Problems For A Realistic First Settlement On Mars

RobertDyck · 2016-10-30 10:14:15

Dook, I've took a serious look at the greenhouses. For transport form Earth, you would use plastic film of a material called PolyChloroTriFluoroEthylene (PCTFE). It's sold by Honeywell under two brand names: Aclar is used as a thin layer with less expensive plastic film for blister packs for pills (pharmaceuticals). Clarus is sold to the military and aerospace industry. A Japanese company sells it under the brand name Neoflon, but they use that name for all fluoropolymers, so you have to ask for Neoflon PCTFE.

This material is stable from +132°C to -240°C. That's 100°C colder than the Mars south pole in southern winter. And this material is highly impermeable to oxygen and nitrogen, and the most impermeable to water of any polymer ever invented. It's highly resistant to UV, and highly transparent. A bit expensive, but anything launched to Mars will be. Strength of this material can be increased by thermally bonding a shim of fibreglass. That means fibreglass cloth with as loose a weave as gauze. "Thermally bonded" means it's heated to melt into the polymer film. The fibreglass shim will add strength, and act as rip-stop. It would as clear as looking through a window that has a screen for insects. Fibreglass is transparent while screens on Earth are metal, new ones made of nylon, so the fibreglass shim would be slightly more transparent.

An inflatable greenhouse would have the same coating that NASA currently uses to block UV, and control IR (radiant heat). That is vacuum deposited layers of gold, nickel, and silver oxide. Only silver is an oxide. Silver oxide reflects IR; here on Earth "Heat Mirror" or "low-e" windows use silver oxide. This metal clogs the pores in polymer film, so not only is PCTFE highly impermeable, but the metal coating will make it even more impermeable. The greenhouse would be built with 2 layers, not 3. The gap between the layers would be filled with argon gas. Argon is less heat conductive than air, and it's large molecule makes it more difficult to get through polymer film. Mars atmosphere is 1.6% argon, as measured by Viking 2 lander, so it can be produced locally.

PCTFE is a light-weight film, so any greenhouse sent from Earth would be made of that. However, making stuff on Mars will not have all the industry Earth now has. It will be a lot easier to make glass on Mars. Just normal conventional glass.

Dook · 2016-10-30 11:03:47

kbd512 wrote:

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.

The TBM just seems like it's too heavy. Too heavy to launch and too heavy to move around Mars. I think the TBM's are better at going through solid rock than loose dirt. And whatever tunnel you dig would have to be supported by one foot thick cement before you could live in it, an inflatable won't hold back loose regolith.

I saw the Omega Garden. It's hydroponics, which is great for some plants like lettuce but it's not going to grow corn or any melon plant, or fruit trees, or any bush. The problem of growing enough food on Mars comes down to water and space. Inflatable greenhouses will work fine for at first but the inflatable material is going to wear out from the extreme temperature changes. Also the inflatable will require a heat source to keep the plants from freezing and the pressure will leak out through the material so you will have to pump them up from time to time. It just seems like a buried greenhouse is the way to go but it's not easy to build and not easily expanded. I think we need an excavator.

The compost pile works in a greenhouse, it would produce some heat and after a while it would be good fertilizer. I'm not sure but I think I read somewhere that using human waste as fertilizer is too strong so you might only use a little bit of it in your compost pile.

A Mars Base will have high power requirements? If the engineers can't keep it simple it will. The landed Mars Habitat that lands the settlers will have solar cells on it's roof, it will have an RTG, and it should have another set of solar panels (should be eight) that can be set outside. The crew can use the Long Range Rover to drive over to the three previous exploration landing sites and bring back the RTG's and external solar arrays. If the three exploration landing sites each have a 300 watt RTG and eight solar panels (1000 w total) that would be a small base of four RTG's, four sets of eight solar arrays. That's 5,200 watts an hour in the day and 1,200 watts at night. The night time watts is on the low side but that's when the crew is sleeping so it's workable. You could maybe add in a bank of batteries that would help the night time power if you had to. I'm not sure how long the RTG's last, the small ones last 30 years or so, think the larger ones last something like 5-10 yrs.

You don't have to import water from the Earth to make water on Mars. You just have to import hydrogen and then burn it with the oxygen you've made on Mars (made with a large MOXIE unit) to produce water vapor that would then have to be made back into water with a dehumidifier. So, you'd need some kind of small machine that would take in the oxygen and hydrogen gas, burn it in a small burner (this machine could be designed to produce some power) then expel the water vapor into another chamber where a small dehumidifier takes in the vapor and makes it water.

Using robots to build your base before colonization? That's way in the future. We're not to the point where we can do that yet.

We can't import all the oxygen and water we need on Mars from the Earth? We can't if you overload Mars with too many people from the get go. The object is to be completely self sufficient but that's not going to happen for 100 years so, you do what you are most sure of first, we know how to grow plants and raise chickens.

Dook · 2016-10-30 13:05:45

louis 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.
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.

You don't see why we can't have continuous settlement? Okay, let me see the launch schedule you have planned to supply all these settlements with oxygen, water, food, and spare parts. At a minimum (just 3 settlers) each settlement is going to need one supply shipment a year of food, hydrogen (for water), and chicken feed, and if it fails the settlers die, and they die because someone was in a hurry.

The very first settlers will have to go out and get the RTG's and solar panels from the previous exploration missions just to have enough electricity to power their settlement so what are the next settlements going to use for power? Let me see the launch schedule, and make sure you are using something reasonable like Mars Direct or Heavy Falcons, not the 1 million pounds to Mars rocket idea.

RTG's are better than solar panels? I think the big RTG's last 10 years or so. So, if your settlement only has RTG's then they will need to be resupplied with them every 8 years. So, not only do your settlements need food, water, and spare parts shipments but they also need shipments of RTG's.

Crops can be grown indoors? They can, show me your FIRST settlement idea, not some 500 years in the future idea that looks like something out of the movie Total Recall. What kind of habitat? Buried? Surface? Made of what material? How many launches does it take to establish? Where do they get their oxygen from? How do the settlers move around Mars? How are you going to warm your habitat? With what power source?

Raising chickens should come later? There's really nothing to it. They would be in cages. You check their food and water once a day, collect the eggs, and pull out the plastic sheet under their cages and clean it then use a small amount of it as fertilizer for your plants. It would take one person about 10 minutes.

Guinea pigs would be better than chickens? Hens lay eggs constantly, almost one a day. One egg is half a days protein for an adult so for a crew of 3, three hens and one rooster would be fine. You would have a 4 year supply of protein. With Guinea's you'd have to let them reproduce then slaughter them. I don't know how many you would have in your habitat, maybe two pairs, and then slaughter once a year or so. Plus the Guinea's are bigger and heavier for launch and would require more food, water, and produce more waste on the trip to Mars. I just think that chickens are the better option.

Meat can easily be imported from Earth? So, you're idea is constant launches of settlers with constant resupplies to each settlement of food, water, oxygen, spare parts. I really want to see this launch schedule you have planned.

Human solid waste can be compost? It can.

Why not use wet wipes instead of having showers? You could. It's not pleasant. The crew is going to probably be using wipes on the trip over to Mars so having a shower on Mars would be nice to have. The thing is this, the water in the shower is entirely recycled. All of it. Not a drop is wasted. It gets filtered and re-used, you just have to change out filters once in a while. Any water that evaporates is collected by a habitat dehumidifier. So why not have a shower?

The focus of the first few (settlers) missions needs to be on health monitoring, developing ISRU, and construction? Uhh, health monitoring??? So people are going to sit around and check their blood pressure and do blood tests? I don't think so.

Developing ISRU? How are you going to do that? You're saying their are going to build their own MOXIE unit and solar panels? Not going to happen on Mars for another 200 years or more. The large MOXIE units have to already be on Mars before settlers arrive and you're going to need at least two for each settlement.

Construction? Yes, they will build but not from scratch. They will assemble habitats from components sent from the Earth.

The earliest habs will be inflatable? Yeah, they will work but you're going to land in some kind of Mars Lander, right? So, why would you leave that lander for an inflatable habitat? You wouldn't. The only good thing the inflatable habitat provides is space to grow plants and a second habitat in case something goes wrong with the lander.

I don't think we will be able to access large quantities of water? Well, I don't think we will be able to access large quantities of clean ice. We'll find ice, we'll probably find a lot of it at the poles but our habitats are going to be at the equator so how do get that far? My Long Range Rover will go a very long ways but it won't go 1,000 miles, you'll run out of oxygen. How do you gather the ice (it's probably going to be harder than Earth ice), separate the frozen CO2 from it, and then separate whatever else is in it, and then warm it to vent the CO2 out, and all this has to happen outside of your rover or habitat otherwise you're bringing CO2 inside a living space.

We can bring the ice to the greenhouse and warm it there? That will work. So you're going to drive out in your rover with a towed cart full of plastic containers, fill the containers with blocks of dirty ice, then drive back to your greenhouse and bring the containers inside to melt the ice? The regolith would settle to the bottom. If it's salt water then we have to steam it and dehumidify it.

The temperature at the equator gets to 78 degrees in the daytime so there isn't going to be any ice near the surface. You're going to have to dig down or drive down into some canyon and dig into the side of it and hope there isn't a rock slide. I just don't see this as being very practical unless we find a small wide canyon, 20 feet deep or so, with ice in the walls.

We would have a central unit to heat the ice so we just need to move regolith? You're talking about industrial scale water collecting to supply an overloaded population. You're going to put in a tremendous amount of work to get a tiny amount of water. Can you do it? Yes. If your water extraction machine breaks, everyone dies, and they die because you were in a hurry.

Most of the settlement water will be recycled, probably 80-90%. The only water lost would be to evaporated moisture that escapes every time someone leaves the habitat. So, you don't really need that much. You can easily supply one small settlement with hydrogen once a year. You can't supply many large settlements with enough hydrogen, and food, and spare parts, and why would you attempt it anyway? What good reason is there to be in a hurry?

The hab would have an airlock? That's what I said, every time you open your air lock there will be some exchange of outside CO2 and inside oxygen. Can you pump out most of the air in your airlock before opening the door? Yes, you can. And, when you are leaving the surface and going in to the airlock, closing the door, you could also pump out the CO2 and then fill your airlock with hab air to minimize it.

We have rovers that travel on Mars? One of the rovers has a stuck wheel that is plowing in the sand. I think they are actually driving it backwards to minimize the effect the stuck wheel has. If your large rover gets stuck you're in serious trouble. If there is a second large rover back at the base then the third crewman could drive out and rescue the stranded crew and hopefully pull out the first stuck rover. If the team hasn't gotten to the second rover yet, they're dead, game over. Some areas of Mars are covered in 2 foot rocks, there's just no way. Other areas are pure sand. We just can't go into some areas of Mars.

We should send automated rovers to Mars to clear rocks? An ATV sized machine might be able to do it while being controlled from the Mars Hab. It would have to have a battery pack and a small RTG built in that would enable it to stay out in the field. The small RTG built in wouldn't be enough to operate the unit for more than about an hour a day, the rest of the time it would be recharging it's batteries. If it had solar cells as well they would help a bit. I'm not sure it's an effective use of time unless it's absolutely necessary, if we can't go around the rocky areas then we might have to do something like that.

I know the solar panels on Mars will be lighter than Earth panels. They wouldn't have the heavy glass over them, they are just the solar cells mounted on fiberglass or the thin rollout ones.

I thought an RTG was included in the Mars Direct ideas. I just checked and the Mars Hab was to be entirely powered by solar cells (5,000 watts worth). The Earth Return Vehicle sites have RTG's (80 kw). So, any settlement can go get the solar arrays and RTG's left behind by the first explorers.

Is the RTG going to be activated on Mars? I assumed it would be active on launch and provide power to the spacecraft as it's on it's way to Mars but I'm not entirely sure. I don't know if the RTG's have a switch or how they are activated.

We should use steam generators on Mars heated by Mars built reflectors? But you just said that we can make power on Mars with lightweight solar arrays? Why try to build reflectors on Mars from scratch when we could just send fiberglass panels covered in reflective mylar so we're up and running quickly.

Manufacturing requires equipment. A case of 100 thin fiberglass reflective panels might weigh about 75 lbs. Trying to send the equipment to make glass thread on Mars, there's just no way. I would like to see your idea for a miniature glass thread making machine and I really, really, really would like to see your launch schedule. I want to see how all of this manufacturing equipment fits in a Heavy Falcon, and then how do you drive out on Mars and lift it and bring it back to your base? And all of that for what, just some reflective panels?

If you're going to manufacture something on Mars it has to be important. It has to provide oxygen, or water, or food, or shelter.

We can make a steam engine with a 3D printer? I don't know a lot about 3D printers but I think they spray epoxy to build up a layer and then use a laser to instantly cure it. They don't make steel or aluminum components. You can't make a steam engine out of epoxy. Well, you can but it would blow apart just before it melted itself.

Again, we have light weight solar arrays. Why do we need to manufacture reflective panels and steam engines?

EDIT: I didn't notice that I typed 80 kw for the RTG at the ERV sites, I was thinking it was only 80 watts. I checked and 80 kw is what it says in Zubrin's book "The Case for Mars". The ERV RTG is supposed to produce 80,000 watts! And weigh 7,000 lbs. The ERV was supposed to produce oxygen from Mars CO2 so I guess that's why it was to need that much power. There's no way we would be able to move a 7,000 lb RTG, well, on Mars it would be about 3,500 lbs but that is still too heavy without some kind of hydraulic crane and even so it would be too heavy for a rover to pull across Mars uneven surface.

Last edited by Dook (2016-10-30 14:05:38)

Dook · 2016-10-30 13:23:12

RobertDyck wrote:

Dook, I've took a serious look at the greenhouses. For transport form Earth, you would use plastic film of a material called PolyChloroTriFluoroEthylene (PCTFE). It's sold by Honeywell under two brand names: Aclar is used as a thin layer with less expensive plastic film for blister packs for pills (pharmaceuticals). Clarus is sold to the military and aerospace industry. A Japanese company sells it under the brand name Neoflon, but they use that name for all fluoropolymers, so you have to ask for Neoflon PCTFE.
This material is stable from +132°C to -240°C. That's 100°C colder than the Mars south pole in southern winter. And this material is highly impermeable to oxygen and nitrogen, and the most impermeable to water of any polymer ever invented. It's highly resistant to UV, and highly transparent. A bit expensive, but anything launched to Mars will be. Strength of this material can be increased by thermally bonding a shim of fibreglass. That means fibreglass cloth with as loose a weave as gauze. "Thermally bonded" means it's heated to melt into the polymer film. The fibreglass shim will add strength, and act as rip-stop. It would as clear as looking through a window that has a screen for insects. Fibreglass is transparent while screens on Earth are metal, new ones made of nylon, so the fibreglass shim would be slightly more transparent.
An inflatable greenhouse would have the same coating that NASA currently uses to block UV, and control IR (radiant heat). That is vacuum deposited layers of gold, nickel, and silver oxide. Only silver is an oxide. Silver oxide reflects IR; here on Earth "Heat Mirror" or "low-e" windows use silver oxide. This metal clogs the pores in polymer film, so not only is PCTFE highly impermeable, but the metal coating will make it even more impermeable. The greenhouse would be built with 2 layers, not 3. The gap between the layers would be filled with argon gas. Argon is less heat conductive than air, and it's large molecule makes it more difficult to get through polymer film. Mars atmosphere is 1.6% argon, as measured by Viking 2 lander, so it can be produced locally.
PCTFE is a light-weight film, so any greenhouse sent from Earth would be made of that. However, making stuff on Mars will not have all the industry Earth now has. It will be a lot easier to make glass on Mars. Just normal conventional glass.

The clear plastic material used for an inflatable greenhouse sounds fine for a temporary (few years maybe) greenhouse. It won't last as long as a built greenhouse would. The stuff is going to have -150 degrees on the outside and 75 degrees on the inside.

The thin plastic can be bonded to a fiberglass panel with a loose weave that is as transparent as glass? Do you have a picture of this clear fiberglass panel? Fiberglass isn't transparent. Can you make an epoxy panel with a few fiberglass strands in it? Yes, but that defeats the purpose of the fiberglass. Epoxy is somewhat clear but it is fragile, adding the fiberglass gives it strength.

Adding silver oxide to the clear plastic will make it UV resistant? For a bit, and then it will flake off. Paint is not going to stick well on smooth thin plastic.

You want to produce argon on Mars? What type of equipment do you need to do that? Is the slight benefit of using argon as a heat insulator over regular CO2 worth shipping the equipment, moving the equipment, and the time that it takes to operate the equipment?

RobertDyck · 2016-10-30 15:32:19

A shim is not fibreglass/epoxy composite. Fibreglass felt used for construction is not woven, it's just fibres pressed to together: felt. Epoxy is painted on the felt, which soaks in and hardens. That isn't what a shim is. A shim is woven, with the same loose weave as gauze. There is no epoxy at all because that would defeat the point. A shim is thermally bonded to polymer film.

Adding silver oxide makes it reflect IR. Adding gold and nickel make it reflect UV.

PCTFE is inherently highly UV resistant for two reasons: first it's a fluoropolymer which is far stronger than any hydrocarbon, second PCTFE is transparent to UV-A, UV-B, and even most of the band of UV-C. It's so UV resistant primarily because UV goes right through.

I presented a paper at the Mars Society convention in 2005 in Boulder, CO. My idea would harvest "diluent gas" that could be mixed with O2 for use in a habitat. The idea was to collect everything but CO2. It would react CO with O2 to form more CO2, and decompose ozone to O2. Mars atmosphere doesn't have much O2, but it has even less CO so there's enough to do that. This is far more energy intensive that freezing dry ice to harvest CO2. It starts with a pressure pump to go from Mars ambient to 10 bars pressure, and chill the bottom of the pressure tank to -100°C while at the same time warm the small rhodium catalyst at the top of the chamber to +24°C. Keep pumping until no more dry ice freezes out, and all CO has been decomposed. Then flash transfer the gas to another holding tank. I calculated resulting gas would be 61% N2, 36.1% Ar, 2.1% O2, 0.75% CO2, and trace amounts of Ne, Kr, Xe.

This "diluent gas" could be further processed to remove nitrogen. Three ways to do that: cryogenically freeze out gas, semipermeable membrane, or make ammonia. To make ammonia first you have to use a sorbent to remove all remaining CO2. Then add hydrogen to burn off O2. Then add more hydrogen to burn with N2, resulting in ammonia. That ammonia will freeze at -77.7°C, you would want to chill it further to reduce vapour pressure, but it doesn't require cryogenic temperature. The ammonia thing ideally would leave you with 99.98% Ar with trace amounts of Ne, Kr, Xe. There are a couple uses for ammonia, one is to further process it to make ammonium nitrate fertilizer. No, I'm not going to post how to do that; I would get in trouble with authorities.

kbd512 · 2016-10-30 16:14:04

Dook wrote:

The TBM just seems like it's too heavy. Too heavy to launch and too heavy to move around Mars. I think the TBM's are better at going through solid rock than loose dirt. And whatever tunnel you dig would have to be supported by one foot thick cement before you could live in it, an inflatable won't hold back loose regolith.

A TBM is not going to be a featherweight piece of machinery.

If the TBM weighs 30t on Earth, then it weighs 11.4t (25,080lbs) on Mars. The fission reactor generates a nominal 400kWe. 4 100 hp electric motors would have no problem at all moving that kind of weight on Mars. That's slightly more than 35hp/t. For comparison purposes, the M1 tank has something like 24hp/t to 27hp/t.

An inflatable pressurized to 1 atm has a force exerted on its walls of roughly 10,332kg/m^2. I don't know enough about this to say for sure.

With a 1.52g/cm^3 regolith bulk density the regolith should exert at pressure of 3113lbs/ft^2 at 10M depth, whereas 1 ATM exerts just 2116lbs/ft^2 on the walls of the inflatable module. In practice, only the top two thirds of the hole bored is subject to collapse. At 6M depth, the soil pressure falls to 1867lbs/ft^2. Is that strong enough? I have no idea. The calculation was very simplistic to determine if the pressurization within the module could hold back the pressure of the regolith.

Dook wrote:

I saw the Omega Garden. It's hydroponics, which is great for some plants like lettuce but it's not going to grow corn or any melon plant, or fruit trees, or any bush. The problem of growing enough food on Mars comes down to water and space. Inflatable greenhouses will work fine for at first but the inflatable material is going to wear out from the extreme temperature changes. Also the inflatable will require a heat source to keep the plants from freezing and the pressure will leak out through the material so you will have to pump them up from time to time. It just seems like a buried greenhouse is the way to go but it's not easy to build and not easily expanded. I think we need an excavator.

If not a TBM, what would you propose?

Dook wrote:

The compost pile works in a greenhouse, it would produce some heat and after a while it would be good fertilizer. I'm not sure but I think I read somewhere that using human waste as fertilizer is too strong so you might only use a little bit of it in your compost pile.

A biogas generator would work and lots of people in third world countries have built them, but the quantity of biomass available for regular digestion is the question that needs an answer.

Dook wrote:

A Mars Base will have high power requirements? If the engineers can't keep it simple it will. The landed Mars Habitat that lands the settlers will have solar cells on it's roof, it will have an RTG, and it should have another set of solar panels (should be eight) that can be set outside. The crew can use the Long Range Rover to drive over to the three previous exploration landing sites and bring back the RTG's and external solar arrays. If the three exploration landing sites each have a 300 watt RTG and eight solar panels (1000 w total) that would be a small base of four RTG's, four sets of eight solar arrays. That's 5,200 watts an hour in the day and 1,200 watts at night. The night time watts is on the low side but that's when the crew is sleeping so it's workable. You could maybe add in a bank of batteries that would help the night time power if you had to. I'm not sure how long the RTG's last, the small ones last 30 years or so, think the larger ones last something like 5-10 yrs.

ISS would require 6 RTG's for heating alone. We're talking about building something comparable to ISS on Mars. The other lift support systems require that scrub CO2 and recycle water require additional power and basically have to run 24/7. Sand storms can last for a month, reducing solar panel output by 60% to 70%.

Dook wrote:

You don't have to import water from the Earth to make water on Mars. You just have to import hydrogen and then burn it with the oxygen you've made on Mars (made with a large MOXIE unit) to produce water vapor that would then have to be made back into water with a dehumidifier. So, you'd need some kind of small machine that would take in the oxygen and hydrogen gas, burn it in a small burner (this machine could be designed to produce some power) then expel the water vapor into another chamber where a small dehumidifier takes in the vapor and makes it water.

Again, no point in building a base on Mars if there's no water there. We might go to Mars just to say we did it, but we're not going to live there if absolutely everything to support human life has to be imported from Earth.

Dook wrote:

Using robots to build your base before colonization? That's way in the future. We're not to the point where we can do that yet.

We have robots that can perform surgery, why not construction?

Dook wrote:

We can't import all the oxygen and water we need on Mars from the Earth? We can't if you overload Mars with too many people from the get go. The object is to be completely self sufficient but that's not going to happen for 100 years so, you do what you are most sure of first, we know how to grow plants and raise chickens.

My goal is near-term self-sufficiency for O2 and H2O. Reliable power, air, water, heating and cooling are requirements for living anywhere. If we can't provide those things for humans on Mars, we have no business colonizing Mars.

Dook · 2016-10-30 16:15:53

RobertDyck wrote:

A shim is not fibreglass/epoxy composite. Fibreglass felt used for construction is not woven, it's just fibres pressed to together: felt. Epoxy is painted on the felt, which soaks in and hardens. That isn't what a shim is. A shim is woven, with the same loose weave as gauze. There is no epoxy at all because that would defeat the point. A shim is thermally bonded to polymer film.
Adding silver oxide makes it reflect IR. Adding gold and nickel make it reflect UV.
PCTFE is inherently highly UV resistant for two reasons: first it's a fluoropolymer which is far stronger than any hydrocarbon, second PCTFE is transparent to UV-A, UV-B, and even most of the band of UV-C. It's so UV resistant primarily because UV goes right through.
I presented a paper at the Mars Society convention in 2005 in Boulder, CO. My idea would harvest "diluent gas" that could be mixed with O2 for use in a habitat. The idea was to collect everything but CO2. It would react CO with O2 to form more CO2, and decompose ozone to O2. Mars atmosphere doesn't have much O2, but it has even less CO so there's enough to do that. This is far more energy intensive that freezing dry ice to harvest CO2. It starts with a pressure pump to go from Mars ambient to 10 bars pressure, and chill the bottom of the pressure tank to -100°C while at the same time warm the small rhodium catalyst at the top of the chamber to +24°C. Keep pumping until no more dry ice freezes out, and all CO has been decomposed. Then flash transfer the gas to another holding tank. I calculated resulting gas would be 61% N2, 36.1% Ar, 2.1% O2, 0.75% CO2, and trace amounts of Ne, Kr, Xe.
This "diluent gas" could be further processed to remove nitrogen. Three ways to do that: cryogenically freeze out gas, semipermeable membrane, or make ammonia. To make ammonia first you have to use a sorbent to remove all remaining CO2. Then add hydrogen to burn off O2. Then add more hydrogen to burn with N2, resulting in ammonia. That ammonia will freeze at -77.7°C, you would want to chill it further to reduce vapour pressure, but it doesn't require cryogenic temperature. The ammonia thing ideally would leave you with 99.98% Ar with trace amounts of Ne, Kr, Xe. There are a couple uses for ammonia, one is to further process it to make ammonium nitrate fertilizer. No, I'm not going to post how to do that; I would get in trouble with authorities.

Okay, so what is the life expectancy of this very thin inflated plastic habitat on Mars? You say it's highly UV resistant, okay, how wear resistant is it? Almost no wear resistance whatsoever. So we have to keep everything away from it. How long will it last after repeatedly being heating to 78 degrees and cooled to -150? How do you fix a doorway to it and keep it from tearing away? Mars wind can feel like a 6 mph breeze, that would be enough to move your inflated plastic habitat. If it touches the surface enough times it breaks.

The silver oxide paint won't stick for long to your smooth plastic. Neither will the gold and nickel paint. This plastic inflatable habitat/greenhouse is going to be folded and placed inside a container for launch to Mars. When the crew on Mars tries to unfold it, the paint will be stuck to paint and it will come off in large sections that might tear the plastic. I think you would have to cover it in some kind of powder, talcum or something.

You could attempt to paint the plastic on Mars as it's being inflated. It just seems like too much work for something that's going to be temporary. I'm not saying it won't work. I'm saying it won't last.

You presented a paper on how we could get a buffer gas from Mars atmosphere? You don't explain how you get everything but CO2 and then separate the gasses. And what equipment you need to cryogenically cool things on Mars?

If we want a buffer gas, rather than sending all of this equipment to cryogenically freeze things on Mars so we can get some nitrogen, couldn't we just send a cylinder full of nitrogen gas?

RobertDyck · 2016-10-30 16:44:16

I wrote my presentation as a PowerPoint, but also converted to a Word document. Here: ISRU atmosphere harvesting

Dupont has said the premium polymer for a greenhouse on Earth is Tefzel. They have a greenhouse in Florida that's over 20 years old and still working. When did I speak to them? 12 years ago? Tefzel is a co-polymer of regular ethylene with TetraFluoroEthylene. The polymer I recommend is PolyChloroTriFluoroEthylene; it's stronger, more UV durable, more gas impermeable, and able to withstand colder temperatures. Of course that means more expensive.

The coating isn't painted on, it's chemical vapour deposition. But you do raise a valid concern.

One means of extending the life of an inflatable greenhouse is to control temperature fluctuations. Keep the inside pressurized, and stable temperature. Atmosphere temperature will fluctuate as you say, but atmosphere is thin so relatively little heat loss. Inside temperature and pressure will be constant. And the greenhouse will be strapped down. The initial designs from "The Case for Mars" conferences, before the founding convention of the Mars Society, called for squashing it. Without hold-down straps the pressure will inflate it to a cylinder. Squash it to limit height to normal ceiling height, but increase the width.

Dook · 2016-10-30 17:32:01

kbd512 wrote:

Dook wrote:
The TBM just seems like it's too heavy. Too heavy to launch and too heavy to move around Mars. I think the TBM's are better at going through solid rock than loose dirt. And whatever tunnel you dig would have to be supported by one foot thick cement before you could live in it, an inflatable won't hold back loose regolith.
A TBM is not going to be a featherweight piece of machinery.
If the TBM weighs 30t on Earth, then it weighs 11.4t (25,080lbs) on Mars. The fission reactor generates a nominal 400kWe. 4 100 hp electric motors would have no problem at all moving that kind of weight on Mars. That's slightly more than 35hp/t. For comparison purposes, the M1 tank has something like 24hp/t to 27hp/t.
An inflatable pressurized to 1 atm has a force exerted on its walls of roughly 10,332kg/m^2. I don't know enough about this to say for sure.
With a 1.52g/cm^3 regolith bulk density the regolith should exert at pressure of 3113lbs/ft^2 at 10M depth, whereas 1 ATM exerts just 2116lbs/ft^2 on the walls of the inflatable module. In practice, only the top two thirds of the hole bored is subject to collapse. At 6M depth, the soil pressure falls to 1867lbs/ft^2. Is that strong enough? I have no idea. The calculation was very simplistic to determine if the pressurization within the module could hold back the pressure of the regolith.
Dook wrote:
I saw the Omega Garden. It's hydroponics, which is great for some plants like lettuce but it's not going to grow corn or any melon plant, or fruit trees, or any bush. The problem of growing enough food on Mars comes down to water and space. Inflatable greenhouses will work fine for at first but the inflatable material is going to wear out from the extreme temperature changes. Also the inflatable will require a heat source to keep the plants from freezing and the pressure will leak out through the material so you will have to pump them up from time to time. It just seems like a buried greenhouse is the way to go but it's not easy to build and not easily expanded. I think we need an excavator.
If not a TBM, what would you propose?
Dook wrote:
The compost pile works in a greenhouse, it would produce some heat and after a while it would be good fertilizer. I'm not sure but I think I read somewhere that using human waste as fertilizer is too strong so you might only use a little bit of it in your compost pile.
A biogas generator would work and lots of people in third world countries have built them, but the quantity of biomass available for regular digestion is the question that needs an answer.
Dook wrote:
A Mars Base will have high power requirements? If the engineers can't keep it simple it will. The landed Mars Habitat that lands the settlers will have solar cells on it's roof, it will have an RTG, and it should have another set of solar panels (should be eight) that can be set outside. The crew can use the Long Range Rover to drive over to the three previous exploration landing sites and bring back the RTG's and external solar arrays. If the three exploration landing sites each have a 300 watt RTG and eight solar panels (1000 w total) that would be a small base of four RTG's, four sets of eight solar arrays. That's 5,200 watts an hour in the day and 1,200 watts at night. The night time watts is on the low side but that's when the crew is sleeping so it's workable. You could maybe add in a bank of batteries that would help the night time power if you had to. I'm not sure how long the RTG's last, the small ones last 30 years or so, think the larger ones last something like 5-10 yrs.
ISS would require 6 RTG's for heating alone. We're talking about building something comparable to ISS on Mars. The other lift support systems require that scrub CO2 and recycle water require additional power and basically have to run 24/7. Sand storms can last for a month, reducing solar panel output by 60% to 70%.
Dook wrote:
You don't have to import water from the Earth to make water on Mars. You just have to import hydrogen and then burn it with the oxygen you've made on Mars (made with a large MOXIE unit) to produce water vapor that would then have to be made back into water with a dehumidifier. So, you'd need some kind of small machine that would take in the oxygen and hydrogen gas, burn it in a small burner (this machine could be designed to produce some power) then expel the water vapor into another chamber where a small dehumidifier takes in the vapor and makes it water.
Again, no point in building a base on Mars if there's no water there. We might go to Mars just to say we did it, but we're not going to live there if absolutely everything to support human life has to be imported from Earth.
Dook wrote:
Using robots to build your base before colonization? That's way in the future. We're not to the point where we can do that yet.
We have robots that can perform surgery, why not construction?
Dook wrote:
We can't import all the oxygen and water we need on Mars from the Earth? We can't if you overload Mars with too many people from the get go. The object is to be completely self sufficient but that's not going to happen for 100 years so, you do what you are most sure of first, we know how to grow plants and raise chickens.
My goal is near-term self-sufficiency for O2 and H2O. Reliable power, air, water, heating and cooling are requirements for living anywhere. If we can't provide those things for humans on Mars, we have no business colonizing Mars.

A TBM is not a featherweight piece of machinery? I know. It's too heavy to get to Mars.

It only weighs 25,080 lbs on Mars? Okay, that's still a lot. You're going to need a serious tracked trailer and rover to move it and you probably won't be able to move it in a straight line if there are rocks in the way or deep sand.

Wouldn't a regular habitat made out of thick fiberglass honeycomb panels be better?

The pressurized hab would exert a force that keeps the Mars regolith from collapsing the inflated hab? There is no way. If a tiny dusting of regolith falls on your inflatable, yeah, it will hold. If the tunnel collapses it's game over and you know it.

If not a TBM, what would I propose? The TBM is not an option, it's too heavy. You can't get it there so it never was an option.

Well, you can land in a very suitable Mars Hab that is 16.5 feet wide and has three bedrooms, oxygen storage, food storage, water storage built into the structure, solar cells already built into the top, a heating/cooling system, a communications system, a shower/toilet area, a dining area, maybe even a mini-MOXIE unit built in to supplement cabin oxygen.

This is the tuna can idea that Zubrin proposed in Mars Direct to put a crew on Mars for 550 days, and he wanted four crew, if we only use three for a settlement the supplies would last even longer. And the tuna can would be on a steel frame and underneath it is an RTG that can be lowered and moved away from the Mars Hab. And there is a Long Range Rover underneath that you can use to go and get the other three Long Range Rovers left behind by the three exploration teams who came before and left.

One or two more launches could bring in all the components for a buried habitat, they would actually already be on the planet before you launched your settlers so all you have to do is drive two Long Range Rovers over there with two Mars Carts and load them up. All the components for my Buried Habitat, a 20'x20' wide fiberglass walled hab, can be carried on two Mars Carts.

The problem is digging. You're going to hit permafrost once you get down a bit, you could just dig a bit then take a break and let the sun melt it and dig in the evenings when it's softened but, I don't know. I think two ATV dozers would be able to do it but an excavator might be needed. I'm going to have to think about how to fit one in or modify on of the ATV's to be an excavator.

The hab on Mars will require 6 RTG's for heating? Six sounds like way too much.

The CO2 scrubber is simply a small fan that blows over a filter. You can have two computer fans running all day long, they each use 3 watts an hour, that's 144 watts a day.

The water recycle system would require very little power, well, unless the engineers over design, and over complicated it. Have you ever taken a shower in a motor home? A small DC pump supplies the water pressure. The grey water would go down into a tank and flow through a filter and be re-used by the shower. No water is lost and the filters have to be changed out at times. The urinal would be next to the shower so urine would go into this grey water tank and be filtered and used in the shower as well. It sounds gross but you can filter out everything so it's pure water.

New drinking water would come from MOXIE made oxygen that is burned with hydrogen shipped from Earth. As I said before, some type of machine would do this. The water vapor from this machine is released into the habitat and then reconstituted by a dehumidifier that would flow the water into a clean drinking water tank. The plants in your habitat release water into the air anyway so you will need to operate a dehumidifier at times regardless.

So, we have a system that re-uses probably over 90% of the habitat water with no energy intensive and over engineered 100% water recycling system. The only water lost is water that is in solid waste and that could be placed into a microwave to steam the water out into your hab air where the dehumidifier collects it.

The dehumidifier runs, I don't know, have to do some research, for maybe 15 minutes a day, might use 150 watts total.
Dust storms on Mars are trouble. They can actually last a whole year, that's one reason why I don't want just solar panels but also RTG's but even so, you can't land supplies and you can't drive in the rover so you're stuck in the habitat. It's something we have to plan for. They have to have enough supplies to last a very long time if that happens.

There's no point in building a Mars Base if there isn't water? Three people would need one supply mission a year of food, hydrogen, chicken feed, and spare parts. Then you send one other mission a year that is full of habitat components. So these three keep building the same style buried habitats near the first one and they fill them all with fruit trees and vegetables grown from seeds they got from the plants in the first habitat. And they would have more chickens as well. It's not perfect but it's doable. No nuclear power plant needed and no "Total Recall" manufacturing of steel, glass, steam generators, or reflective panels.

We have robots perform surgery? A completely independent robot with no human control? Uhh, you're going to have to send me the website link for that one.

Once they get enough buried habs they won't be totally self sufficient but they won't need food shipments. The full self sufficiency thing was never going to happen on the timescale that some of you thought.

Dook · 2016-10-30 18:00:14

RobertDyck wrote:

I wrote my presentation as a PowerPoint, but also converted to a Word document. Here: ISRU atmosphere harvesting
Dupont has said the premium polymer for a greenhouse on Earth is Tefzel. They have a greenhouse in Florida that's over 20 years old and still working. When did I speak to them? 12 years ago? Tefzel is a co-polymer of regular ethylene with TetraFluoroEthylene. The polymer I recommend is PolyChloroTriFluoroEthylene; it's stronger, more UV durable, more gas impermeable, and able to withstand colder temperatures. Of course that means more expensive.
The coating isn't painted on, it's chemical vapour deposition. But you do raise a valid concern.
One means of extending the life of an inflatable greenhouse is to control temperature fluctuations. Keep the inside pressurized, and stable temperature. Atmosphere temperature will fluctuate as you say, but atmosphere is thin so relatively little heat loss. Inside temperature and pressure will be constant. And the greenhouse will be strapped down. The initial designs from "The Case for Mars" conferences, before the founding convention of the Mars Society, called for squashing it. Without hold-down straps the pressure will inflate it to a cylinder. Squash it to limit height to normal ceiling height, but increase the width.
http://www.hudsonfla.com/marsview5.jpg

There is a greenhouse made of this polymer in Florida that is 20 yrs old? It made it through hurricanes? Uhhh... hurricanes!? They're lying to you.

One way to extend the life of an inflatable greenhouse is to control temperature fluctuations? But you can't do that on Mars. The outside temperature is going to go from 78 to -150 every day.

The atmosphere is thin so there will be relatively little heat loss? Do you have something, a website or paper, that shows that? I would like to see it. We know that Mars temperature goes from a daytime high of 78 to -150 at night so are you saying that isn't as much as it would be with a thicker atmosphere? Even so, at 32 degrees F fruit freezes, it turns black and falls off the tree.

The picture is one of Zubrin's Mars Direct tuna cans with regolith bags on the roof. The tall launcher is an Earth Return Vehicle. There is no way they will be in the same place. NASA can't land things that close together on Mars, they could be as much as 800 kilometers apart from each other. Elon Musk might be able to do it but it's going to take more rocket fuel than a NASA vehicle would need, not saying it's impossible, just that his launch rocket would need to be bigger than a Mars Direct rocket to carry the same load.

The little rover would be a local use rover only, it would run on batteries that would have to be recharged by something. I don't see the point in having it unless it's just for local exploration.

The large opening in the tuna can makes no sense whatsoever. You don't have to bring your local rover inside the hab, well, unless you want to keep the batteries from freezing but all you have to do is have battery warmers under them and maybe cover the unit with a thick tarp.

The surface greenhouses will need to be heated to keep the plants from freezing. Any ideas on how to do that?

And far in the left background is a pretty large array of solar panels. Nice.

RobertDyck · 2016-10-30 19:23:11

Ok. Newbie. Time to go over the basics. Again, and again, and again.

The rate of heat transfer depends on the temperature differential, heat transfer coefficient of the barrier (plastic film), thermal coefficient of the gas outside, and density of that gas. Lower pressure results in lower density. Want more?
Wikipedia: Heat transfer physics

I was concerned about thermal insulation in a spacesuit. Current spacesuits use multi-layer insulation. That's aluminized Mylar, with fishnet spacers. It reflects radiant heat. The vacuum of space acts as the universe's largest vacuum bottle (Thermos bottle) so all you have to worry about is radiant heat. Spacers deal with conductive heat, but in the end only radiant heat from the outside surface of the suit results in heat gain or loss. Spacesuits in LEO or on the Moon suffer heat gain in direct sunlight, and heat loss in shade. Multilayer insulation works great in vacuum, but I'm worried it won't work in the atmosphere of Mars. In fact, the aluminum will act as a heat sink, causing faster heat loss. So I proposed Thinsulate, which is insulation used on Earth for ski pants and ski jackets. However, engineers tell me heat loss is not the worry. The astronaut will lose heat so slowly that metabolic heat from his/her body will result in heat gain. The astronaut will get hot. Sitting on a cold rock could freeze your butt, but just standing or walking could get hot. Apollo had patches of insulation sewn into the ass and knees of suits intended for the surface of the Moon, and insulated soles of Moon boots. Mars will need that too, but I still contend a Mars suit will need Thinsulate or something like it rather than multi-layer insulation.

"The Case for Mars" papers talked about an aluminized mylar curtain drawn across the ceiling of the greenhouse at night. To reflect radiant heat (IR) back in. That's to prevent cooling at night. At first I suggested using this too, but after mentioning spectrally selective coatings, some members of the Mars Society suggested the curtain isn't necessary if you have that. The spectrally selective coating only reflects about 40% of IR, so we may need the ceiling curtain as well.

One point is with high pressure/high density air inside the greenhouse maintained at a constant temperature, and low density pressure/low density atmosphere outside fluctuating dramatically, the polymer film may experience only mild changes in temperature.

Many members of the Mars Society do not understand the Mars Direct habitat. The first version of Mars Direct had only a single deck/floor to the habitat. Below was life support equipment, propellant tanks, landing rockets, and legs. Think of the Apollo CSM, the service module was not accessible. That first version had mass allocation for a rover, and one use was as emergency backup. In case the hab landed too far from the ERV. The rover would have fuel for up to a maximum of 1,000km one-way travel. If the hab landed within walking distance of the ERV, then the rover could be used for exploration.

However, before Mars Direct was even a single year old, one issue raised was where the rover would be stored during landing. If it was just suspended by cables beneath the hab, then exhaust from landing rockets would kick up rocks that could damage the rover. So a storage compartment was needed. And with a 6 month transit from Earth, astronauts may need access to life support equipment for maintenance. Since then ISS was built, and experience on ISS has confirmed astronauts need access to life support equipment. So a lower deck was added. But realize the lower deck is not usable space. The lower deck will be:

landing rocket engines
propellant tanks (fuel & oxidizer) for landing rockets
legs with shock absorbers (folded during launch from Earth)
RCS thrusters used for mid-course maneouvres during transit from Earth
propellant tanks for RCS thrusters
airlock
storage compartment for rover, surface science equipment, inflatable greenhouse. (aka garage)
life support equipment. On ISS this occupies 3 full size science racks, plus additional space for the regenerable CO2 sorbent.
solar arrays. Folded during launch from Earth, deployed during transit, folded again during Mars atmospheric entry and landing.
batteries. During transit in space, sunlight will be 24/7, however on Mars there is day and night. You can't tell astronauts to hold their breath between sun-down and sun-up. So you need batteries to store power, at least enough to run life support at night.

Once on Mars, the solar arrays will be removed and setup on the surface. With power cables back to the hab.

All this means the lower deck is just an airlock, garage, and solid equipment. The garage will be about the size of a single car garage. Think of a car in a garage with lawn equipment packed around; it'll be that packed. The inflatable greenhouse would be deflated, folded, and stored on the rover. That way the rover could be used as a cart to pull the greenhouse out. The "garage door" will open down to form a ramp. It will be a steep ramp, requiring a winch to get the rover back in. Under normal conditions, once on Mars all that stuff will be deployed outside, never come in again. So on Mars the lower deck is basically an empty single car garage. That's it. Don't expect the lower deck to be usable like MDRS or FMARS.

The painting above is by an artist. Here is an alternate image, from the year 2000 movie "Mission to Mars". Note the upper deck is full diameter, but the lower deck is smaller with equipment sticking out. And a soft inflated tunnel from the habitat to the greenhouse. Not sure the landing legs would be as bulky as shown here, but the rest is more realistic.

Landing: The only criteria is how far they have to be to ensure the second lander doesn't pelt the first one with rocks. The ERV or whatever lands first will include a landing beacon. Using that beacon, the hab or second lander could land with as much precision as SpaceX.

Vehicles: Robert Zubrin's vision for Mars Direct includes a rover with the habitat. Again, intended as emergency in case the hab lands too far, but normally used for exploration. The ERV would include an autonomous truck to carry the nuclear reactor a safe distance from the ERV, with power cable trailing back. The reactor would be dropped in the bottom of a deep crater, so the reactor is not visible from the ERV or hab. He envisioned the truck being usable as a utility vehicle once astronauts arrives. I wrote a thread "updating Mars Direct" where I proposed bolting mobility stuff identical to the Curiosity rover directly onto the reactor: wheels, suspension arms, motors, navigation camera, warm electronics box for computer. But this would have no science stuff what so ever. No MastCam, no high gain antenna, no UHF antenna, no science arm, no instruments at all. It would communicate via cable to the ERV, and since it would carry a nuclear reactor it certainly wouldn't need an RTG. Some members here didn't like the idea of losing the truck.

Dook · 2016-10-30 21:19:27

RobertDyck wrote:

Ok. Newbie. Time to go over the basics. Again, and again, and again.
The rate of heat transfer depends on the temperature differential, heat transfer coefficient of the barrier (plastic film), thermal coefficient of the gas outside, and density of that gas. Lower pressure results in lower density. Want more?
Wikipedia: Heat transfer physics
I was concerned about thermal insulation in a spacesuit. Current spacesuits use multi-layer insulation. That's aluminized Mylar, with fishnet spacers. It reflects radiant heat. The vacuum of space acts as the universe's largest vacuum bottle (Thermos bottle) so all you have to worry about is radiant heat. Spacers deal with conductive heat, but in the end only radiant heat from the outside surface of the suit results in heat gain or loss. Spacesuits in LEO or on the Moon suffer heat gain in direct sunlight, and heat loss in shade. Multilayer insulation works great in vacuum, but I'm worried it won't work in the atmosphere of Mars. In fact, the aluminum will act as a heat sink, causing faster heat loss. So I proposed Thinsulate, which is insulation used on Earth for ski pants and ski jackets. However, engineers tell me heat loss is not the worry. The astronaut will lose heat so slowly that metabolic heat from his/her body will result in heat gain. The astronaut will get hot. Sitting on a cold rock could freeze your butt, but just standing or walking could get hot. Apollo had patches of insulation sewn into the ass and knees of suits intended for the surface of the Moon, and insulated soles of Moon boots. Mars will need that too, but I still contend a Mars suit will need Thinsulate or something like it rather than multi-layer insulation.
"The Case for Mars" papers talked about an aluminized mylar curtain drawn across the ceiling of the greenhouse at night. To reflect radiant heat (IR) back in. That's to prevent cooling at night. At first I suggested using this too, but after mentioning spectrally selective coatings, some members of the Mars Society suggested the curtain isn't necessary if you have that. The spectrally selective coating only reflects about 40% of IR, so we may need the ceiling curtain as well.
One point is with high pressure/high density air inside the greenhouse maintained at a constant temperature, and low density pressure/low density atmosphere outside fluctuating dramatically, the polymer film may experience only mild changes in temperature.
Many members of the Mars Society do not understand the Mars Direct habitat. The first version of Mars Direct had only a single deck/floor to the habitat. Below was life support equipment, propellant tanks, landing rockets, and legs. Think of the Apollo CSM, the service module was not accessible. That first version had mass allocation for a rover, and one use was as emergency backup. In case the hab landed too far from the ERV. The rover would have fuel for up to a maximum of 1,000km one-way travel. If the hab landed within walking distance of the ERV, then the rover could be used for exploration.
http://matus1976.com/local_mirrors/mars … ubrin5.gif
However, before Mars Direct was even a single year old, one issue raised was where the rover would be stored during landing. If it was just suspended by cables beneath the hab, then exhaust from landing rockets would kick up rocks that could damage the rover. So a storage compartment was needed. And with a 6 month transit from Earth, astronauts may need access to life support equipment for maintenance. Since then ISS was built, and experience on ISS has confirmed astronauts need access to life support equipment. So a lower deck was added. But realize the lower deck is not usable space. The lower deck will be:
landing rocket engines
propellant tanks (fuel & oxidizer) for landing rockets
legs with shock absorbers (folded during launch from Earth)
RCS thrusters used for mid-course maneouvres during transit from Earth
propellant tanks for RCS thrusters
airlock
storage compartment for rover, surface science equipment, inflatable greenhouse. (aka garage)
life support equipment. On ISS this occupies 3 full size science racks, plus additional space for the regenerable CO2 sorbent.
solar arrays. Folded during launch from Earth, deployed during transit, folded again during Mars atmospheric entry and landing.
batteries. During transit in space, sunlight will be 24/7, however on Mars there is day and night. You can't tell astronauts to hold their breath between sun-down and sun-up. So you need batteries to store power, at least enough to run life support at night.
Once on Mars, the solar arrays will be removed and setup on the surface. With power cables back to the hab.
All this means the lower deck is just an airlock, garage, and solid equipment. The garage will be about the size of a single car garage. Think of a car in a garage with lawn equipment packed around; it'll be that packed. The inflatable greenhouse would be deflated, folded, and stored on the rover. That way the rover could be used as a cart to pull the greenhouse out. The "garage door" will open down to form a ramp. It will be a steep ramp, requiring a winch to get the rover back in. Under normal conditions, once on Mars all that stuff will be deployed outside, never come in again. So on Mars the lower deck is basically an empty single car garage. That's it. Don't expect the lower deck to be usable like MDRS or FMARS.
The painting above is by an artist. Here is an alternate image, from the year 2000 movie "Mission to Mars". Note the upper deck is full diameter, but the lower deck is smaller with equipment sticking out. And a soft inflated tunnel from the habitat to the greenhouse. Not sure the landing legs would be as bulky as shown here, but the rest is more realistic.
http://alanschuyler.files.wordpress.com … w-mars.jpg
Landing: The only criteria is how far they have to be to ensure the second lander doesn't pelt the first one with rocks. The ERV or whatever lands first will include a landing beacon. Using that beacon, the hab or second lander could land with as much precision as SpaceX.
Vehicles: Robert Zubrin's vision for Mars Direct includes a rover with the habitat. Again, intended as emergency in case the hab lands too far, but normally used for exploration. The ERV would include an autonomous truck to carry the nuclear reactor a safe distance from the ERV, with power cable trailing back. The reactor would be dropped in the bottom of a deep crater, so the reactor is not visible from the ERV or hab. He envisioned the truck being usable as a utility vehicle once astronauts arrives. I wrote a thread "updating Mars Direct" where I proposed bolting mobility stuff identical to the Curiosity rover directly onto the reactor: wheels, suspension arms, motors, navigation camera, warm electronics box for computer. But this would have no science stuff what so ever. No MastCam, no high gain antenna, no UHF antenna, no science arm, no instruments at all. It would communicate via cable to the ERV, and since it would carry a nuclear reactor it certainly wouldn't need an RTG. Some members here didn't like the idea of losing the truck.

Do I want more? It would be nice to know how cold the greenhouses will get at night.

Rocks could be kicked up by the landing rockets and damage the rover so it needs a compartment? The rover would have a fiberglass repair kit and various sizes of fiberglass panel to repair any holes in the structure. I don't know that I would say a compartment is needed for the rover but it might be a good idea as long as it's not too heavy. Another benefit to a compartment is that it keeps direct sun off the rover so wheel pads don't melt. The rover would be covered in reflective mylar anyway but still it would get hot if it was exposed to the sun.

I think the Mars Hab should have solar panels bolted to the top and fly with it's top facing the sun. You don't have to mess with folding/unfolding the panels and they could be removed and placed on the surface of Mars before the top of the Mars Hab is covered with sand bags.

Also, the rover would probably have cables to lower it after landing on Mars but it should also have the wheels rest on curved plates that are bolted to the landing struts. The top of the vehicle could fit in a depression in the underside of the Mars Hab and the wheel springs of the rover would be completely compressed so the vehicle couldn't move.

By adding this garage under the Mars Hab what is the increase in weight? The inflatable greenhouse is also not in Zubrin's calculations. What did you remove from Zubrin's Mars Direct weight chart to add these things?

The landing legs just fold in and out, right? Not underneath the vehicle?

The Mars Hab can land with as much precision as SpaceX? It aero brakes in the Mars atmosphere, ejects the heat shield, then deploys the parachutes, then near the surface it ejects the parachutes and fires the landing rockets and lands on it's struts. So, for the Mars Hab to land closer to a target like SpaceX you're talking about ejecting the parachutes much earlier and using a lot more rocket fuel to maneuver. Possible? Yes. But more fuel means less cargo.

I disagree that the rover in Mars Direct is just for emergency case, in case the Mars Hab lands too far from the ERV. SpaceX can land a small rocket on a landing pad but that rocket isn't aero braking in the Earth's atmosphere and then trying to hit the pad, it's going up and coming right back down. It's not the same thing. You want them close but not too close, still, what you want and what you can do are two different things. With no SpaceX rocket maneuvering the Mars Hab and ERV could land as much as 800 kilometers away from each other.

RobertDyck · 2016-10-30 21:57:18

Robert Zubrin added the garage. I could post the mass chart from his June 1990 presentation to NASA, the one that didn't have a lower deck. But his book "The Case for Mars" has updated mass estimates including the lower deck. So Dr. Zubrin himself did it.

My estimates started with using the SAFE-400 reactor instead of SP-100. Both designed by the same team, but SP-100 was under development when Dr. Zubrin and his partner David Baker were working on Mars Direct in 1989 & 1990. Development of SP-100 was complete in 1992. Robert Zubrin had hoped a reactor to produce 85 kWe would mass a little less than one that produces 100 kWe. Unfortunately the reactor design team said the 85 kWe reactor would have the same mass. So the final mass for the reactor was greater than Dr. Zubrin's estimate. Oops. Work on SAFE-400 was completed in 2007; it's a lot newer. Every part was updated. The most dramatic was use of a better power converter. Both produce 100 kWe, but SP-100 requires 2,000 kW thermal while SAFE-400 can do it with 400 kW thermal. That means a smaller reactor core. And everything in the core is newer, lighter. This is the most dramatic mass reduction for the ERV.

I then used ISS equipment for life support, and Tesla power wall for the battery. Well, mass density, the hab would require a bigger one than the maximum configuration of "Power Wall". Power Wall uses lithium ion batteries. But ISS life support equipment is now known, we don't need to estimate. However, it's heavier than Dr. Zubrin's estimates. For the ERV capsule, I used SpaceX Dragon. But had to add a pressurized cargo module (PCM) from Cygnus basic (not extended) to house the recycling life support equipment.

Rather than repeat further, that thread is: Light weight nuclear reactor, updating Mars Direct

Landing: I would continue to use ADEPT for the heat shield that deploys like an umbrella. Dr. Zubrin doesn't use that name in his book, but that's the NASA heat shield he used. And land the same way. You don't think landing that way is sufficiently precise? Ok. As long as the hab lands within walking distance of the ERV, good enough. But you claim 800 km separation? That isn't good enough.

kbd512 · 2016-10-30 22:35:59

Dook wrote:

A TBM is not a featherweight piece of machinery? I know. It's too heavy to get to Mars.

The Mars Direct tuna can weighs 28t. If the TBM is too heavy to get to Mars, so is the tuna can proposed by Dr. Zubrin.

Dook wrote:

It only weighs 25,080 lbs on Mars? Okay, that's still a lot. You're going to need a serious tracked trailer and rover to move it and you probably won't be able to move it in a straight line if there are rocks in the way or deep sand.

The TBM would have four tracks, each independently steerable like an all-weel drive and all-wheel steering car. Each track would be powered by a 100hp electric motor. It's actual hp/t ratio on Mars is significantly better than a M1 tank on Earth. The tracks are connected to the deck that holds the TBM. The deck can push smaller rocks out of its way, like a makeshift grading tool. The TBM itself is the part that holds the nuclear reactor, the electric motor that powers the blade, and the spoil removal system, is suspended above the ground and is actually above the deck.

The TBM's nuclear reactor has some shielding, but the shielding is insufficient for humans to work in close proximity to the operating reactor. You can't be closer than 10m to the reactor when the reactor is operating. The tool has an exclusion zone, but that zone is much smaller since the reactor itself is shielded rather than shielded by the environment.

Dook wrote:

Wouldn't a regular habitat made out of thick fiberglass honeycomb panels be better?

It would be better insulated.

The reason for burying the habitat modules has nothing to do with insulation and everything to do with blocking GCR's (intergalactic particles in the GeV range, typically protons but also some even nastier heavy ions), SPE's (solar particles in the MeV range), CME's (more solar particles in the MeV range), and the TBM reactor's radiation (gamma and neutrons). The habitat modules are thin spectra (a stronger kevlar variant), dacron, and kapton fabrics that can't block any of that.

Dook wrote:

The pressurized hab would exert a force that keeps the Mars regolith from collapsing the inflated hab? There is no way. If a tiny dusting of regolith falls on your inflatable, yeah, it will hold. If the tunnel collapses it's game over and you know it.

The bottom third of tunnels won't collapse. If the bottom third collapsed, then you're right, there's no way the pressurization of the module could over come the force of the regolith surrounding it. I have seen vertical shafts that were more than 10m in height here on Earth that had no concrete liner. However, I'd defer to an expert here. If I'm wrong, I'll drop this idea.

Dook wrote:

If not a TBM, what would I propose? The TBM is not an option, it's too heavy. You can't get it there so it never was an option.

If the TBM is too heavy, so is the tuna can.

Dook wrote:

Well, you can land in a very suitable Mars Hab that is 16.5 feet wide and has three bedrooms, oxygen storage, food storage, water storage built into the structure, solar cells already built into the top, a heating/cooling system, a communications system, a shower/toilet area, a dining area, maybe even a mini-MOXIE unit built in to supplement cabin oxygen.

Are you talking about living in Orion for a year? You stated how wide the habitat module would be. How long would it be?

There's physically not enough space to store the consumables, life support systems, and crew in Orion, which would include the deep-space only habitat variant (basically a miniature node module) proposed.

In numerous presentations, NASA and JPL depict inflatable habitat modules on Mars that weigh 40t delivered using ADEPT and retro-propulsion. That's not the weight of the EDL hardware and habitat module, that's the weight of the habitat module alone. That was and is considered a minimum requirement for a crew of four to six astronauts.

Dook wrote:

This is the tuna can idea that Zubrin proposed in Mars Direct to put a crew on Mars for 550 days, and he wanted four crew, if we only use three for a settlement the supplies would last even longer. And the tuna can would be on a steel frame and underneath it is an RTG that can be lowered and moved away from the Mars Hab. And there is a Long Range Rover underneath that you can use to go and get the other three Long Range Rovers left behind by the three exploration teams who came before and left.

A steel frame is unnecessary. The RTG is not a significant radiation hazard to the tuna can. Even if it was, it'd be easier and less expensive to dig a small hole for the RTG than to make the habitat heavier. One astronaut can dig a hole and one astronaut can carry the RTG and place it in the hole.

The RTG's emit intense beta and some low energy gamma. NASA technicians routinely touch RTG's with their hands here on Earth whilst wearing T-shirts and jeans. The RTG is not a fission reactor. The PU238 fuel emits intense beta and low energy gamma. Your skin will block all beta radiation, but gamma is far more penetrating. However, RTG's are encased in heavy metals that block almost all gamma.

Dook wrote:

One or two more launches could bring in all the components for a buried habitat, they would actually already be on the planet before you launched your settlers so all you have to do is drive two Long Range Rovers over there with two Mars Carts and load them up. All the components for my Buried Habitat, a 20'x20' wide fiberglass walled hab, can be carried on two Mars Carts.

Can you provide a list of dimensions, materials, and weights, just for the structural stuff?

Dook wrote:

The problem is digging. You're going to hit permafrost once you get down a bit, you could just dig a bit then take a break and let the sun melt it and dig in the evenings when it's softened but, I don't know. I think two ATV dozers would be able to do it but an excavator might be needed. I'm going to have to think about how to fit one in or modify on of the ATV's to be an excavator.

You're right, digging in hard ground is difficult. That's why a TBM would be really useful, even if it's heavy.

Dook wrote:

The hab on Mars will require 6 RTG's for heating? Six sounds like way too much.

The RTG provides 300We. The robotic Dragon's solar panels generate 5kWe (5,000We). Orion's solar panels generate 11kWe (11,000We). Spacecraft, space stations, and Mars bases are power intensive operations. Declaring something unnecessary won't change reality.

RTG's generate 4.4kWt, but only .3kWe. If the graphene-based thermionic converters that University of Singapore is working on can actually deliver the 45% thermal-to-electric conversion efficiency promised, that's still less than 2kWe.

Dook wrote:

The CO2 scrubber is simply a small fan that blows over a filter. You can have two computer fans running all day long, they each use 3 watts an hour, that's 144 watts a day.

You're quoting a power requirement figure for an individual space suit. A space suit requires ~102We to provide all life support functions.

Dook wrote:

The water recycle system would require very little power, well, unless the engineers over design, and over complicated it. Have you ever taken a shower in a motor home? A small DC pump supplies the water pressure. The grey water would go down into a tank and flow through a filter and be re-used by the shower. No water is lost and the filters have to be changed out at times. The urinal would be next to the shower so urine would go into this grey water tank and be filtered and used in the shower as well. It sounds gross but you can filter out everything so it's pure water.

MIT MOXIE (O2 generator): 360We - Scaled up to generate enough O2 to replace what one person consumes in one hour

Hamilton Sundstrand CAMRAS (CO2 scrubber): 12We - Dumps 17lbs of O2 during vacuum regeneration of amine bed

Paragon SDC IWP (H2O recycler): 56We - Requires 23.7kWh for one cycle of 416 hours, so multiple IWP's required for recycling

Heating and Cooling: #We? - ISS requires 1.8kWe; the temperature swing on Mars isn't nearly as bad, but likely 1kWe, 24/7

What kind of solar panels are you taking with you? One RTG alone can't provide nearly enough power. A fuel cell would be a better option. Each Space Shuttle fuel cell, technology decades behind what NASA currently has in the labs, weighed 112kg and produced 7kWe with peak output capability of 12kWe.

If you want to import the hydrogen and combine it in a fuel cell to make water, that can feasibly provide enough power for your base. I would skip the RTG idea entirely. Fission reactors are the only nuclear power sources that produce enough output to make sense for human exploration of Mars. The new Infinity fuel cells that output 3kWe weigh less than RTG's, output ten times the amount of electrical power, and contain no radioactive material.

Dook wrote:

New drinking water would come from MOXIE made oxygen that is burned with hydrogen shipped from Earth. As I said before, some type of machine would do this. The water vapor from this machine is released into the habitat and then reconstituted by a dehumidifier that would flow the water into a clean drinking water tank. The plants in your habitat release water into the air anyway so you will need to operate a dehumidifier at times regardless.

Fuel cells would work for electrical power and drinking water requirements, but burn hydrogen? Probably not.

Dook wrote:

So, we have a system that re-uses probably over 90% of the habitat water with no energy intensive and over engineered 100% water recycling system. The only water lost is water that is in solid waste and that could be placed into a microwave to steam the water out into your hab air where the dehumidifier collects it.

Paragon SDC's IWP comes very close to the mark, recovering 85% of the water from brine (a combination of sweat, urine, and grey water) and power requirement is nominal.

Dook wrote:

The dehumidifier runs, I don't know, have to do some research, for maybe 15 minutes a day, might use 150 watts total.
Dust storms on Mars are trouble. They can actually last a whole year, that's one reason why I don't want just solar panels but also RTG's but even so, you can't land supplies and you can't drive in the rover so you're stuck in the habitat. It's something we have to plan for. They have to have enough supplies to last a very long time if that happens.

CAMRAS would take care of de-humidification.

Dook wrote:

There's no point in building a Mars Base if there isn't water? Three people would need one supply mission a year of food, hydrogen, chicken feed, and spare parts. Then you send one other mission a year that is full of habitat components. So these three keep building the same style buried habitats near the first one and they fill them all with fruit trees and vegetables grown from seeds they got from the plants in the first habitat. And they would have more chickens as well. It's not perfect but it's doable. No nuclear power plant needed and no "Total Recall" manufacturing of steel, glass, steam generators, or reflective panels.

The nuclear power plant is attached to the apparatus that buries habitat modules.

Dook wrote:

We have robots perform surgery? A completely independent robot with no human control? Uhh, you're going to have to send me the website link for that one.

Yes and yes.

Robot Surgeon Succeeds Without Help from Human Doctors

Robots don't consume oxygen, water, or food, they don't sleep, and they make no mistakes if their programming was defect-free. Machines are superb at performing repetitive tasks.

Dook wrote:

Once they get enough buried habs they won't be totally self sufficient but they won't need food shipments. The full self sufficiency thing was never going to happen on the timescale that some of you thought.

Can you predict the future?

If I told you thirty years ago that there would be a computer that would fit in your pocket that was more powerful than the Cray supercomputers of the time, would you have believed that?

Dook · 2016-10-30 23:24:57

RobertDyck wrote:

Robert Zubrin added the garage. I could post the mass chart from his June 1990 presentation to NASA, the one that didn't have a lower deck. But his book "The Case for Mars" has updated mass estimates including the lower deck. So Dr. Zubrin himself did it.
My estimates started with using the SAFE-400 reactor instead of SP-100. Both designed by the same team, but SP-100 was under development when Dr. Zubrin and his partner David Baker were working on Mars Direct in 1989 & 1990. Development of SP-100 was complete in 1992. Robert Zubrin had hoped a reactor to produce 85 kWe would mass a little less than one that produces 100 kWe. Unfortunately the reactor design team said the 85 kWe reactor would have the same mass. So the final mass for the reactor was greater than Dr. Zubrin's estimate. Oops. Work on SAFE-400 was completed in 2007; it's a lot newer. Every part was updated. The most dramatic was use of a better power converter. Both produce 100 kWe, but SP-100 requires 2,000 kW thermal while SAFE-400 can do it with 400 kW thermal. That means a smaller reactor core. And everything in the core is newer, lighter. This is the most dramatic mass reduction for the ERV.
I then used ISS equipment for life support, and Tesla power wall for the battery. Well, mass density, the hab would require a bigger one than the maximum configuration of "Power Wall". Power Wall uses lithium ion batteries. But ISS life support equipment is now known, we don't need to estimate. However, it's heavier than Dr. Zubrin's estimates. For the ERV capsule, I used SpaceX Dragon. But had to add a pressurized cargo module (PCM) from Cygnus basic (not extended) to house the recycling life support equipment.
Rather than repeat further, that thread is: Light weight nuclear reactor, updating Mars Direct
Landing: I would continue to use ADEPT for the heat shield that deploys like an umbrella. Dr. Zubrin doesn't use that name in his book, but that's the NASA heat shield he used. And land the same way. You don't think landing that way is sufficiently precise? Ok. As long as the hab lands within walking distance of the ERV, good enough. But you claim 800 km separation? That isn't good enough.

I don't know how precise landings will be on Mars. I don't know that anyone knows that yet. Can we land like SpaceX does? Yes, it's going to take more fuel.

Dook · 2016-10-31 00:41:42

kbd512 wrote:

Dook wrote:
A TBM is not a featherweight piece of machinery? I know. It's too heavy to get to Mars.
The Mars Direct tuna can weighs 28t. If the TBM is too heavy to get to Mars, so is the tuna can proposed by Dr. Zubrin.
Dook wrote:
It only weighs 25,080 lbs on Mars? Okay, that's still a lot. You're going to need a serious tracked trailer and rover to move it and you probably won't be able to move it in a straight line if there are rocks in the way or deep sand.
The TBM would have four tracks, each independently steerable like an all-weel drive and all-wheel steering car. Each track would be powered by a 100hp electric motor. It's actual hp/t ratio on Mars is significantly better than a M1 tank on Earth. The tracks are connected to the deck that holds the TBM. The deck can push smaller rocks out of its way, like a makeshift grading tool. The TBM itself is the part that holds the nuclear reactor, the electric motor that powers the blade, and the spoil removal system, is suspended above the ground and is actually above the deck.
The TBM's nuclear reactor has some shielding, but the shielding is insufficient for humans to work in close proximity to the operating reactor. You can't be closer than 10m to the reactor when the reactor is operating. The tool has an exclusion zone, but that zone is much smaller since the reactor itself is shielded rather than shielded by the environment.
Dook wrote:
Wouldn't a regular habitat made out of thick fiberglass honeycomb panels be better?
It would be better insulated.
The reason for burying the habitat modules has nothing to do with insulation and everything to do with blocking GCR's (intergalactic particles in the GeV range, typically protons but also some even nastier heavy ions), SPE's (solar particles in the MeV range), CME's (more solar particles in the MeV range), and the TBM reactor's radiation (gamma and neutrons). The habitat modules are thin spectra (a stronger kevlar variant), dacron, and kapton fabrics that can't block any of that.
Dook wrote:
The pressurized hab would exert a force that keeps the Mars regolith from collapsing the inflated hab? There is no way. If a tiny dusting of regolith falls on your inflatable, yeah, it will hold. If the tunnel collapses it's game over and you know it.
The bottom third of tunnels won't collapse. If the bottom third collapsed, then you're right, there's no way the pressurization of the module could over come the force of the regolith surrounding it. I have seen vertical shafts that were more than 10m in height here on Earth that had no concrete liner. However, I'd defer to an expert here. If I'm wrong, I'll drop this idea.
Dook wrote:
If not a TBM, what would I propose? The TBM is not an option, it's too heavy. You can't get it there so it never was an option.
If the TBM is too heavy, so is the tuna can.

Dook wrote:
Well, you can land in a very suitable Mars Hab that is 16.5 feet wide and has three bedrooms, oxygen storage, food storage, water storage built into the structure, solar cells already built into the top, a heating/cooling system, a communications system, a shower/toilet area, a dining area, maybe even a mini-MOXIE unit built in to supplement cabin oxygen.
Are you talking about living in Orion for a year? You stated how wide the habitat module would be. How long would it be?
There's physically not enough space to store the consumables, life support systems, and crew in Orion, which would include the deep-space only habitat variant (basically a miniature node module) proposed.
In numerous presentations, NASA and JPL depict inflatable habitat modules on Mars that weigh 40t delivered using ADEPT and retro-propulsion. That's not the weight of the EDL hardware and habitat module, that's the weight of the habitat module alone. That was and is considered a minimum requirement for a crew of four to six astronauts.
Dook wrote:
This is the tuna can idea that Zubrin proposed in Mars Direct to put a crew on Mars for 550 days, and he wanted four crew, if we only use three for a settlement the supplies would last even longer. And the tuna can would be on a steel frame and underneath it is an RTG that can be lowered and moved away from the Mars Hab. And there is a Long Range Rover underneath that you can use to go and get the other three Long Range Rovers left behind by the three exploration teams who came before and left.
A steel frame is unnecessary. The RTG is not a significant radiation hazard to the tuna can. Even if it was, it'd be easier and less expensive to dig a small hole for the RTG than to make the habitat heavier. One astronaut can dig a hole and one astronaut can carry the RTG and place it in the hole.
The RTG's emit intense beta and some low energy gamma. NASA technicians routinely touch RTG's with their hands here on Earth whilst wearing T-shirts and jeans. The RTG is not a fission reactor. The PU238 fuel emits intense beta and low energy gamma. Your skin will block all beta radiation, but gamma is far more penetrating. However, RTG's are encased in heavy metals that block almost all gamma.
Dook wrote:
One or two more launches could bring in all the components for a buried habitat, they would actually already be on the planet before you launched your settlers so all you have to do is drive two Long Range Rovers over there with two Mars Carts and load them up. All the components for my Buried Habitat, a 20'x20' wide fiberglass walled hab, can be carried on two Mars Carts.
Can you provide a list of dimensions, materials, and weights, just for the structural stuff?

Dook wrote:
The problem is digging. You're going to hit permafrost once you get down a bit, you could just dig a bit then take a break and let the sun melt it and dig in the evenings when it's softened but, I don't know. I think two ATV dozers would be able to do it but an excavator might be needed. I'm going to have to think about how to fit one in or modify on of the ATV's to be an excavator.
You're right, digging in hard ground is difficult. That's why a TBM would be really useful, even if it's heavy.
Dook wrote:
The hab on Mars will require 6 RTG's for heating? Six sounds like way too much.
The RTG provides 300We. The robotic Dragon's solar panels generate 5kWe (5,000We). Orion's solar panels generate 11kWe (11,000We). Spacecraft, space stations, and Mars bases are power intensive operations. Declaring something unnecessary won't change reality.
RTG's generate 4.4kWt, but only .3kWe. If the graphene-based thermionic converters that University of Singapore is working on can actually deliver the 45% thermal-to-electric conversion efficiency promised, that's still less than 2kWe.
Dook wrote:
The CO2 scrubber is simply a small fan that blows over a filter. You can have two computer fans running all day long, they each use 3 watts an hour, that's 144 watts a day.
You're quoting a power requirement figure for an individual space suit. A space suit requires ~102We to provide all life support functions.
Dook wrote:
The water recycle system would require very little power, well, unless the engineers over design, and over complicated it. Have you ever taken a shower in a motor home? A small DC pump supplies the water pressure. The grey water would go down into a tank and flow through a filter and be re-used by the shower. No water is lost and the filters have to be changed out at times. The urinal would be next to the shower so urine would go into this grey water tank and be filtered and used in the shower as well. It sounds gross but you can filter out everything so it's pure water.
MIT MOXIE (O2 generator): 360We - Scaled up to generate enough O2 to replace what one person consumes in one hour
Hamilton Sundstrand CAMRAS (CO2 scrubber): 12We - Dumps 17lbs of O2 during vacuum regeneration of amine bed
Paragon SDC IWP (H2O recycler): 56We - Requires 23.7kWh for one cycle of 416 hours, so multiple IWP's required for recycling
Heating and Cooling: #We? - ISS requires 1.8kWe; the temperature swing on Mars isn't nearly as bad, but likely 1kWe, 24/7
What kind of solar panels are you taking with you? One RTG alone can't provide nearly enough power. A fuel cell would be a better option. Each Space Shuttle fuel cell, technology decades behind what NASA currently has in the labs, weighed 112kg and produced 7kWe with peak output capability of 12kWe.
If you want to import the hydrogen and combine it in a fuel cell to make water, that can feasibly provide enough power for your base. I would skip the RTG idea entirely. Fission reactors are the only nuclear power sources that produce enough output to make sense for human exploration of Mars. The new Infinity fuel cells that output 3kWe weigh less than RTG's, output ten times the amount of electrical power, and contain no radioactive material.
Dook wrote:
New drinking water would come from MOXIE made oxygen that is burned with hydrogen shipped from Earth. As I said before, some type of machine would do this. The water vapor from this machine is released into the habitat and then reconstituted by a dehumidifier that would flow the water into a clean drinking water tank. The plants in your habitat release water into the air anyway so you will need to operate a dehumidifier at times regardless.
Fuel cells would work for electrical power and drinking water requirements, but burn hydrogen? Probably not.
Dook wrote:
So, we have a system that re-uses probably over 90% of the habitat water with no energy intensive and over engineered 100% water recycling system. The only water lost is water that is in solid waste and that could be placed into a microwave to steam the water out into your hab air where the dehumidifier collects it.
Paragon SDC's IWP comes very close to the mark, recovering 85% of the water from brine (a combination of sweat, urine, and grey water) and power requirement is nominal.
Dook wrote:
The dehumidifier runs, I don't know, have to do some research, for maybe 15 minutes a day, might use 150 watts total.
Dust storms on Mars are trouble. They can actually last a whole year, that's one reason why I don't want just solar panels but also RTG's but even so, you can't land supplies and you can't drive in the rover so you're stuck in the habitat. It's something we have to plan for. They have to have enough supplies to last a very long time if that happens.
CAMRAS would take care of de-humidification.
Dook wrote:
There's no point in building a Mars Base if there isn't water? Three people would need one supply mission a year of food, hydrogen, chicken feed, and spare parts. Then you send one other mission a year that is full of habitat components. So these three keep building the same style buried habitats near the first one and they fill them all with fruit trees and vegetables grown from seeds they got from the plants in the first habitat. And they would have more chickens as well. It's not perfect but it's doable. No nuclear power plant needed and no "Total Recall" manufacturing of steel, glass, steam generators, or reflective panels.
The nuclear power plant is attached to the apparatus that buries habitat modules.
Dook wrote:
We have robots perform surgery? A completely independent robot with no human control? Uhh, you're going to have to send me the website link for that one.
Yes and yes.
Robot Surgeon Succeeds Without Help from Human Doctors
Robots don't consume oxygen, water, or food, they don't sleep, and they make no mistakes if their programming was defect-free. Machines are superb at performing repetitive tasks.
Dook wrote:
Once they get enough buried habs they won't be totally self sufficient but they won't need food shipments. The full self sufficiency thing was never going to happen on the timescale that some of you thought.
Can you predict the future?
If I told you thirty years ago that there would be a computer that would fit in your pocket that was more powerful than the Cray supercomputers of the time, would you have believed that?

Well which is the TBM, 20 or 30 tons? I think we're going to have to agree to disagree on it. You can have your idea and I can have mine.

It would be better insulated from cosmic rays? Your vertical tunnel with inflatable hab would? A buried fiberglass habitat would have just over 8 feet of regolith on top of it so that should be fine.

The tunnels won't collapse? I think it's not just a risk, it's a huge risk and not necessary because we can build a buried hab and cover it with sand, or we can even build a half buried hab and cover it with enough regolith to protect against cosmic rays.

If the TBM is too heavy, so is the tuna can. I think that was one of the problems with Zubrin's idea, people thought his weight estimates were a bit off and it was going to be heavier than he predicted. Still, the tuna can wasn't just a tuna can, it had lab equipment, two open rovers, another pressurized rover, field science equipment, a crew of four, and 3.5 tonnes for spares. So, there's room to remove some things. For settlement, we don't need lab equipment or the two open rovers or the field science equipment and we can do it with a crew of three.

Am I talking about living in Orion for a year? Nope, not Orion, the tuna can. I don't remember what the size was for Zubrin's tuna can so I used the Orion size.

How long would it be? You're asking me to look all that up? Maybe someone here has all of it handy.
There's not enough space to store consumables, life support, and crew in Orion? Well what is NASA going to do with Orion if it doesn't have enough room for life support? I hope they never use it then.

NASA has a 40 ton inflatable habitat? You know, I don't doubt it one bit. You should see some of the absolutely ridiculous stuff they come up with, there's this crazy machine that looks like a giant daddy long legs spider with short fat wheels that are going to get stuck in sand but they can swivel all the way around and this thing only goes something like 2 mph and it's supposed to be a Mars Rover. It only holds two people so it won't be enough to move a crew from a Mars Hab to an ERV and you can get out and walk faster than this thing goes. I think when people are too smart they don't want to use simple ideas even though the simple ideas work best. They have to make it way more complex than necessary.

The steel frame is not necessary for the Mars Hab? It's absolutely necessary. The steel frame has the landing struts and holds the rocket engines for landing. Steel isn't for the RTG shielding, actually Zubrin's Mars Hab didn't include an RTG, but one drawn picture I saw had a small RTG under the hab so, I don't know.

Can I give you a list of dimensions, materials, and weights for my Buried Habitat? I'm still working on it but:

It's two stories, buried under 8.2 feet of regolith. It's 20'x20', walls are made of 1' long by 6" tall by 6" thick fiberglass lego blocks. Just like lego blocks they are mostly hollow, most of the walls are already assembled, the floors and ceiling panels are 6" thick fiberglass honeycomb panels that are 10'x10' each with lego fittings on the edges for the lego blocks to fit into.

There is a central fiberglass support column for both levels, and a fiberglass access tube with a pressure hatch at the top that opens into a fiberglass depressurization area that has a pressure door. The upper level of the hab has three rooms with dividing walls (no doors), a bathroom/shower, and a common area. The walls are fiberglass honeycomb and fit into and support the upper ceiling. The lower level is the growing area with hydroponics, tubs of trees, other vegetables, the four chickens, and a plastic locker for growing mushrooms.

I've already described the toilet/shower.

And 22 solar panels come with it. I think I can move all of it in one Mars Direct launch and all of the components could be moved on Mars with two of my Long Range Rovers towing my Mars Carts.

Still need to figure out how to warm it without using electric heater and how to dig out the area on Mars, and how to hook a large MOXIE unit to it, and more.

I think two ATV dozers could dig out an area of soft dirt but they might need some kind of excavator also so I need to design one. The ATV dozers are on a separate launch but so is the Long Range Rover and Mars Carts.

The Mars Hab will require six RTGs because the ISS requires that much power just to heat it? Space is colder than Mars is and we can use other methods for heating the habitat, like maybe pumping habitat air through a pipe that goes to the surface and is heated by a circle of mirrors to warm the hab before nightfall.

My watt estimate for CO2 scrubbing is too low? Okay, how much air do you think we need to move then? Four computer fans? That's 288 watts. It's nothing compared to other electricity needs. The wattage used by LED lights would be more.

The MOXIE unit would be outside the Buried Habitat. I think two large mobile MOXIE units should be delivered years before any humans launch to Mars. They would need to have an RTG built in so they can self operate and fill their oxygen tanks before humans even depart.

What kind of solar panels am I taking? Uhh, thin sheet of fiberglass with solar cells glued to one side type.

One RTG can't provide nearly enough power? It only has to provide power for night time, the solar panels and the RTG provide power in the day.

A fuel cell would be a better option? Not if I can get everything done with just the solar panels and RTG. Remember, there will be three exploration landings before we send settlers so there will be three RTG's and three sets of solar panels and three Long Range Rovers already on the planet. We just have to drive over and get them and once we have two rovers we can bring one back to the base and leave it there in case the other one gets stuck or breaks down somewhere.

I do like the idea of using the fuel cell to make power and water from the hydrogen and oxygen gas, I did need a good way to make water, something to consider.

Robots can perform surgery? Well, the website showed a surgeon supervising the robot but still that's more than I thought we could do. If we want to wait, I'm sure there will come a day when we can have robots on Mars do all kinds of things.

Can I predict the future? Yes. You mean you can't? I predict that some Islamic terrorist is going to shoot some people in Europe or the US in the future. I predict that in the future California will experience a drought. I predict that in the future the Kardashians will do something I think is really stupid. I predict that the sun will rise tomorrow morning. I predict that next summer it's going to be really freaken hot. I predict that Haley's Comet will show up in, ooh, I don't know, maybe 2061. You want some more or is that enough?

kbd512 · 2016-10-31 03:44:03

Dook wrote:

Well which is the TBM, 20 or 30 tons? I think we're going to have to agree to disagree on it. You can have your idea and I can have mine.

Actual weight depends greatly on how it's constructed.

Examples:

The deck could be steel, aluminum, or composite. Steel is a lot heavier than composite.

You could use standard industrial 375kW motors that weighs 2t to 3t, but there are motors that weigh substantially less using different materials.

Dook wrote:

It would be better insulated from cosmic rays? Your vertical tunnel with inflatable hab would? A buried fiberglass habitat would have just over 8 feet of regolith on top of it so that should be fine.

Martian regolith is 1520kg per cubic meter and you want 2.4m of regolith over the top. That's 3706kg of regolith per cubic meter. If pressurization ever fails, it'd have to be a very sturdy fiberglass habitat.

Dook wrote:

The tunnels won't collapse? I think it's not just a risk, it's a huge risk and not necessary because we can build a buried hab and cover it with sand, or we can even build a half buried hab and cover it with enough regolith to protect against cosmic rays.

You're worried about a vertical shaft collapse, but putting 3.7t/m^3 worth of material over the top of every square meter of your habitat. There are numerous photographs of vertical shafts that are wider in diameter and deeper that haven't collapsed. It's not the problem you're making it out to be on a planet where the water is frozen. The shaft is only 10M deep and 5m wide.

Dook wrote:

If the TBM is too heavy, so is the tuna can. I think that was one of the problems with Zubrin's idea, people thought his weight estimates were a bit off and it was going to be heavier than he predicted. Still, the tuna can wasn't just a tuna can, it had lab equipment, two open rovers, another pressurized rover, field science equipment, a crew of four, and 3.5 tonnes for spares. So, there's room to remove some things. For settlement, we don't need lab equipment or the two open rovers or the field science equipment and we can do it with a crew of three.

Dr. Zubrin's habitat was 28.42t or 62,524 lbs. If you use Dr. Zubrin's weight estimates, that removes just 2.75t from the 28.42t tuna can. That's still just as heavy as the TBM. Either you're proposing something markedly different from what Dr. Zubrin proposed or you're arguing in circles about how much smaller and lighter your habitat would be.

Dook wrote:

Am I talking about living in Orion for a year? Nope, not Orion, the tuna can. I don't remember what the size was for Zubrin's tuna can so I used the Orion size.

The tuna can was 8.4m or 33ft in diameter and 11.1m or 36ft tall.

Dook wrote:

How long would it be? You're asking me to look all that up? Maybe someone here has all of it handy.

I did your research for you. The numbers are listed above.

Mars Direct: Humans to the Red Planet within a Decade

Dook wrote:

There's not enough space to store consumables, life support, and crew in Orion? Well what is NASA going to do with Orion if it doesn't have enough room for life support? I hope they never use it then.

In the last post I responded to, you gave a habitat diameter that corresponds to the base diameter of Orion.

Orion has life support and it has storage space, but not nearly enough for the 180 day trip to or from Mars nor the 500 day surface stay for a conjunction class mission.

Dook wrote:

NASA has a 40 ton inflatable habitat? You know, I don't doubt it one bit. You should see some of the absolutely ridiculous stuff they come up with, there's this crazy machine that looks like a giant daddy long legs spider with short fat wheels that are going to get stuck in sand but they can swivel all the way around and this thing only goes something like 2 mph and it's supposed to be a Mars Rover. It only holds two people so it won't be enough to move a crew from a Mars Hab to an ERV and you can get out and walk faster than this thing goes. I think when people are too smart they don't want to use simple ideas even though the simple ideas work best. They have to make it way more complex than necessary.

ATHLETE? Yeah, that's a crazy looking robot. It was designed to make the surface habitat mobile, except it uses wheels and the habitats NASA wants to use would create an incredible ground pressure at half the weight they proposed. NASA created ATHLETE so the habitat module could be lifted off the EDL hardware by that robot. The concept is, well, it's definitely NASA.

Dook wrote:

The steel frame is not necessary for the Mars Hab? It's absolutely necessary. The steel frame has the landing struts and holds the rocket engines for landing. Steel isn't for the RTG shielding, actually Zubrin's Mars Hab didn't include an RTG, but one drawn picture I saw had a small RTG under the hab so, I don't know.

The tuna can uses aluminum. Mars Direct included a 100kWe nuclear fission reactor. That's how Dr. Zubrin intended to power the base. If you have that kind of power on tap, you don't have to have the worlds most efficient life support systems.

Dook wrote:

Can I give you a list of dimensions, materials, and weights for my Buried Habitat? I'm still working on it but:
It's two stories, buried under 8.2 feet of regolith. It's 20'x20', walls are made of 1' long by 6" tall by 6" thick fiberglass lego blocks. Just like lego blocks they are mostly hollow, most of the walls are already assembled, the floors and ceiling panels are 6" thick fiberglass honeycomb panels that are 10'x10' each with lego fittings on the edges for the lego blocks to fit into.

Is this what you want to use?

HexWebTM Honeycomb Attributes and Properties

Dook wrote:

There is a central fiberglass support column for both levels, and a fiberglass access tube with a pressure hatch at the top that opens into a fiberglass depressurization area that has a pressure door. The upper level of the hab has three rooms with dividing walls (no doors), a bathroom/shower, and a common area. The walls are fiberglass honeycomb and fit into and support the upper ceiling. The lower level is the growing area with hydroponics, tubs of trees, other vegetables, the four chickens, and a plastic locker for growing mushrooms.

How are you sealing this building?

Dook wrote:

I've already described the toilet/shower.

Ok.

Dook wrote:

And 22 solar panels come with it. I think I can move all of it in one Mars Direct launch and all of the components could be moved on Mars with two of my Long Range Rovers towing my Mars Carts.

What kind of panels? What would they weigh? What's the output? What would the batteries weigh?

Dook wrote:

Still need to figure out how to warm it without using electric heater and how to dig out the area on Mars, and how to hook a large MOXIE unit to it, and more.

Ok.

Dook wrote:

I think two ATV dozers could dig out an area of soft dirt but they might need some kind of excavator also so I need to design one. The ATV dozers are on a separate launch but so is the Long Range Rover and Mars Carts.

What's going to power the ATV's?

Dook wrote:

The Mars Hab will require six RTGs because the ISS requires that much power just to heat it? Space is colder than Mars is and we can use other methods for heating the habitat, like maybe pumping habitat air through a pipe that goes to the surface and is heated by a circle of mirrors to warm the hab before nightfall.

Are you trying to build a base or just one module?

Dook wrote:

My watt estimate for CO2 scrubbing is too low? Okay, how much air do you think we need to move then? Four computer fans? That's 288 watts. It's nothing compared to other electricity needs. The wattage used by LED lights would be more.

I provided the power usage for MOXIE and CAMRAS. Those were actual power consumption figures given by NASA technical reports. CAMRAS was flown in space aboard ISS, so there's no ambiguity there. The MOXIE power consumption figures come from ground testing on Earth since it's not going to Mars until 2020.

Dook wrote:

The MOXIE unit would be outside the Buried Habitat. I think two large mobile MOXIE units should be delivered years before any humans launch to Mars. They would need to have an RTG built in so they can self operate and fill their oxygen tanks before humans even depart.

Why not just bring O2 with you? Sending something to Mars isn't cheap. RTG's aren't cheap. Pu238 is $6M/kg. The Pu238 in a RTG costs more than SAFE-400.

Dook wrote:

What kind of solar panels am I taking? Uhh, thin sheet of fiberglass with solar cells glued to one side type.

What's the weight and power output?

Dook wrote:

One RTG can't provide nearly enough power? It only has to provide power for night time, the solar panels and the RTG provide power in the day.

Fuel cells need oxygen and hydrogen and produce water when they make electricity. The Space Shuttle crews received their drinking water from the fuel cells onboard. You said you wanted to bring hydrogen from Earth. Is there some better use for the hydrogen? A 75kg fuel cell can provide 3000We, day or night. The reactor can provide 300We, day or night. That extra zero on the end really helps, the RTG can't make water, and the fuel cell costs substantially less than the Pu238 in the RTG. It's true that the RTG will keep producing power for decades, but the fuel cell produces a lot more and drinking water.

Dook wrote:

A fuel cell would be a better option? Not if I can get everything done with just the solar panels and RTG. Remember, there will be three exploration landings before we send settlers so there will be three RTG's and three sets of solar panels and three Long Range Rovers already on the planet. We just have to drive over and get them and once we have two rovers we can bring one back to the base and leave it there in case the other one gets stuck or breaks down somewhere.

Your plan is to travel all over Mars, collecting RTG's, so you can build a base?

Dook wrote:

I do like the idea of using the fuel cell to make power and water from the hydrogen and oxygen gas, I did need a good way to make water, something to consider.

If you're going to bring hydrogen gas from Earth, fuel cells make more sense than RTG's. The only use of RTG's in human space exploration was to power some science experiments on the moon. Fuel cells and batteries provided power for Apollo and the LEM.

Dook wrote:

Robots can perform surgery? Well, the website showed a surgeon supervising the robot but still that's more than I thought we could do. If we want to wait, I'm sure there will come a day when we can have robots on Mars do all kinds of things.

Supervising is typically a fancy word for standing around and watching. The robot did the work and the surgeon watched it work.

Dook wrote:

Can I predict the future? Yes. You mean you can't? I predict that some Islamic terrorist is going to shoot some people in Europe or the US in the future. I predict that in the future California will experience a drought. I predict that in the future the Kardashians will do something I think is really stupid. I predict that the sun will rise tomorrow morning. I predict that next summer it's going to be really freaken hot. I predict that Haley's Comet will show up in, ooh, I don't know, maybe 2061. You want some more or is that enough?

Good one.

Dook · 2016-10-31 11:33:51

kbd512 wrote:

Dook wrote:
Well which is the TBM, 20 or 30 tons? I think we're going to have to agree to disagree on it. You can have your idea and I can have mine.
Actual weight depends greatly on how it's constructed.
Examples:
The deck could be steel, aluminum, or composite. Steel is a lot heavier than composite.
You could use standard industrial 375kW motors that weighs 2t to 3t, but there are motors that weigh substantially less using different materials.
Dook wrote:
It would be better insulated from cosmic rays? Your vertical tunnel with inflatable hab would? A buried fiberglass habitat would have just over 8 feet of regolith on top of it so that should be fine.
Martian regolith is 1520kg per cubic meter and you want 2.4m of regolith over the top. That's 3706kg of regolith per cubic meter. If pressurization ever fails, it'd have to be a very sturdy fiberglass habitat.
Dook wrote:
The tunnels won't collapse? I think it's not just a risk, it's a huge risk and not necessary because we can build a buried hab and cover it with sand, or we can even build a half buried hab and cover it with enough regolith to protect against cosmic rays.
You're worried about a vertical shaft collapse, but putting 3.7t/m^3 worth of material over the top of every square meter of your habitat. There are numerous photographs of vertical shafts that are wider in diameter and deeper that haven't collapsed. It's not the problem you're making it out to be on a planet where the water is frozen. The shaft is only 10M deep and 5m wide.
Dook wrote:
If the TBM is too heavy, so is the tuna can. I think that was one of the problems with Zubrin's idea, people thought his weight estimates were a bit off and it was going to be heavier than he predicted. Still, the tuna can wasn't just a tuna can, it had lab equipment, two open rovers, another pressurized rover, field science equipment, a crew of four, and 3.5 tonnes for spares. So, there's room to remove some things. For settlement, we don't need lab equipment or the two open rovers or the field science equipment and we can do it with a crew of three.
Dr. Zubrin's habitat was 28.42t or 62,524 lbs. If you use Dr. Zubrin's weight estimates, that removes just 2.75t from the 28.42t tuna can. That's still just as heavy as the TBM. Either you're proposing something markedly different from what Dr. Zubrin proposed or you're arguing in circles about how much smaller and lighter your habitat would be.
Dook wrote:
Am I talking about living in Orion for a year? Nope, not Orion, the tuna can. I don't remember what the size was for Zubrin's tuna can so I used the Orion size.
The tuna can was 8.4m or 33ft in diameter and 11.1m or 36ft tall.
Dook wrote:
How long would it be? You're asking me to look all that up? Maybe someone here has all of it handy.
I did your research for you. The numbers are listed above.
Mars Direct: Humans to the Red Planet within a Decade
Dook wrote:
There's not enough space to store consumables, life support, and crew in Orion? Well what is NASA going to do with Orion if it doesn't have enough room for life support? I hope they never use it then.
In the last post I responded to, you gave a habitat diameter that corresponds to the base diameter of Orion.
Orion has life support and it has storage space, but not nearly enough for the 180 day trip to or from Mars nor the 500 day surface stay for a conjunction class mission.
Dook wrote:
NASA has a 40 ton inflatable habitat? You know, I don't doubt it one bit. You should see some of the absolutely ridiculous stuff they come up with, there's this crazy machine that looks like a giant daddy long legs spider with short fat wheels that are going to get stuck in sand but they can swivel all the way around and this thing only goes something like 2 mph and it's supposed to be a Mars Rover. It only holds two people so it won't be enough to move a crew from a Mars Hab to an ERV and you can get out and walk faster than this thing goes. I think when people are too smart they don't want to use simple ideas even though the simple ideas work best. They have to make it way more complex than necessary.
ATHLETE? Yeah, that's a crazy looking robot. It was designed to make the surface habitat mobile, except it uses wheels and the habitats NASA wants to use would create an incredible ground pressure at half the weight they proposed. NASA created ATHLETE so the habitat module could be lifted off the EDL hardware by that robot. The concept is, well, it's definitely NASA.
Dook wrote:
The steel frame is not necessary for the Mars Hab? It's absolutely necessary. The steel frame has the landing struts and holds the rocket engines for landing. Steel isn't for the RTG shielding, actually Zubrin's Mars Hab didn't include an RTG, but one drawn picture I saw had a small RTG under the hab so, I don't know.
The tuna can uses aluminum. Mars Direct included a 100kWe nuclear fission reactor. That's how Dr. Zubrin intended to power the base. If you have that kind of power on tap, you don't have to have the worlds most efficient life support systems.
Dook wrote:
Can I give you a list of dimensions, materials, and weights for my Buried Habitat? I'm still working on it but:
It's two stories, buried under 8.2 feet of regolith. It's 20'x20', walls are made of 1' long by 6" tall by 6" thick fiberglass lego blocks. Just like lego blocks they are mostly hollow, most of the walls are already assembled, the floors and ceiling panels are 6" thick fiberglass honeycomb panels that are 10'x10' each with lego fittings on the edges for the lego blocks to fit into.
Is this what you want to use?
HexWebTM Honeycomb Attributes and Properties
Dook wrote:
There is a central fiberglass support column for both levels, and a fiberglass access tube with a pressure hatch at the top that opens into a fiberglass depressurization area that has a pressure door. The upper level of the hab has three rooms with dividing walls (no doors), a bathroom/shower, and a common area. The walls are fiberglass honeycomb and fit into and support the upper ceiling. The lower level is the growing area with hydroponics, tubs of trees, other vegetables, the four chickens, and a plastic locker for growing mushrooms.
How are you sealing this building?
Dook wrote:
I've already described the toilet/shower.
Ok.
Dook wrote:
And 22 solar panels come with it. I think I can move all of it in one Mars Direct launch and all of the components could be moved on Mars with two of my Long Range Rovers towing my Mars Carts.
What kind of panels? What would they weigh? What's the output? What would the batteries weigh?
Dook wrote:
Still need to figure out how to warm it without using electric heater and how to dig out the area on Mars, and how to hook a large MOXIE unit to it, and more.
Ok.
Dook wrote:
I think two ATV dozers could dig out an area of soft dirt but they might need some kind of excavator also so I need to design one. The ATV dozers are on a separate launch but so is the Long Range Rover and Mars Carts.
What's going to power the ATV's?
Dook wrote:
The Mars Hab will require six RTGs because the ISS requires that much power just to heat it? Space is colder than Mars is and we can use other methods for heating the habitat, like maybe pumping habitat air through a pipe that goes to the surface and is heated by a circle of mirrors to warm the hab before nightfall.
Are you trying to build a base or just one module?
Dook wrote:
My watt estimate for CO2 scrubbing is too low? Okay, how much air do you think we need to move then? Four computer fans? That's 288 watts. It's nothing compared to other electricity needs. The wattage used by LED lights would be more.
I provided the power usage for MOXIE and CAMRAS. Those were actual power consumption figures given by NASA technical reports. CAMRAS was flown in space aboard ISS, so there's no ambiguity there. The MOXIE power consumption figures come from ground testing on Earth since it's not going to Mars until 2020.
Dook wrote:
The MOXIE unit would be outside the Buried Habitat. I think two large mobile MOXIE units should be delivered years before any humans launch to Mars. They would need to have an RTG built in so they can self operate and fill their oxygen tanks before humans even depart.
Why not just bring O2 with you? Sending something to Mars isn't cheap. RTG's aren't cheap. Pu238 is $6M/kg. The Pu238 in a RTG costs more than SAFE-400.
Dook wrote:
What kind of solar panels am I taking? Uhh, thin sheet of fiberglass with solar cells glued to one side type.
What's the weight and power output?
Dook wrote:
One RTG can't provide nearly enough power? It only has to provide power for night time, the solar panels and the RTG provide power in the day.
Fuel cells need oxygen and hydrogen and produce water when they make electricity. The Space Shuttle crews received their drinking water from the fuel cells onboard. You said you wanted to bring hydrogen from Earth. Is there some better use for the hydrogen? A 75kg fuel cell can provide 3000We, day or night. The reactor can provide 300We, day or night. That extra zero on the end really helps, the RTG can't make water, and the fuel cell costs substantially less than the Pu238 in the RTG. It's true that the RTG will keep producing power for decades, but the fuel cell produces a lot more and drinking water.
Dook wrote:
A fuel cell would be a better option? Not if I can get everything done with just the solar panels and RTG. Remember, there will be three exploration landings before we send settlers so there will be three RTG's and three sets of solar panels and three Long Range Rovers already on the planet. We just have to drive over and get them and once we have two rovers we can bring one back to the base and leave it there in case the other one gets stuck or breaks down somewhere.
Your plan is to travel all over Mars, collecting RTG's, so you can build a base?
Dook wrote:
I do like the idea of using the fuel cell to make power and water from the hydrogen and oxygen gas, I did need a good way to make water, something to consider.
If you're going to bring hydrogen gas from Earth, fuel cells make more sense than RTG's. The only use of RTG's in human space exploration was to power some science experiments on the moon. Fuel cells and batteries provided power for Apollo and the LEM.
Dook wrote:
Robots can perform surgery? Well, the website showed a surgeon supervising the robot but still that's more than I thought we could do. If we want to wait, I'm sure there will come a day when we can have robots on Mars do all kinds of things.
Supervising is typically a fancy word for standing around and watching. The robot did the work and the surgeon watched it work.
Dook wrote:
Can I predict the future? Yes. You mean you can't? I predict that some Islamic terrorist is going to shoot some people in Europe or the US in the future. I predict that in the future California will experience a drought. I predict that in the future the Kardashians will do something I think is really stupid. I predict that the sun will rise tomorrow morning. I predict that next summer it's going to be really freaken hot. I predict that Haley's Comet will show up in, ooh, I don't know, maybe 2061. You want some more or is that enough?
Good one.

It's not that I want 2.4 meters of regolith over the top of the Buried Habitat, that's what Zubrin says is needed to shield against cosmic rays.

It has to be sturdy but fiberglass can be made strong. The ceiling panels are 6" thick, they could be made of a 1" fiberglass panel on top and bottom then alternating, 1/2" honeycomb, and 1/2" thick panels in between. I don't know the weight of each panel yet, have to figure that out. The edges of the ceiling and floor panels have lego knobs on them so they lock into the walls on their top and bottom, and there are thin lego style backing plates that go underneath the ceiling and floor panels to lock them together. Everything is sealed before assembly. About 70% of the wall blocks are already assembled.

Also, there is a 1' hollow fiberglass cylinder that has a 2'x2' lego pad on top and bottom that also locks into the underside of the ceiling panels where they all come together at the center of the room. The ceiling and floor panels are 10'x10' so it takes eight ceiling panels and four floor panels to make the two story 20'x20' habitat.

We're going to have to agree to disagree about the tunnel boring machine on Mars. Even if we can get it there. You can keep your idea and I can keep mine.

I'm not going in circles. I posted my Buried Habitat idea made of lego blocks weeks ago.

You did my research for me? It wasn't my research, you're the one who wanted to know.

Orion is not enough space for a trip to Mars? I didn't say it was. I also didn't say that it might just launch from the Earth and dock with a transfer vehicle already in orbit.

Athlete is what that stupid machine is called? It's a waste of probably $1 million of my tax dollars.

The tuna can is aluminum? I'm sure it is, maybe the landing legs are made of aluminum too. I don't know, don't really care. They're going to do what they want to do, not what I think they should do. I would use steel landing legs but that's me.

Zubrin planned to have a 100 kw nuclear fission reactor? Maybe he did, it's not listed on the weights for a Mars Direct mission so maybe he mentioned it somewhere else, I don't know. Having a lot of power is great. I didn't say it wasn't. I'm just saying that when simple works, use it and don't over design when it's not necessary.

After the Apollo missions what we've gotten from NASA isn't efficiency, it's mostly waste. We went to the moon with 1960's knowledge and equipment then got stuck in low Earth orbit with the Space Shuttle. Hubble was messed up and they never tested it on the ground. They screwed up the 90 report to President Bush then when Zubrin gives them Mars Direct instead of jumping all over it they're embarrassed and try to dismiss it. Orion is about useless, why go back to the moon? The Mars Rovers have done well but that's small candy, we could have put men on Mars ten years ago.

I couldn't pull up the web page you posted on honeycomb. Fiberglass honeycomb is standard stuff used in radomes on fighter jets and some floor panels for aircraft. It's very light and very strong in one direction.

How am I sealing my Buried Habitat? Silicone sealant, or we could have a tape like sealant roll that the crew just tears off a piece and places it in before putting on the next lego block.

The ATV's are powered by three batteries each.

Am I trying to build a base or just one module? Every Base has to have a first building. We'd have the Mars Hab to live in, dig out and assemble the Buried Hab somewhere close, then dig out the next spot and get the next shipment of Buried Habitat components and just keep going. I think it would take one shipment a year with food, hydrogen, chicken feed, and spare parts, and a second shipment of Buried Habitat components. Two crew work outside driving the rovers and building the habitats while one stays back to tend to the chickens, plants, and communications each day. They could rotate. Also, if the two in the rover break down somewhere the one back at the base can drive one of the other rovers out to get them.

I have to look at the MOXIE more in depth. My plan is to have at least two operating large mobile MOXIE units on Mars with already full oxygen tanks before the crew leaves the Earth. The crew can drive the rover over and pull them back to base.

Why not just bring O2 with you? The Mars Hab lander will certainly have O2 storage on board for the long trip to Mars and surface stay. Why not attempt to have years worth of oxygen storage on board? Weight, that's why. And you won't have to if you know that you have two large mobile operational MOXIE units on Mars with full oxygen tanks. If one of the MOXIE's isn't working you don't go.

Sending RTG's to Mars isn't cheap? But they will already be there. The exploration missions would have already sent RTG's. Three explorations missions, then two large MOXIE missions, then one Buried Habitat mission, all have to land safely and be operating, then we send the crew.

What is the weight and power of the solar panels? Zubrin's chart says 5 kw is 1 tonne.

Is there some better use for hydrogen on Mars than making water? You get pure water out of it, that's pretty darned good.

My plan is to travel all over Mars collecting RTG's? Not just collecting RTG's but solar arrays left behind, hydrogen and oxygen tanks left at the ERV sites, getting hab components, getting supply shipments. We don't know how close things are going to be delivered yet. Everyone here thinks every supply shipment is going to land next to the base because SpaceX can launch and land a rocket on a pad. But that SpaceX rocket didn't perform an aerobrake entry into an atmosphere. Things are going to be all over the place and you might not be able to travel in straight lines, you're going to have to drive around rock fields. You might actually have to get out and move a rock at a time for days and days to make a road that the rover and towed Mars Cart can get through.

Fuel cells make more sense than RTG's? But the RTG's are already there and we can get the oxygen and hydrogen tanks also.
The robot did the surgery? Fine then, use that robot with your TBM. You can have your idea and I can keep my idea.

Last edited by Dook (2016-10-31 11:36:31)

kbd512 · 2016-10-31 18:25:36

Ok, Dook. Sounds great.

SpaceNut · 2016-10-31 19:38:05

Glad that some one finally posted a reply without quoting an entire post in quote......its not needed...it just makes it harder to read the posting, try to not quote entire post... Thanks.

Dook · 2016-11-01 11:53:24

Another problem/idea: The ERV will have a small capsule that takes the exploration team into orbit where they will dock with a transfer vehicle. The large MOXIE unit will be left behind. If it had wheeled tracks that large MOXIE could be towed to the Mars Base and used by the first settlers. They would need to refill the hydrogen tank.

JoshNH4H · 2016-11-01 15:51:52

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

Glad to hear it, but I find that when people have posts modified they're upset more often than not. Civil discussion is important of course but it's bad for the forum if moderation drives away our users.

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

Agreed that an imported greenhouse should not be made of glass. Getting ahead of myself!

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.
[...]
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.

It's true that plants produce oxygen at low rates, but it's also true that they grow food at low rates. What I'm getting at is that when you use plants to make food, the carbon cycle will always (approximately) balance out. Plants take CO2 and water (and some other stuff) and turn it into Oxygen and Food (and some other stuff). People do the reverse. If the greenhouse is there to supply some portion of the colony's food, then it can also supply a similar portion of the colony's oxygen.

On the other hand, if the greenhouse is experimental or if oxygen is found to be extremely cheap to produce perhaps you don't care. Perhaps the mass savings is important enough that it's worth using electrical energy to make oxygen.

I can offer the following reasons why I believe hab-pressure greenhouses make sense. There are other reasons (chief among them lighter and simpler greenhouses) why you would want a lower pressure or a different atmospheric condition, but I believe that this argument is persuasive.

A food-producing greenhouse will also produce breathable oxygen
Agricultural labor will be more productive in a breathable vs. non-breathable atmosphere. (This seems like a good place to note that there's no way food production will be entirely automatic. But even if it is, who will service the machines?)
An open-air space with breathable air and views of the outside will be a nice break from small, windowless rooms.
Produce may be damaged by the transition from low pressure to breathable pressure. Have you ever tried to take an apple from one atmosphere to 1.25 or 1.5? I haven't, but I wouldn't be surprised if it were worse for the experience.
In addition to their oxygen producing qualities, plants are pretty good at cleaning the air of various other bad chemicals
By controlling the air flow rate with the rest of the colony, the greenhouse can be used for thermal control (see below)

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.

RobertDyck has given his normal schtick on greenhouse materials. The one he suggests seems fine.

Based on a research/modelling project I did in college, equilibrium temperature is not such a big issue in a greenhouse with several layers of IR-opaque material. It turns out that most IR-absorptive materials are, if anything, too absorptive, especially if you have three layers. A bigger problem is thermal stability: Even if the average temperature is right where you want it to be, the greenhouse can get extremely hot during the day and pretty cold at night.

There are three basic ways to reduce the amplitude of diurnal temperature variations. The first is to heat and cool the greenhouse as necessary to get to the right temperature. The second is to design a greenhouse whose thermal properties can be modified to affect its internal temperature (for example, by pulling something like a blanket over it at night or having adjustable reflector mirrors), and the third is to increase its thermal inertia by connecting it to a larger thermal mass.

One example of a large thermal mass would be the colony's water supply. An example of an even larger thermal mass is the entire colony. Yep, if you're using the greenhouse as the lungs of the colony, you might also be able to use it as its thyroid and regulate temperature with airflow.

To some extent, you'll probably use all three strategies. You'll probably want the colony to run hot because it's probably cheaper to radiate heat away than it is to generate more.

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.

As opposed to an atmosphere with no buffer gas, where sudden depressurization will lead to a slightly less painful death for everyone

Accidents are probably going to be the leading cause of death for Martian colonists, so safety measures like this will probably be critical.

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?

Based on my somewhat limited knowledge of the biology of atmospherics, I would make the atmosphere look something like this

50 kPa total:

17 kPa (34%) Oxygen (comparable to Denver, CO or Mexico City, Mexico)
16 kPa (32%) Argon
16 kPa (32%) Nitrogen (The ratio of Argon to Nitrogen should be the same as that in the Martian atmosphere so that you don't have to separate one from the other)
0.5 kPa (1%) Water (Relative Humidity of 20%)
0.5 kPa (1%) CO2 (Per the Minimal Atmospheres link I posted earlier, this will probably aid plant growth without harming humans in any way after a brief adjustment period)

There's some room for pressure reduction in this atmosphere. You could probably get the pressure down to 40 kPa if you really wanted to by reducing Oxygen a bit and buffers a lot. More testing is needed.

As far as Nitrogen goes, Earth's atmosphere has 78 kPa, and it's partial pressures rather than percent composition that matter for health effects. With about 80% less Nitrogen, I would expect the decompression routines to be much simpler, if they're necessary at all.

Space Suits use 30 kPa of pure Oxygen, meaning that you have a 70 kPa pressure change from the ISS and lose 78 kPa of Nitrogen. Using this hab atmosphere and the same suit atmosphere, you would see a 20 kPa pressure change between inside and outside and a 16 kPa reduction in Nitrogen. That's about the same as coming up from a dive 2 meters below the surface of the ocean.

Mechanical Counter Pressure suits (Possibly the only thing we all agree on?) are much more maneuverable than the spacesuits NASA uses. NASA uses a 30 kPa suit pressure because lower pressure=easier to move around. If the decompression routine is troublesome it's possible the colonists will decide to up the suit pressure and lower the hab pressure to meet in the middle.

Dook · 2016-11-01 17:59:45

The greenhouse can supply oxygen? I think you're idea is that the greenhouse is connected to the rest of the habitat so the oxygen that the greenhouse makes is used in breathing. My idea is to have the greenhouse built over the buried hab, the hab would have a regular pressurized atmosphere while the greenhouse is at 2 psi.

Agricultural labor is more productive in a breathable atmosphere? Yes, but I think your idea of a first greenhouse is something much larger than the one I was thinking of. A small greenhouse wouldn't need much labor at all, water the trees once a day, run a dehumidifier once in a while, check the pressure inside and turn on the pump if it needs a boost. You can do that in a Mars Suit. I don't know about oxygenating the greenhouse to a level that would allow humans to breathe inside of it, kind of seems like a waste of oxygen. I'll have to think about that one.

I didn't consider that fruit would be damaged by moving it from a low pressure greenhouse to a higher pressure habitat. The fruit would probably get distorted but you can still eat it.

The inflatable greenhouse seems fine? For how long? It's plastic bag thin. Mars wind at 6 mph will move it around and temperature changes will have an effect on it over time. What if someone is using a shovel near the sidewall? If you're okay with it lasting a year then that's fine but why not just build something a little stronger?

The thing about plants is that they can get fooled by temperature changes. They will go dormant and drop their leaves. Fruit dies if the temperature hits freezing. So if you're going to heat your greenhouse, are you going to use waste heat from a nuclear plant or RTG?

I like the mirror heating idea. I wonder if there could be some kind of heat sink we could develop inside the greenhouse? Maybe a storage tank full of water that the mirror heats during the day? Not sure if it would give you very much.

If there was a sudden depressurization loss inside your habitat, either with normal nitrogen atmosphere or just oxygen, you should be able to get to a Mars Suit breather or to an emergency Spare Air cannister and then slip on a Mars Suit. But if they are using a normal nitrogen atmosphere they will have to get the spare air and run to the Mars Hab lander or maybe the pressurized rover and slowly decompress or die a painful death. Without nitrogen, once you get your Mars Suit on you can work the problem. I don't know if a Mars Suit would work as a decompression device?

If the nitrogen level is lower then the decompression routines would be much simpler? Okay, that sounds good.

Last edited by Dook (2016-11-01 18:04:54)

kbd512 · 2016-11-01 21:35:32

Using a RTG to heat the greenhouse is actually a pretty good idea. The 4.4kWt that the RTG produces would be trapped inside the greenhouse. Depending on the size of the greenhouse and degree of insulation, it could conceivably be left on the surface of the planet. The minor amount of electricity produced should be enough to power the greenhouse and some LED lighting to increase the growth rate of the crops by providing 24/7 sunlight. The RTG could charge a small battery during the day to power the LED's at night.

There's one minor design consideration. RTG's have pressure relief valves to vent Helium. Some of the decay products are radioactive, so the vent needs to be connected to a hose to dump the gas outside the greenhouse.

If we're going to keep the RTG in the greenhouse, then we could conceivably use the RTG to create a better heat engine by placing the RTG in a small tank of water. The RTG would heat the water to produce steam to drive a steam engine. I'm sure the astronauts would appreciate having hot showers. At the very least, we could get enough electricity that way to power the LED lights without batteries.

SpaceNut · 2016-11-01 22:09:14

Sounds like a win win for putting the RTG inside the greenhouse once on Mars, when designed with the cooling protection blanket that could be powered by the RTG's power and sensed by simple solar cells or photosensitive circuits to tell when it needs to be drawn close and for when it should be open to natural lighting.

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