Problems For A Realistic First Settlement On Mars

Dook · 2016-10-29 10:19:24

Some of you have skipped completely over the initial settlement building phase and went right to the "Total Recall" phase and called it a "first settlement". This topic may not be for you. This topic is about discussing problems of establishing a realistic first settlement on Mars using Mars Direct type launches.

The first settlement would come after exploration missions to Mars with the crews returning home. So, if there are three exploration missions to Mars there would be three Mars Habs with three RTG's, three sets of solar arrays, and three Earth Return Vehicle sites with three Long Range Rovers just sitting there. The ERV launch sites would have almost empty oxygen/hydrogen tanks that can be used to store compressed oxygen back at our Mars Base.

I think a crew of three is best for exploration and settlement because that means they will use less oxygen, less water, less food, and less power than four would and three is enough for two to drive the Long Range Rover and bring back another LRR while one stays at the base.

Problems:
Some fruit trees require a certain amount of chilling over winter (I think apple trees do) before they will produce fruit in spring but citrus trees will die if the temperature gets below freezing. I guess you would have the greenhouse area of your settlement drop down to 55 degrees for a month or so to simulate winter while the living area stayed warmer.

Mars night time temperatures are -150 degrees so a surface greenhouse would have to be heated at night or have some kind of significant heat storage, cement, or large water tank, and the walls of the greenhouse would have to be something more than just thin fabric.

What would be the best choice for the first animals on Mars? I think three hens would be the best. I think hens lay about an egg every other day so the crew could boil water in a microwave and have hard boiled eggs. One egg is enough protein for an adult a day, so that would be half the crews protein requirement. They might be able to grow some kind of chicken feed, not sure.

The other protein source would probably be soybeans mixed in a salad. The letttuce could be grown in hydroponic systems. Even so, they won't be self sustaining for a long time. They will need yearly food resupply.

A self contained shower could filter it's water and re-use it over and over again. I think you can do the same thing with urine, simply filter it and re-use it in the self contained shower system or to water the plants. Not sure how often you would have to change out the filters. Solid waste would go into mylar bags and sealed and stored until they could be disposed of outside on Mars in a pit.

A surface habitat would need 2.5 meters of sand bags on top to fully protect the crew so I think it might as well be a buried habitat. A buried habitat would be surrounded by permafrost so it's going to get cold inside. Electric heating is incredibly energy intensive. A small electric heater on high uses 1,500 watts an hour, which is way too much power to heat anything other than a small space. I was thinking of using a long loop of 1" wide thickly insulated aluminum tubing that would extend about 2' above the surface and be heated during the day by a circle of mirrors. The tubing would have a small fan in the hab that would blow habitat oxygen through it. On the surface there could be a 2' wide aluminum panel fixed to the tubing to help with heat transfer. The mirrors could be simple fiberglass panels covered with reflective mylar. The negative is that it won't provide heat at night but a benefit is that it could also be used to cool the habitat if the fan was turned on at night when the tubing would be cool.

The recycled water used on the plants would evaporate in the warm habitat so a dehumidifier would have to be operated at times to recover the moisture but still, I think water would be the biggest problem initially. Almost all of the water would be recycled but you're going to lose some of evaporated water every time you open the pressure hatch on the hab.

Almost all of the water on Mars is frozen near the poles. The habitat will be at the equator so it's way too far to drive to get water and bring it back, you would run out of oxygen. There must be some moisture in the atmosphere on Mars, would it be possible to operate a dehumidifier on the surface during the warm daytime and get water that way? I don't know if there is enough evaporated moisture in the atmosphere for it to work.

If you did find some ice on Mars it will be mixed with frozen CO2 and regolith so you would have to place it inside some kind of portable container, electrically warm it, and then the CO2 would evaporate and leave behind dirty water. You wouldn't want to do this in the rover or hab, you don't want CO2 gas in a living space.

Also, the water that you do find is probably going to be salt water. So, then you have to heat it until it turns to steam, then send it into a condenser before you get pure water. Are you going to do this in your rover just to get, what, a half a gallon of water at a time?

I just don't see gathering ice on Mars for water as being realistic unless your habitat is at the poles but then you would freeze to death. Delivering hydrogen to Mars to combine with oxygen to make water is going to be necessary. That's why you need to start with three people and keep it at three for a very long time, less is better.

Any supplies landed on Mars would have rocket fuel tanks that would have some liquid oxygen and liquid hydrogen in them. You could install a line between the two tanks and the oxygen and hydrogen gasses would combine to make water. It may not make a lot of water but if you're going to take the tanks and use them back at the base as oxygen storage containers you may as well convert the hydrogen into something useful and safe.

Another thing to consider, CO2 is heavier than oxygen so if the buried habitat has a hatch, when opened, it would allow CO2 to flow down into your access tube and displace the oxygen in your habitat. A surface depressurization area with a hatch and an a pressure door would be a better option.

Driving on Mars is going to be impossible in some places. There are just too many big rocks. Other places are pure sand so you need tall wheels to spread out the footprint, tracks would be better for heavy towed vehicles. We need to pick the right location and it has to be near the equator.

These ideas for a gas cooled reactor on Mars and for a 50-100 kw reactor are great but they don't tell you the most important thing, what's the final size of it and how much does it weigh? Most likely we're going to be using RTG's and solar panels.

Last edited by Dook (2016-10-29 10:32:27)

Dook · 2016-10-29 11:01:34

I thought the oxygen and hydrogen gas would combine to make water but it has to be burned to turn into water vapor. Maybe have a line from the oxygen and hydrogen tanks go to a very tiny internal combustion engine inside your habitat that will burn the two gasses and produce water vapor. Then the dehumidifier in the hab could turn it into water.

Once this is finished the empty tanks could be used to store oxygen gas produced by a large MOXIE unit.

Void · 2016-10-29 11:34:57

Dook,

I will try to comply with your wishes.
Water: KBD512? helped me to understand that the regolith of Mars contains about 2% to 60% water. As you intend to be near the equator, I expect we would hope for 2%. It has to be baked out, most likely you would use a focused solar energy.

The type of regolith I would try to work with would be sand dunes:
https://www.bing.com/images/search?q=sa … &FORM=IGRE

If I understand your projected scale and scope, I recommend some type of an hourglass hopper to shovel the stuff into.
https://en.wikipedia.org/wiki/Hourglass

I would hope to impinge on the flow with a hot focused solar concentration, and to suction off the vapors resulting, pumping them into a condenser bag perhaps.

Granted, the flow of granuals may be too quick so perhaps a mechanized "Bowl" or "Spoon" to hold collected granuals in the hot spot. And it would dump periodically.

Just a rough start. Maybe better could be done. Not sure dune materials hold 2% water, but I would presume they would.
If you only got the water locked into associated salts, and did not "Damage" the sand, then you might put it back and it might recharge with water over time. However dunes are big, in many cases, and there are a lot of them.

Last edited by Void (2016-10-29 12:11:29)

RobS · 2016-10-29 12:05:41

Presumably you want to choose your landing site where there is ice in the ground. There are so spots.

JoshNH4H · 2016-10-29 13:45:26

Great questions, dook.

Although the temperature of Mars is very cold, its atmosphere is very thin. This is sort of a redeeming factor from a thermal perspective because there's virtually no heat lost to convection.

Greenhouses should be made from several layers of glass or polymer with air in between. I think three layers is the right amount. This is good for two reasons:

If there's a leak in one layer, there are two additional layers of material to hold it in.
The primary source of heat loss for a greenhouse will be through radiation, and most materials absorb infrared. It turns out that with three layers to your greenhouse, cooling is a bigger issue than heating. This is a good problem to have on a cold planet!

2.5 meters of regolith might be enough for radiation shielding, but I think you would want 5 m. Assuming a density of 2500 kg/m^3, 5 meters is the amount of regolith required to generate a pressure of half an atmosphere. I believe half an atmosphere is the optimal amount of internal pressure for a habitat on Mars, at something like 35-40% oxygen (giving the same partial pressure of Oxygen as Earth) and the balance being Nitrogen and Argon at the same ratio as you find them in the martian atmosphere. This means that the hab will only have to contain pressure in two directions instead of in three. I believe the optimal way to construct buildings on Mars is as follows:

Key:

Foundation and Insulation
Insulation
Bulldozed Regolith for radiation shielding
Rounded outer tensile elements
Inner floors double as tensile support
Stacked regolith contains atmospheric pressure and provides radiation shielding

This type of building makes sense because it gets cheaper as you build it taller, and because it can be square or rectangular. Square or rectangular spaces are more useful than rounded ones. Most pressure vessels have to be rounded.

Incidentally, I was inspired in this idea by looking at some buildings in northern Iceland, on the outskirts of the city of Akureyri.

kbd512 · 2016-10-29 14:02:01

Dook wrote:

Some of you have skipped completely over the initial settlement building phase and went right to the "Total Recall" phase and called it a "first settlement". This topic may not be for you. This topic is about discussing problems of establishing a realistic first settlement on Mars using Mars Direct type launches.

I proposed a first settlement using inflatable modules embedded in the regolith using a tunnel boring machine powered by a nuclear fission reactor that be used as the settlement's power supply after completing boring operations.

Dook wrote:

The first settlement would come after exploration missions to Mars with the crews returning home. So, if there are three exploration missions to Mars there would be three Mars Habs with three RTG's, three sets of solar arrays, and three Earth Return Vehicle sites with three Long Range Rovers just sitting there. The ERV launch sites would have almost empty oxygen/hydrogen tanks that can be used to store compressed oxygen back at our Mars Base.

Ok.

Dook wrote:

I think a crew of three is best for exploration and settlement because that means they will use less oxygen, less water, less food, and less power than four would and three is enough for two to drive the Long Range Rover and bring back another LRR while one stays at the base.

Apollo style.

Dook wrote:

Problems:
Some fruit trees require a certain amount of chilling over winter (I think apple trees do) before they will produce fruit in spring but citrus trees will die if the temperature gets below freezing. I guess you would have the greenhouse area of your settlement drop down to 55 degrees for a month or so to simulate winter while the living area stayed warmer.
Mars night time temperatures are -150 degrees so a surface greenhouse would have to be heated at night or have some kind of significant heat storage, cement, or large water tank, and the walls of the greenhouse would have to be something more than just thin fabric.

Why contend with the problems you already noted with surface greenhouses? How big do you suppose the greenhouse will be?

Dook wrote:

What would be the best choice for the first animals on Mars? I think three hens would be the best. I think hens lay about an egg every other day so the crew could boil water in a microwave and have hard boiled eggs. One egg is enough protein for an adult a day, so that would be half the crews protein requirement. They might be able to grow some kind of chicken feed, not sure.

Seems like a good first choice. A chicken only requires .25 pounds of feed per day. However, there are already commercial egg and meat substitutes currently sold in stores. It's probably reasonable to assume that within the next ten years, there will be lab grown eggs, chicken, beef, shrimp, and fish that are indistinguishable from the real thing.

Dook wrote:

The other protein source would probably be soybeans mixed in a salad. The letttuce could be grown in hydroponic systems. Even so, they won't be self sustaining for a long time. They will need yearly food resupply.

Hopefully food resupply is not for more than the first several missions or so.

Dook wrote:

A self contained shower could filter it's water and re-use it over and over again. I think you can do the same thing with urine, simply filter it and re-use it in the self contained shower system or to water the plants. Not sure how often you would have to change out the filters. Solid waste would go into mylar bags and sealed and stored until they could be disposed of outside on Mars in a pit.

Feces contains a lot of water and methane. Why not use a composting pit to produce power instead of just dumping it?

Dook wrote:

A surface habitat would need 2.5 meters of sand bags on top to fully protect the crew so I think it might as well be a buried habitat. A buried habitat would be surrounded by permafrost so it's going to get cold inside. Electric heating is incredibly energy intensive. A small electric heater on high uses 1,500 watts an hour, which is way too much power to heat anything other than a small space. I was thinking of using a long loop of 1" wide thickly insulated aluminum tubing that would extend about 2' above the surface and be heated during the day by a circle of mirrors. The tubing would have a small fan in the hab that would blow habitat oxygen through it. On the surface there could be a 2' wide aluminum panel fixed to the tubing to help with heat transfer. The mirrors could be simple fiberglass panels covered with reflective mylar. The negative is that it won't provide heat at night but a benefit is that it could also be used to cool the habitat if the fan was turned on at night when the tubing would be cool.

ISS is already in a more extreme thermal environment than the one encountered on the surface of Mars, but the Martian atmosphere is a near vacuum and the same methods for thermal control that work for ISS would also work on Mars.

Dook wrote:

The recycled water used on the plants would evaporate in the warm habitat so a dehumidifier would have to be operated at times to recover the moisture but still, I think water would be the biggest problem initially. Almost all of the water would be recycled but you're going to lose some of evaporated water every time you open the pressure hatch on the hab.

True, but there's also lots of water on Mars that isn't located at the poles, in the form of glaciers buried beneath the regolith.

Dook wrote:

Almost all of the water on Mars is frozen near the poles. The habitat will be at the equator so it's way too far to drive to get water and bring it back, you would run out of oxygen. There must be some moisture in the atmosphere on Mars, would it be possible to operate a dehumidifier on the surface during the warm daytime and get water that way? I don't know if there is enough evaporated moisture in the atmosphere for it to work.

There are glaciers in the northern and southern hemispheres that are quite a ways from the poles. There's very little water vapor in the atmosphere. It's too cold and the atmospheric pressure is too low.

Dook wrote:

If you did find some ice on Mars it will be mixed with frozen CO2 and regolith so you would have to place it inside some kind of portable container, electrically warm it, and then the CO2 would evaporate and leave behind dirty water. You wouldn't want to do this in the rover or hab, you don't want CO2 gas in a living space.

CO2 would boil off before the water and if additional heat was applied, the water would also boil off at Mars sea level, which is why there's very little water vapor in the atmosphere. Mars is too cold and the pressure is too low to hold much water vapor in the atmosphere.

Dook wrote:

Also, the water that you do find is probably going to be salt water. So, then you have to heat it until it turns to steam, then send it into a condenser before you get pure water. Are you going to do this in your rover just to get, what, a half a gallon of water at a time?

You're going to obtain water using an unpressurized regolith bin (a dirt bucket with a semi-circular lid on it that forms a non-air-tight seal), outside of the rover. You're only going to apply heat. Water boils at 10C on Mars and CO2 boils at -57C because the atmospheric pressure is so low. The salts are in-solution, so evaporating the water leaves most of the salts behind and what you end up with is mostly just water condensate on the lid of the bucket.

Dook wrote:

I just don't see gathering ice on Mars for water as being realistic unless your habitat is at the poles but then you would freeze to death. Delivering hydrogen to Mars to combine with oxygen to make water is going to be necessary. That's why you need to start with three people and keep it at three for a very long time, less is better.

It's not realistic for a settlement or colony, but is entirely realistic for two to four people. It's also been experimentally proven to work, here on Earth, using Martian regolith simulants and Mars atmospheric pressures (6mb CO2) and temperatures.

Dook wrote:

Any supplies landed on Mars would have rocket fuel tanks that would have some liquid oxygen and liquid hydrogen in them. You could install a line between the two tanks and the oxygen and hydrogen gasses would combine to make water. It may not make a lot of water but if you're going to take the tanks and use them back at the base as oxygen storage containers you may as well convert the hydrogen into something useful and safe.

The only plans for transporting and using liquid hydrogen on Mars that I'm aware of involve converting it into LCH4. You could do what you stated, but there's quite a bit of water in the glaciers on Mars and enough water in the regolith to support a handful of explorers. Why not explore near a glacier if the ultimate goal is to create a colony on Mars?

Dook wrote:

Another thing to consider, CO2 is heavier than oxygen so if the buried habitat has a hatch, when opened, it would allow CO2 to flow down into your access tube and displace the oxygen in your habitat. A surface depressurization area with a hatch and an a pressure door would be a better option.

An airlock could purge the CO2 after the astronauts seal the hatch, but the quantity of CO2 trapped in an airlock at 6mb of pressure is not significant.

Dook wrote:

Driving on Mars is going to be impossible in some places. There are just too many big rocks. Other places are pure sand so you need tall wheels to spread out the footprint, tracks would be better for heavy towed vehicles. We need to pick the right location and it has to be near the equator.

Tracks are always better than wheels in off-road environments, which is what the entire surface of Mars is, and enables 28% more payload for a vehicle of the same weight here on Earth. Wheels work best on hard surfaces, like roads.

Dook wrote:

These ideas for a gas cooled reactor on Mars and for a 50-100 kw reactor are great but they don't tell you the most important thing, what's the final size of it and how much does it weigh? Most likely we're going to be using RTG's and solar panels.

A CO2 cooled reactor would be great, but not necessary for explorers.

A 100kWe reactor weighs 1200kg or less (less with current radiator technology), complete and ready to produce power. A base plate to "drill" it into 1m to 2m into the regolith would add 100kg or so and a 1t rover can slowly rotate the reactor on its baseplate to bury it.

SAFE-400 is a real physical piece of power production hardware that was manufactured with the technology available 15 years ago. The core weighed 512kg, the entire thing weighed 1200kg, and the entire reactor and radiator system (folded, not deployed) fit inside a 55 gallon drum. A 400kWe design would be a couple inches wider and still fit inside a 55 gallon drum. The power output of nuclear fission reactors doesn't scale linearly with size. A 4MWe reactor would be a couple inches wider still, but would use coolant technology (primary and secondary coolant loops) that was not part of the SAFE program.

Dook · 2016-10-29 15:24:02

Void wrote:

Dook,
I will try to comply with your wishes.
Water: KBD512? helped me to understand that the regolith of Mars contains about 2% to 60% water. As you intend to be near the equator, I expect we would hope for 2%. It has to be baked out, most likely you would use a focused solar energy.
The type of regolith I would try to work with would be sand dunes:
https://www.bing.com/images/search?q=sa … &FORM=IGRE
If I understand your projected scale and scope, I recommend some type of an hourglass hopper to shovel the stuff into.
https://en.wikipedia.org/wiki/Hourglass
I would hope to impinge on the flow with a hot focused solar concentration, and to suction off the vapors resulting, pumping them into a condenser bag perhaps.
Granted, the flow of granuals may be too quick so perhaps a mechanized "Bowl" or "Spoon" to hold collected granuals in the hot spot. And it would dump periodically.
Just a rough start. Maybe better could be done. Not sure dune materials hold 2% water, but I would presume they would.
If you only got the water locked into associated salts, and did not "Damage" the sand, then you might put it back and it might recharge with water over time. However dunes are big, in many cases, and there are a lot of them.

Zubrin went over the idea of baking water out of Mars regolith with either a heated tent or a microwave machine on wheels. He estimated that Mars regolith had about 3% water at the time but that was 20 years ago. 2 or 3 percent is almost nothing. I don't see this as being reasonable at all. Is it possible? Yes. Is it reasonable to provide water for a settlement? No.

You're going to drive around Mars in your rover with a big tent, then get out and inflate the tent that has a dehumidifier in it, set up some giant mirrors outside the tent to heat the regolith in the tent, then wait because it's going to take a while, then after a while you plug the dehumidifier into your rover power source and it makes, what, maybe a quarter cup of water?

GW Johnson · 2016-10-29 15:40:16

I'm not at all sure "Mars Direct" is the right basis for calculating what your settlement might be. Different starting assumptions yield drastically-different results. There's Mars Direct, there's what Elon Musk has recently proposed, and there is my update to the 1950's orbit-based mission.

These are quite different in detail. But, all three are valid approaches. Sorry, they just simply are valid approaches, but they do make vastly-different assumptions. Which is why they look so different in terms of outcomes. The mission (men on Mars) does NOT define the assumptions you make. I'm sorry, but that's just another little inconvenient fact of life. Get used to it.

As for chickens: given a suitable environment, chickens will lay just below 1 egg per day, up to about age 4 years. Call it 20-25 eggs per 30-day period. At least, that is what I saw with both Rhode Island Reds and Brown Leghorns. One of my Brown Leghorns survived as a pet to age 9, most did not. Average age at death was not that far beyond age 4 or 5. It varied widely, though.

Just how many real engineers are there with real experience on a farm raising chickens? Actually, I am that exception.

Given some equivalent to concrete, and some source of glass for 3-layer panes, it is very easily possible to build substantial buildings of a ""mushroom" form that should serve quite well as greenhouses, among other uses. This does require local masonry and concrete-casting on Mars.

But if you wash the perchlorates out of the regolith, and add human sewage materials for nutrients and microbes, it should be fairly easy to create real agricultural soil out of the local regolith. "Mushroom" building structures benefit from sunlight reflectors disposed outside, to double (or more) intensity. They also provide considerable radiation protection.

See "Aboveground Mars Houses", dated 1-26-13, at http://exrocketman.blogspot.com

GW

Dook · 2016-10-29 15:42:42

JoshNH4H wrote:

Great questions, dook.
Although the temperature of Mars is very cold, its atmosphere is very thin. This is sort of a redeeming factor from a thermal perspective because there's virtually no heat lost to convection.
Greenhouses should be made from several layers of glass or polymer with air in between. I think three layers is the right amount. This is good for two reasons:
If there's a leak in one layer, there are two additional layers of material to hold it in.
The primary source of heat loss for a greenhouse will be through radiation, and most materials absorb infrared. It turns out that with three layers to your greenhouse, cooling is a bigger issue than heating. This is a good problem to have on a cold planet!
2.5 meters of regolith might be enough for radiation shielding, but I think you would want 5 m. Assuming a density of 2500 kg/m^3, 5 meters is the amount of regolith required to generate a pressure of half an atmosphere. I believe half an atmosphere is the optimal amount of internal pressure for a habitat on Mars, at something like 35-40% oxygen (giving the same partial pressure of Oxygen as Earth) and the balance being Nitrogen and Argon at the same ratio as you find them in the martian atmosphere. This means that the hab will only have to contain pressure in two directions instead of in three. I believe the optimal way to construct buildings on Mars is as follows:
https://i.imgsafe.org/4fb0883408.jpg
Key:
Foundation and Insulation
Insulation
Bulldozed Regolith for radiation shielding
Rounded outer tensile elements
Inner floors double as tensile support
Stacked regolith contains atmospheric pressure and provides radiation shielding
This type of building makes sense because it gets cheaper as you build it taller, and because it can be square or rectangular. Square or rectangular spaces are more useful than rounded ones. Most pressure vessels have to be rounded.
Incidentally, I was inspired in this idea by looking at some buildings in northern Iceland, on the outskirts of the city of Akureyri.

A triple pane greenhouse sounds great. Glass is way too heavy but plastic will do. What size are you thinking of for a first greenhouse? How are you going to put the pieces together, nuts and bolts and sealant? How many Mars Direct launches to get all the pieces to Mars and what kind of scaffolding are you going to use to assemble the greenhouse?

I could be wrong but I don't think a surface greenhouse needs to be pressurized at all. Do plants need to be in a pressurized atmosphere? I don't know. They like a lot of CO2 so I think a regular Mars atmosphere would be fine, we just have to control the temperature and plant the fruit trees in plastic tubs so the water doesn't escape and then use a dehumidifier to capture evaporated water.

I may be confused about your atmosphere pressure idea. It looks like you are using the weight of the regolith on top of your habitat to produce pressure inside your habitat? The only way that would work is if the ceiling can float, move up and down, then the weight or mass of material on top would produce pressure inside your habitat. If so, the ceiling would have to be very stiff and have a giant O-ring seal around it to seal against the sidewalls of the habitat and the walls would have to stay perfectly clean. Dirt would scratch the O-ring and wear it out quickly. That isn't practical in a dusty environment like Mars. Also, if you open a door the roof falls in on you.

You don't have to do that to have a pressurized habitat. You can just open an oxygen bottle inside once it's finished and that will pressurize your hab. You would need to do that anyway to fill it with oxygen.

I don't think the habitat should have a buffer gas. If there is a sudden loss of pressure everyone falls to the floor in pain from the bends and they can't work to fix the problem. And you have to go through a procedure like divers go through every time you leave and enter the hab. Without nitrogen you don't have to do any of that.

Void · 2016-10-29 16:51:32

Dook said:

Void wrote:
Dook,
I will try to comply with your wishes.
Water: KBD512? helped me to understand that the regolith of Mars contains about 2% to 60% water. As you intend to be near the equator, I expect we would hope for 2%. It has to be baked out, most likely you would use a focused solar energy.
The type of regolith I would try to work with would be sand dunes:
https://www.bing.com/images/search?q=sa … &FORM=IGRE
If I understand your projected scale and scope, I recommend some type of an hourglass hopper to shovel the stuff into.
https://en.wikipedia.org/wiki/Hourglass
I would hope to impinge on the flow with a hot focused solar concentration, and to suction off the vapors resulting, pumping them into a condenser bag perhaps.
Granted, the flow of granuals may be too quick so perhaps a mechanized "Bowl" or "Spoon" to hold collected granuals in the hot spot. And it would dump periodically.
Just a rough start. Maybe better could be done. Not sure dune materials hold 2% water, but I would presume they would.
If you only got the water locked into associated salts, and did not "Damage" the sand, then you might put it back and it might recharge with water over time. However dunes are big, in many cases, and there are a lot of them.
Zubrin went over the idea of baking water out of Mars regolith with either a heated tent or a microwave machine on wheels. He estimated that Mars regolith had about 3% water at the time but that was 20 years ago. 2 or 3 percent is almost nothing. I don't see this as being reasonable at all. Is it possible? Yes. Is it reasonable to provide water for a settlement? No.
You're going to drive around Mars in your rover with a big tent, then get out and inflate the tent that has a dehumidifier in it, set up some giant mirrors outside the tent to heat the regolith in the tent, then wait because it's going to take a while, then after a while you plug the dehumidifier into your rover power source and it makes, what, maybe a quarter cup of water?
Offline

You appealed for help. What's wrong with you?
What a creepy response.

I worked at a research center, and I never encountered such behaviors from those people

So where are you going to get your water on the equator mister Amigdala?

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

I said dunes did not mention rovers.

Here's the deal, I am not going to put up with being mistreated. If you want help, be decent.

Yes, I already know what I am going to get back, and I don't care. Not impressed.

Last edited by Void (2016-10-29 16:52:33)

Dook · 2016-10-29 17:19:32

kbd512 wrote:

Dook wrote:
Some of you have skipped completely over the initial settlement building phase and went right to the "Total Recall" phase and called it a "first settlement". This topic may not be for you. This topic is about discussing problems of establishing a realistic first settlement on Mars using Mars Direct type launches.
I proposed a first settlement using inflatable modules embedded in the regolith using a tunnel boring machine powered by a nuclear fission reactor that be used as the settlement's power supply after completing boring operations.
Dook wrote:
The first settlement would come after exploration missions to Mars with the crews returning home. So, if there are three exploration missions to Mars there would be three Mars Habs with three RTG's, three sets of solar arrays, and three Earth Return Vehicle sites with three Long Range Rovers just sitting there. The ERV launch sites would have almost empty oxygen/hydrogen tanks that can be used to store compressed oxygen back at our Mars Base.
Ok.
Dook wrote:
I think a crew of three is best for exploration and settlement because that means they will use less oxygen, less water, less food, and less power than four would and three is enough for two to drive the Long Range Rover and bring back another LRR while one stays at the base.
Apollo style.
Dook wrote:
Problems:
Some fruit trees require a certain amount of chilling over winter (I think apple trees do) before they will produce fruit in spring but citrus trees will die if the temperature gets below freezing. I guess you would have the greenhouse area of your settlement drop down to 55 degrees for a month or so to simulate winter while the living area stayed warmer.
Mars night time temperatures are -150 degrees so a surface greenhouse would have to be heated at night or have some kind of significant heat storage, cement, or large water tank, and the walls of the greenhouse would have to be something more than just thin fabric.
Why contend with the problems you already noted with surface greenhouses? How big do you suppose the greenhouse will be?
Dook wrote:
What would be the best choice for the first animals on Mars? I think three hens would be the best. I think hens lay about an egg every other day so the crew could boil water in a microwave and have hard boiled eggs. One egg is enough protein for an adult a day, so that would be half the crews protein requirement. They might be able to grow some kind of chicken feed, not sure.
Seems like a good first choice. A chicken only requires .25 pounds of feed per day. However, there are already commercial egg and meat substitutes currently sold in stores. It's probably reasonable to assume that within the next ten years, there will be lab grown eggs, chicken, beef, shrimp, and fish that are indistinguishable from the real thing.
Dook wrote:
The other protein source would probably be soybeans mixed in a salad. The letttuce could be grown in hydroponic systems. Even so, they won't be self sustaining for a long time. They will need yearly food resupply.
Hopefully food resupply is not for more than the first several missions or so.
Dook wrote:
A self contained shower could filter it's water and re-use it over and over again. I think you can do the same thing with urine, simply filter it and re-use it in the self contained shower system or to water the plants. Not sure how often you would have to change out the filters. Solid waste would go into mylar bags and sealed and stored until they could be disposed of outside on Mars in a pit.
Feces contains a lot of water and methane. Why not use a composting pit to produce power instead of just dumping it?
Dook wrote:
A surface habitat would need 2.5 meters of sand bags on top to fully protect the crew so I think it might as well be a buried habitat. A buried habitat would be surrounded by permafrost so it's going to get cold inside. Electric heating is incredibly energy intensive. A small electric heater on high uses 1,500 watts an hour, which is way too much power to heat anything other than a small space. I was thinking of using a long loop of 1" wide thickly insulated aluminum tubing that would extend about 2' above the surface and be heated during the day by a circle of mirrors. The tubing would have a small fan in the hab that would blow habitat oxygen through it. On the surface there could be a 2' wide aluminum panel fixed to the tubing to help with heat transfer. The mirrors could be simple fiberglass panels covered with reflective mylar. The negative is that it won't provide heat at night but a benefit is that it could also be used to cool the habitat if the fan was turned on at night when the tubing would be cool.
ISS is already in a more extreme thermal environment than the one encountered on the surface of Mars, but the Martian atmosphere is a near vacuum and the same methods for thermal control that work for ISS would also work on Mars.
Dook wrote:
The recycled water used on the plants would evaporate in the warm habitat so a dehumidifier would have to be operated at times to recover the moisture but still, I think water would be the biggest problem initially. Almost all of the water would be recycled but you're going to lose some of evaporated water every time you open the pressure hatch on the hab.
True, but there's also lots of water on Mars that isn't located at the poles, in the form of glaciers buried beneath the regolith.
Dook wrote:
Almost all of the water on Mars is frozen near the poles. The habitat will be at the equator so it's way too far to drive to get water and bring it back, you would run out of oxygen. There must be some moisture in the atmosphere on Mars, would it be possible to operate a dehumidifier on the surface during the warm daytime and get water that way? I don't know if there is enough evaporated moisture in the atmosphere for it to work.
There are glaciers in the northern and southern hemispheres that are quite a ways from the poles. There's very little water vapor in the atmosphere. It's too cold and the atmospheric pressure is too low.
Dook wrote:
If you did find some ice on Mars it will be mixed with frozen CO2 and regolith so you would have to place it inside some kind of portable container, electrically warm it, and then the CO2 would evaporate and leave behind dirty water. You wouldn't want to do this in the rover or hab, you don't want CO2 gas in a living space.
CO2 would boil off before the water and if additional heat was applied, the water would also boil off at Mars sea level, which is why there's very little water vapor in the atmosphere. Mars is too cold and the pressure is too low to hold much water vapor in the atmosphere.
Dook wrote:
Also, the water that you do find is probably going to be salt water. So, then you have to heat it until it turns to steam, then send it into a condenser before you get pure water. Are you going to do this in your rover just to get, what, a half a gallon of water at a time?
You're going to obtain water using an unpressurized regolith bin (a dirt bucket with a semi-circular lid on it that forms a non-air-tight seal), outside of the rover. You're only going to apply heat. Water boils at 10C on Mars and CO2 boils at -57C because the atmospheric pressure is so low. The salts are in-solution, so evaporating the water leaves most of the salts behind and what you end up with is mostly just water condensate on the lid of the bucket.
Dook wrote:
I just don't see gathering ice on Mars for water as being realistic unless your habitat is at the poles but then you would freeze to death. Delivering hydrogen to Mars to combine with oxygen to make water is going to be necessary. That's why you need to start with three people and keep it at three for a very long time, less is better.
It's not realistic for a settlement or colony, but is entirely realistic for two to four people. It's also been experimentally proven to work, here on Earth, using Martian regolith simulants and Mars atmospheric pressures (6mb CO2) and temperatures.
Dook wrote:
Any supplies landed on Mars would have rocket fuel tanks that would have some liquid oxygen and liquid hydrogen in them. You could install a line between the two tanks and the oxygen and hydrogen gasses would combine to make water. It may not make a lot of water but if you're going to take the tanks and use them back at the base as oxygen storage containers you may as well convert the hydrogen into something useful and safe.
The only plans for transporting and using liquid hydrogen on Mars that I'm aware of involve converting it into LCH4. You could do what you stated, but there's quite a bit of water in the glaciers on Mars and enough water in the regolith to support a handful of explorers. Why not explore near a glacier if the ultimate goal is to create a colony on Mars?
Dook wrote:
Another thing to consider, CO2 is heavier than oxygen so if the buried habitat has a hatch, when opened, it would allow CO2 to flow down into your access tube and displace the oxygen in your habitat. A surface depressurization area with a hatch and an a pressure door would be a better option.
An airlock could purge the CO2 after the astronauts seal the hatch, but the quantity of CO2 trapped in an airlock at 6mb of pressure is not significant.
Dook wrote:
Driving on Mars is going to be impossible in some places. There are just too many big rocks. Other places are pure sand so you need tall wheels to spread out the footprint, tracks would be better for heavy towed vehicles. We need to pick the right location and it has to be near the equator.
Tracks are always better than wheels in off-road environments, which is what the entire surface of Mars is, and enables 28% more payload for a vehicle of the same weight here on Earth. Wheels work best on hard surfaces, like roads.
Dook wrote:
These ideas for a gas cooled reactor on Mars and for a 50-100 kw reactor are great but they don't tell you the most important thing, what's the final size of it and how much does it weigh? Most likely we're going to be using RTG's and solar panels.
A CO2 cooled reactor would be great, but not necessary for explorers.
A 100kWe reactor weighs 1200kg or less (less with current radiator technology), complete and ready to produce power. A base plate to "drill" it into 1m to 2m into the regolith would add 100kg or so and a 1t rover can slowly rotate the reactor on its baseplate to bury it.
SAFE-400 is a real physical piece of power production hardware that was manufactured with the technology available 15 years ago. The core weighed 512kg, the entire thing weighed 1200kg, and the entire reactor and radiator system (folded, not deployed) fit inside a 55 gallon drum. A 400kWe design would be a couple inches wider and still fit inside a 55 gallon drum. The power output of nuclear fission reactors doesn't scale linearly with size. A 4MWe reactor would be a couple inches wider still, but would use coolant technology (primary and secondary coolant loops) that was not part of the SAFE program.

How heavy is the tunnel boring machine? What is it's size? Is it launched all in one piece or many pieces? How heavy is the nuclear reactor and it's size? Maybe, if it's not classified, you could tell us what the weight, size, and power output of the nuclear reactors on submarines is and how much cooling water they use?

Elon Musk's Heavy Falcon will put 29,980 lbs on Mars. So, how many launches will it take for your idea to work? How are you going to support the tunnel after the boring machine goes through it, cement? An inflated hab won't hold up if the dirt over the top of it collapses.

Why contend with the problems a surface greenhouse has? Yeah, that's true. I think initially a buried habitat is fine with two levels, one for growing plants and one for living in but after some time you would want to expand. A surface greenhouse built over your buried habitat would enable you to increase the amount of fruit trees you have. I'm working on a 20'x20' pyramid greenhouse idea now. I think I can get the initial Mars Landing Habitat with Long Range Rover, all the components of the buried habitat, and two large MOXIE machines to Mars in 5 Mars Direct or Heavy Falcon launches. That would be after three exploration landings on Mars with crew return.

Lab grown chickens? That would eliminate the hassle of launching them to Mars on a rocket. They would have to go with humans so the people could force feed them and force water into them somehow. I think they're feet would have to be tied down so they don't float around their containers and cleaning up after them would be a mess. They would have to be in plastic containers with small ventilation holes.

Food resupply to Mars would be for very long time. There's just no way around it. Hydroponics works for some plants like lettuce, not so good for corn or watermelon. A good semi-dwarf fruit tree can produce over 100 fruit per tree but even so for a crew of three that's only about 2 fruit a day for two weeks. That's not nearly enough food and it's very low in protein. Some species of fruit trees produce fruit in early summer, some in late summer so you would want to have it spread out but still it won't be nearly enough until you have multiple greenhouses on Mars and multiple buried habitats. And that's just to feed three people.

Solid waste has a lot of water and methane, why not use it? I guess I just don't know enough about it. Maybe you can educate us all about it?

We can use the same methods that the ISS uses to heat and cool the habitat on Mars? We could. How are you going to power your heating/cooling system?

Is it possible to collect water from Martian regolith? Yes, a quarter cup full at a time and each time you have to go farther and farther from your base. I just don't see it as being reasonable for 2, 4, or 100 people. Seems to me the initial crew should be working on expanding the base so they can be able to grow enough food for themselves as soon as possible. You're going to have to send food and spare parts once a year anyway, why not just send hydrogen as well?

Then, after five years or so you would have five buried habitats with surface greenhouses over them and a whole flock of chickens so you wouldn't have to send food. The only thing you would send is spare parts and hydrogen but the amount of hydrogen would be big so it would last them much longer, maybe a launch every two years or so.

Why not build the habitat near a glacier? Where is there a glacier on Mars? Do the scans say how deep the ice is and the purity?

Tracks are always better in off road environments? Maybe as far as traction goes but tracks take more power to drive than wheels. I have a 2 wheel drive ATV that goes up almost anything but it steamplows in 6 inches of snow and I've never tried it in deep dry sand. I think my Long Range Rover would be okay with tall wheels that are 1 foot wide but it might be a good idea to send tracks with it that could be installed if necessary.

Last edited by Dook (2016-10-29 18:15:00)

Dook · 2016-10-29 17:36:05

The content of this post has been deleted for flaming. Please abstain from name calling in the future. If you disagree with someone, do so civilly or abstain from responding.

Thank you.

-Josh (JoshNH4H)

If you have any question I encourage you to email me.

Dook · 2016-10-29 18:10:48

GW Johnson wrote:

I'm not at all sure "Mars Direct" is the right basis for calculating what your settlement might be. Different starting assumptions yield drastically-different results. There's Mars Direct, there's what Elon Musk has recently proposed, and there is my update to the 1950's orbit-based mission.
These are quite different in detail. But, all three are valid approaches. Sorry, they just simply are valid approaches, but they do make vastly-different assumptions. Which is why they look so different in terms of outcomes. The mission (men on Mars) does NOT define the assumptions you make. I'm sorry, but that's just another little inconvenient fact of life. Get used to it.
As for chickens: given a suitable environment, chickens will lay just below 1 egg per day, up to about age 4 years. Call it 20-25 eggs per 30-day period. At least, that is what I saw with both Rhode Island Reds and Brown Leghorns. One of my Brown Leghorns survived as a pet to age 9, most did not. Average age at death was not that far beyond age 4 or 5. It varied widely, though.
Just how many real engineers are there with real experience on a farm raising chickens? Actually, I am that exception.
Given some equivalent to concrete, and some source of glass for 3-layer panes, it is very easily possible to build substantial buildings of a ""mushroom" form that should serve quite well as greenhouses, among other uses. This does require local masonry and concrete-casting on Mars.
But if you wash the perchlorates out of the regolith, and add human sewage materials for nutrients and microbes, it should be fairly easy to create real agricultural soil out of the local regolith. "Mushroom" building structures benefit from sunlight reflectors disposed outside, to double (or more) intensity. They also provide considerable radiation protection.
See "Aboveground Mars Houses", dated 1-26-13, at http://exrocketman.blogspot.com
GW

The reason for specifying a Mars Direct type mission is to make it within reason. Elon Musks idea of a single BFR that puts a million pounds on Mars is not reasonable. I don't care if people want to use Mars Direct or the Heavy Falcon, just don't use the million pounds to Mars one.

Men on Mars does not define the assumptions I made? Okay, can you elaborate?

Chickens lay about 20-25 eggs in 30 days for about 4 years? Okay, I didn't know they stopped laying at age 4 so that would mean we have to bring a rooster and hatch baby chicks on Mars every year or so. But that also means that you can slaughter a hen after it stops laying eggs to provide some fresh meat but that would only be a few hens every 4 years or so.

We might be able to manufacture concrete and glass on Mars? Enough concrete for a building would take almost all of your water to cure, most of it gets permanently trapped but a lot would be lost to the atmosphere. You would have to send a lot of wood or plastic beams to be used to build boxes to pour the concrete into. Also, I think concrete absorbs oxygen, not sure if it's only in the curing stage, think I read somewhere that the Biosphere habitat had a problem of the concrete absorbing oxygen from the atmosphere.

There's definitely sand on Mars so there is a large resource for making glass, not sure how you would separate the impurities. How are you going to power the kiln? Are you going to have your kiln outside on Mars or inside another Mars Hab that was sent to Mars?

It just seems to me that these things are for a much later time on Mars. Why attempt to make glass on Mars and use water in concrete when we can send two missions with the components for a medium sized habitat, maybe 20' x 20', and then maybe two more missions for all the components of a greenhouse the same size?

Void · 2016-10-29 19:41:51

Dook,

I apologize to you and to this board for my part in our little tiff.

I will try to be a better discussion partner in the future.

kbd512 · 2016-10-29 20:25:39

Dook wrote:

How heavy is the tunnel boring machine? What is it's size? Is it launched all in one piece or many pieces? How heavy is the nuclear reactor and it's size? Maybe, if it's not classified, you could tell us what the weight, size, and power output of the nuclear reactors on submarines is and how much cooling water they use?

A Tunnel Boring Machine (TBM) 5M in diameter and 5M in length would weigh between 20t and 30t, powered by a 400kWe fission reactor, and would be a single piece of machinery. TBM's use diesel engines and electric motors on Earth, but our TBM would use a fission reactor and electric motor.

The TBM would be raised and lowered into the hole using a tracked carrier and autonomously operated, as is already the case for some TBM's used here on Earth. It's going to be used to drill vertical holes 10M in depth, so no cranes or other pieces of equipment are required to operate the TBM. The reactor core itself is around 16" in diameter and 20" long, which is comparable in size to a propane tank used for grilling, although it's substantially heavier.

The size, weight, power output, and shielding requirements for PWR's used on submarines with lots of people in very close proximity to a reactor pumping out 100MWt to 300MWt isn't relevant to our application. SAFE-400 is not a PWR design, it uses heat pipes and flowing gas for coolant. Water is the most typical coolant for ships and submarines because ships are sitting in sea water. Compact high-output reactors typically use gases, molten salts, and liquid metals as coolants. Apart from using the same type of Uranium fissile material as US Navy PWR's, it has nothing else in common with a PWR.

Dook wrote:

Elon Musk's Heavy Falcon will put 29,980 lbs on Mars. So, how many launches will it take for your idea to work? How are you going to support the tunnel after the boring machine goes through it, cement? An inflated hab won't hold up if the dirt over the top of it collapses.

Falcon Heavy can throw 29,980 lbs on an orbital transfer trajectory that will intercept Mars, but it can't deliver that much to the surface of Mars. You have to allocate more mass for a heat shield and propellant for retro-propulsion if the payload is to make it to the surface of Mars in one piece. Using SEP for in-space propulsion, 2 Falcon Heavy launches are required.

Dook wrote:

Why contend with the problems a surface greenhouse has? Yeah, that's true. I think initially a buried habitat is fine with two levels, one for growing plants and one for living in but after some time you would want to expand. A surface greenhouse built over your buried habitat would enable you to increase the amount of fruit trees you have. I'm working on a 20'x20' pyramid greenhouse idea now. I think I can get the initial Mars Landing Habitat with Long Range Rover, all the components of the buried habitat, and two large MOXIE machines to Mars in 5 Mars Direct or Heavy Falcon launches. That would be after three exploration landings on Mars with crew return.
Lab grown chickens? That would eliminate the hassle of launching them to Mars on a rocket. They would have to go with humans so the people could force feed them and force water into them somehow. I think they're feet would have to be tied down so they don't float around their containers and cleaning up after them would be a mess. They would have to be in plastic containers with small ventilation holes.

I can't imagine astronauts, or even colonists, being willing to clean up bird poop in microgravity.

Dook wrote:

Food resupply to Mars would be for very long time. There's just no way around it. Hydroponics works for some plants like lettuce, not so good for corn or watermelon. A good semi-dwarf fruit tree can produce over 100 fruit per tree but even so for a crew of three that's only about 2 fruit a day for two weeks. That's not nearly enough food and it's very low in protein. Some species of fruit trees produce fruit in early summer, some in late summer so you would want to have it spread out but still it won't be nearly enough until you have multiple greenhouses on Mars and multiple buried habitats. And that's just to feed three people.

Mars would need food resupply at the beginning, but for a starter colony with sufficient agriculture it could be substantially less. The cost equation becomes more lopsided in favor of producing food on Mars with each additional mouth to feed and each passing day. To your point, for exploration purposes you're basically stuck with importing all the food required.

Dook wrote:

I guess I just don't know enough about it. Maybe you can educate us all about it?

Some farmers provide their own electrical power for heating and cooling by building biogas generators using composting pits (air tight plastic bins that hold grass, leaves, and feces) constructed of HDPE containers, PVC piping, and a small ICE that burns the biogas to turn a generator to produce electricity. On Mars we'd also have to produce oxygen for combustion, so efficiency would be lower.

My limited understanding of the process is that it's a lot more efficient at producing heat than electricity, but it could potentially provide heating, which would still be better than simply burying the stuff and getting nothing in return. At the very least, the plant matter and feces should be desiccated to extract the water.

Dook wrote:

We can use the same methods that the ISS uses to heat and cool the habitat on Mars? We could. How are you going to power your heating/cooling system?

ISS heating requires 1.8kWe. I can't recall electrical power requirements for the coolant pumps, but I don't believe it's as much as is required for heating.

Dook wrote:

Is it possible to collect water from Martian regolith? Yes, a quarter cup full at a time and each time you have to go farther and farther from your base. I just don't see it as being reasonable for 2, 4, or 100 people. Seems to me the initial crew should be working on expanding the base so they can be able to grow enough food for themselves as soon as possible. You're going to have to send food and spare parts once a year anyway, why not just send hydrogen as well?

How much further? Another two feet? Can't you make a donut around the base? The further you dig down, the greater the water content, according to our rovers on Mars. Reasonable for 100 people? Absolutely not. Reasonable for just 4 people? Why not let a small robotic rover collect water four times a day while you're playing with space rocks or constructing modules? If the rover is a small robot with a 100 gallon tank, who cares if it's doing donuts around the base and collecting water while you're busy building the base?

Why not LH2 storage? LH2 is incredibly difficult to store and very low density, which means giant tanks. The hydrogen embrittlement and repeated pressurization/depressurization cycles cause cracking in the storage tanks. It also requires a power hungry cryocooler that has to run reliably 24/7.

Dook wrote:

Then, after five years or so you would have five buried habitats with surface greenhouses over them and a whole flock of chickens so you wouldn't have to send food. The only thing you would send is spare parts and hydrogen but the amount of hydrogen would be big so it would last them much longer, maybe a launch every two years or so.

We'd have that work done before we allowed colonists to set foot on the planet.

Dook wrote:

Why not build the habitat near a glacier? Where is there a glacier on Mars? Do the scans say how deep the ice is and the purity?

The glaciers ring the planet, but the ice sheets are kilometers wide and tens of meters deep, more in some places like the Hellas Basin.

Dook wrote:

Tracks are always better in off road environments? Maybe as far as traction goes but tracks take more power to drive than wheels. I have a 2 wheel drive ATV that goes up almost anything but it steamplows in 6 inches of snow and I've never tried it in deep dry sand. I think my Long Range Rover would be okay with tall wheels that are 1 foot wide but it might be a good idea to send tracks with it that could be installed if necessary.

I didn't say that a wheeled vehicle can't or won't work, just that here on Earth tracked vehicles have more mobility and payload carrying capacity for a vehicle of equivalent weight. If your body is the only payload, a wheeled vehicle is more appropriate. If you're carrying a heavy payload, then the wheeled vehicle works best on hard ground. There's ample evidence of this from Viet Nam, Iraq, and Afghanistan.

The Stryker weighs 16t and is virtually immobilized in the sands of Iraq, so it's restricted to roads. Ground pressure is too high at its operating weight and wheel area in contact with the ground. The M113 weighs 12t and can go anywhere in Iraq. The volume under armor in the M113 is also greater than the Stryker. However, the M113's only cost $275K whereas the Stryker's cost $4M per vehicle, so naturally our tax money paid for the less capable and more expensive vehicles when the M113's were already available.

The M113's have 275hp diesels and the Strykers have 350hp diesels. The Strykers are faster on roads, which is great, because we can't use them off-road on soft ground. Off-road on hard ground, the maximum speed of both vehicles is equal. If you put 350hp diesels in the M113's, you'd have tracked vehicles that are just as fast on roads as the Strykers, at which point the US Army is unable to explain why they purchased light wheeled, air-mobile vehicles that don't actually fit in C-130's like the M113's do and cost more to operate.

None of that is supposition on my part. It's the US Army's own assessment from actual combat use and testing. There's very little logic to what the US Army did, but more tax dollars were taken from the tax payers and "invested" in less capable equipment than we had decades ago, so mission accomplished!

Dook · 2016-10-29 21:16:01

Void wrote:

Dook,

I apologize to you and to this board for my part in our little tiff.
I will try to be a better discussion partner in the future.

Okay, my bad too. Not sure what upset you, I wasn't trying to start an argument. I simply disagreed is all.

There are some things I'm good at, some things I don't know a damn thing about. I'm really good at efficiency, seeing the easiest way to do things, not so good at complicated math.

I think too many engineers today don't want to do things the easy way even when easy works. That's why NASA failed so bad on the 90 day report and Zubrin came up with Mars Direct and even so it's been 20 years since Mars Direct and we're still not there.

Last edited by Dook (2016-10-29 22:26:40)

Dook · 2016-10-29 22:29:06

kbd512 wrote:

Dook wrote:
How heavy is the tunnel boring machine? What is it's size? Is it launched all in one piece or many pieces? How heavy is the nuclear reactor and it's size? Maybe, if it's not classified, you could tell us what the weight, size, and power output of the nuclear reactors on submarines is and how much cooling water they use?
A Tunnel Boring Machine (TBM) 5M in diameter and 5M in length would weigh between 20t and 30t, powered by a 400kWe fission reactor, and would be a single piece of machinery. TBM's use diesel engines and electric motors on Earth, but our TBM would use a fission reactor and electric motor.
The TBM would be raised and lowered into the hole using a tracked carrier and autonomously operated, as is already the case for some TBM's used here on Earth. It's going to be used to drill vertical holes 10M in depth, so no cranes or other pieces of equipment are required to operate the TBM. The reactor core itself is around 16" in diameter and 20" long, which is comparable in size to a propane tank used for grilling, although it's substantially heavier.
The size, weight, power output, and shielding requirements for PWR's used on submarines with lots of people in very close proximity to a reactor pumping out 100MWt to 300MWt isn't relevant to our application. SAFE-400 is not a PWR design, it uses heat pipes and flowing gas for coolant. Water is the most typical coolant for ships and submarines because ships are sitting in sea water. Compact high-output reactors typically use gases, molten salts, and liquid metals as coolants. Apart from using the same type of Uranium fissile material as US Navy PWR's, it has nothing else in common with a PWR.
Dook wrote:
Elon Musk's Heavy Falcon will put 29,980 lbs on Mars. So, how many launches will it take for your idea to work? How are you going to support the tunnel after the boring machine goes through it, cement? An inflated hab won't hold up if the dirt over the top of it collapses.
Falcon Heavy can throw 29,980 lbs on an orbital transfer trajectory that will intercept Mars, but it can't deliver that much to the surface of Mars. You have to allocate more mass for a heat shield and propellant for retro-propulsion if the payload is to make it to the surface of Mars in one piece. Using SEP for in-space propulsion, 2 Falcon Heavy launches are required.
Dook wrote:
Why contend with the problems a surface greenhouse has? Yeah, that's true. I think initially a buried habitat is fine with two levels, one for growing plants and one for living in but after some time you would want to expand. A surface greenhouse built over your buried habitat would enable you to increase the amount of fruit trees you have. I'm working on a 20'x20' pyramid greenhouse idea now. I think I can get the initial Mars Landing Habitat with Long Range Rover, all the components of the buried habitat, and two large MOXIE machines to Mars in 5 Mars Direct or Heavy Falcon launches. That would be after three exploration landings on Mars with crew return.
Lab grown chickens? That would eliminate the hassle of launching them to Mars on a rocket. They would have to go with humans so the people could force feed them and force water into them somehow. I think they're feet would have to be tied down so they don't float around their containers and cleaning up after them would be a mess. They would have to be in plastic containers with small ventilation holes.
I can't imagine astronauts, or even colonists, being willing to clean up bird poop in microgravity.
Dook wrote:
Food resupply to Mars would be for very long time. There's just no way around it. Hydroponics works for some plants like lettuce, not so good for corn or watermelon. A good semi-dwarf fruit tree can produce over 100 fruit per tree but even so for a crew of three that's only about 2 fruit a day for two weeks. That's not nearly enough food and it's very low in protein. Some species of fruit trees produce fruit in early summer, some in late summer so you would want to have it spread out but still it won't be nearly enough until you have multiple greenhouses on Mars and multiple buried habitats. And that's just to feed three people.
Mars would need food resupply at the beginning, but for a starter colony with sufficient agriculture it could be substantially less. The cost equation becomes more lopsided in favor of producing food on Mars with each additional mouth to feed and each passing day. To your point, for exploration purposes you're basically stuck with importing all the food required.
Dook wrote:
I guess I just don't know enough about it. Maybe you can educate us all about it?
Some farmers provide their own electrical power for heating and cooling by building biogas generators using composting pits (air tight plastic bins that hold grass, leaves, and feces) constructed of HDPE containers, PVC piping, and a small ICE that burns the biogas to turn a generator to produce electricity. On Mars we'd also have to produce oxygen for combustion, so efficiency would be lower.
My limited understanding of the process is that it's a lot more efficient at producing heat than electricity, but it could potentially provide heating, which would still be better than simply burying the stuff and getting nothing in return. At the very least, the plant matter and feces should be desiccated to extract the water.
Dook wrote:
We can use the same methods that the ISS uses to heat and cool the habitat on Mars? We could. How are you going to power your heating/cooling system?
ISS heating requires 1.8kWe. I can't recall electrical power requirements for the coolant pumps, but I don't believe it's as much as is required for heating.
Dook wrote:
Is it possible to collect water from Martian regolith? Yes, a quarter cup full at a time and each time you have to go farther and farther from your base. I just don't see it as being reasonable for 2, 4, or 100 people. Seems to me the initial crew should be working on expanding the base so they can be able to grow enough food for themselves as soon as possible. You're going to have to send food and spare parts once a year anyway, why not just send hydrogen as well?
How much further? Another two feet? Can't you make a donut around the base? The further you dig down, the greater the water content, according to our rovers on Mars. Reasonable for 100 people? Absolutely not. Reasonable for just 4 people? Why not let a small robotic rover collect water four times a day while you're playing with space rocks or constructing modules? If the rover is a small robot with a 100 gallon tank, who cares if it's doing donuts around the base and collecting water while you're busy building the base?
Why not LH2 storage? LH2 is incredibly difficult to store and very low density, which means giant tanks. The hydrogen embrittlement and repeated pressurization/depressurization cycles cause cracking in the storage tanks. It also requires a power hungry cryocooler that has to run reliably 24/7.
Dook wrote:
Then, after five years or so you would have five buried habitats with surface greenhouses over them and a whole flock of chickens so you wouldn't have to send food. The only thing you would send is spare parts and hydrogen but the amount of hydrogen would be big so it would last them much longer, maybe a launch every two years or so.
We'd have that work done before we allowed colonists to set foot on the planet.
Dook wrote:
Why not build the habitat near a glacier? Where is there a glacier on Mars? Do the scans say how deep the ice is and the purity?
The glaciers ring the planet, but the ice sheets are kilometers wide and tens of meters deep, more in some places like the Hellas Basin.
Dook wrote:
Tracks are always better in off road environments? Maybe as far as traction goes but tracks take more power to drive than wheels. I have a 2 wheel drive ATV that goes up almost anything but it steamplows in 6 inches of snow and I've never tried it in deep dry sand. I think my Long Range Rover would be okay with tall wheels that are 1 foot wide but it might be a good idea to send tracks with it that could be installed if necessary.
I didn't say that a wheeled vehicle can't or won't work, just that here on Earth tracked vehicles have more mobility and payload carrying capacity for a vehicle of equivalent weight. If your body is the only payload, a wheeled vehicle is more appropriate. If you're carrying a heavy payload, then the wheeled vehicle works best on hard ground. There's ample evidence of this from Viet Nam, Iraq, and Afghanistan.
The Stryker weighs 16t and is virtually immobilized in the sands of Iraq, so it's restricted to roads. Ground pressure is too high at its operating weight and wheel area in contact with the ground. The M113 weighs 12t and can go anywhere in Iraq. The volume under armor in the M113 is also greater than the Stryker. However, the M113's only cost $275K whereas the Stryker's cost $4M per vehicle, so naturally our tax money paid for the less capable and more expensive vehicles when the M113's were already available.
The M113's have 275hp diesels and the Strykers have 350hp diesels. The Strykers are faster on roads, which is great, because we can't use them off-road on soft ground. Off-road on hard ground, the maximum speed of both vehicles is equal. If you put 350hp diesels in the M113's, you'd have tracked vehicles that are just as fast on roads as the Strykers, at which point the US Army is unable to explain why they purchased light wheeled, air-mobile vehicles that don't actually fit in C-130's like the M113's do and cost more to operate.
None of that is supposition on my part. It's the US Army's own assessment from actual combat use and testing. There's very little logic to what the US Army did, but more tax dollars were taken from the tax payers and "invested" in less capable equipment than we had decades ago, so mission accomplished!

If you're TBM weighs 40,000 lbs it can't go on a Heavy Falcon, so how are you going to get it to Mars?

If the TBM is already too heavy the 400k reactor would have to go on a separate launch and you're going to have to drive out in a rover and pick it up somehow and bring it to the TBM.

The tracked carrier would also have to be launched on a separate rocket. How do you move it to the TBM?

And you would need a Mars Hab that lands the crew on Mars and they can live in while they are working on the outside hab so, that is at least three Heavy Falcon launches. I don't know how you are going to get the TBM there.
Once the TBM drills down, how do you get it out?

With sufficient agriculture you don't have to import food from the Earth? Exactly, that's the problem. Everyone is skipping the details and drawing pretty pictures of what Mars will look like in 500 years and thinking it's all going to happen in their lifetime when it won't. The only way to grow enough food on Mars is to limit your population while increasing the growing space.

A compost pile can produce power? Seems to me it would have to be huge pile, also, I think the habitat should be a pure oxygen atmosphere so you wouldn't want to have something that produces methane inside. Maybe once the greenhouse is built that would be a better place for it.

The ISS requires 1.8 kwe for heating? If that's a day, that's only 75 watts an hour, that's a light bulb. If that's an hour then that is huge, that's over 43,000 watts a day. Using electricity for heating is easy if you can power it, if not you have to find some other heating source. A small home electric heater uses 1,500 watts an hour. If you run it for 15 minutes it will heat about a 16' x 16' room when the temperature is 50 degrees outside. Mars is -150 at night. Running that same small electric heater constantly would use 36,000 watts a day and you wouldn't have solar panels at night so you would be running it entirely from your RTG, which has to be the biggest RTG they make, or you have to go and get all the other RTG's left behind by the exploration teams and put them together.

Can't we just keep digging around the base to get water? Yeah, it can get you some water but we're talking about such small amounts, a few cups. I don't know if we're far enough along for a robot vehicle to do it. It would have to scoop material, pour it into it's hopper, close the lid, heat, then operate an internal dehumidifier to get the evaporated water and have it flow into an onboard water tank. I think someone would have to remote operate it, which would be possible. Hmm, don't know.

Hydrogen is difficult to store? I was thinking of storing hydrogen gas not liquid.

We would have five buried habitats and greenhouses before sending colonists to Mars? I guess your idea of colonists is different than mine is. To me, if they're building the first permanent base they should stay there. If the goal is to rotate them back to the Earth you just increased your missions to Mars because now they need a Mars Ascent Vehicle that probably docks with a larger transfer vehicle in Mars orbit.

The glaciers ring the planet? Is it mixed with salt? Something else? Frozen CO2? Certainly it's mixed with some regolith. I'm sure at some point settlers will harvest ice on Mars, I just don't know that it's something you want to do at the beginning. Expanding your base so you can grow more plants is something knowable, it's a certainty. In just one 20'x20' hab you can start a hundred small seedlings, you just need more hab or greenhouse space to plant them. But if you go out day after day searching for some ice and find it mixed with CO2, certainly it will be mixed with regolith, or mixed with salt or even something else, well, you just wasted your time that could have been spent doing something that would definitely make room on future supply missions. Looking for water is a roll of the dice. Building habs and greenhouses is a knowable benefit.

JoshNH4H · 2016-10-29 23:07:11

Hi Dook,

I would like to begin this post by reiterating my previous message that if you have any questions about my moderation you should email me. My email is my newmars username at yahoo.com.

Now, regarding the content of your post:

Dook wrote:

A triple pane greenhouse sounds great. Glass is way too heavy but plastic will do. What size are you thinking of for a first greenhouse? How are you going to put the pieces together, nuts and bolts and sealant? How many Mars Direct launches to get all the pieces to Mars and what kind of scaffolding are you going to use to assemble the greenhouse?

I suggested the following method in this post:

I wrote:

I envision that greenhouses would be constructed as follows:
Mount each glass pane on a frame element
Build the greenhouse by putting together the frames
Wrap steel rope (like you see in suspension bridges) around the frame
Increase pressure in the greenhouse up to hab pressure
I am not in the construction industry but I'm sure the Martians will be quite clever in developing ways to put greenhouses together in the most cost-effective and safe way possible.

If the greenhouse is imported, you would probably make it inflatable and constructed out of some clear polymer, perhaps with Steel, Carbon Fiber, or Kevlar ropes used for tensile bracing.

dook wrote:

I could be wrong but I don't think a surface greenhouse needs to be pressurized at all. Do plants need to be in a pressurized atmosphere? I don't know. They like a lot of CO2 so I think a regular Mars atmosphere would be fine, we just have to control the temperature and plant the fruit trees in plastic tubs so the water doesn't escape and then use a dehumidifier to capture evaporated water.

I'm not sure how pressurized the greenhouse needs to be, but the Martian atmosphere is definitely not enough pressure. Midoshi did an excellent review of atmospheres which can now be found here.

There are three primary benefits to keeping the greenhouse at the same atmospheric conditions as the rest of the habitable spaces.

The greenhouse can be the "lungs" of the settlement, filtering out Carbon Dioxide and other air contaminants to keep the colony's air breathable
Anyone working on agriculture can do so in normal clothing
I have no data to back this up, only dead reckoning, but I don't think produce response well to large changes in pressure

I may be confused about your atmosphere pressure idea. It looks like you are using the weight of the regolith on top of your habitat to produce pressure inside your habitat? The only way that would work is if the ceiling can float, move up and down, then the weight or mass of material on top would produce pressure inside your habitat. If so, the ceiling would have to be very stiff and have a giant O-ring seal around it to seal against the sidewalls of the habitat and the walls would have to stay perfectly clean. Dirt would scratch the O-ring and wear it out quickly. That isn't practical in a dusty environment like Mars. Also, if you open a door the roof falls in on you.

I do think you're misunderstanding a bit. I challenge you to draw a force diagram of the ceiling. What you'll find is that if the weight of the radiation shielding is equal to the upwards atmospheric pressure, the ceiling doesn't need to actually be able to move for this to counteract it. It's true that the roof will need to have some stiffness to it but if the radiation shielding takes the form of sandbags the pressure actually will be distributed pretty evenly across.

The goal is to reduce the number of axes in which you need to contain pressure.

Let's say the structure is designed to be able to allow depressurization from 500 mb to 400 mb, e.g. to support 10,000 N of weight per square meter of roof space. You would load the roof up to 100 mb of pressure, then release gases within the hab until the internal pressure is 100 mb. You would then add more shielding, then more gas, etc. until they balance out at 500 mb.

Perhaps each structure will have a depressurization chamber down inside the foundation. In the event of a loss of pressure, everyone would run into there and lock the door. This would protect them both from the depressurization and from the possibility of a structural collapse.

Depending how often depressurizations happen, buildings might be designed to handle the full compressive load as a safety measure. I think it's easier to design for compression than for tension.

I don't think the habitat should have a buffer gas. If there is a sudden loss of pressure everyone falls to the floor in pain from the bends and they can't work to fix the problem. And you have to go through a procedure like divers go through every time you leave and enter the hab. Without nitrogen you don't have to do any of that.

The reason why you would have a buffer gas is to increase the boiling point of water (cooking and human comfort) and to reduce the degree of fire hazard. What I take from the minimal atmospheres link (above) is that a 500 mb atmosphere with 200 mb Oxygen and the rest being various buffer gases and 5 or so mb of CO2 is safe for all people, good for plants, and fire resistant. The ratio of Argon to Nitrogen in the martian atmosphere is about 1:1, so 300 mb of buffer would only contain about 150 mb of Nitrogen. Compared to 780 mb of Nitrogen on ISS, that's a pretty mild pre-breathe.

kbd512 · 2016-10-29 23:14:57

Dook,

I looked at the yield of methane from human feces and plant waste of the kind we'd have from the crops we could grow on Mars. It won't be favorable for our purposes until we have considerably more waste to contribute to the process. However, we can still desiccate it to extract the water.

The methane content of biogas is typically only 50%-75% and methane's energy density is only .0364MJ/L.

1kg of human feces only yields about 50L of biogas
1,000kg of alfalfa waste would yield 340m^3 to 500m^3, so that's something like 3.4MWh to 5.1MWh (actual conversion efficiency is 50% or lower going from heat to electricity, with 25% being most realistic, although I suspect we'd just use it to generate heat)

Edit: Crops of cannabis sativa could potentially be fermented to produce ethanol and methane. The stalks can produce fiber for clothing. The seeds are rich in oils, protein, and fatty acids. It also grows like a weed. Sorry, I couldn't resist.

So that idea went out the window pretty fast.

Methane is actually a pretty effective greenhouse gas, far more so than CO2. Maybe that frozen rock needs more of it in the atmosphere to trap more heat. There's no EPA on Mars. Who would stop us?

Last edited by kbd512 (2016-10-29 23:41:12)

kbd512 · 2016-10-30 00:42:45

Dook wrote:

If you're TBM weighs 40,000 lbs it can't go on a Heavy Falcon, so how are you going to get it to Mars?

Falcon Heavy can deliver 53t to LEO, so a complete TBM would make it to LEO with lots of mass to spare, which is a good thing because a SEP tug and EDL hardware would be attached to it. The second launch would deliver an upper stage with 53t of extra propellant. The upper stage from the second rocket would send the TBM to Mars. The SEP tug would make trajectory corrections only. At Mars, the EDL hardware would aerobrake and land the TBM.

Dook wrote:

If the TBM is already too heavy the 400k reactor would have to go on a separate launch and you're going to have to drive out in a rover and pick it up somehow and bring it to the TBM.

It's too massive to deliver to Mars with one Falcon Heavy, not two Falcon Heavies.

Dook wrote:

The tracked carrier would also have to be launched on a separate rocket. How do you move it to the TBM?

See above.

Dook wrote:

And you would need a Mars Hab that lands the crew on Mars and they can live in while they are working on the outside hab so, that is at least three Heavy Falcon launches. I don't know how you are going to get the TBM there.
Once the TBM drills down, how do you get it out?

The boring machine is connected to the carrier. The carrier is an electrically driven platform powered by the reactor. If the carrier is moving, the boring machine is retracted.

Dook wrote:

With sufficient agriculture you don't have to import food from the Earth? Exactly, that's the problem. Everyone is skipping the details and drawing pretty pictures of what Mars will look like in 500 years and thinking it's all going to happen in their lifetime when it won't. The only way to grow enough food on Mars is to limit your population while increasing the growing space.

All I'm saying is that it's not impossible to achieve. However, more efficient grow operations are required. Google "Omega Garden". The power requirement is .38kWh and 150ft^2 of floor space per pound of food grown. It's a commercial product that anyone with the money can purchase. NASA can figure out how to use that system inside an inflatable module.

Dook wrote:

A compost pile can produce power? Seems to me it would have to be huge pile, also, I think the habitat should be a pure oxygen atmosphere so you wouldn't want to have something that produces methane inside. Maybe once the greenhouse is built that would be a better place for it.

I addressed this in a separate post, but it's a good point. It's not favorable until we're producing a serious amount of bio waste. I don't know off the top of my head how much waste plant matter our little grow operation would produce on a regular basis, so I can't say at what point it would be favorable to retain the waste to produce heat or electricity. At some point, we'd want to do that to heat our crops.

Dook wrote:

The ISS requires 1.8 kwe for heating? If that's a day, that's only 75 watts an hour, that's a light bulb. If that's an hour then that is huge, that's over 43,000 watts a day. Using electricity for heating is easy if you can power it, if not you have to find some other heating source. A small home electric heater uses 1,500 watts an hour. If you run it for 15 minutes it will heat about a 16' x 16' room when the temperature is 50 degrees outside. Mars is -150 at night. Running that same small electric heater constantly would use 36,000 watts a day and you wouldn't have solar panels at night so you would be running it entirely from your RTG, which has to be the biggest RTG they make, or you have to go and get all the other RTG's left behind by the exploration teams and put them together.

ISS requires 1.8kWe to heat the station. Yes, that's a lot of juice. Solar panels and RTG's won't cut it on the surface of Mars. A Mars base has power requirements so high only a fission reactor is a feasible solution.

The only mechanical moving parts of SAFE-400 are the control drums, the hinges on the radiator panels, and the electric generators driven by the hot flowing gas. There are no control rods or coolant pumps.

Dook wrote:

Can't we just keep digging around the base to get water? Yeah, it can get you some water but we're talking about such small amounts, a few cups. I don't know if we're far enough along for a robot vehicle to do it. It would have to scoop material, pour it into it's hopper, close the lid, heat, then operate an internal dehumidifier to get the evaporated water and have it flow into an onboard water tank. I think someone would have to remote operate it, which would be possible. Hmm, don't know.

You have to import water from Earth or make water on Mars. Between the two, given the cost of importing things from Earth, I'd rather make water and oxygen on Mars.

Dook wrote:

Hydrogen is difficult to store? I was thinking of storing hydrogen gas not liquid.

Hydrogen gas tanks are typically high pressure and typically leak a little. It's not a safety thing, it's an engineering and money thing.

Dook wrote:

We would have five buried habitats and greenhouses before sending colonists to Mars? I guess your idea of colonists is different than mine is. To me, if they're building the first permanent base they should stay there. If the goal is to rotate them back to the Earth you just increased your missions to Mars because now they need a Mars Ascent Vehicle that probably docks with a larger transfer vehicle in Mars orbit.

I want to use a robotic TBM to dig holes. I want another robot to emplace and inflate the modules. Then I want yet another robot to connect the cabling and pressure test the modules. Then and only then do I want to send a commissioning crew to outfit the modules and start operations. If at all possible, I'd like to have water in the water processor module before the commissioning crew lands. I'm not asking for much, am I?

Anyway, that's two years to robotically dig seven 5M x 10M holes, position, connect, and test the modules.

Dook wrote:

The glaciers ring the planet? Is it mixed with salt? Something else? Frozen CO2? Certainly it's mixed with some regolith. I'm sure at some point settlers will harvest ice on Mars, I just don't know that it's something you want to do at the beginning. Expanding your base so you can grow more plants is something knowable, it's a certainty. In just one 20'x20' hab you can start a hundred small seedlings, you just need more hab or greenhouse space to plant them. But if you go out day after day searching for some ice and find it mixed with CO2, certainly it will be mixed with regolith, or mixed with salt or even something else, well, you just wasted your time that could have been spent doing something that would definitely make room on future supply missions. Looking for water is a roll of the dice. Building habs and greenhouses is a knowable benefit.

All the water sampled on the planet contains some salts. Again, it's not a major problem. If you evaporate sea water, you get sea salt crystals, right? We need water and oxygen from Mars because we can't import all of what we require from Earth. If we can't make our own oxygen and water, we should not colonize Mars because the planet doesn't have the resources required to support human life.

elderflower · 2016-10-30 02:55:08

A TBM normally inserts a segmented tunnel liner as to moves forward. This is then grouted in place behind the machine face. This prevents tunnel wall collapse, which may happen in vertical bores as well as horizontal ones. TBMs also have a large spoil disposal arrangement behind them. You need a solution to these issues.

louis · 2016-10-30 05:58:18

The first settlement would come after exploration missions to Mars with the crews returning home. So, if there are three exploration missions to Mars there would be three Mars Habs with three RTG's, three sets of solar arrays, and three Earth Return Vehicle sites with three Long Range Rovers just sitting there. The ERV launch sites would have almost empty oxygen/hydrogen tanks that can be used to store compressed oxygen back at our Mars Base.

I don't see why you can't have continuous and expanding settlement. So crews overlap. I don't see either why you would have three separate sites. I think we would know enough about a target site before humans arrive to concentrate all our efforts there.

Use of RTGs rather than solar panels is a matter of preference in my view.

I think a crew of three is best for exploration and settlement because that means they will use less oxygen, less water, less food, and less power than four would and three is enough for two to drive the Long Range Rover and bring back another LRR while one stays at the base.

I like to develop mission structure on crews of 3. Although I would double up the two crews - so you have teams of 6 compromised of two crews.

Some fruit trees require a certain amount of chilling over winter (I think apple trees do) before they will produce fruit in spring but citrus trees will die if the temperature gets below freezing. I guess you would have the greenhouse area of your settlement drop down to 55 degrees for a month or so to simulate winter while the living area stayed warmer.

Mars night time temperatures are -150 degrees so a surface greenhouse would have to be heated at night or have some kind of significant heat storage, cement, or large water tank, and the walls of the greenhouse would have to be something more than just thin fabric.

Crop growing can be done in perfect conditions in indoor farms under artificial light and with temperature control. These problems you are referring to are self-inflicted.

What would be the best choice for the first animals on Mars? I think three hens would be the best. I think hens lay about an egg every other day so the crew could boil water in a microwave and have hard boiled eggs. One egg is enough protein for an adult a day, so that would be half the crews protein requirement. They might be able to grow some kind of chicken feed, not sure.

Chickens are ideal on Earth but I am not so sure about on Mars - they put a lot of pollution in the air system and their diseases can easily spread to humans. I think guinea pigs - the large types that are eaten in South America may be a better choice. But I think animal husbandry is something that needs to come in at a much later stage. I think we don't have enough labour time available in the early stages to devote to raise animals for eating. Meat can easily be imported from Earth to supplement the food grown on Mars. Also, we might look at more innovative protein sources like earth worms that might be raised automatically.

The other protein source would probably be soybeans mixed in a salad. The letttuce could be grown in hydroponic systems. Even so, they won't be self sustaining for a long time. They will need yearly food resupply.

A self contained shower could filter it's water and re-use it over and over again. I think you can do the same thing with urine, simply filter it and re-use it in the self contained shower system or to water the plants. Not sure how often you would have to change out the filters. Solid waste would go into mylar bags and sealed and stored until they could be disposed of outside on Mars in a pit.

Human faeces could be used to manufacture compost. Why not continue using wet wipes as in space, at least for the first few missions? The focus of the first few missons needs to be on health monitoring, developing ISRU and construction. Can we justify the water storage and filtering requirements at that early stage?

A surface habitat would need 2.5 meters of sand bags on top to fully protect the crew so I think it might as well be a buried habitat. A buried habitat would be surrounded by permafrost so it's going to get cold inside. Electric heating is incredibly energy intensive. A small electric heater on high uses 1,500 watts an hour, which is way too much power to heat anything other than a small space. I was thinking of using a long loop of 1" wide thickly insulated aluminum tubing that would extend about 2' above the surface and be heated during the day by a circle of mirrors. The tubing would have a small fan in the hab that would blow habitat oxygen through it. On the surface there could be a 2' wide aluminum panel fixed to the tubing to help with heat transfer. The mirrors could be simple fiberglass panels covered with reflective mylar. The negative is that it won't provide heat at night but a benefit is that it could also be used to cool the habitat if the fan was turned on at night when the tubing would be cool.

Some good ideas there I think. For the earliest missions, I imagine we will be looking to inflatable habs. Maybe then we will move to burying habs in the ground and topping with sand bags like you say. I hope from an early stage we start building complete ISRU pressurised spaces. Initially these will probably be used for storage, and crop growing.

The recycled water used on the plants would evaporate in the warm habitat so a dehumidifier would have to be operated at times to recover the moisture but still, I think water would be the biggest problem initially. Almost all of the water would be recycled but you're going to lose some of evaporated water every time you open the pressure hatch on the hab.

Your comments seem to be premised on the idea we aren't goingto be able to access large quanities of water. I think the reverse. There is plenty of evidence of water presence on Mars. An upper figure for drinking water would be about 3 kgs a day - so for a 10 person base that would be 30 kgs a day or about 11 tonnes a year. Maybe quadruple that figure for food use (hydrating dried food, cooking etc), hygiene, ISRU activities and agriculture. Let's make it a round 50 tonnes. If we can locate a glacier a 10 person colony should be able to mine that much in a couple of days.

Almost all of the water on Mars is frozen near the poles. The habitat will be at the equator so it's way too far to drive to get water and bring it back, you would run out of oxygen. There must be some moisture in the atmosphere on Mars, would it be possible to operate a dehumidifier on the surface during the warm daytime and get water that way? I don't know if there is enough evaporated moisture in the atmosphere for it to work.

Yes, it should be possible. Much less effective than on earth of course.

If you did find some ice on Mars it will be mixed with frozen CO2 and regolith so you would have to place it inside some kind of portable container, electrically warm it, and then the CO2 would evaporate and leave behind dirty water. You wouldn't want to do this in the rover or hab, you don't want CO2 gas in a living space.

But OK in a farm hab?

Also, the water that you do find is probably going to be salt water. So, then you have to heat it until it turns to steam, then send it into a condenser before you get pure water. Are you going to do this in your rover just to get, what, a half a gallon of water at a time?

No you have a central unit to do all that.

I just don't see gathering ice on Mars for water as being realistic unless your habitat is at the poles but then you would freeze to death. Delivering hydrogen to Mars to combine with oxygen to make water is going to be necessary. That's why you need to start with three people and keep it at three for a very long time, less is better.

Any supplies landed on Mars would have rocket fuel tanks that would have some liquid oxygen and liquid hydrogen in them. You could install a line between the two tanks and the oxygen and hydrogen gasses would combine to make water. It may not make a lot of water but if you're going to take the tanks and use them back at the base as oxygen storage containers you may as well convert the hydrogen into something useful and safe.

No I don't accept that need at all. If you really can't locate water resources on Mars you aren't doing the job properly.

Another thing to consider, CO2 is heavier than oxygen so if the buried habitat has a hatch, when opened, it would allow CO2 to flow down into your access tube and displace the oxygen in your habitat. A surface depressurization area with a hatch and an a pressure door would be a better option.

Surely you must have an air lock for all hab exit points?

Driving on Mars is going to be impossible in some places. There are just too many big rocks. Other places are pure sand so you need tall wheels to spread out the footprint, tracks would be better for heavy towed vehicles. We need to pick the right location and it has to be near the equator.

Agreed, but this should be a relatively easy one to deal with. We have after all landed several working rovers in the right place. What I would say is that we should probably send automated rovers working on simple software to clear boulders from the landing zone over a couple of years.

These ideas for a gas cooled reactor on Mars and for a 50-100 kw reactor are great but they don't tell you the most important thing, what's the final size of it and how much does it weigh? Most likely we're going to be using RTG's and solar panels.

When doing your final calculations don't assume your PV panels on Mars have to be like PV panels on houses on Earth i.e. heavy and built into support structures. The Weather on Mars is benign . I think we will be able to roll out ultra-light PV panels direct on rock surfaces (although the very first panel systems may be more conventional). Also don't factor in sun tracking mechanisms or anything like that.

When talking about RTGs please explain whether they are going with the crew in the human ITS. If so, is it going to be activated on the Mars surface? If so you have a "power gap" that may need meeting.

I think we should also send to Mars purpose built small scale steam engines with electric power generators attached. We can then build solar reflectors on Mars to heat the water in the engines.

Once small scale ISRU industrialisation is under way on Mars we can start using 3D printers to make the parts for the steam engine. I am also wondering whether the boiler itself could be constructed simply out of the regolith i.e. make a volume space in the ground and tile with basalt. That would minimise the need for steel construction.

SpaceNut · 2016-10-30 09:20:27

It looks to me that the first mission needs a manifest list of items with mass for each and a payload to surface match of listed items to what we want to preload at the landing site in the cargo landers.

Once we have that we can think about what will launch these to mars.

This does assume that the outward bound crew only takes with them the bare minimum and that a seperate return vehicle contains the rest for safe return after a mission is complete.

Dook · 2016-10-30 09:48:53

JoshNH4H wrote:

Hi Dook,
I would like to begin this post by reiterating my previous message that if you have any questions about my moderation you should email me. My email is my newmars username at yahoo.com.
Now, regarding the content of your post:
Dook wrote:
A triple pane greenhouse sounds great. Glass is way too heavy but plastic will do. What size are you thinking of for a first greenhouse? How are you going to put the pieces together, nuts and bolts and sealant? How many Mars Direct launches to get all the pieces to Mars and what kind of scaffolding are you going to use to assemble the greenhouse?
I suggested the following method in this post:
I wrote:
I envision that greenhouses would be constructed as follows:
Mount each glass pane on a frame element
Build the greenhouse by putting together the frames
Wrap steel rope (like you see in suspension bridges) around the frame
Increase pressure in the greenhouse up to hab pressure
I am not in the construction industry but I'm sure the Martians will be quite clever in developing ways to put greenhouses together in the most cost-effective and safe way possible.
If the greenhouse is imported, you would probably make it inflatable and constructed out of some clear polymer, perhaps with Steel, Carbon Fiber, or Kevlar ropes used for tensile bracing.
dook wrote:
I could be wrong but I don't think a surface greenhouse needs to be pressurized at all. Do plants need to be in a pressurized atmosphere? I don't know. They like a lot of CO2 so I think a regular Mars atmosphere would be fine, we just have to control the temperature and plant the fruit trees in plastic tubs so the water doesn't escape and then use a dehumidifier to capture evaporated water.
I'm not sure how pressurized the greenhouse needs to be, but the Martian atmosphere is definitely not enough pressure. Midoshi did an excellent review of atmospheres which can now be found here.
There are three primary benefits to keeping the greenhouse at the same atmospheric conditions as the rest of the habitable spaces.
The greenhouse can be the "lungs" of the settlement, filtering out Carbon Dioxide and other air contaminants to keep the colony's air breathable
Anyone working on agriculture can do so in normal clothing
I have no data to back this up, only dead reckoning, but I don't think produce response well to large changes in pressure
I may be confused about your atmosphere pressure idea. It looks like you are using the weight of the regolith on top of your habitat to produce pressure inside your habitat? The only way that would work is if the ceiling can float, move up and down, then the weight or mass of material on top would produce pressure inside your habitat. If so, the ceiling would have to be very stiff and have a giant O-ring seal around it to seal against the sidewalls of the habitat and the walls would have to stay perfectly clean. Dirt would scratch the O-ring and wear it out quickly. That isn't practical in a dusty environment like Mars. Also, if you open a door the roof falls in on you.
I do think you're misunderstanding a bit. I challenge you to draw a force diagram of the ceiling. What you'll find is that if the weight of the radiation shielding is equal to the upwards atmospheric pressure, the ceiling doesn't need to actually be able to move for this to counteract it. It's true that the roof will need to have some stiffness to it but if the radiation shielding takes the form of sandbags the pressure actually will be distributed pretty evenly across.
The goal is to reduce the number of axes in which you need to contain pressure.
Let's say the structure is designed to be able to allow depressurization from 500 mb to 400 mb, e.g. to support 10,000 N of weight per square meter of roof space. You would load the roof up to 100 mb of pressure, then release gases within the hab until the internal pressure is 100 mb. You would then add more shielding, then more gas, etc. until they balance out at 500 mb.
Perhaps each structure will have a depressurization chamber down inside the foundation. In the event of a loss of pressure, everyone would run into there and lock the door. This would protect them both from the depressurization and from the possibility of a structural collapse.
Depending how often depressurizations happen, buildings might be designed to handle the full compressive load as a safety measure. I think it's easier to design for compression than for tension.
I don't think the habitat should have a buffer gas. If there is a sudden loss of pressure everyone falls to the floor in pain from the bends and they can't work to fix the problem. And you have to go through a procedure like divers go through every time you leave and enter the hab. Without nitrogen you don't have to do any of that.
The reason why you would have a buffer gas is to increase the boiling point of water (cooking and human comfort) and to reduce the degree of fire hazard. What I take from the minimal atmospheres link (above) is that a 500 mb atmosphere with 200 mb Oxygen and the rest being various buffer gases and 5 or so mb of CO2 is safe for all people, good for plants, and fire resistant. The ratio of Argon to Nitrogen in the martian atmosphere is about 1:1, so 300 mb of buffer would only contain about 150 mb of Nitrogen. Compared to 780 mb of Nitrogen on ISS, that's a pretty mild pre-breathe.

I don't have any questions about your moderating. You're doing your job.

Glass for a greenhouse is too heavy and it's too fragile, the panes might break from the vibration of launch.

I had planned on having the greenhouse have a Mars atmosphere, meaning, no pressure, but I had forgotten that the lower pressure would cause water to evaporate and at a lower temperature, 50 degrees F. So, the greenhouses have to be pressurized to have liquid water.

An inflatable heated greenhouse would work. I don't really like the idea because anything inflatable is just not going to last as long as something built out of more sturdy material. I think it would have to have three separate inflatable sections to hold in heat, one inside the other, and gas is going to leak through the material so it will need to be filled at times. Also, the material won't be completely transparent unless it's clear plastic material but that wouldn't be durable at all.

The greenhouse plants can change CO2 into oxygen? Yes, but we're talking at extremely low rates. A giant tree on the earth produces something like only 8 cu in of oxygen a day. A semi-dwarf fruit tree would be a fraction of that.

The buried habitats pressure is perfectly balanced by the mass of the regolith on top? Okay, got it, makes sense.

If the buried habitat's atmosphere has a buffer gas, nitrogen, then having an internal depressurization chamber would probably be a necessity, otherwise, any sudden pressure loss equals a painful death for everyone.

The buffer gas reduces the fire hazard? It does. What would the percent of nitrogen be in the habitat atmosphere and what would the procedure be for leaving the hab and going out on Mars? Is there a decompression procedure before going outside the hab?

Dook · 2016-10-30 09:54:55

kbd512 wrote:

Dook,
I looked at the yield of methane from human feces and plant waste of the kind we'd have from the crops we could grow on Mars. It won't be favorable for our purposes until we have considerably more waste to contribute to the process. However, we can still desiccate it to extract the water.
The methane content of biogas is typically only 50%-75% and methane's energy density is only .0364MJ/L.
1kg of human feces only yields about 50L of biogas
1,000kg of alfalfa waste would yield 340m^3 to 500m^3, so that's something like 3.4MWh to 5.1MWh (actual conversion efficiency is 50% or lower going from heat to electricity, with 25% being most realistic, although I suspect we'd just use it to generate heat)
Edit: Crops of cannabis sativa could potentially be fermented to produce ethanol and methane. The stalks can produce fiber for clothing. The seeds are rich in oils, protein, and fatty acids. It also grows like a weed. Sorry, I couldn't resist.
So that idea went out the window pretty fast.
Methane is actually a pretty effective greenhouse gas, far more so than CO2. Maybe that frozen rock needs more of it in the atmosphere to trap more heat. There's no EPA on Mars. Who would stop us?

So you heat the solid waste to evaporate the water then capture the water with a dehumidifier. Yeah, that would work but it produces methane. I may have to change my idea of having a pure oxygen atmosphere in the habitat to one with a nitrogen buffer gas. There's going to be some amount of methane in the hab always anyway.

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