on human health a lot less scary.

So the 20REM surface dose per year estimate appears to be solid, as it does account for the RBE of cosmic radiation. If you were at the top of Olympics Mons, the dose rate would be about 30REM per year. Interestingly, the Martian atmosphere is most effective at shielding the most dangerous heavy ion radiation. This includes things like iron nuclei moving at a large fraction of c. The Martian atmosphere appears to screen out most of that type of radiation. This is important because this type could result in deterministic effects by killing nerve cells. At low altitudes, the Martian atmosphere screens out almost all of this type. What remains is mostly low LET protons.

Assuming that a 'farmer' spends 40 hours per week on the surface of Mars at average sea level equivalent elevation, every week between the ages of 20 and 60, then by my estimation, he will lose about 3 years of life expectancy, I.e. average life expectancy would fall from 80 to 77. If, as Louis suggests, real exposure is more like 500 hours per year, loss of life expectancy would be <1 year. It would likely be lost in statistical noise. One interesting factor: the older a person is when they receive a radiation dose, the less life expectancy they tend to lose. This is partly because a man dying at 60 has less life expectancy to lose than say a 20 year old. But it is also because cancers tend to grow more slowly as cell division rate falls with old age. It is less likely to be fatal and if it is, it will take longer.

Generally, from these calculations, I get the impression that radiation is not something that would be a primary concern on Mars, especially in lower altitude settlements in the northern hemisphere. There are places on Earth where background gamma radiation doses reach these sorts of levels. And the LET is similar to protons. I think Martian settlers will probably decide to go with the flow, so to speak. Interestingly, even on the surface of the moon, doserates from cosmic rays would be about 2.5x those on the Martian surface. Whilst one would not want spend their entire working life in those conditions, an average of a few hundred hours a year would probably not result in a measurable loss of life expectancy.

The cold may necessitate special measures for agriculture. I keep meaning to put together a heat transfer spreadsheet for a Martian greenhouse. I will get round to it in the days ahead.

Last edited by Calliban (2021-02-08 11:24:15)

Oldfart1939 · 2021-02-08 11:23:50

My experience in running my ranch in Wyoming for 23 years indicates a lot less time outdoors in the fields afoot. Most of the time spent was using a tractor to move hay bales and do the haying operations. In winter, I don't think I ever spent more than 2 hours a day outdoors feeding cattle. In the summer, the time increased due to irrigation work, but given the advent of center-pivot irrigation systems, this would be greatly reduced. Most of the labor on a farm or ranch is centered on keeping the machinery working, repairs to fencing, or other maintenance jobs. I had 77 acres of gravity-flow, flood irrigated acres of mixed grass and clover hay, and that took quite a bit of outdoor time seasonally, but that was for about 6-8 weeks in spring/early summer. If I took an average of time actually spent playing Farmer in the Dell, it would be more like 15 hours per work week of "exposure."

Last edited by Oldfart1939 (2021-02-08 11:36:47)

RobertDyck · 2021-02-08 12:13:43

louis wrote:

If you are talking about being outside on the surface in the near vaccuum of Mars, then getting suited up in a traditional space suit will be a real pain - you could be spending maybe 3 hours getting in and out of your suit. We may be able to get that time down with MCP suits but even so I expect with safety procedures and checks you will probably have to spend an hour or more getting in and out of a suit.

Yes, I'm expecting people will want to put on a spacesuit and go outside. Just to get out of the house. Cabin fever. I live in Winnipeg; as I write this it's 11:35am, temperature outdoors is -29°C, 56% humidity, 28km/h wind from the west. Weather website says "feels like" -44°C. That happens a lot this time of year. There's only snow on the ground 5 months of the year, and bitterly cold the middle 3 months, but it happens every year. There can be mild days when the daytime high gets to +1°C, but we can get a "cold snap" that lasts 2 weeks at a time. During a cold snap the daytime high does not get above -20°C (-4°F) real temperature, and overnight low is below -30°C. Winnipeg is know for -40°C in winter, real temperature. Actually, that doesn't happen often, but does happen. Last time was one night in January 2019, and before that one night in January 2005. So 14 years between occurrences; rare but does happen. I remember one day when I was in my 20s, drove with my brother to a Christmas dinner. It was late afternoon, but after sundown. It gets coldest after sundown. Temperature that day was -36°C. A tire went flat. The cold was the reason. But changing a tire in -36°C? If I wore my mitts, I couldn't turn lug nuts. Without mitts, my fingers got frostbite and numb as soon as they touched the metal. My brother and I changed the tire together, it was hard. But we got there in time for dinner.

The point is you can't stay inside all winter. You do go outside. When I was a preschooler, my father would take us tobogganing on weekends. He was early 30s. When it's bright and sunny. Winnipeg is flat, but there's a toboggan run on the floodway. That's a big ditch around the city, intended to redirect water when the river floods in spring. In winter it's empty so you can run a toboggan downhill. Dirt from the floodway piled on the sides, increasing the depth of water it can carry. They built up a small hill on top of the side at one point, to give an even longer toboggan run.

When it's as cold as today, you dress with underwear, and long underwear over shorts, socks, jeans, T-shirt, long-sleeve shirt, down-filled parka, touque, mitts, and snow boots. Children wear mittens rather than gloves, because it keeps your fingers warmer. Mothers often insist children also wear a scarf. If it's really cold, also wear a sweater. The reason Canadians wear a touque in winter is to keep our head warm. When it's this cold, you want clothing that fits closely to your body. Any cold breeze under a hat or loose clothing will feel damn cold! Americans call it a knit cap. The reason a touque is folded back at the edge is a double layer over your ears. When it's that cold, wear two pair of socks. Yes, that means one sock over the other.

My point is how is this different than putting on a spacesuit for Mars? An MCP suit will have an elastic body stocking, air bladder vest, then ski pants and parka. Yes, MCP glove, then insulated glove over that. Is an insulated glove really any different than a winter ski glove? And yes, an MCP suit has pressurized boots with air dam at the ankle. Is that really different than ski boots? A helmet and PLSS backpack. Is this really much different than going out in winter to go tobogganing or skiing?

(Spring Hill is too short for skiing, but people do cross-country ski. You could drive further to Holiday Mountain Resort or Agassiz Ski Resort, 1:45 or 2:45 drive respectively. Both actually an escarpment, not a "mountain".)

tahanson43206 wrote:

There are some in this forum who are cavalier about the risks of radiation damage to human cells. One even went so far as to taunt prospective Mars settlers with the expression "if you don't want to deal with radiation, then don't go to Mars." (or words to that effect).

I think that was me. But understand what I mean. You do have to be careful, but with a properly shielded habitat, you only need limit time outside to 40 hours per week. And time in a greenhouse on the surface must be included in that.

Calliban · 2021-02-08 13:02:25

RobertDyck wrote:

I think that was me. But understand what I mean. You do have to be careful, but with a properly shielded habitat, you only need limit time outside to 40 hours per week. And time in a greenhouse on the surface must be included in that.

Works out at 2000 hours per year. You could do a lot more than 40 hours a week some weeks and then less on others and get the same risk profile. You could for example, go on a 3 month rover expedition to the polar caps, where you were exposed 24/7 if the next 9 months were spent undertaking low dose activities. For a geologist that might be about the right balance. Or lets say we need to build a base in northern summer. You want to complete work when temperatures are mild and daylight hours are long. People might average 12 hour days and 60 hour weeks for 8 months. The following 16 months would have a lot more indoor time.

Spending 40 hours a week on the Martian surface for 40 years will cut life expectancy by three years. Interestingly, this is about the same loss of life expectancy as is attributed to air pollution here on Earth.
https://academic.oup.com/cardiovascres/ … 10/5770885

So being out on the surface of Mars imparts about the same risk of cancer as walking down an urban street. Robert would probably have about the same risk from radiation on Mars as he has living in Winnipeg right now. Likewise, most of the people on this forum. If we assume that air pollution will be less of an issue of Mars, it is unlikely that people working on the surface on Mars will have noticeably reduced life expectancy.

Last edited by Calliban (2021-02-08 13:33:16)

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