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#251 Life support systems » Swine » 2016-01-24 23:18:55

IanM
Replies: 42

Plot 0034

Here's an animal second- and third-wave colonists can use as a meat source. Although it is not necessarily the most efficient protein source, pork is one of the most popular meats on Earth, and includes such popular meats as salami, ribs, and bacon.

According to the USDA, roughly a total of 110,000 metric tons of pork were consumed worldwide (http://apps.fas.usda.gov/psdonline/circ … oultry.pdf). There are 7 billion people in the world, but several religions, with many adherents, forbid pork consumption. I shall therefore for the sake of defensive pessimism use the countries where pork is the most popular, which in sheer numbers is China. Using the same source, China has a per-capita consumption of .043 kg of pork. Extrapolating the data gives us 4.3 kg of pork necessary for a colony of 100. A single 250-lb (~125 kg) hog provides 144 lb (~72 kg) of retail pork cuts (http://www.oda.state.ok.us/food/fs-hogweight.pdf), which satisfies this need quite nicely, and provides a huge surplus that can be cured and saved for later. More specifically, rounding the yearly need up to 5 kg, and the hog yield down to 70 kg, one hog would provide enough pork for the colony for 14 Earth years. However, regular, non-cured pork can keep in the refrigerator for only around five days and in the freezer for around eight months (http://www.offthegridnews.com/off-grid- … rving-meat), but can last indefinitely when cured and dried (idem). Much of the most popular pork, such as pepperoni and bacon, is cured and dried, so this shouldn't be too much an issue for those, but some more such as porkchops and ribs, in addition to the pork in such regional dishes as Tacos Al Pastor, isn't, and such pork wouldn't last the colony one (Earth) year, let alone 14.

Let's see what this entails in terms of feed. I suggest the colony breeds its own pigs, rather than have to rely on imports, both for the sake of self-sufficiency and of immediacy. Let's assume we start with one breeding sow and preserved hog semen; this is the initial hard times for the colony; obviously they can't kill the sow, and it'll take a while before the piglets mature before the slaughter. Therefore, it'll be all cost and no benefit. But what is this cost? According to http://edis.ifas.ufl.edu/pdffiles/AN/AN03600.pdf, there are several diets that pigs can be fed, most if not all of which will be mentioned and accounted for here. This breeding sow would be fed a gestation diet normally, a farrowing diet in the days immediately preceding and following giving birth to a litter, and a lactation diet in the 7-8 days following the farrowing diet.

There are, on average, 9-11 piglets per litter (http://www.thepigsite.com/articles/304/ … tter-size/), and given that lower gravity may adversely affect breeding, I'll choose an arbitrarily lower number such as 6. A sow usually farrows 2 litters per year (http://www.homesteadingtoday.com/livest … -time.html), but the colony needs only a hog for every 8 months, and that combined with likely breeding difficulties at lower gravity would mean that there'd likely be only one litter for every 8 months. 

Let us first focus only on the breeding sow. Let's assume that she is imported to the colony fully-grown and ready to breed, her nutrition beforehand being a black box. Gestation diets are fed to her up to 3.5 to 5 pounds (~1.75 to 2.5 kg) per day (this is for Earth days; however, the difference between days on the two planets are around 39 minutes, which I shall treat as negligible). This gestation diet for every American ton (2,000 lb) of feed, or every 400 to 570 days, includes:

-1,642 lb of Ground Corn
-250 lb of Soybean Meal
-40 lb of Choice White Grease
-27 lb of Monocalcium Phosphate
-23 lb of Ground Limestone
-10 lb of Salt
-4 lb of Vitamin mix (proprietary in the source)
-1 lb of 200 ppb Chromium Picolinate
-3 lb of Choline Chloride

A conjunction mission would happen roughly every 910 days, while an opposition mission would happen roughly every 640 days (http://redcolony.com/art.php?id=0208170#null). Therefore, while I would usually support conjunction missions, since this supply convoy would just be on Mars very briefly before returning, I shall use opposition missions here. This leads to up to:
-2,627.2 lb of Ground Corn
-400 lb of Soybean Meal
-64 lb of Choice White Grease
-43.2 lb of Monocalcium Phosphate
-36.8 lb of Ground Limestone
-16 lb of Salt
-6.4 lb of Vitamin mix (proprietary in the source)
-1.6 lb of 200 ppb Chromium Picolinate
-4.8 lb of Choline Chloride

This is important, as essentially everything in the diet other than the corn and soybean meal would have to be imported, at least initially. As for the corn and soybeans themselves, I'll use a pessimistic low of 123.4 bushels per acre for corn (as in 2012, http://cornandsoybeandigest.com/blog/us … roduction), and 39.6 bushels per acre for soybeans (also as in 2012, idem). This results in the need of 2.211 acres (https://www.unc.edu/~rowlett/units/scales/bushels.html), roughly equivalent to     8,947.6 square meters or 96,311.16 square feet, for corn, and 0.168 acres (idem), roughly equivalent to 679.87 square meters or 7,318.08 square feet, for soybeans, in addition to that already necessary for human sustenance.


This is just for the breeding sow for now, and even then outside of farrowing; I'll elaborate on her pregnancy, lactation, and litters later. As always, any corrections, comments, and concerns are welcome and encouraged.

#252 Re: Civilization and Culture » New New York » 2016-01-04 13:05:21

I posted this in the "Mars City - Your Vision" thread, but I calculated that New New York could theoretically hold up to roughly 250 million people, New Manhattan alone having roughly 25 million, so I doubt any horizontal expansion would be an issue with it, despite what some, including initially myself, might worry about it.

#253 Re: Exploration to Settlement Creation » Mars City - Your vision? » 2016-01-04 12:55:07

I'm usually a fan of mini-domes, simply for expansion purposes. What if, for example, we'd eventually need to build New Westchester County, New Long Island, New Connecticut, etc., for when we fill the crater with people? I then realized that the crater, by virtue of being a crater, would already hinder expansion. I was going to express suspicion on the idea on those grounds, but I began to wonder, what would be the "maximum population" of this New New York?

Let's be like the Dutch and start settlement of the city from "Lower New Manhattan". From this, we'll use the land area of simply New Manhattan, which, per Wikipedia, would be 22.83 square miles (59.13 km^2 for you metric folks). Manhattan already has a population density of 71,672 residents per square mile (27,673/km^2), which is already impressive - it has more people than my entire 2.5-square mile neighborhood of Chicago in one square mile. But let's establish some sort of maximum population density. It could theoretically be infinite, but in practice the human body has non-zero size so eventually we'd be literally packed like sardines in a can. I'll use the densest population ever recorded - that of the Kowloon Walled City in 1987, a whopping 1,255,000 people per square mile (3,250,000/km^2) as the max.

Using such figures, New Manhattan alone would have a population of 28,651,650, more than the population of New York STATE, and the greater part of those of Texas and California. Now let's proceed to use that for all of New New York. I'll assume that it is a perfect circle with a radius of 8 miles, and as such, its area would be 64*pi, or roughly 201.06, square miles (165.759*pi and 520.74 km^2, respectively); this is excluding the portion thereof that is water, but this is an informal estimation in any case. Using the figures again, New New York in total would have 252,332,722 residents, more than all but the top 3 countries on EARTH, and the greater part of the total population of the United States.

So, I think New New York would likely build up, and by the time it would be cramped, terraformation would likely be well on its way, and even if it isn't, it'd still be somewhat cool to have a Coruscant-like domed crater. Therefore, I doubt horizontal expansion is that necessary.

#254 Re: Life support systems » Soil Manufacture on Mars » 2015-12-29 21:19:36

I think the soil should also be manufactured so that these conditions are all self-replicating, to aid in Terraformation. |

I also wonder how former volcanic activity could affect the soil. On earth, former volcanoes leave behind cooled lava, which make the soil more fertile. (http://www.ctahr.hawaii.edu/mauisoil/b_andisol.aspx)  This would seem to make such places as the base of Olympus Mons and such planitiae as Syrtis Major Planum. The fertility effect is reduced if the soil is highly-weathered, but on pre-terraformed Mars that shouldn't be an issue. However, the minerals present therein also bind to phosphorus, leaving less of it for the plants, which would require more of it for the colonists. Also, this entire branch of thought assumes that the volcanic activity of Mars is similar to that on Earth, not unreasonable but also not, to the best of my knowledge, certain.

#255 Re: Martian Politics and Economy » Martian Calender - I have created a martian calender... » 2015-12-27 21:11:42

That is a very good point, Louis. I was thinking the witching hour would be the same throughout all time zones (i.e., it could be 22:60-22:99 in Elysium and 16:60-16:99 in Valles Marineris), but that is also complicated and potentially defeating the purpose of the hour.

#256 Re: Martian Politics and Economy » Martian Calender - I have created a martian calender... » 2015-12-27 19:39:07

You forget that we also measure heart rate every 6 seconds in order to multiply by ten to get beats per minute.

Which leads to another thing, to play the devil's advocate, against redefining the minute, similar to why redefining the second is bad. Even though a minute is not an SI unit like the second, and therefore its redefinition wouldn't throw completely everything into cahoots, there are still several things defined by it. In addition to beats per minute, the rotational velocity of automotive engines is often measured in rotations per minute, or rpm. Such units would be confused between Earth and Mars.

That is the caveat on redefining any unit of time below that of the day. That's why I'm not enthusiastic of any such redefinitions. If we must redefine one of the three units (hours, minutes, or seconds), though, it should be the minute, as that has the least effect.

#257 Re: Martian Politics and Economy » Martian Calender - I have created a martian calender... » 2015-12-27 12:57:43

I know that is a rhetorical question, but indeed, as I've said earlier, redefining solely the minute would result in a 73-second minute, a prime number that is therefore not nearly as easily divisible as 60. Redefining only the hour would similarly result in a 73-minute hour, with similar division problems.

That being said, getting paid by the hour indeed implies an equivalent per minutam wage. So, I think getting paid during the witching hour would, depending on the calendar, be getting paid for 65% of the normal hour.

#258 Re: Exploration to Settlement Creation » Mars City - Your vision? » 2015-12-26 02:05:18

I think that NASA video is a good representation of an early Mars settlement, suit and greenhouse issues aside. For the greenhouse, some want hydroponics; I can go for that, but I'd also like to see some tilling of the regolith to aid in terraformation, but that's another conversation.

I think such a hodge-podge would work decently enough in the early days, but I feel roads will become inevitable, even if only as building/block separators, especially with a city of 80,000 as Musk wishes, as such an arrangement with that many people would feel cramped and hostel-like, with insufficient bonds between residents, though it is quite possible that the original setup would survive in the city center, either as a hotel or museum.

The power is similarly fine given the type of settlement; I'm leaning pro-nuclear by the time the city reaches 80,000, but who says we can't have both? The bigger issue would be distribution - assuming above-ground buildings and blocks with their mini-domes, power lines could be put through the domes, but that could be a structural defect and vulnerability. Rather, they could be brought through the connections of the domes - I originally thought of such connections at ground level, where the domes immediately touch, but an underground or overground tunnel system, similar to Minneapolis or as you've said Winnipeg, would work. The power lines could be brought through such connectors, but bringing such high-voltage lines near where the people are is not the best idea.

The truck would be useful for out of city or simply agricultural purposes. The Martian landscape is not the most forgiving when it comes to vehicles, and I doubt many people would be avid drivers unless out of necessity. Perhaps it can be specialized to be a tractor, steamroller, street sweeper, bulldozer, and what have you.

#259 Re: Exploration to Settlement Creation » Mars City - Your vision? » 2015-12-26 00:35:04

I was thinking more of Logan's Run, but with city blocks in a square grid. I agree with Robert that the modules would be stationary and permanent until terraformation advances enough to allow their removal. I think it'd be a better idea for a city that expands over time as opposed to a fixed dome that might ultimately need to be replaced as expansion goes on.

That being said, my vision was a city with a grid system for its streets, much like Manhattan, Chicago, or most other North American cities. However, such a grid would result in squares or rectangles, and we said that the most efficient dome/module with respect to atmosphere is a hemisphere. Obviously, the two shapes don't align well. We could just put the dome within the city block, but that wastes valuable space at the edges. We could also have a dome that has a square/rectangular base but which becomes hemispherical, but that transformation, unless the dome is made piecemeally like a geodesic one, might manifest itself as a structural defect and vulnerability. Or we could have a novel grid system based on a geometry more friendly to circles, but circles don't tessellate in any geometry.

#260 Re: Martian Politics and Economy » Martian Calender - I have created a martian calender... » 2015-12-25 21:32:14

I'm still suspicious of the redefinition of the second. I know it's been done before in simulations, and I know Louis insists that scientists, etc., would still use Earth seconds for SI purposes, but the second ultimately defines so many of the SI units for things not even directly related to time such as the meter, and thence the Newton and the Ampere, Ohm, and Volt, and so much more. The margin of error for seconds is roughly 2.08%, close to the Earth second but noticeably different at large quantities. The margin of error in most of the derived units, especially those not directly derived from the seconds, would likely be much smaller, but all the same nonzero, and thus noticeably different at a sufficiently large quantities. Ultimately, a new second would ultimately uproot the vast majority of the metric system as we know it. Especially in public consciousness, this would likely result in a dual system of Earth-based SI and Mars-based SI. That might be hypocritical of me to say, as I proposed a dual calendar, but it's still something to consider. Otherwise, I like Louis's idea.

#261 Re: Exploration to Settlement Creation » Mars City - Your vision? » 2015-12-25 21:03:06

I think once we reach the hockey stick of population, the city/town/zero-horse municipality would expand much too rapidly for a static dome to be feasible. Rather, I think we should have modular pressurized "habitats" - whether they be city blocks, underground apartment modules, or whatnot  - that would be much like LEGO blocks; they could be easily interconnected, with an emergency entrances/exits in case of emergency depressurization. I further think that such modules, if overground, would vary in height in order to accommodate buildings of different heights, and that some modules surrounding industrial corridors would have vents at the top to let emissions by the industry therein out, both to maintain local air cleanliness and to promote early terraformation.

#262 Re: Exploration to Settlement Creation » Mars City - Your vision? » 2015-12-24 21:59:16

Thank you for your feedback, Louis.

1) The way you put it, a colony of initially 400 makes sense. With regards to "the right stuff", trying to control that with children born in the colony is dangerously close to eugenics, but I realize I might have been overly optimistic with reproduction, and few of the colonists in practice would be natives. Especially prior to the layman having any comfort in a harsh environment, most of those willing are either hardcore civilians and/or professional/governmental astronauts. I also took a Mars One view of it being a one-way trip, which, while IMO ideal, is also unfeasible. In practice, I think most colonists would voluntarily return at old age.

2) While true, the resort would likely still want to make some profit somehow. That being said, a debit/credit card, or for the old-fashioned even a Traveler's Check issued in the tourist's native currency, would likely suffice, thus making a currency moot until economic output becomes serious. Criminal penalties often involve fines, but until a currency is developed this can also be simply replaced with a point-rationing system, fines being levied in points.

4) I personally think it'll be based in large part on the dominant nationality/culture of the colony. It would be useful, and indeed natural to those from the Anglosphere, to have common law fill in the gaps of codification, so to speak having common-law mortar with statutory bricks to form the wall of law. However, that leads to such nebulousness as common-law offenses and common-law marriage, which might be abolished by statute. Though, as you said, a lot of it will be dictated by unwritten social norms, as I said earlier.

In conclusion, I thought of a more mature colony, in that stayers are a sizeable part, if not the majority, of the populace, and a more libertarian colony, wherein the colonists are far more individually autonomous, which is indeed an indicator of maturity. I still stand by such a vision, and indeed still think of it as expanding enough such that a single dome would be constrictive, and thus also stand by the small modular dome model, but have pushed back the timeline upon hearing your remarks.

#263 Re: Exploration to Settlement Creation » Mars City - Your vision? » 2015-12-24 19:59:25

SpaceNut wrote:

Did I miss the definition of the number that is in the (*).....

He said that the total population of the colony would be around 400, so I assume it's relative to that.

#264 Re: Exploration to Settlement Creation » Mars City - Your vision? » 2015-12-24 19:26:27

I imagine a city, not necessarily the first on Mars, that is more industrially than educationally based; I'm not saying education won't be important to these colonists, as they'd initially be, or descended from, some of the more educated Earthlings, and such education would be passed on, but the backbone would be less eds and meds and more either natural resources or manufacturing, or a combination of the two. There might also be services to prevent it from going the way of the Rust Belt (although it is on the Rust Planet haha), but ultimately this means that there might be a local University, but one which does not influence local culture nearly as much as in Louis's city. 

This city is otherwise initially almost identical to Louis's city. I'll detail here how it starts to diverge a it matures.

I imagine that, like Louis's city, it would originate under the provenance of a Earth-based consortium that initially finances and controls it. However, it would gain independence, whether by peaceful or violent means here irrelevant, within its first fifty years, as such consortium becomes increasingly distant to local affairs, and thus possibly resented.

As of 20 years since its founding, it would likely have far more than 400 inhabitants, but, unless it's on a rare-on-Earth resource mine, it would likely experience only steady growth, and thus be at most moderately sized by Earth standards, although it would be a contender for the largest on Mars.

I imagine an infrastructure based on a grid system of roads subject to local geography, much like Manhattan and especially my hometown of Chicago. The city would be built for expansion, and thus a single dome would be unsuitable for it. I imagine a series of many modular square domes, usually being one city block in size but often being bigger for agricultural purposes. They would have an entrance on each side, whereby they'd be connected to each other, allowing the city to grow at a natural pace without having to replace an entire dome at certain points. As for buildings themselves, government buildings would be at the center, with industry being at one section and agricultural homesteads at another, with residences placed where suited. It would be mostly, if not entirely, overground, essentially an Earth city on Mars. The government would initially be a Mayor/Governor appointed by the consortium, and post-independence an elected Mayor and City Council, the latter mostly by wards.

Using the five same points as Louis:
a) Money would initially be absent from the colony much for the same reasons as it is in Louis's city; there is little if any external interaction with an outside economy, and a points rationing system would thus be more useful. "He who will not work shall not eat" could very well be a factor in such a system, but I assume that the initial colonists are motivated enough where this isn't an issue. However, as it's an industrial city, there will inevitably be exports from it to Earth, and thus plenty of exposure to the outside economic universe. As such, even if only for the travelers on business trips or tourists, currency becomes a must; in the absence of any sufficiently scarce resource to back the currency, it would almost certainly be fiat, and thus backed by the colony's economy. To be completely honest, however, I think the colony would use the United States Dollar or a similar highly-used currency, at least until "nationalism" makes an independent currency symbolically desirable.
b) Criminal Justice would also not be an issue with the initial colonists, who all know each other, thus making the shame of engaging in criminal justice both a sufficient deterrent and a punishment in its own right to stop most crime. However, as the colony grows larger and people become more distant, some sort of codified rules would be necessary; the actual contents thereof are irrelevant here, belonging rather to the Dorsa Brevia subfora, but such criminal offenses, procedure, and punishments would initially be as in Louis's city, some sort of semi-summary judgment by an executive, until there are enough people to sustain a judicial branch, Department of Corrections, legal profession, etc., thereafter becoming much like on Earth. Whether it would be Common Law, as in the Anglosphere, or Civil Law, as in most of the rest of Earth, would likely be based on the predominant nationality/culture of the colonists.
c) English would likely be used as a lingua franca, as on Earth. Depending on how many nationalities are represented and how diverse they are, a pidgin might develop. Neologisms would also develop.
d) Industries would dominate the culture, being collectively the sole employer other than the consortium or homesteads.
e) There would likely be a far higher proportion of stayers; as they are the Martian working class, and especially if technology allows them to contact loved ones on Earth remotely, there is little if any reason for them to ever return other than on vacation.

#266 Re: Martian Politics and Economy » Martian Calender - I have created a martian calender... » 2015-12-22 00:00:57

I have a couple thoughts.

Since the Martian sol is only roughly half hour longer than an Earth day, it could be that the time of day of Mars would be identical to that on Earth, e.g., a valid time would be 18:07 or 6:07 p.m., as the case may be. This is important if, say, a colony wants to impose a curfew on its residents; no one under the age of 18 shall leave his or her house/room/domicile after 22:00/10:00 p.m. unless for legitimate business, for example. This is particularly easy for the earthling natives to be accustomed to, but that half-hour difference is artificial as Clark says, building up over time, to the point where it could be possible for it to be high noon during "midnight", and vice versa! The colonists could simply, as Rob has put, make minutes and seconds 1.22 times longer, but an issue with that is that the second is the SI unit of time, and redefining it would entail having to redefine, among other things, the speed of light and other SI and SI-derived units such as the Newton and even the meter, thus complicating science considerably. A redefinition of only the minute to be 1.22 times longer would still lead to a 73.2-second minute, which is not an integer, and a rounded-down 73 isn't nearly as easily divisible as 60. On the other hand, the colonists could indeed simply ignore the incongruity and artificiality, and use darkened blinds when the sun is shining (to the extent that it can given Mars's extra distance) at midnight, and artificial lights when it's almost pitch black at noon, but this might be a waste of resources, and especially of energy in the latter case. Which solution the colony chooses in practice will be interesting.

My curfew example above gives the age limit for a curfew of "18", which is meaningless without specifying 18 of what. Obviously on Earth it's implied 18 years, but on Mars that's itself meaningless without a specification of what is defined by a year. If we define it as 18 martian years, that would be the equivalent of a person being in his mid-30s on Earth still being subject to a law intended for teenagers! We could indeed simply reduce the age to 9 or around so, but that leads to the question of how to measure birthdays and whatnot.

Both the time problem and the date problem show there are two options, with both of their pitfalls; make a calendar based mostly on Martian cycles, or one based mostly on Earth cycles. A potential solution, if rather inelegant, is to use two calendars: one Anno Domini, or the Gregorian Calendar, exactly, and the other a calendar based on the Martian calendars, independent of the Anno Domini calendar.
The A.D. calendar would mostly be intended and used for administrative and legal purposes, as well as interfaces with Earth; such years would be marked in statute/law/etc. as "years of our Lord" or something of that effect, such as "the age of majority for this colony shall be eighteen years of our Lord." The Martian calendar, on the other hand, would be used as an Almanac sort of time, with actual relevant seasons that exist on the surface, rather than dates for legalese. These two purposes could eventually lead to some class differences, A.D. possibly being "city time" and the Martian calendar "country time", or the like, though ideally everyone in the colony would learn both. The advantage of this would be that the disadvantages of each respective calendar are balanced out by the advantages of the other, reducing if not outright eliminating the need for compromising either. The disadvantage would be that each colonist would need to learn two dates, each of systems that might not perfectly line up.

#267 Re: Life support systems » Power generation on Mars » 2015-12-20 20:10:37

I forgot that we needed Oxygen to combust things lol, I guess that rules out any traditional coal or oil power plant. For nuclear, I would gander that perhaps a colony mature enough to be able to handle the waste of nuclear would be able to either import or make coolant. IIRC, the most common coolant is water, which the colony might mine and process from the regolith, in which case the challenge would be cooling it.

I think the colonists would use some sort of Flywheel storage on their grid; it is essentially taking the power and accelerating a flywheel to a high speed, storing the electrical energy as rotational energy of the flywheel. The energy could then be harnessed back by slowing the wheel down. This would store some excess energy for later, and hopefully reduce some immediate production needs of the plant.

Also, in my city (Chicago), and I would assume several others, ComEd (the power company), is installing some "smart meters", which relay the amount of energy used by a household to the power plants, allowing certain trends in usage to be determined. I think this would be a further boon to power in the colony.

#268 Re: Life support systems » Power generation on Mars » 2015-12-20 18:33:53

Indeed. I personally think a lot of the larger applications, like greenhouse heat, and some of the more essential ones, like the air pressurization apparatus for the colony, would have their own power sources or generators, either exclusively or as backup, either to accommodate their own power needs or as a failsafe whenever blackouts happen.

As for the original question of generation, I'm pro-nuclear for a colony that is mature enough to handle the waste, but I think either solar or a biofuel-powered power plant is the way to go for a small nascent colony.

#269 Re: Life support systems » Power generation on Mars » 2015-12-19 22:32:23

I'm not sure whether this should be its own thread, or if it's already been discussed, but I think something worthy of consideration is power distribution for the colony.

The traditional method for this since the first current wars has been Alternating Current (AC), which has the advantage of easier conversion of voltages between the main transmission lines and customers, but which involves more losses at high distances over High-Voltage Direct Current (HVDC). I think the colony, especially in its earlier years, would use AC since distances are likely to be small due to colony size. That, however, raises the question as to which AC system (i.e., phase, voltage, current, etc.) it would use. This would be most prominent as to what plug it would use. I think since many household appliances would be imported from Earth (as they would be unduly difficult to manufacture at the nascent colony) by the colonists, the colony's choice would likely reflect the dominant nationality of the colonists (i.e., a primarily American/Canadian colony would likely use an American/Canadian plug, a European colony a European plug, etc.). This, in turn, would likely vary by colony (there might be, for instance, a primarily American-backed colony somewhere, a European-backed one elsewhere, etc.), leading to, IMO, the necessity of HVDC lines connecting the unsynchronous systems as Martian globalization takes place, and maybe even a "universal plug" from which adaptors to the different local plugs could be made. Just my two cents.

#270 Re: Life support systems » Pressurized Air in Suits » 2015-12-16 01:15:31

Thank you all for the welcome. The Mechanical Counterpressure Suit looks like it would be the most feasible, in my opinion. It seems like it is the most efficient and, as is the intent, the most flexible. I thought it could be used, sans life support, as underwear within the colony, much like a union suit or long johns, continuously to avoid having to go through the trouble of donning, but circulation problems seem to put a damper on that, and it would still have to be donned daily due to showering, etc. Nonetheless, outside the colony, it would indeed help with longer expeditions, being limited only by the oxygen available.

#271 Life support systems » Pressurized Air in Suits » 2015-12-15 22:29:33

IanM
Replies: 5

I was wondering how much oxygen would be needed for the suits colonists would wear for activity outside of the colony, once the colony is set up. Further, I am looking at to what extent such oxygen would be pressurized above normal, and whether a colonist would thus need any sort of precaution from the bends on his return.

NASA has a spacesuit wherein the oxygen is put at one third of the normal atmospheric pressure (=0.333 atm) and that allows, with a carbon dioxide removal unit, up to 6 to 8.5 hours of EVA. However, such suit is, as NASA admits, clunky and unergonomical (http://spaceflight.nasa.gov/shuttle/ref … q/eva.html), and although the volume is not given, per Boyle's Law it would be three times the volume of the same amount of oxygen on earth - not a very practical option for Martian expeditions, as we'll see later. Due to the same space considerations as NASA, I shall suppose pure oxygen is used here.

According to http://members.shaw.ca/tfrisen/how_much … person.htm, a person needs around 6 L/minute of oxygen at rest, and 50 L/minute after a bout of hard exercise. In the absence of anything to the contrary, I assume this is at standard temperature and pressure (25.00 C (298.15 K) and 1.000 atm, respectively).

I'm assuming that most of a colonist's time would be in a sort of pressurized habitat at exactly 1.000 atm; whether this is a dome, or inflatable covered with regolith, or anything else is irrelevant. As such, the amount of Oxygen needed in a suit would be much less than what is noted above would imply. I further assume that a typical out-of-colony expedition would, depending on its purpose, vary in length anywhere from 30 minutes to 8 hours. This results in a range of

30 min * 6 L/min =180 L oxygen,
30 min * 50 L/min = 1,500 L oxygen
8 hr * 60 min/hr * 6 L/min = 2,880 L oxygen
8 hr * 60 min/hr * 50 L/min = 24,000 L oxygen

180 to 2,880 L for someone always at rest, and 1,500 to 24,000 L for someone always exercising hard. This is a really wide range, and in any case an unacceptably large amount of idle space for someone to carry for such an extended period of time. Therefore, the air will have to pressurized in order to accommodate it, much like scuba diving.

The rest of these calculations will involve the van der Waals equation of state for gasses, which expands the ideal gas law:
PV=nRT
into
(P+a(n^2/V^2)) (V-nb) =nRT
which in turn gives the pressure thus:
P=((nRT)/V-nb) - a (n^2/v^2)

For all of these:
-P is the pressure of the gas, in atm
-V is the volume of the gas, in L
-T is the temperature of the gas, in K, which will always be 25.00C (298.15 K) for these calculations
-n is the number of moles of the gas
-R is the ideal gas constant, here 0.0820578 atmL/Kmol
-a is a constant related to attractive forces between the molecules, for oxygen 1.360 atmL^2/mol^2
-b is a constant related to repulsive forces between the molecules, for oxygen 0.032 L/atm

The number of moles of oxygen calculated from this ranges from 7.348 mol to 753,255.346 mol.

There is a maximum pressure in practice; rental scuba tanks are rated up to 3,000 psi (204.138 atm). Using the latter, rounded down to 200.000 atm , as the absolute maximum, the minimum volume will range from 0.810 L to 83,082.450 L, the latter of which is actually higher than that at STP. Given that the absolute maximum only applies with 8 straight hours of hard exercise, it is unlikely, and the value of roughly 30 minutes of hard exercise, 1,500 L at STP, is more likely, especially combined with the 8 hours of rest, which would give 4,380 L at STP; this in turn gives a volume at the maximum pressure of 14.714 L, which is a far more manageable, if still a bit large, number.

So, it seems like 15 L of oxygen compressed at 200 atm would be a good fit for a suit. However, as assumed earlier, the colony would be pressurized at 1.000 atm, a difference by a factor of 200, quite a lot. In fact, 200 atm is the pressure roughly 2 km deep in the ocean (http://www.calctool.org/CALC/other/games/depth_press). Erring on the side of caution per the NOAA (http://divetables.info), no ascents should ever be faster than 9 meters/minute, equivalent to a decrease in pressure of 0.900 atm/minute. Given that there is a 199 atm pressure difference, that would require at least 221.111 minutes of decompression, a whopping 2 hours in addition to the time of the journey.

The volume of the human body is 66.4 L (http://www.wolframalpha.com/input/?i=volume+human+body). Taking advantage of lower Martian gravity, let us use 75 L as the maximum desired volume. This, with the maximum number of moles, would result in a pressure of 30.249 atm, with a resulting decompression time of slightly more than 32.5 minutes, far more manageable, even with a slightly clunkier. Therefore, 75 L of pure oxygen compressed at 30.249 atm should be used for suits.

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