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As much as we hunt and search, a Martian colony will not be located atop perfect concentrations of Iron ore, Aluminium ore, Silica, Ice, and the various other raw materials which will be needed to sustain a colony on the Red Planet. Therefore, it will be absolutely necessary to transport these materials from the location where they were extracted to the location where they are to be refined and/or used. Viable concentrations of useful resources could be located (conceivably) as far as across the planet. However, more reasonably I will assume that by selecting a good colony location, cargo needs to be hauled an average of 500 km.
To get an order-of-magnitude idea of how much "stuff" we would be carrying around, I looked at Steel. Insofar as the Martian economy would be a rapidly growing economy based around manufacturing and production with a smaller service sector it has a fair amount in common with China's economy. China consumed 470 kg of Steel per person in 2011. Given that there are some uses for Iron besides turning it into steel, that the colony will have use for many materials other than Steel, given that the resource of interest is often a fraction of the mass of the raw materials, I will assume that a transportation capacity equivalent to 2,500 kg per person per (earth) year will be needed. This means that a total transportation capacity of 1,250,000 kg-km per person-year will be needed.
On Earth, there are three primary ways in which cargo is transported: Road, Rail, and Sea.
I'm going to say right off the bat that sea transport is totally irrelevant on Mars. That leaves Road and Rail.
Rail transport is better than road insofar as it enables unmanned transports without the need for any kind of guidance system. All you need to do is set the speed via mechanical means and turn it on. It also has lower friction than road transport. The downside is of course that you need to actually build a rail network. Rail profiles vary, but we'll probably need at least 20 kg of steel per m of railroad track. Over 500 km, this is 10,000 tonnes of Steel. Realistically, we will need railroads going to multiple different places. Needless to say, this is a lot of rail; probably an unjustifiable amount, especially at the early stages of a colony (If a colony of 1000 people were using its entire transportation allotment to produce Steel, it would take four years to build each line. And before you ask, yes, I am assuming that transports will have to use the same rail line going to and from, so that it will only be possible to go in one direction at any one time).
Road has a lower startup cost: At a minimum, to build a road one simply has to plow rocks out of the way. Larger boulders can be avoided by making the road go around them. While a self-driving car would be relatively easy to program on Mars if you have an Aeropositioning System (APS), this will require imported electronics. Though, in all honesty this is a pretty negligible cost. If launch costs from LEO are $2,500/kg, and we have a fleet of reusable transport craft (I'm thinking just take the 2 year free return trajectory recommended by Zubrin, release your cargo near Mars (Perhaps rendezvousing with some cargo of Martian origin as you do so), and then swing back with two months to spare before the next launch window opens. Cargo costs shouldn't exceed $5,000/kg. If 10g of electronics are required per vehicle, that's an added cost of $50 per vehicle, plus the cost of the electronics-- which could be $100. What I'm saying is that the economics here aren't very different from those on Earth, and it's still definitely cheaper to have electronics aboard. This is true even though the exchange rate between Martian and Terran currencies is likely to be such that buying things in dollars is significantly more expensive than in Martian money.
So, we have self-driving cars on unpaved highways. But obviously there's a lot more to the engineering of a transportation system than simply specifying APS-controlled cars on an unpaved road. We've been discussing optimal fuel choices in the other thread, and I'm pretty happy with either Ammonia/N2O4 or Methanol/N2O4. Ammonia is cheaper from an energy standpoint and is less toxic (and also has a stronger odor so that you can tell if there's a leak), but methanol is liquid at room temperature. Especially because both will be useful in producing other things, a mixture of the two is pretty feasible so long as they are soluble in each other. Google suggests that such a mixture is highly flammable, and while liquid at room temperature it inherits the toxicity issues of both Ammonia and Methanol.
In any case, we have a fuel and an oxidizer. But there are many different ways to turn that into kinetic energy, of varying efficiency.
On Earth, by far the most common way that this is done in vehicles is with an internal combustion engine. Though not particularly efficient (Typical values ~14%), an ICE has a very high power density and produces a lot of torque. To back up: There are three primary factors of importance in the design of this engine. These are cost, reliability, and functionality. It is based on these three that I will evaluate potential designs.
The basic function of the engine is to turn chemical energy into mechanical energy. Usually this is done through a combustion process, but it doesn't have to be. Fuel cells, for example, can run off methanol. However, because electrical systems such as that are hard to build I am in favor of a combustion-based system.
Which combustion based system is open to debate, of course. The two basic classes of these are internal and external combustion engines. Internal combustion engines typically have efficiencies in the range of (according to Wikipedia) 18%-20%. This is for automobile engines manufactured on Earth. We can expect lower values on Mars because there will probably be worse quality control and higher machining tolerances.
Now, Wikipedia has a great hagiography to offer on the benefits of Stirling Cycle engines, but I suspect that its article on the subject is less than entirely truthful. It is my belief that it may have been written by an overzealous editor. This opinion is corroborated by the information in the textbook Stirling Engines: Inner Workings and Design, which states that while Stirling cycles have some benefits relative to Internal Combustion Engines and Brayton Cycles, they are not the amazing solution that they have at times been claimed to be.
I am going to admit that any further analysis in this field is beyond me, and rather than press ahead I will end this post with a question:
What kind of heat engine is best to turn chemical energy into mechanical energy for a small vehicle on Mars? Why?
-Josh
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If the cargo truck is unmanned, why not using an electric engine powered by a 100 KW SAFE 400 nuclear reactor?
It may be simpler than develop a new technology for an ICE adapt to Mars environment.
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Unfortunately, you have to import nuclear reactors, which even before transport costs are going to be very expensive.
I would suggest looking at a gas turbine electric hybrid, so that we can avoid the gearing that would be necessary if we were using the power directly. Even converting chemical to rotary to electric to rotary, we'd still get much higher efficiencies than an ICE.
"I'm gonna die surrounded by the biggest idiots in the galaxy." - If this forum was a Mars Colony
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I love the efficiency of the gas turbine, but I don't love the necessity of very precise manufacturing, plus various other complex systems typically associated therewith.
Energy stuff is lose-lose, usually. In terms of gearing I was thinking that the vehicles wouldn't go any faster than 15-20 kph, which would eliminate the need to build big wheels on it.
-Josh
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The end goal we see but where do we start when we will need to bring key infrastructure elements first in order to build from insitu materials the remaining items that we need in order to be at the finish line end goal.
We can do lots of combined technolgies in order to power the rovers of which what about nitrogen/hydrogen fuel cell that outputs amonia which we capture and then later electrolysis back to its starting elements sure its going to take power but we will need to recycle just about everything in order to gain a settlement hold on mars.
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A Nitrogen-Hydrogen fuel cell? I'm not sure that's possible and even If it were it wouldn't be desirable because ammonia has a low energy of formation.
I would say that an external combustion Brayton Cycle design might be the best way to go. I think it's worth mentioning that the low atmospheric pressure can be leveraged here for cooling: if the internal pressure of the cooling loop is significantly lower than atmospheric, phase change can be used to cool the cooler end of the cycle very effectively. I'm thinking that a brayton cycle would be more efficient than a Stirling cycle and simpler/more reliable than a turbine.
If we have any alloys that are possible to produce abd better at high temperatures than stainless steel, this would be the place to use them.
Perhaps GW has some input on this one?
-Josh
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I'd very much query the figure of 470 kg for the needs of early Mars colonists. Are these early Mars colonists going to be buying private cars to drive on Mars? No. Are they going to be flying around in aeroplanes? No. Are they going to be building bridges? No. Are they going to be putting up office skyscrapers ? No.
I suspect the initial demand for steel will be very small. It might be need for a few things like maybe shelving for hydroponic agriculture or tools or steel supports for construction. I'd say 50 kgs would be much nearer the mark.
Of course the early Mars economy may within a few years be able to develop simple rockets (like the Armadillo rockets) and at that stage perhaps more steel will be needed.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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The brayton engine is a closed (main) loop system for the working loop that has 2 heat exchangers used to create the differential of temperatures on the working fluid in the main loop. Heat is provided before the generator turbine with power take off shaft that compresses the return part of the generators output side exhaust. The output side of the generator is cooled by the secondary heat exchanger before entering the compression input before it exits to the heating exchanger.
That said the sources of heat for the first exchanger are solar and chemical fuels that we bring until we can make them on mars. The secondary exchangers cooling can come from a large radiator and blower fan of course mounting it on the vehicle would allow additional air cooling from movement.
The size of the volume of the loop and the difference between the hottest temperature which if solar generated is a time of use to the coldest is the power limitation even if we have a good storage system.
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As a matter of practical heat transfer, the kind of cooling "radiator" (a misnomer, it works primarily by convection, not radiation) and fan that works on vehicles here, will not work well at all on Mars. The air is 0.7% as dense there as it is here, and transfers 0.7% of the energy, all other things equal. Those things are flow speed, radiator area, temperature difference, and "air" heat capacity.
Temperature difference and heat capacity aren't free parameters under your control, they are artifacts of what you are doing. Flow speed and radiator area are inversely related, but their product will be a constant driven to enormous size by the low density, roughly 140 times larger than we are used to, designing radiator-fan systems here. Sorry, that's just heat transfer facts-of-life.
You'd have better luck on Mars with true radiative cooling, except that requires far higher radiator fluid temperatures (T^4 dependence of Boltzmann's law). If it weren't for being mobile, I'd say your best cooling bet is convection directly into the cold regolith as a heat sink. That takes a field of buried pipes. For mobile operation, at high power, you might get away with brief surges by using a sacrificial phase-change coolant. Dump your heat into ice and expel it as steam. Very wasteful, requires a lot of water. Tons not kg for a very few HP-hours.
The much-higher rejection "reservoir" (sink) temperature of a true thermal radiator operating in vacuum or near-vacuum conditions drastically lowers the Carnot efficiency of your associated heat engine cycle, which is a fundamental upper bound on what you can do with heat engines. Your real cycle efficiency is far lower than Carnot (by factor 2 or worse). Carnot efficiency is 1 - Tc/Th where Th is the hot source temperature and Tc is the cold sink temperature. Sorry, that's the facts-of-life from Classical Thermo 101.
The thermal radiator is the only thing that works closed-loop in space. We already know that. The thin air on Mars is a close cousin to the vacuum of space, that's why automotive-type radiator-fan combinations will be ineffective there.
That unfavorable outcome sort-of argues against using heat engines for mobile operation. Fuel cell electric is not a heat engine, and does not directly suffer the same thermo and heat transfer limits, operating in a near vacuum like that.
But for stationary operation, heat engines make a great deal of sense, using the regolith heat-sink approach. If the pipe field is large enough, convection through the regolith to outside the field makes the cold sink look "infinite" in size, allowing steady-state operation. That effect will likely size such sink fields on Mars; not something we usually run into here, so very much.
GW
Last edited by GW Johnson (2014-03-17 09:39:03)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Josh asked something about higher-temperature alloys just above. I used one in a reducing environment that was quite strong. I think it would function in a neutral environment, too. That was TZM, a moly alloy doped with Ti and Zr. It oxidizes-away rapidly above 1300 F, but if you avoid oxygen exposure, you can take it a lot hotter with near-room temperature strength. I used it up to 2200 F like that, in thin tubes subject to lots of internal pressure. I think it melts close to 4000 F, but I'm no longer sure. That was 30 years ago. I think it's available in bar, tube, and plate. I doubt it's available in sheet. It's machinable with some difficulty. I don't believe it's formable at all (sort of like 6-4V Ti in that respect).
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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I'd very much query the figure of 470 kg for the needs of early Mars colonists. Are these early Mars colonists going to be buying private cars to drive on Mars? No. Are they going to be flying around in aeroplanes? No. Are they going to be building bridges? No. Are they going to be putting up office skyscrapers ? No.
I suspect the initial demand for steel will be very small. It might be need for a few things like maybe shelving for hydroponic agriculture or tools or steel supports for construction. I'd say 50 kgs would be much nearer the mark.
Of course the early Mars economy may within a few years be able to develop simple rockets (like the Armadillo rockets) and at that stage perhaps more steel will be needed.
Just to be clear, I'm talking about a colony with say 500-1000 people that is independent of Earth with the exception of a few items of low mass and high specific cost such as computer items, medicines, and catalysts, as well as of course immigrants. In terms of population growth I'm thinking 10% per year with economic expansion at 15% per year. These numbers are both extraordinarily high by Terran standards, but my feeling is that when you have a population with 90%+ workforce participation (Compare to about 40% of the total US population of 315 million actually employed with the rest ultimately dependent thereon). Now consider that unlike the US economy, in which the service sector represents 73% of GDP, manufacturing, agriculture, engineering, and construction will be the primary fields, with a small, rotating number of people around to smooth out the rough edges and direct the whole operation.
Anyway, ask yourself this: What does most steel used in the US go to? Unsurprisingly, construction and manufacturing. The thing to ask ourselves is how the amount of Steel used in construction on earth will compare to the amount of construction on Mars. My answer: Because of the need to contain pressure, universally more. While we won't be building skyscrapers, each building will need to be able to support the weight of the roof in the case of a blowout. Further, while the volume of internal habitable volume per person will probably be lower than on Earth, consider that the economic growth rate I'm calling for is twice as high as that of China, and consider that the population growth rate is twenty times higher than China (more people means more buildings!) and you'll perhaps begin to think that my estimate is more reasonable. It could be an over or underestimate, but it's certainly not an order of magnitude too high.
-Josh
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GW: I'm thinking that the vehicles that haul cargo on Mars won't be particularly powerful. Driving slowly with large wheels to minimize the effect of bumpy roads, I would expect to need no more than 1 HP per tonne. I think that this is entirely reasonable given negligible air resistance and slow speeds. It very well may be possible to go lower. Anyway, at 0 C and an emissivity of .8, a radiator will radiate 275 W/m^2, meaning that 3 m^2 per tonne will be needed. Seeing as these trucks will be transporting water anyway, 3 m^2 is the top and sides of the container. With a radiation temperature of 0 C, the cool side temperature can be maybe 10-20 C. I'm proposing that we use evaporative cooling for the heat engine, whatever it may be. At these low horsepower, we'll have to be okay with low accelerations. The time to go from 0 to 20 km/hr will be a minimum of 20 s, but I see no real issue with that. If, for whatever reason, the vehicle increases itself to 2 HP/tonne, the radiation temperature will have to increase to 50 C and the cold side temperature to 60-70 C. This will result in a loss of efficiency but not a malfunction; Cooling system pressure will increase to about 50 kPa, which is still quite reasonable.
The question remains, though: Brayton (Turbine), Stirling, Rankine (Steam engine), or internal combustion engine?
-Josh
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Hi Josh:
I honestly don't know which engine might be better. The piston types handle varying load better than turbine, and by far. You can get around that issue, by using the turbine to drive a generator, and go electric drive. Add in some batteries to handle surges, and you can reduce the size of the engine to a minimum, and get better efficiency by a factor approaching 2. That's the secret of the series hybrid here. Not just cars, but locomotives and submarines, too.
There are reactants the turbine could use that fuel cells cannot. I don't know about actual cycle efficiencies, but I'd hazard the guess that a turbine electric hybrid would be competitive with a fuel cell electric. But, the turbine electric hybrid is a lot more versatile as to reactant identities. Here, turbines can be universal-fuel, if you just design it that way. It's not that hard to do.
Your biggest problem with turbines is the blading. It has to be restricted to survivable temperatures, and likely in the presence of some oxygen. Those aren't carbon steel. Typically, they're superalloys like Haynes, or Rene, or Hastelloy. The gas temperature approaching the blades cannot exceed about 2200 F in the very strongest military designs. Those alloys are difficult to make, even here, and quite expensive. A radial flow design might ease some of the structural demands, if you sacrifice a little efficiency.
For any sort of combustion engine, I'm worried about the gas feeds to it. Here, the biggest massflow coming in is the air stream, which needs compression from 1 to a few dozen atm. There, it will be your oxidant plus any diluent gases. A compressor for gas flows of similar magnitude on Mars, going from 0.6% of an atm to a few dozen atm, is going to be way too big and power-hungry to be practical. You'll have to generate these gas flows, likely from stored liquids, real-time and very rapidly in some sort of feed plenum chamber, at near 1 atm. It's a really tough problem, no matter how you look at it.
That's why I keep iterating back to fuel cell electric. It's the one thing we already know exactly how to do at Martian conditions.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Went searching for links on space radiator design. Looking at the papers the radiator is more a kin to a flat plate collector that Solar Hot water sandwich.
http://www.engopt.org/nukleo/pdfs/0564_ … diator.pdf
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GW-
While I get where you're coming from in terms of fuel cell-electric, I have to disagree from a manufacturing/materials standpoint. Fuel cells typically require platinum and need very precise construction if they are to actually work. I gather it's the kind of situation where small changes in quality result in large reductions in efficiency. Add in that they can't handle the fuels we would otherwise want to use (with very good reason, I might add!) and perhaps you see why I am not really in favor of fuel cells for Mars.
It's also the reason why I shy away from turbines.
Staged electric drive, on the other hand, is certainly worth considering to me. I don't know if it makes sense for a Rankine/Stirling Cycle. I suppose it probably doesn't.
On Earth, Rankine Cycles will beat out Stirling Cycles almost every time, and I would expect this to be the case on Mars as well. According to Wikipedia, Internal combustion engines typically beat out Steam engines for automobile applications because they have a higher specific power and therefore higher performance. It is my feeling that because we're not looking for high performance, steam powered might be the way to go.
On the other hand, fuel is cheaper on Earth than it will be on Mars. This pushes towards higher efficiency to reduce consumption of costly fuel. Just comparing the number of processes required to make fuel on Earth vs. Mars:
Earth:
Extract from Ground
Fractional Distillation
Additives (Small portion of total fuel)
Mars:
Electrolyze water
Pressurize the atmosphere (Obtain CO2)
Obtain Nitrogen via condensation of CO2, Argon
React CO2 with Hydrogen to produce Methanol
React Nitrogen with Hydrogen to produce Ammonia
React Ammonia with Oxygen to produce NO
React NO with O2 to produce NO2
Pressurize and liquefy product
Additionally, on Mars unlike on Earth the energy is not "already there", but has to be produced at significant expense. If gasoline had to be produced at 50% efficiency from energy derived from a solar power plant, it would cost $14/gal ($3.75/L), just in energy costs. Probably at least $20/gal ($5/L) all told. It would of course be even higher in European countries that tax fuel at a higher rate.
Meanwhile, although energy on Mars will likely be somewhat more expensive than here on Earth, Steel should be a similar price and manufacturing shouldn't cost that much more. Steel on Earth costs $719/tonne. The coal required to produce this Steel (to say nothing of the Carbon content that makes it steel) costs about $15. However, if smelting were done instead with Hydrogen derived from solar energy, energy costs would amount to about $350 per tonne of steel, increasing the price by 45%. So more expensive, yes, but the increase will be smaller than the increase in fuel costs. I would add that ore costs will probably be lower because the ore will be higher quality. My basic point is that the increase in fuel costs will outpace the increase in manufacturing costs, thus meaning that better technology to decrease fuel usage is more economically viable on Mars than on Earth.
I need to pull out a "Central Planner" hat and get a Matlab script going that will give some idea of prices on Mars.
-Josh
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The earth side of the fuel equation also includes drilling for gas pockets that are piped to tanks ready to use. With some data on mars indicating gas is leaking from with in the planet one might want to try and pinpoint where the source is.
You do meantion coal and at one point earth did rely heavily on it for powering until oil was found. Mars will not have this.
Then there is the plant light in trees that did do the same before coal was found and on mars we will be a long time into planet taraforming before we will eeven think of cutting a tree for fuel.
As you note we are starting out with an energy deficit on mars when we compare sources to earth. So the question is one of if nuclear is not used how do we over come this deficit. Since there are no complete fuels systems since natural oxidizers do not exit on mars.
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"You do meantion coal and at one point earth did rely heavily on it for powering until oil was found." --- even today, the majority of the electricity made on Earth is made using coal.
What made wood, coal, whale oil, and petroleum oil feasible and economic to use on Earth was our oxidizing atmosphere. By far, the largest massflow through any sort of combustion device is the oxidizer. All we had to do was find a fuel.
It's not like that on Mars: the atmosphere is inert. You have to find or create both fuel, and the far-more-massive oxidizer. I have my doubts about combustion engines ever proving to be truly practical there, precisely because of that problem.
GW
Last edited by GW Johnson (2014-03-25 10:15:40)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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"Ever" is a long time. Having thought about it, it is my rejection that the default heat engine on Mars well probably be a Steam Engine because of high efficiency, relatively high power density compared to Stirling cycles, and the fact that it's a generally well known technology.
Of course, there is a warm up time, abd this costs energy. Would it be possible to design a Steam engine that will modify its internal pressure based on temperature so that it will generate power at any temperature? I don't know but it might be.
-Josh
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Since we need rocket propellants anyway to have combustion in the inert atmosphere of Mars, why not burn them in a rocket engine, and use MHD to extract a lot of the energy directly as DC electricity?
Then use the remaining heat and velocity energy of the stream as the heat source to some sort of closed-loop steam cycle? That could generate electricity, too.
Have some batteries on board for a certain amount of storage and surge volume, and use electric drive at the wheels. It's then a series hybrid with all those advantages, but the prime generator is actual two things, not just one.
Just a really wild idea that that hit me just before I nodded off after drinking lots of beer. Brain cell lubricant, it seems to be! Ha ha ha!
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Highways under Martian canals[
I think originally placed this in the wrong section Martian culture and society, but it seems to me possible to have covered highways eventually, and their are trenches already where they may be placed. Think of them as stretched out domes. I believe this counts as Martian transportation infrastructure.
This idea came to me as I was driving down a highway. Imagine a paved highway on Mars made of asphalt. There are three lanes going one way and three lanes going the other, and a green space between the two directions on the highway just like on Earth, we also place an equal amount of green space on either side of the highway. So lets assume each lane is 10 feet wide (3 meters). There are three lanes going in one direction of the highway, that's 30 feet, plus we have breakdown lanes on either side, that's 10 feet wide on the inside and 10 feet wide on the outside for 50 feet in one direction, we have a 50-foot wide median and then another 50 feet for the 3 lanes and 2 breakdown lanes going the other direction, and we add 50 feet of green space on either side of the highway, for a total width of 250 feet, and we seal that in a plastic tube that is pressurized at a one-Earth atmosphere mixture of nitrogen and oxygen. to help hold all that air pressure in we place the plastic tunnel at the bottom of a Martian canal that we dig for this purpose, or perhaps we could use a natural river bed that may already exist on Mars for this purpose to save work. We put an outer plastic tube over this ancient river bed or canal and we pressurize to twice or three times the normal atmospheric pressure of Mars, this pressure is still to thin to allow breathing by a normal human, but it will allow liquid water to exist within a narrow temperature range. The atmospheric pressure of Mars is 0.087 psi, so lets triple this to 0.254 psi I think liquid water can exist under these conditions. The pressure within the highway tunnel will be 14.69 psi, same as Earth at sea level. A cubic meter of water weighs a ton under earth gravity and a ton is approximately 2200 pounds. On Mars this same amount of water would weigh 836 pounds. A meter cube of water is about 1600 square inches of a foot print, so divide what a cube of water weighs by the square inches of its foot print and we get 836/1600 = 0.5225 psi, we want to get to 14.69 psi so we divide 14.69 psi/0.5225 psi to get 28.11 meters of water on top of the highway tunnel, subtract half a meter of water to get 27.6 meters of water, the bottom of which equalizes with the air pressure of the highway tunnel. We also have 0.254 psi of compressed Martian atmosphere on top of the canal to allow for a liquid surface on top. So each cubic meter holds 1000 liters of water. Since the highway will be 250 feet wide with all the green space, each 10 feet translates to 3 meters. 25 * 3 = 75 meters, so a section of canal that was 75 meters wide by 75 meters which is 27.6 meters deep would contain 155250 cubic meters of water or 155,250,000 liters of water. Since we need to keep the interior of the highway tunnel habitable for humans, it needs to be heated, this would mean that some of the water above would be liquid but as we got closer to the surface in would be frozen most of the time, assuming we have some decent insulation of the tunnel walls. The plastic should be clear to let in sunlight and the 27.6 meters of water should also be clear to let in sunlight so it filters down into the highway tunnel below. Besides holding in the air pressure, 27 meters of water also makes great radiation shielding, in case of a solar flare. The Tunnels would contain highways that allow the passage of air breathing cars, perhaps hydrogen fuel cell vehicles. electrolysis plants crack the water into hydrogen and oxygen, and the hydrogen is sold in pressurized form at fuel stations placed inside the highway tunnels to refuel the cars inside at need, that way the cars don't need to be pressurized, only the tunnels do and since there is less leakage with less surface area per unit volume than individual cars, this would be a safer mode of transportation that traveling outside on the Martian surface in pressurized vehicles with airlocks.
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City to city tunnels are much later in the continued infrastructure building but not all that practical for mining and transportation to the city for useage into the processes which will lead to more structure building.
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Seems to me two cities can be located along an ancient Martian river bed, there are numerous examples of these as water once flowed on Mars.
1. Okay then next step is to pitch a clear plastic tend over the ancient river bed.
Place walls at both ends of the tube and seal the plastic to them. Pressurize the plastic tent to three times the atmospheric pressure on mars, then pitch a lower plastic tent along the bottom of the river bed inside the larger one, pressurize that to six times the Martian atmospheric pressure. Then pour water on top of the inner tent, and increase the air pressure pushing up to equal the water pressure pushing down, and then pour about 27 meters of water on top of that inner tend until both the inside pressure and the water pressure on top equal 1 bar or 14.69 psi. Probably it would be a good idea to cover the walls of the river bed in plastic to keep the water from becoming too murky, we want to keep it clear to let in sunlight.
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City to city tunnels are much later in the continued infrastructure building but not all that practical for mining and transportation to the city for useage into the processes which will lead to more structure building.
I agree - why devote so much tonnage of material to building and maintaining a tunnel, when you can just have a number of pressurised vehicles that pass from air lock to air clock, with passengers never needing to get in or out of space suits.
It's going to take a long time for Mars to get to even a planet-wide community of 100,000. That in itself will be a stupendous achievement - but inter-settlement traffic is unlikely to be huge in such circumstances. You probably wouldn't expect it to be greater than say - arbitrarily - 1,000 per day, or 25 busloads.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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The sort of equipment that we will need are simular to the earth moving but modified for Mars use. Things like bull Dozers will be in great demand. Just as important will be the means used to power,
just a few links for the bull dozers and there must be more...
This a light weight design:
http://www.ecofriend.com/electric-dozer … -safe.html
Desiel battery hybrid powered
http://greenbigtruck.com/2010/01/caterp … bulldozer/
The dozer is a 60,000 pound machine equipped with a C9 engine producing 175kW of power for two AC motors that power the differential steering and driving treads.
Heavier than I thought...
more specifics
http://www.constructionequipment.com/ca … oductivity
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SpaceNut wrote:City to city tunnels are much later in the continued infrastructure building but not all that practical for mining and transportation to the city for useage into the processes which will lead to more structure building.
I agree - why devote so much tonnage of material to building and maintaining a tunnel, when you can just have a number of pressurised vehicles that pass from air lock to air clock, with passengers never needing to get in or out of space suits.
It's going to take a long time for Mars to get to even a planet-wide community of 100,000. That in itself will be a stupendous achievement - but inter-settlement traffic is unlikely to be huge in such circumstances. You probably wouldn't expect it to be greater than say - arbitrarily - 1,000 per day, or 25 busloads.
For one thing, it would be easier to maintain on Mars than on Earth. For example the dome that covers the trench. the roof is supported by internal air pressure, so you don't need columns to hold up the structure as you would on Earth. think of it this way, One bar of Atmospheric pressure is about 10 tons per square meter, On Earth that means that pressure can hold ten meter cubes of water on top of it, on Mars where the gravity is less, you need even more water to balance out the internal air pressure below. One can do the same thing with domes at the bottom of craters. You have an inner dome and an outer dome. The inner dome has 1 bar of atmospheric pressure, they outer dome has just enough pressure to allow for the presence of liquid water inside, you fill up the crater inside the outer dome with water, and the water pressure around the inner dome, where people live prevents that inner dome from rupturing. Relying on water pressure reduces the maintenance because there is less stress on the inner and outer domes, most of the work in holding in that air pressure is done by the weight of the water in he crater. Mars has water that can be used for that purpose, and it also makes excellent radiation shielding in case of a solar flare. I believe someone named Marshall Savage (Of he Millennial Foundation) once proposed these double dome structures with water in between the inner and outer domes on the Moon. On the Moon, you'd probably need 60 meters of water to do this same job because of low gravity. But if the water is clear, it should let the sunlight right through.
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