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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.
Using silanes or boranes are remedying that issue as they burn in CO2; however, can iron filling also burn in CO2 ? Say a small amount of silane mixture or solution (a liquid, details below) as a fire starter reacts with CO2 to drive the reaction between Fe and CO2, which releases more energy until all Fe filling is burnt. According to the Ellingham diagram, iron can reduce carbon dioxide to carbon while oxidizing itself to the thermodynamically stabler iron oxides. The iron oxides and carbon products can be dumped onto the ground: the Martian regolith is mostly composed of iron oxides anyway. The carbon can be recycled. In essence, the iron filling is "coal" on Mars.
Or if liquid fuel is needed, how about picking a silane/organic solvent solution with a broad liquid phase that mostly lie within the temperature range on Mars surface. Say some ionic iron or silicon hydride salts (for example Mg2FeH6 magnesium iron hexahydride) in a diethylsilane (m.p. −132 °C, b.p. 56 °C all under earth atmospheric pressure) and hydrogen/silane solvent suspension.
As a note, if Mg2FeH6 can be made, could something like MgSiH6 also be made ?
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http://www.scientificamerican.com/artic … -at-night/
That and either Liquid/Solid C02, or Liquid Air (On Mars, mostly the gasses that are not CO2).
Heat from the environment + Stored hight temperature Solar Molten Salt Heat + Steam Power
If you have a "Steam Jacket" surrounding your molten salt you reduce heat loss to the universe, and also it can be noted that the ambient thermal conditions on Mars will usually add heat to CO2, and will almost always add heat to Liquid Air (On Mars, mostly the gasses that are not CO2).
Of course water could be the working fluid as well, but is precious in many locations on Mars. You might want to be able to recapture some of it after it condenses, but that would reduce power most likely.
Done.
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Knightdepaix-
First of all, welcome to Newmars!
Iron can't be burned in a carbon dioxide atmosphere becuase CO2 likes to hold onto its oxygens more than Iron does.
I like the idea of molten salts for vehicles. It wouldn't work on planes because the energy density is too low, but for a car of some kind I bet it would.
-Josh
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Knightdepaix-
First of all, welcome to Newmars!
Iron can't be burned in a carbon dioxide atmosphere becuase CO2 likes to hold onto its oxygens more than Iron does.
Thank you for having me.
For the reaction between Fe and CO2, obviously under the Martian surface temperature range (-20° C to -132° C), CO2 is thermodynamically more stable then iron oxides. However, if some CO2 can be reduced to carbon monoxide, this CO loses oxygen to iron for that temperature range, which is why a reaction starter like silane is needed. The energy generated from reaction of Fe and CO splits more CO2 to CO and continues this late reaction. In essence, the reaction between Fe and CO in the temperature range produces energy for transportation use. More input if counter reasoning is ok.
I like the idea of molten salt too. As Martian atmosphere is almost CO2 and regolith is often iron oxides, how about using inorganic/ionic carbonate or organic orthocarbonate esters solvent or colloid of both as the molten salt ? Because of lower Martian temperature range, salt with a higher temperature liquid phase like table salt is not sought after as much as on Earth. Native sodium and chloride are harder to find than iron, silicon, aluminum and CO2 anyway. On the other hand, ionic carbonate decomposes to oxides and CO2 on earth upon heating, lower Martian surface temperature decreases the chance of that decomposition during machine operation. In essence, find an organic orthocarbonate or orthosilicate ester colloid with ionic iron carbonate, obviously the liquid phase of that orthoester itself shall lie within Martian surface temperature range. Such colloid would separate into gaseous orthoester and solid iron carbonate if more heat input into the system of molten salt, useful for maintenance. In worse case and accident scenario to machines, the orthoester and iron carbonate decompose to solid iron oxides, gaseous ether and carbon dioxide. Because of the absence of oxygen and ether not reacting with CO2, both gases escape to atmosphere without further harm.
I imagine such colloid as blood, where iron compounds flow in blood plasma. Conducting electricity and acting as buffer are great advantages for such colloid; obviously more additives can be desired in that colloid, just like glucose and ions in blood.
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knightdepaix-
What is the source for your assertion that Iron reacting with carbon monoxide is exothermic? Everything I've ever heard suggests that the opposite is true. I don't quite understand where you're going with the colloid suggestion
-Josh
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knightdepaix-
What is the source for your assertion that Iron reacting with carbon monoxide is exothermic? Everything I've ever heard suggests that the opposite is true. I don't quite understand where you're going with the colloid suggestion
For colloid, Void's suggestion of molten salt as heat sink (as suggested in the SciAm article) prompted me to think of a colloid that can also use as a heat sink and electrolyte.
I was looking at these reactions at Martian temperature, let me assume to be below 300K.
C --> CO
C ---> CO2
H ---> H2O
Fe + O ---> iron oxides
CO + O ---> CO2
Si + O ---> SiO2
According to the Ellingham diagrams below 300K, the free energy for oxidation of iron is more negative than those of oxidation of carbon to carbon monoxide or carbon dioxide. However, the oxidation of Si to SiO2 is the most negative in free energy; also the oxidation of CO to CO2 is the more negative in free energy than that of oxidation of Fe. So a reaction starter like silane providing silicon to reduce CO2 to CO; the CO produced is consumed by Fe fillings to form carbon; however the tricky part is how to let the silicon not reduce CO2 all the way to carbon but only produce CO. So as I wrote, "More input if counter reasoning is ok."
For iron metallurgy on earth, furnace needs to operate at above about 1000K so that carbon can reduce iron oxides.
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It was my understanding that that was a reaction rate thing more than a gibbs free energy thing. But either way, at low temperatures the reaction rate is presumably quite slow (Have you ever heard of issues stemming from Iron in a Carbon Dioxide atmosphere?), and the only way to speed it up (heating) will prevent it from occurring.
-Josh
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Regarding the use of silanes and their derivatives, the following is a list of m.p.'s and b.p.'s (from wikipedia) at Earth's atmospheric pressure
Silane m.p.−185 °C (−301.0 °F; 88.1 K) b.p.−112 °C (−170 °F; 161 K)
Disilane Melting point −132 °C (−206 °F; 141 K) Boiling point −14 °C (7 °F; 259 K)
Trisilane Melting point −117 °C (−179 °F; 156 K) Boiling point 53 °C (127 °F; 326 K)
Dimethylsilane Melting point −150 °C (−238 °F; 123 K) Boiling point −20 °C (−4 °F; 253 K)
Diethylsilane Melting Point: -132 °C Boiling Point: 56 °C (from Chem Spider)
Trimethylsilane m.p. −135.9 °C (−212.6 °F; 137.2 K) b.p. 6.7 °C (44.1 °F; 279.8 K)
Triethylsilane m.p. −156.1 °C (−249.0 °F; 117.0 K) b.p. 107-108 °C
Tetramethylsilane Melting point −99 °C (−146 °F; 174 K) Boiling point 26 to 28 °C (79 to 82 °F; 299 to 301 K)
Tetraethylsilane Melting Point: -82.5 °C Boiling Point: 153-155 °C (from Chem Spider)
Observation:
1) having a long alkyl chain will broaden the liquid phase temperature range; an important characteristic for silanes use as liquid fuel
2) More substituted silane will increase both the m.p. and b.p.
So:
1) use ethyl-substituted silane: According to "The Case for Mars", ethene can be prepared from hydrogen and carbon dioxide. I believe it can then react with mono-silane in appropriate stoichiometric proportion to make ethyl-substituted silanes.
2) The temperature range for ethyl-substituted silanes will shift to lower temperature due to lower Martian atmospheric pressure. So tri- or tetra- ethylsilane can be a good fuel solvent with some mixture of silanes and hydrogen dissolved as "reaction starter" fluid. The silane fluid will first reaction with Martian atmospheric carbon dioxide to jump start the much larger scale reaction of triethylsilane (for example) with CO2.
3) Instead of the pure carbon and silicon dioxide products from the reaction between monosilane and carbon dioxide per "The Case for Mars", using alkyl-substituted silane could produce potentially poisonous carbon monoxide, which shall be exhausted well or chemically fixed as metal carbonyls in the engine. However, this could be remedied by introducing more "hydrogen" or "silicon" content to the fuel.
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For Mars the Melting Point as well as the Boiling point will shift as part of the very low atmospheric pressure and gravity....
The Differing in situ values have been reported for the average temperature on Mars, with a common value being −55 °C (218 K; −67 °F). Surface temperatures may reach a high of about 20 °C (293 K; 68 °F) at noon, at the equator, and a low of about −153 °C (120 K; −243 °F) at the poles. Actual temperature measurements at the Viking landers' site range from −17.2 °C (256.0 K; 1.0 °F) to −107 °C (166 K; −161 °F). The warmest soil temperature on the Mars surface estimated by the Viking Orbiter was 27 °C (300 K; 81 °F). The Spirit rover recorded a maximum daytime air temperature in the shade of 35 °C (308 K; 95 °F), and regularly recorded temperatures well above 0 °C (273 K; 32 °F), except in winter.
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Inert material such as ores could be transported over distances of 500km using a gas gun. The weaker Martian gravity and tenuous atmosphere would allow ranges for ballistic projectiles that are unachievable on Earth.
A smooth bore gas gun would show significant dispersal over that sort of range, but if you are prepared to set aside 30km2 of Martian desert as a 'target area' you could allow projectiles to accumulate for several months and simply collect them at the end of the year.
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Inert material such as ores could be transported over distances of 500km using a gas gun. The weaker Martian gravity and tenuous atmosphere would allow ranges for ballistic projectiles that are unachievable on Earth.
A smooth bore gas gun would show significant dispersal over that sort of range, but if you are prepared to set aside 30km2 of Martian desert as a 'target area' you could allow projectiles to accumulate for several months and simply collect them at the end of the year.
Excellent idea.
However, I think from a practical point of view, it's probably just as easy (since you've got to collect the stuff anyway) to have robotic solar powered vehicles ferrying materials from mining sites etc. They don't have to travel at speed. Once you have your chain supply established, speed becomes pretty irrelevant as long as the supply is constant.
Routes can be cleared of boulders by specialised bulldozer vehicles at the outset to facilitate wheeled transport.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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For Mars the Melting Point as well as the Boiling point will shift as part of the very low atmospheric pressure and gravity....
The Differing in situ values have been reported for the average temperature on Mars, with a common value being −55 °C (218 K; −67 °F). Surface temperatures may reach a high of about 20 °C (293 K; 68 °F) at noon, at the equator, and a low of about −153 °C (120 K; −243 °F) at the poles. Actual temperature measurements at the Viking landers' site range from −17.2 °C (256.0 K; 1.0 °F) to −107 °C (166 K; −161 °F). The warmest soil temperature on the Mars surface estimated by the Viking Orbiter was 27 °C (300 K; 81 °F). The Spirit rover recorded a maximum daytime air temperature in the shade of 35 °C (308 K; 95 °F), and regularly recorded temperatures well above 0 °C (273 K; 32 °F), except in winter.
How about a turboshaft powered car or truck (or military vehicles, for sake of discussion) with dissolved silane and hydrogen in triethylsilane mixture fuel ? Turboshaft engines have been already available nowadays, as Honeywell AGT1500 in M1 Abrams series.
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Silanes produce slag, which does not "mix" well with turbomachinery. or even piston/cylinder stuff.
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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Maybe hybrid electric vehicle with 2 or more power sources
1a) Electricity from fuel cell inside the vehicle
1b) electricity from sterling engine on silane
2) solar power
gas station on Earth becomes hybrid fuel (electricity and silanes) station on Mars. Electricity source of each station depends on localities: geothermal, solar, wind, nuclear.
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Here's how to do it, Solar electric battery powered modular land Train.
Your train consists of a universal 40ft flatbed car resembling a rail-car with electric powered drive trucks (the little groups of 2 axes at each end of a rail car), but rather then running on rails they have tires and travel over simple roads scrapped clear of large boulders by a bulldozer. Each car can carry 2 standard 20ft containers in single stack, 4 in double-stack and the containers attach to the bed. Each car is electrically connected with the one ahead and behind and can share power with the whole train, in addition each car is individually computerized and navigated though they synchronize to move together without any one car pulling the rest. Large batteries filling whole 20ft containers are placed/plugged into some cars making thouse cars 'battery cars', these cars provide power to the whole train with some ratio of battery/non-battery cars being needed for any particular range desired.
As the train goes along it's route and it's battery cars run down it stops at a solar/nuclear/pick-your-source power station that exists specifically to top off these trains. The train splits apart where ever a depleted battery car exists and the depleted cars plug themselves into the electric supply, full cars take their place and the train re-assembles (the depleted cars may need a few days to recharge and wait till another train needs them). As all cars are wheeled and the train can split in multiple places simultaneous this requires no complex switching yards and takes very little time. The re-assembled train continues on and when it comes to it's ultimate destination the individual cargo containers are placed onto small vehicles resembling regular trucks for delivery to specific buildings.
But their is more...
These same trucks are what pick up the 20ft containers from the reusable SSTO landing capsules, each capsule holds several such containers in a roll-on roll-off configuration similar to jumbo jet (but side to side rather then end to end to fill a round capsule cross section rather then a long fuselage) and a scissor lift truck. The capsules load the containers in Low Mars Orbit by robotic arms and take them from a massive 'brick' assembled from hundreds of containers held together by the standard male-female twist connectors used today (and on the trains and trucks too). The whole brick is sent from Earth to Mars via slow ion propulsion provided by a detachable buss that leaves the brick in orbit and returns to Earth. The cargo brick is assembled in Earth Orbit the reverse of how it's disassembled in Mars obit, a bit at a time by capsules equipped with robotic arms launching from and returning to Earth's surface, though the launch is multi rather then SSTO.
Now you have a fully functional inter-modal transport system that includes the Earth-surface, Space and the Mars-surface. If it can fit in a 20ft shipping container (which virtually everything dose) then it can be packed up in a factory on Earth and sent to it's final destination on the Martian surface without being unpacked anywhere along the way and with no discarded vehicles.
SpaceX would make all the capsules and rockets but might buy the Ion systems, Tesla would make all the Mars surface vehicles.
Last edited by Impaler (2014-11-21 23:21:00)
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Something to keep in mind with transportation on Mars is that we want to keep it as simple as possible. We need to ask ourselves: How little energy can we use, how weak can we make our motors, etc.
My proposal is this: Robotic driving would be easiest with a "rail" made of bricks laid down for the car to follow. This is solely a guide rail and the entire weight and maneuvering forces on the car would be on the ground. The car can travel at speeds as low as 5 m/s (18 kph; 11 mph) or less. The path can be designed to have inclines below 10 degrees. Maybe it's fine if the cars turn off at night. Maybe on an incline the vehicle will "gear down" so as to use less power by going slower.
But, thinking about it, chemical fuels are probably the way to go. They have really high volumetric and specific energy densities and can be pretty easy to manufacture and store. Oxidizer is kind of tricky, but we don't necessarily need a very powerful one. Chlorine is a liquid at ambient martian temperatures, for example. We don't need to worry about polluting Mars. In fact, CF4 is a very powerful greenhouse gas. The best argument for not releasing it is that it may be worth keeping the chlorine for reuse. Oxygen isn't as good because it's not liquid at Mars pressures, but you could get a reasonably high density by pressurizing. Then there are compounds like Ammonium Nitrate, which are relatively safe, oxidizing solids that can also be dissolved in water.
My point is this: Keep it simple and low-powered, and chemical, and it'll work for a long time at low cost.
-Josh
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Something to keep in mind with transportation on Mars is that we want to keep it as simple as possible. We need to ask ourselves: How little energy can we use, how weak can we make our motors, etc.
My proposal is this: Robotic driving would be easiest with a "rail" made of bricks laid down for the car to follow. This is solely a guide rail and the entire weight and maneuvering forces on the car would be on the ground. The car can travel at speeds as low as 5 m/s (18 kph; 11 mph) or less. The path can be designed to have inclines below 10 degrees. Maybe it's fine if the cars turn off at night. Maybe on an incline the vehicle will "gear down" so as to use less power by going slower.
But, thinking about it, chemical fuels are probably the way to go. They have really high volumetric and specific energy densities and can be pretty easy to manufacture and store. Oxidizer is kind of tricky, but we don't necessarily need a very powerful one. Chlorine is a liquid at ambient martian temperatures, for example. We don't need to worry about polluting Mars. In fact, CF4 is a very powerful greenhouse gas. The best argument for not releasing it is that it may be worth keeping the chlorine for reuse. Oxygen isn't as good because it's not liquid at Mars pressures, but you could get a reasonably high density by pressurizing. Then there are compounds like Ammonium Nitrate, which are relatively safe, oxidizing solids that can also be dissolved in water.
My point is this: Keep it simple and low-powered, and chemical, and it'll work for a long time at low cost.
I agree with that approach. But simpler than bricks are white lines at intervals. Robot vehicles have no problem following those.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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I'd think with a Mars global positioning system no lines are necessary at all. Given how useful thouse system have been on Earth it seems a no brainer to put one in position at Mars right along side any road system this elaborate.
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That's not exactly in-situ technology...
"I'm gonna die surrounded by the biggest idiots in the galaxy." - If this forum was a Mars Colony
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Obviously not made and launched from the surface, just dropped off in orbit by the incoming transport vessels that are bringing in 99% of everything being used right at the initial infrastructure build up. Your probably going to put in the satellites when your still at the <100 humans living on the surface just for the safety of surface navigation. About the point when people would start doing routine geologic surveying would be the time to put it in and that's likely before you have a need for autonomous ground freight vehicles and well established roads.
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Why not grade the road with pre-formed deep ruts in it? The wheels follow the ruts automatically, much like railroad, but simpler to build. Some sort of tractor pulls a series of trailers, much like a freight train. Could be done without drivers, as long as someone somewhere can oversee the trips to detect and correct problems.
About the only downside is periodic maintenance: you have to remove wind-blown dust before it fills up the ruts.
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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Impaler- The downside to GPS is that it's more expensive and less precise than more physical methods. The road is only going to be so wide, after all-- realistically, about as wide as the cars that will travel on it. That gives very little room for error, and GPS is +/- about 5 m. Furthermore, a mechanical system could be simpler to implement, having literally zero electronic components and being 100% fixable on the Martian surface.
It's not impossible of course, not by any means. But I think a physical mechanism makes more sense in this context.
Something to think about: Programming is a non-trivial task. I've been looking for jobs lately, and if you search job postings at and major company for "engineer" you're gonna see a lot more postings for software engineers than mechanical or chemical or electrical engineers. It can take a lot of time and/or money to get these things right. Intellectual property isn't going away any time soon, nor is North Korea colonizing Mars (Its entire economy is about as large as NASA's budget during Apollo), so if a software package is expensive on Earth it will also be expensive on Mars.
So, that's the reason to use simple, primarily mechanical systems in place of more capable but more complex computerized systems.
In terms of guiderails, I still think that protruding ones are better than a guide-rut (so to speak). A rut would presumably be made from Martian regolith and would be subject to collapse, which would be a problem. I would orient the bricks vertically, about 2/3 underground and 1/3 above-ground for stability, and grout them together.
-Josh
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Merry Christmas, guys!
As for self-guiding roads, what I was thinking of is less about road construction per se, and more about the jeep/pickup and cattle trails you see on farms and ranches. The trails are single (cattle) or double (vehicle) depressed places where the surface is worn (and surface vegetation gone). They won't quite guide the vehicle, but the tendency is definitely there, you feel it in the steering wheel, especially with non-power steering. The deep ones do guide vehicles fairly effectively. So we know it would work.
I'm thinking we do the same sort of thing on Mars, just deliberately form it initially. You don't grade a whole roadway, just use two narrow drag buckets behind some kind of crawler tractor to scrape out the wheel ruts, spaced correctly. Then run the crawler back and forth on the "rutway" to pack the bottoms of the ruts down with its treads. Pick out any rocks you missed, most of the time with the buckets. Might have to jack-hammer some into submission. Not many, though.
This is not real well-formed structure, just two fairly-deeply depressed ruts in which the wheels "naturally" want to roll. Once vehicles begin to use it, it will tend to stay worn in place. I'd hazard the guess that we could equip the vehicles with "dust blowers" of some type down near each wheel, just to keep the windblown dust blown out of the ruts, each time a vehicle traverses.
You'd probably want to equip driverless vehicles with something that could detect front wheels climbing out of the ruts, and have it add a steering input to put them back down in the ruts where they belong. It need not be computerized. Might be as simple as a transverse mechanical inclinometer that trips a servo valve in the hydraulics that steer the vehicle when the angle gets too high. These vehicles are likely to be about the size of 18-wheel rigs. It'll take hydraulics to steer them on rough ground anyway.
The advantage of such a scheme is this: that's about the lowest effort required to create a roadway suitable for slow truck traffic in rough country.
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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The one size fits all might work with a road but the vehicle applications comes back to what is to power it.
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