Trains on Mars - Could a rail system provide martian need

GuyMontag · 2008-04-30 10:09:21

I don't think you take the possibility of corrosive dust on the rails seriously enough.

If you are referring to this study:
http://www.whatsnextnetwork.com/technol … eroxide_sn

First, these results make a lot of "what if" conclusions that haven't been verified independently.

Second, the study is about the effects on organic matter, not iron rails.

Third, if it really does “rain” hydrogen peroxide then corroding rails will be the least of the worries for mars explorers.

JoshNH4H · 2008-04-30 13:53:45

sterling is compatible with the previously mentioned design in my last post.

But to answer the main question of this thread, Trains would be enough.

JoshNH4H · 2008-05-01 14:20:21

I would suggest that it would be more like many single freight cars, with one engine each.

GW Johnson · 2012-02-10 16:07:42

Why not think some sort of paved roadway, and a rubber-tired truck-trailer-trailer-***-trailer rig? Extremely simple.

We've been talking about concrete substitutes in some of the other threads. We just need a minimally-paved fairly-smooth surface for rubber tires.

The tractor/locomotive unit could be electric, steam, chemical fuels, whatever turns out to be best. It's train, just no tracks. They run 3 and 4 trailer trucks on the highways in Australia, as I understand it.

GW

JoshNH4H · 2012-02-10 17:48:19

I was actually thinking about this the other day. There's no particular need for a paved road, per se. This is not based on any particular geological knowledge, but I would suspect that it would be relatively hard. I'm thinking like dirt roads here on Earth, which at least makes sense to me seeing as I don't believe that there would have been much weathering taking place. and I know that water tends to result in a loss of quality for dirt roads (Which is an overly scientific way of saying that water+dirt=mud, and on a cold, dry planet like Mars we will not see significant amounts of either dirt or mud).

Instead, I would just have a bulldozer push all the rocks out of the way and lay down a single rail. It would serve as a guiderail. It would be made of either brick or cast basalt (I haven't looked in detail as to whether one is better than the other yet, though my gut actually does like cast basalt). The cars would be unmanned and be powered probably by chemical fuels, either in an internal combustion engine or a brayton turbine (I hesitate to say which because the colony's power plants will be based on brayton turbines and so the colony will have to make those anyway, while it is at least my impression that ICEs are potentially simpler. You would actually probably know a lot more about this than I would). For fuel we're probably looking at Methanol-NO2, unless someone can think of an oxidizer that would work better. I think methanol is a very good fuel choice, though: Easier to make than the heavier hydrocarbons (We need Fisher-Tropsh for that-though reading the Wikipedia article it's really not as bad as I thought it would be, and hydrocarbons may even be preferable to Methane), but liquid down to pretty low temperatures. NO2 is hard to make, but so is every oxidizing chemical and we're unlikely to find any real reprieve here. I suppose it's also not totally inconceivable that the cars could be solar powered and only operate during the day. That would be a lot more efficient, but I can't really comment on which is better. We're not looking for very high speed, of course. Anyone have ideas?

GW Johnson · 2012-02-10 18:35:14

If it's unmanned, slow is OK. Use fuel cell electric, water and sunlight are all over Mars. Just load enough H2 and O2 bottles to make the trip.

GW

JoshNH4H · 2012-02-11 01:53:59

Will we want to use fuel cells, though? They're pretty hard to build. Now that I think about it, electricity storage may present an issue for the colony. Elementary batteries are simple enough to build, but don't exactly store a lot of energy. They're also usually not rechargeable, though this does depend somewhat on the specific reaction that is chosen.

In any case I do think the basic principle here is pretty solid: Chemical fuel tied to a heat engine, steered by a guiderail. Quite simple and with a minimal use of resources.

louis · 2012-02-11 08:54:09

In the early years of the colony, speed isn't really of the essence - supply is.

The trains could run on solar power alone. You would have a freight section and then a Km long photovoltaic section (PV Panels fixed to light weight cars). The train might generate anything up to a megawatt of energy. It could be computer controlled. Not sure how much you could pull but probably something like 10-20 tonnes over 4-5 hours every day at maybe 40-50 KPH. No need for batteries.

Alternatively - how about a methane engine?

GW Johnson · 2012-02-11 09:26:10

Now there's an idea I hadn't thought of: solar PV with the panels on the freight cars. Neat.

Heat engines on Mars should use something that will react with a CO2 atmosphere. If you have to carry both reactants, that's like rocket vs airbreather: a real disadvantage. Magnesium will, but it's awfully smoky. Raw soot carbon plus solid mag oxide for the "exhaust".

Batteries? Not very energy-dense compared to chemistry of liquid reactants generally, but lithium ion seems to work the best.

GW

SpaceNut · 2012-02-11 21:06:06

The H O fuel cell out in the open? since the train would not need to be in a dome would be a bad thing as the water is more valueable to the settlement....

Had thoughts of taking a solar panel and wiring them to the train tracks thus using the rails as an electrical grid not only for the train but back to the settlement or processing plant....

Last edited by SpaceNut (2012-02-12 09:34:37)

JoshNH4H · 2012-02-12 15:06:37

Well, first of all, photovoltaics are not really in the cards as something that will be produced ISRU by an early colony. They require extremely high purity silicon and rare dopants, which must be added in incredibly precise quantities. This will be very difficult for a colony to do. As with power generation in general, Conentrated Solar Power is really the only option for power generation (By the way, at an efficiency of 20%, and peak insolation of 325 W/m^2, you would need 15,400 m^2 of collector area. That's equivalent to covering the roof of over 500 40 foot long intermodal containers with solar panels. That would be enough capacity to carry nearly 14,000 tonnes- for which there is no need whatsoever).

I think that some kind of chemically fuelled heat engine, be it Internal Combustion, brayton, or sterling, would be the best way to get the our train moving. Apparently reacting Carbon Monoxide with Hydrogen at elevated temperatures and pressures does not result in methanol but rather with longer chain hydrocarbons (I'm talking about the fisher-tropsch process), so the fuel of choice will probably be hydrocarbons. Oxidizer will still presumably be NO2 unless someone can think of a different one. I don't think it's a big deal that we have to carry our oxidizer on board. This isn't a rocket, after all, and the amount of fuel needed will be absolutely minimal compared to the total mass of the engine or its cargo. I would see transportation proceeding at a very slow rate compared to Earth: Perhaps 40 kph, tops, or maybe even lower, just plodding on day after day until it gets where it's going.

I agree with GW that batteries aren't very good at storing energy on a per-mass or per-volume basis, but if you're looking to store electrical energy they're a whole lot better than doing it through the intermediary of a hydrocarbon fuel. Lithium Ion batteries are definitely beyond the production abilities of an early colony- they're very complicated, plus require Lithium, which even on Earth is pretty rare. When we need to store electrical energy, I think we'll probably be looking at a much simpler but also probably much less desirable (At least, on Earth) kind of rechargeable battery.

Glandu · 2012-02-13 02:35:59

About the rail vs road debate, don't forget that the rail allows bette usage of energy. Friction is lower. If you are to rely on relatively low-punch solar energy, then rails might be mandatory.

Here on earth, the rail vs road debate is about cost of infrastructure vs cost of exploitation. But there is more : the biggest ground transports can be made only by rail. And costs can be strongly reduced by the use of narrow gauge

JoshNH4H · 2012-02-13 16:11:47

I'm not quite so sure about that. Mars, after all, doesn't necessarily have a whole lot of friction. To start with, the gravity is only 38% as much as it is here on Earth, which should result in a proportionate fall in friction. Further, the atmosphere is pretty negligible, while it is not necessarily so. Further, whatever kind of transport is used on Mars is certainly going to move slower than Earth-based forms of transport, and its engine will be designed to give optimal efficiency at that lower speed.

I do support roads, however, for a pretty simple reason: Railroads are going to use a lot of steel. Even if we do a railroad with a small gauge and a low top speed there will still be a significant amount of mass involved. The smallest size that I could find that meets regular use anywhere in the world is 30 kg/m, which is the smallest standard size in Australia (I get my information from the wikipedia article on "Rail Profile"). Say we go a lot smaller than that, though, and Martians build their rails at 10 kg/m. Now this requires 20 kg of steel per meter of track, since you need to have two of them. Say your silica mine is 50 km (31 miles- Not far at all!) from the main colony. This means that you need to build 100 km of rails, 50 to get there and 50 to get back. Obviously you cannot simply have the trains running in opposite directions on the same track.

100,000 m of track at 20 kg/m: That would require 2,000 tonnes of steel. That's a lot of steel. Now you have to build another rail line over to the Iron ore mine, the Aluminium ore mine, your Basalt outcropping, and your all important water mine. I think it makes a lot more sense to go with transportation like cars, and then switch to rail once the colony is more established.

JoshNH4H · 2012-02-13 16:28:35

Oh, and another thought which just occurred to me: Since we are not going be importing all of our rails, (They're far too heavy; My guess would be that if the colony were to be rail-based its rail lines could mass 10,000 tonnes of steel, plus ties, plus whatever else you need to build a railroad), we will have to make them. But seeing as this requires a fully operational colony, we will have to have transportation to all of those places anyway. This will have to occur via land vehicles. Therefore the question becomes not if we should use land vehicles, but for how long. I think that it makes more sense to invest in the rails once the colony is really flourishing and would really benefit from the advantages of rail transit without having to devote too large a proportion of the colony's steel production to railmaking.

That said, it probably makes sense to design your land vehicles so that switching to a rail vehicle will not involve anything more complex than changing the wheels. Due to the lower friction, I think we could expect capacity to increase almost instantly due to the increased pulling capacity coming from the lower friction.

JoshNH4H · 2012-03-15 12:33:04

GW made a post very relevant to this thread in the thread where we were talking about concrete. Because both are important topics and I wouldn't want to derail (so to speak) one thread with a conversation that belongs in another, I have quoted his post here and will be writing a response:

Railroads of one type or another would make very good sense for hauling large loads to specific destinations on Mars, just like they do here. It was rail that opened up the American west, not wagon roads. (Bit of history.)
Railroad construction as we know it here uses "gravel" as the roadbed, yes, but not the gravel you are thinking of (the rounded stuff we also use in concrete). It's an angular crushed stone, sieved to size. There's layers of this stuff in different sizes, capped by the half-inch stuff you typically see. The cross-ties are embedded in this stuff, those being (here on Earth) timbers almost a foot square in section.
Some railroads have used concrete ties (the high-speed 150 mph+ ones), but timbers are far cheaper and more cost-effective here on Earth, even considering periodic replacement for ordinary freight at ordinary speeds. (And don't kid yourself about speeds, I've seen freights moving 60-80 mph right here in Texas. All it takes is well-maintained track to make that safe.)
The rails are spiked to the ties with "nails" that are about 10 inches long, and about an inch thick steel, not round, either. These days, rails are welded, and about
6 or 7 inches tall. That's to hold the steady upward growth in railcar weights I've seen the last several years. I've seen hopper cars labeled as 245,000 lb loaded going by at crossings. A lot of these are using aluminum in their structure now, as evidenced by unloaded weights creeping down from around 62,000 lb to about 41,000 lb.
Not sure what a railroad might look like on Mars, given that steel will not be generally available for a long time after the first bases are established, except as an expensive import. Could be a guideway-modified roadway with pneumatic tires at first, although the rolling friction with that is orders of magnitude higher than steel wheel on steel rail. I'm afraid maglev will always be too expensive for routine freight, even here. It's just hard to beat that low-friction rail transport, even after 3 centuries.
The power source for the locomotive needs some serious thought, since the only "fuel" I know of that burns with carbon dioxide is magnesium. Nuclear? Electric? There's several possibilities. The electric train with a central power plant supply might make the most sense.
GW

The original post was made here

JoshNH4H · 2012-03-16 12:53:31

There are actually a lot of different points in that post worth responding to:

Firstly and most generally, there will be steel on Mars. Because its production will be energy intensive, it will be replaced where possible with Basalt fiber, Icecrete, Cast Basalt, and other materials. But it will still exist and it will be used where necessary. Rails are likely one of those places (Unless we could get away with something like Cast Basalt?). I agree that rails are good for regular transportation routes; but I suspect that martians will likely use a significantly smaller gauge than Earth rails, because they will probably want to get a railroad up as soon as possible, to reduce transportation costs. Using a narrow gauge also reduces the amount of steel or iron needed to build a rail line (admittedly, for a corresponding decrease in payload capacity). Low capital investment is a good thing in a rapidly expanding colony, though, because as the colony grows the existing infrastructure will indubitably become obsolete or need massive expansions in its capacity.

I would envision early railroads running as pretty slow speeds. There is no real reason why water, Iron ore, etc. needs to go faster than 20 mph, or in fact slower. Going slower tends to reduce the complexity of equipment as well as make it much more practical to automate, as well as safer (If you have a small train moving 15-20 mph go out of control, that's hardly catastrophic). For the few instances where faster transportation may be needed (for example, ferrying people from one colony to one that is farther away) there will presumably be a few faster rail-less transports.

For an early colony, I would expect that trains would be fueled chemically because there aren't many other options. Probably hydrocarbons (produced by the Fischer-Tropsch Process) and some oxidizer, maybe a nitrate or NO2 (Unfortunately, there aren't many oxidizers that are both storable and easy to make chemically). Later on, nuclear powered trains make sense if your train is really really huge, but otherwise we could do what they do on Earth and use an electric generator to electrify the tracks. Just my opinion, though, given I'm not really aware of the relative benefits of each method.

RobS · 2012-03-16 22:52:21

Regarding trains versus roads, if Mars has enough communications satellites and they include GPS capacity, and that capacity is super-precise (centimeters, versus several meters) then a robotic vehicle could make its way down a dirt track just fine. If you don't have GPS, you can install posts with bar codes on them every hundred meters or so. The robotic vehicle could navigate from bar-coded post to bar coded post. It is also possible that terrain recognition software (such that is used to guide cruise missiles) would be sufficient. We now have competitions where robotic vehicles cross miles of desert from point A to point B all by themselves, so I think whatever system was chosen would work fine.

Considering that we will be importing vehicles a long time before we import trains, I am sure Mars will start out this way. Mars colonies would switch to trains when the added transport efficiency is economic.

As for fuels, silane burns in carbon dioxide. Zubrin favors making methane and oxygen for vehicles because there will already be those fuels for the Mars ascent vehicle. Methanol/oxygen would work as well. He was projecting vehicles with a 500 to 1000 km range.

If you have two colonies several thousand kilometers apart, I'd install automated, solar-powered refueling stations every 500 kilometers. Each one would have a water well (most likely, almost anywhere you go on Mars, there's water 100 or 200 meters down), a solar thermal power system (the spare heat being injected into the well to melt ground ice and produce an exhaust rich in water vapor), a Sabatier reactor, and a cryogenic refrigerator. It would make methane and oxygen from local water and CO2. A robotic truck would come along, dock to it, refuel, and dump its tank of "waste" water in the filling station's reservoir, so it could be converted back into methane and oxygen. You'd size the filling station to make enough fuel every week or so, so you could support frequent round trips, and maintain enough storage for several refills so that you have emergency capacity. If a vehicle had a 1,000 km range and you had filling stations every 500 km, it could stop at each one to top off its tank, and if the refilling mechanism didn't work, it could go on to the next station.

JoshNH4H · 2012-03-16 23:43:04

First, welcome back RobS!

In the stage where we're importing things I think that roads are definitely a good idea. Even early on in the ISRU stage railroads are going to make almost no sense. But later we will almost certainly transition.

I like the idea of using a simple guiderail- it could be made of brick or rock or just regolith, shaped into a mound, or icecrete, but the vehicle could simply have a guide-rail that makes it follow in that direction. Simple and cheap, I think, as well as pretty reliable.

louis · 2012-03-17 19:11:39

The problem I have with any rail system at an early stage is you are straight away into maintenance - even with simple guideways.

Much better to stick with road. All we need to is identify firm ground and then have machines clear the boulders out of the way. In some parts we may need to erect dune barriers. Of course the routes might have to be quite circuitous, given the cratered terrain but as has already been noted vehicle speed is not a huge issue in the early colony - steady security of supply is what is required.

SpaceNut · 2012-03-18 09:10:51

Thank You RobS for your post and welcome back...
It had reminded me of a thought for a marsDrive mission concept that I will need to follow up on....

GW Johnson · 2012-03-18 16:03:32

It would be difficult to generate significant horsepower with the ambient atmosphere of Mars, because it is so thin. At ordinary compression ratios (numbers under 30), you are looking at engine combustion chamber pressures of under 200 mbar (1/5 atm), compared to the 20 or 30 atm we are used to looking at. It is difficult to extract much energy from hot gas expansion at pressures that low, no matter the engine type, or that the exhaust back-pressure is next to zero.

This is why compression of the extremely-thin Martian atmosphere as a source of CO2 is such a big issue with me. It is to all engineers who actually look closely at the issue. Tenuous gases really aren't of much use, given any of the technologies that we actually have.

That is why I suggested closed-vessel evaporation of mined dry ice as a source of self-compressing CO2. The closer the fit between the dry ice chunk and the closed vessel, the less heat energy this will require to reach compressed CO2 at, say, the around-150 atm of a "typical" welding gas bottle. It's only heat, you can get it easily from concentrated solar. The only trouble with this is that dry ice is only known to exist at the poles, or maybe only the south pole, of Mars.

GW

JoshNH4H · 2012-03-18 22:59:45

Louis- The maintenance issue with railroads is a valid point. On the other hand, so are considerations of fuel savings and increased pulling capacity of each engine (because of the lower friction on rails). In this case, it's a question of what tonnage per day, over what distance, makes it worth it to have a rail line. Very early on, it simply won't be worth it. But once the colony is really expanding quickly I think rail lines make a lot of sense for things that aren't too far from the colony. I'm thinking in the tens of kilometers. The low gravity in combination with slow speeds makes it possible to build some really sturdy (read: long-lasting) rails that are still lighter than those used on Earth.

GW- I would think that the best option would be to keep both fuel and oxidizer on board, and combust them without a change in pressure, except when they're let out the back. On the other hand, we don't need quite so much horsepower, especially if we're using rails. There is little need to accelerate quickly, climb steep hills, or go very fast.

I'm going to make that thread on gas compression soon, I promise! Just as soon as I fill my other posting commitments

Glandu · 2012-03-20 07:03:57

JoshNH4H wrote:

(.../...) Rails are likely one of those places (Unless we could get away with something like Cast Basalt?). (.../...)

Nope.

Cast Basalt is 1/1000 mechanical resistance of basalt fiber. I know lower gravity means lower mechanical constraints, but not to that point. Even for the sleeper/tie, it would be damaged far too easily.

JoshNH4H · 2012-03-20 12:04:59

By mechanical resistance, do you mean tensile strength? Or shear strength? I accept that cast basalt is not feasible to build rails out of, but I thought it was at least worth bringing up.

GW Johnson · 2012-03-21 13:52:20

Rails, like any beam gravity-loaded on top, typically resist the worst heavy bending loads between the crossties, and the worst shear as low-to-moderate shear forces at the ties. The support case is continuous span across many ties, not the "simply-supported beam" case.

Bending is tension in the "fibers" away from the loaded side (on the bottom), and compression in the "fibers" close to the load (on the top). Up to the elastic limit, the stress distribution is linear between the tension and compression extrema, and zero at the "neutral axis" somewhere in between. Once you exceed the elastic limit, another more complicated model applies, plus you permanently bend the beam.

You're going to need a shape that takes advantage of tension resistance (the bottom flange) and a stable compressive column (another flange in most I beams, the rail cap in RR rail), and a thin web continuously-connecting them that resists the shear. Rails are just modified I-beam shapes, configured to match up with flanged tapered wheels.

For use this way, the material requires considerable tensile strength. That's why we like hardened alloy steel for RR rails (nope, it's not just plain carbon steel, it's extremely tough to withstand the heavy pounding and the wear). In metals, shear strength is usually around 60+% of tensile test strength. In other materials like rock fiber and crystals, nope. The compressive strength comes from the stable column geometry, not the true material compressive strength.

Concrete (and similar) materials are strong in material compression strength, and have some strength in shear, but are very weak in tension. That's why we add reinforcement of good tensile strength, and high stiffness (!!!), to make concretes that can take some bending. These reinforced concrete materials get used mainly in compression columns and foundations with compressive loads, and maybe a little bending and shear, but only if reinforced for it, like erectable wall panels. The extreme case is the pre-stressed concrete bridge beam. Very complicated reinforcement.

In a composite like a reinforced concrete, you have to pay very careful attention to how much of each material is present, and how stiff each material is (Young's modulus and some geometry). The stiffer one wants to pick up more than its share of load first, and may fail before the other component can even load up. The details of actually doing that kind of design analysis are neither simple nor easy.

With metals like steel and aluminum, you also have to consider how many times the structure gets loaded ("fatigue"). On a log-log plot, the load level vs cycles-to-failure is a descending linear line, down to a fatigue limit stress, where the line is horizontal, no matter how many cycles. That fatigue limit stress is way below the tensile yield stress, and way-to-hell-and-gone far below the ultimate tensile stress for the material.

The fatigue limit for steel is typically a bit higher relative to its yield than with aluminum. That's why we build things that don't have to fly out of steel way more often than we do with aluminum. Things that fly, the higher strength/weight of aluminum is better, unless it gets too hot.

Concrete and organic composites (and wood) are quite different from the metals. Concrete life is limited by weathering of the surface and corrosion of the internal steel reinforcement. Shrinkage and weathering cracks are inevitable; that's how water gets in to do its evil corrosion work. Organic composite life is limited mainly by UV damage or simple impact damage. Wood life is limited by wet or dry rot.

All suffer nuclear radiation damage, but it really does take quite a lot.

GW

New Mars Forums

Announcement

#101 2008-04-30 10:09:21

Re: Trains on Mars - Could a rail system provide martian need

#102 2008-04-30 13:53:45

Re: Trains on Mars - Could a rail system provide martian need

#103 2008-05-01 14:20:21

Re: Trains on Mars - Could a rail system provide martian need

#104 2012-02-10 16:07:42

Re: Trains on Mars - Could a rail system provide martian need

#105 2012-02-10 17:48:19

Re: Trains on Mars - Could a rail system provide martian need

#106 2012-02-10 18:35:14

Re: Trains on Mars - Could a rail system provide martian need

#107 2012-02-11 01:53:59

Re: Trains on Mars - Could a rail system provide martian need

#108 2012-02-11 08:54:09

Re: Trains on Mars - Could a rail system provide martian need

#109 2012-02-11 09:26:10

Re: Trains on Mars - Could a rail system provide martian need

#110 2012-02-11 21:06:06

Re: Trains on Mars - Could a rail system provide martian need

#111 2012-02-12 15:06:37

Re: Trains on Mars - Could a rail system provide martian need

#112 2012-02-13 02:35:59

Re: Trains on Mars - Could a rail system provide martian need

#113 2012-02-13 16:11:47

Re: Trains on Mars - Could a rail system provide martian need

#114 2012-02-13 16:28:35

Re: Trains on Mars - Could a rail system provide martian need

#115 2012-03-15 12:33:04

Re: Trains on Mars - Could a rail system provide martian need

#116 2012-03-16 12:53:31

Re: Trains on Mars - Could a rail system provide martian need

#117 2012-03-16 22:52:21

Re: Trains on Mars - Could a rail system provide martian need

#118 2012-03-16 23:43:04

Re: Trains on Mars - Could a rail system provide martian need

#119 2012-03-17 19:11:39

Re: Trains on Mars - Could a rail system provide martian need

#120 2012-03-18 09:10:51

Re: Trains on Mars - Could a rail system provide martian need

#121 2012-03-18 16:03:32

Re: Trains on Mars - Could a rail system provide martian need

#122 2012-03-18 22:59:45

Re: Trains on Mars - Could a rail system provide martian need

#123 2012-03-20 07:03:57

Re: Trains on Mars - Could a rail system provide martian need

#124 2012-03-20 12:04:59

Re: Trains on Mars - Could a rail system provide martian need

#125 2012-03-21 13:52:20

Re: Trains on Mars - Could a rail system provide martian need

Board footer