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#151 2019-04-22 19:25:20

kbd512
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Re: Trains on Mars - Could a rail system provide martian need

As long as the resin in the composite matrix can resist the temperatures and chemical properties of whatever is being transported, a CNT composite pipe would work just as well as a steel pipe.  It'd be a heck of a lot stronger and lighter.  There are various resins, plastics, and rubbers that have varying abilities to resist chemical attack against different chemicals.  Some are good against acids, some against bases, some resist chemicals containing benzene rings, etc.  Pick the correct resin and the CNT has substantially more strength than Carbon Fiber.

There are also ceramic binders used in special high temperature Carbon Fiber tubing for vehicle intake or exhaust manifolds, for example, although metals are far more common for those applications because they're so much cheaper and easier to work with when it comes to modifying the shape of the material to go through whatever twists and turns are required to enter / exit the engine.  High end race cars use these specialty CF composites to save weight.

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#152 2020-07-10 19:31:49

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

tahanson43206 wrote:

This post is for Calliban ....

While trying to find the story reported in Void's ice/brine topic, Google showed me a collection of imaged Popular Mechanics magazines from 1927 and 1928 which contained articles about steam engines active in that period.  Electric locomotives were giving the steam designs a good run for their money, but it was still early in the competition at that point.  The article I found caught my attention, and I read for far longer than I had intended, because I can still remember the last days of steam after the end of World War II.

I have not thought about steam engines at all for some time, and not at all about the details of design to try to wrestle increasing power/speed combinations out of the limited capability of simple steam propulsion, while staying within the limitations of bridges, tunnels, rails and curves of the time.

The article included images of British monster locomotives as well as American ones.

(th)

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#153 2020-07-10 19:32:29

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

Calliban wrote:

Thanks TH.

There are several basic problems that render rail based steam engines impractical as a mode of propulsion, compared to diesel and electric engines.
1. They rely upon heat transfer into a separate working fluid, which limits power to weight ratio, as heat transfer is rate limited and boilers are heavy.
2. They are non-condensing and non-regenerative cycles, hence much energy is wasted in the residual energy of saturated steam, which carries away a substantial amount of enthalpy.  This makes them inefficient.
3. The low efficiency and high inherent weight, raise the requirement for huge quantities of fuel, which add even more to weight.  Range is also limited, requiring frequent and time consuming refuelling stops.
4. The high inherent weight and low power of the system, results in poor acceleration and limits to speed.
5. The high consumption of solid fuels, incompletely combusted, raises severe problems with air pollution in urban areas.

It was this final problem that led to the replacement of steam power by DC third rail in London, South East England, Merseyside and Newcastle, between about 1900 and 1960.  People were literally dying in their thousands in toxic smogs, in large part due to steam engine pollution.  I find it mildly humorous that so many people consider steam to be a romantic age.  They were archaic, slow, dirty, stinking things.  In just one night in London in 1952, smog from steam engines and open fires killed more people than all of the radiation released by Chernobyl.

The UK hung onto the steam engine for too long.  The steam railways simply weren't able to compete with private cars for people transport and they were too slow, expensive, inflexible and cumbersome to compete in goods transportation.

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#154 2020-07-11 14:56:36

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

kbd512 wrote:

tahanson43206,

Although it wouldn't be practical on Earth due to air resistance, I wonder if Stirling engines and solar concentrators could be used on Mars to provide motive power for a train by supplying each rail car with its own motors and solar concentrator array.

Infinia has a 30kW 6-cylinder free piston balanced Stirling engine that produces that kind of power using a 10m to 12m reflector dish using a 1kW/m^2 solar radiation flux.  We'd get less than half of that on Mars, but Mars also has 38% of Earth's gravity, so the train would require less than half of the motive power of an Earth-bound train for equivalent performance.

As you can see, Infinia and NASA have been working on this for quite some time:

REPORT ON STATE-OF-THE-ART DISH-ENGINE APPLICATIONS

30 kW Maintenance Free Stirling Engine for High Performance Dish Concentrating Solar Power

Dish Systems for CSP

It's not compact or lightweight, but it's extremely durable and reliable.

The production 6-piston Stirling engine is expected to weigh around 540kg.  I've been trying to figure out how much the solar concentrator would weigh, but I'm guessing lightweight materials could make something in the 2,250kg range feasible using Aluminum alloys.  That power-to-weight ratio is nothing to write home about, but this is a distributed propulsion system (1 or 2 dishes per rail car) mounted to 45t steel rail cars or perhaps lighter composite rail cars with Aluminum rolling stock with steel rims.

I based my weight estimate for the dish off of this design, admittedly not very mass-efficient for a number of reasons:

Solar Concentrator (Solar Dish) Dimensions

I was trying to factor in worst case scenario numbers to the total mass of the system.  Note that the 9m dish is only 292kg on its own and it only weighs 111kg on Mars and doesn't have to be stiff enough to withstand Earth-associated wind pressures.  There won't be any infrastructure or trees or other obstacles around the railroad track, either.  It's entirely conceivable that the complete system would produce better power-to-weight performance than Earth-based diesel electric locomotives.

An Earth-bound diesel electric locomotive weighs just shy of 200t and produces 6,000hp.  This distributed system would require 150 cars to produce 6,000hp, but the propulsion would be highly redundant and long haul freight trains routinely have at least 100 cars here in America.  We could also make the cars from rock wool-based composites to reduce the weight of individual cars to compensate for any relative increase in mass over the steel-based cars and locomotives used here on Earth to produce equivalent power-to-weight performance to an ordinary diesel electric locomotive.

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#155 2020-07-11 17:05:02

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

kbd512 wrote:

tahanson43206,

It's pretty simple.  You bolt 2 of these solar concentrator dishes to each rail car and they provide about 30kW of power per rail car.  Earth-bound diesel electric trains provide about 60hp or 45kW per rail car with 100 cars.  If you figure each rail car has a loaded weight of around 100t, that works out to about .45kW/t.  If the Mars-bound train weighs 38% of the Earth-bound train as a function of the gravity difference, then the Mars-bound train has 1.25kW/t.  Alternatively, you use a smaller power system that provides 20kW of power per rail car and that still works out to .53kW/t.  Overall, your power provisioning system still ends up weighing less than a diesel electric locomotive producing equivalent power.  There are some limitations such as only operating during daylight hours, obviously, but between the lighter propulsion system, no stops for refueling, and lighter rail cars, you end up with equivalent performance.  I figure this system is good for a rated speed of around 120km/hr and 720km/sol.

A standard boxcar is 16.9m in length and the long ones are 20.6m in length, so the overhead solar concentrator dishes would be staggered on either side of a rail car.  Each bogie would have its own electric motors, so individual cars could move under their own power, as required, or in series, if operating as part of a train.  This would allow us to run trains of arbitrary lengths with no requirement for specialized locomotives to move them around.

A rock wool fiber has roughly 6 times the tensile strength of a mild steel, so it's entirely possible to build lighter railcars using composite beds and boxes, and maybe even tanks, dependent upon what you're hauling (water, mostly, though industrial chemicals would probably still require stainless steel).  So the rail cars would be made from rock wool composite and Aluminum to roughly halve their empty weight, which would have the knock-on effect of further reducing the size and weight of the solar power system to provide equivalent power-to-weight.

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#156 2020-07-11 19:27:43

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

Depending on the length of the rail cars and how many are coupled to the rail for use we might get away with smaller units that can ride in more positions to create the energy required but it is more complex that using a larger single use.

Wondering if we can use  lenses and a multiple trough concentrator on the top of each car might work as well.

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#157 2020-07-11 20:03:34

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

kbd512 wrote:

tahanson43206,

I'm not for or against any idea because I came up with it or somebody else came up with it or anything like that.  The math behind the basic engineering involved with making something work either checks out or it doesn't.  If it doesn't, then it doesn't matter how enamored anyone is with the idea, including me.  There are no trees or power lines or other terrain obstructions on most candidate overland routes in most places on Mars and very little air resistance that something of the size of a 10m solar concentrator dish would otherwise create at Earth sea level.  That's why I proposed this.  It's technically feasible because it would meet the power-to-weight requirements for a train on Mars, it uses very robust and thoroughly proven Stirling engine technology, and it would be relatively simple to maintain without computers or other advanced electronics.

I would think that we'd use Earth-standard train component and shipping container dimensions and call it a day, rather than starting over from scratch.  There are good reasons to use lighter fabrication materials, but not many good reasons to "reinvent trains" or "reinvent cargo containers", as NASA would no doubt try to do.  The shipping industry has already figured out the dimensions and weights of cargo for optimal shipment using existing infrastructure and designs.  They already have steel, Aluminum, and fiberglass shipping containers.

Aluminum Applications in the Rail Industry

BNSF Aluminum Rotary Gondola Rail Car

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#158 2020-07-11 20:20:35

kbd512
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Re: Trains on Mars - Could a rail system provide martian need

SpaceNut,

I hereby give you permission to move, not simply repost, anything that I post in whatever topic you think it belongs in.  Seriously, just move the content where you think it belongs.  If everyone else is happier with the content somewhere else, then let's move it there.

tahanson43206 asked a question related to trains and I responded with something that could feasibly work on Mars.  I don't care where the content ends up.  We've run over the same old ground so many times that I just kept the content in the thread I was responding to, rather than creating a new thread or adding several additional posts to some old thread started years ago and long since forgotten.

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#159 2020-07-11 20:54:25

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

This forums software does not allow for the splitting and merging of posts from one topic to the next by any other method.
We lost that ability when we changed software.....

So that leaves copying and quoting the post by this method only....
We will do the best that we can to keep topics going in the manner that we always have as we have little choice with this software package.
Thanks for the solar concentration as it applied to a few others for mars.

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#160 2020-07-12 06:57:00

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

elderflower wrote:

Pressurised cars will have round bodies, like earth aircraft fuselages, because this is efficient structurally. Therefore the railway must be built with this in mind, so as to allow passenger transits without suiting up. Such a car could mate directly with an airlock assembly. With such a railway the cargo transport arrangements would also mimic earth aircraft cargo arrangements, rather than marine/terrestrial containers, I would expect.

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#161 2020-07-12 07:52:28

Calliban
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From: Northern England, UK
Registered: 2019-08-18
Posts: 486

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

A slightly different approach to rail based freight transport, though still of topic I think: the pneumatic capsule pipeline.
http://onlinepubs.trb.org/onlinepubs/ar … on4liu.pdf

This is heavily used in Japan and has been discussed in other places, but there is generally no appetite for developing new transport systems that would leave the old modes redundant.

Most serious applications of this technology involve the use of small, non-powered rail vehicles running through a tube and powered forward by a differential pressure between them.  On Mars, the pressure would be provided by compressed CO2, which may be stored as liquid and boiled using solar heat.

Most useful if the goal is to move large amounts of bulk material over a distance, ie. Mined material to a processing centre.  The hydraulic capsule pipeline is simpler still, carrying stream of floating capsules along with moving water.  It is however, much slower and at Martian temperatures, the brine within the tubes would be quite viscous.

Typically, the tubes are 1-2m in diameter.  Not something that would be suitable for people transport, but perfect for bulk goods.

Last edited by Calliban (2020-07-12 07:59:00)


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#162 2020-07-25 04:08:39

kbd512
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Re: Trains on Mars - Could a rail system provide martian need

SpaceNut,

A trough concentrator would be more space-efficient, likely mass-efficient as well, but thermal efficiency would suffer.  Still, if it could be made lighter and more compact, then it would be a more practical design.  Some kind of hybrid may even work here on Earth.  This seems like a practical use of solar power that doesn't require absurd design compromises.  If we can supply the same horsepower per ton, I see little reason why we shouldn't at least trial this here on Earth, making it useful to everyone here first.

In Australia, they're able to run a daily passenger train service solely using solar panels mounted to the roof of an old 1940's era passenger train with an onboard 77kWh battery from an electric car and a backup diesel engine.  Apparently, it's been in service for several years now.  It's nearly dead silent and has enough reserve power to handle the various different grades along its service route without using the engine.  It weighs 70 tons but only has 6.5kW of roof-mounted PV panels.  Using composite vs steel and iron construction and aerodynamics better than a house on wheels, we could feasibly make that thing haul.  It looks like at least half the roof is devoid of panels, so a wrap-around thin film array on something resembling a bullet train could be every bit as fast as the passenger trains here in America are allowed to run.

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#163 2020-07-25 05:39:18

Calliban
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Posts: 486

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

Why not just use banks of stationary solar panels to feed current into a third rail that runs alongside the running rails?  On Mars, night time temperatures decline as low as 100K and the insulation properties of regolith are as good as rock wool.  We might reasonably employ a buried superconducting cable to supply the third rail with power.  The return current can be through the running rails.  In fact, a simple monopole arrangement may suffice, with return currents going to ground.

On Earth, third rail is less popular than catenery cables because of rapid voltage drop along the rail and the need for regular transformer stations every few miles along the track.  That wouldn't be an issue on Mars if we can use a superconducting cable to transmit power to the track.  Electrocution isn't really a problem either, given that everyone on the surface will be wearing spacesuits.

Magnesium diboride would be a relatively low cost superconducting material, with a critical temperature of 39K.

Last edited by Calliban (2020-07-25 05:48:48)


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#164 2020-07-25 06:31:35

tahanson43206
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Re: Trains on Mars - Could a rail system provide martian need

For Calliban re #163

Thanks for the tip about magnesium diboride superconducting at 39K.  I'd missed that update in the superconducting research, so appreciate your adding it.

It seems to me your proposal could be the basis of a business plan, in competition with the alternative as proposed recently, to secure solar power needed for movement, heating and lighting on the train itself.

There are pro's and con's to each approach.

We have members with backgrounds that touch on economics.  I'd appreciate someone taking a look at the tradeoffs, to see which might be more appealing to which class of investors.

(th)

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#165 2020-07-25 08:45:11

Calliban
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Posts: 486

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

Calliban wrote:

Why not just use banks of stationary solar panels to feed current into a third rail that runs alongside the running rails?  On Mars, night time temperatures decline as low as 100K and the insulation properties of regolith are as good as rock wool.  We might reasonably employ a buried superconducting cable to supply the third rail with power.  The return current can be through the running rails.  In fact, a simple monopole arrangement may suffice, with return currents going to ground.

On Earth, third rail is less popular than catenery cables because of rapid voltage drop along the rail and the need for regular transformer stations every few miles along the track.  That wouldn't be an issue on Mars if we can use a superconducting cable to transmit power to the track.  Electrocution isn't really a problem either, given that everyone on the surface will be wearing spacesuits.

Magnesium diboride would be a relatively low cost superconducting material, with a critical temperature of 39K.

Probably not a practical idea as it turns out.  A temperature of 39K is beneath the freezing point of nitrogen and argon, so it would be expensive to keep the cable cool enough.  The cable would need to be embedded in a liquid hydrogen pipe.  And even at Martian night time temperatures, a heat pump would be needed to keep hydrogen liquid.

A third rail would therefore need solar power stations with energy storage built into them every 10 miles along the track.  Mounting a solar dynamic engine with trough collector on top of the train, is probably much cheaper.  You would not want to run the train at night anyway, as the steel rails would be brittle in that sort of cold.  A problem, I would suggest, for any train concept on Mars.

Last edited by Calliban (2020-07-25 08:46:12)


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#166 2020-07-25 14:32:05

kbd512
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Re: Trains on Mars - Could a rail system provide martian need

Calliban,

If the train has its own built-in power supply that doesn't require any additional infrastructure to power it, then that would be ideal, especially given the vast expanses of terrain that may have no human presence nearby to maintain it.  I think a monorail that supports lighter rolling stock would be useful for lowering the tonnage of the materials required to build both the trains and the railway.  The fewer materials required, the less energy that has to be expended to build and power them.  A superconducting power cable may be ideal if the people and infrastructure existed to build and maintain it, but they don't and the only way for Mars to support more people is to locally build the infrastructure required for more people to be delivered from Earth.

The track for that solar powered train in Australia is pretty flat, but they only have about half the roof of that old passenger train covered with PV and it runs back and forth over a 3km circuit, every day, between PV powered railway stations.  A Mars solar powered train that uses PV or solar concentrators would collect about half as much sunlight, and a lot less than that during dust storms, but it would also weigh 38% of what it does on Earth and there's near-zero air resistance on Mars, so no special consideration need be given to aerodynamics.

Either way, humanity has hit upon a practical transportation use for solar power that can feasibly drive very large and heavy vehicles at modest speeds with very minor alterations that don't materially affect the performance of trains.  A more comprehensively engineered solution could easily deliver like-kind performance with our prototypical diesel-electric locomotives.

Based upon the design I saw, there's no technological or engineering reason why that Earth-bound train couldn't mount triple the solar panel surface area and weigh half as much when empty, simply by constructing it with Aluminum and composites vs Iron.  A rock wool composite flat car should be every bit as functional as steel in most cases.  If it weighs half as much and has 3 times as much power, then performance is going to be remarkably similar to any other diesel powered train in most practical use cases.  Distributing the power production capability to all cars in a train should also mean fewer runaway trains or need for tugs in switching yards.  The solar concentrator idea has to do with the possibility of running 24/7 service between destinations using tanks of molten salt or molten silicon and a working fluid such as water or CO2.  There's no technical reason why solar powered trains couldn't become the cheapest form of land transport available.

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#167 2020-07-27 17:52:36

SeaDragon
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Posts: 20

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

I think trains are probably the best way to move cargo on a large scale. As a cheap early alternative to railways though has anyone thought about cablecars?

Using mounds of frozen regolith (melted in a temporary dome into mud, piled up and left to freeze again) and connecting them with thin steel cables (or basalt fibre, whatever's going cheapest that can do the job) you can have a cablecar hanging from the cable with a motor to pull itself along, perhaps even powered by electricity sent across a second overhanging wire as with some trains on Earth. This way you get much more route length per kg of cable than per kg of railroad track. In addition, problems of dust buildup and having to build colossal bridges/tunnels/take massive detours to get around the features of the  Martian landscape are completely sidestepped: if you're 20 metres above the ground you don't need to care whether it's flat or not below you!

Of course, the bobbing motion of a cable car moving between regolith mounds along a cable that sags under it will make this unpleasant for humans but they take rockets or rovers etc., this is probably better for freight if for instance you can only get copper or zinc or something from ore veins under Olympus Mons but your growing city borders Arcadia Planitia a few thousand kilometres to the North West (which is where Elon suggested previously as a good place to set up a base).

Cablecars of course can't compete with railways in the long run so you just replace them for the popular routes naturally: when it comes time to install major updates to a cablecar route after 10 years service or something you can simply choose to decommission it by taking down all the cable and then build a railway next to it instead if it's a popular enough route.

Transmission of power over long distances requires long lengths of cable anyway so you might well have the infrastructure in place; just stick in a freight-bearing cable beneath it!

Last edited by SeaDragon (2020-07-27 17:58:12)

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#168 2020-07-27 19:09:00

tahanson43206
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Re: Trains on Mars - Could a rail system provide martian need

For SeaDragon re #167

You're really getting into the flow here << grin >>

I like your idea but would like to raise you one ... There is no reason (that I can see) to put up with the sagging your word picture suggests.

By erecting the towers on either side of the path of the line, they can support the transport line in a straight line.

It is possible to deliver sketches to this environment.  The procedure is:

1) Make a sketch and add labels (I've found 8 1/2 by 11  works)
2) Scan the document (multiple methods ... I use an inkjet printer scanner)
3) Upload the jpg or png to imgur.com
4) Left click on the image as displayed at imgur.com (You'll be given a list of link formats - chose bbcode format)
5) Log out of imgur.com and log into this forum
6) Post the copied link from imgur.com into a post

This is necessary because some years ago, the forum IT support decided to stop trying to support images.

At the time a reader pulls up your post, the link is translated into a call to imgur.com, and the image is rendered for display to the reader.

(th)

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#169 2020-07-27 19:36:19

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

Passing power through frozen iron oxide mounds and with steel conductors make for power being lost along the conduction path as heat which melts the mound. The rails need to be isolated if both are to act as power conductors and if a third rail is use they still need to be isolated. These rails need support members crossways like rail ties.

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#170 2020-07-27 20:02:31

tahanson43206
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Re: Trains on Mars - Could a rail system provide martian need

For SpaceNut re #169

Here is a link to a PBS education site that shows the forces at work in a suspension bridge.

https://www.pbs.org/wgbh/buildingbig/br … orces.html

If you run across an image that fits the situation described by SeaDragon, it would help readers to follow along.

As you can see in the bridge image at the PBS site, the cable SeaDragon described would sag between towers.

However, if the cable on which the Mars transport rides is held in a level position, like the roadway of the bridge, then the transport cars would maintain a constant elevation above the terrain.

In this scenario, the transport system would be a suspended monorail, and there would be no rails on the ground at all.

In earlier post in this series, I'm pretty sure it was Calliban who brought up the impact of cold on steel rails that might be set on the ground on Mars.

It's not clear to me how cold would impact a suspension system such as the one (I think) SeaDragon was describing.

(th)

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#171 2020-07-28 10:34:07

SeaDragon
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From: Merry Old England
Registered: 2020-07-25
Posts: 20

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

tahanson43206,

Indeed, this place is amazing, I was starting to get scared that there was no good discussion group online for technical discussions of space colonisation, I've been across a whole bunch of Discord groups and Forums and so on, this Forum is the best by far!

Unfortunately I think cablecars are doomed to sagging, hopefully the sketch below (using Imgur as instructed) illustrates:
cwEq6uw.png
In order to keep some mass suspended from a cable held taught between two supporting pylons the weight of the cablecar must be cancelled by tension in the cables. If the cables are perfectly horizontal then the tension force they can provide (which is always acting along their length) is also perfectly horizontal. As in the right hand side image, the relation between the vertical force (which holds up the cablecar) and horizontal force components for one side of the cable is basically a right angle triangle with the length of the cable as the longer side (hypotenuse). Thus the grim truth of the matter:

- The ratio between the total distance between pylons and the difference in height between the middle of that distance and the pylon tops where the cable is connected is very close to half the ratio between vertical force component that holds up the cablecar and horizontal force component.
Put another way, you need tremendous tension to hold the cable taught as a cablecar moves across it.

Taking for example a spacing between pylons of 100 metres and a pylon height of 10 metres, say you wanted the cablecar to drop down 1 metre towards the middle (so now it's only 9 m above the ground) and climb back up again to reach the next pylon on the other side. You would need 50 times as much tension in the cable as the weight of the cablecar (plus the weight of the cable of course but assuming that's negligible).

A 1 tonne cablecar thus needs 50 tonnes tension pulling either end of the cable to manage to only sag 1 metre at its middle!

This is probably still fine for freight though, I presume humans can use something else: nobody wants to ride a rollercoaster for 3 hours every time they need to start their shift at the factory. The weight and complexity savings from having a thin cable over railways are likely substantial though and could give a decent throughput for mining operations so that we can coordinate resources and not have to rely just on what can be mined from one spot to power our industry.

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#172 2020-07-28 11:01:57

SeaDragon
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From: Merry Old England
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Posts: 20

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

Now, overall I envisage something like the following:
35l9IFd.png
The hanging weights at either end of a length of cable provide cable tension to counter sagging as a cablecar passes between two pylon supports, probably just a big mass of regolith piled into a bucket attached to the cable.
The pylons themselves are built from frozen regolith melted under a moving dome as mud and piled up before being left to freeze again as per a previous post. In normal operation the tension in cable either side of a pylon cancels out and the pylon is fine. However, if a cable snaps the neighbouring pylon has to suddenly take a large force acting from the adjacent cable attached to it that is unbroken. If it can't stand up to that, the pylon will collapse, putting a similar stress situation on the next pylon along, which also collapses...

...And a few hundred broken pylons and snapped cables later I get fired, never to work in the Martian transport industry again.

To avoid this fate such a design must have some combination of:

- Nice thick frozen regolith pylons, perhaps reinforced with regolith brick or steel rebar but those are pricey
- Closely spaced pylons
- Lightweight cablecars
- Lots of sagging that we just live with

Of the four, the last one offers the best cost savings, though it does mean that the tensioning weights have to move substantially every time a cablecar passes through. Friction between the weights and the pylons from which they hang is something I've yet to figure out and it's probably quite serious at night when everything gets cold and brittle (yes, cold steel cables is probably very bad, will discuss below). A pulley system might work well, giving lots of extra slack for the cable to sag for only modest movement up and then down again of the tensioning weights but I'm not sure yet.
The easiest fixes therefore are the other 3, though they're unattractive because they mean less freight per unit time for the same infrastructure cost!

I dunno. It's not without difficulties but if one could figure them out it might be very competitive. Getting practical local transport on Mars keeps me up at night.

On the bright side, if heating steel cables by using them to transfer power to a cablecar is impractical (I don't want to pay electricity for anything like that if I can afford it, electricity is a precious commodity on Mars), it might make sense to use another kind of cable entirely.  Basalt fibres are very strong, lightweight, and easy to make in large quantities. I know that magnesium alloys actually get much better at cryogenic temperatures (at least according to Dieringa: https://www.researchgate.net/publicatio … s_A_Review ). This is no good for a conductor because alloys are always worse electrical conductors than their pure metals but if this holds true also for pure magnesium or aluminium (or at least that they don't become unacceptably brittle) then we could use reinforced magnesium or aluminium cable and transfer power for the cablecar through it as well! Pure magnesium is a slightly worse conductor than aluminium but it's less dense such that the same weight of cable can carry about the same current with the same low thermal losses so both are possible and both are present in large amounts in all Martian soil. If you have a non loadbearing cable overhead of Al or Mg and a boom that makes contact between your cablecar and this cable you can pass a current through the overhead power cable, to the cablecar and away through the loadbearing basalt fibre reinforced lower cable and to ground.

I dunno. If I get accepted into the finals for this year's Mars colony competition then I've got to include something juicy for Mars intercity transportation at the Mars Society convention or else it's a massive problem for any long term colony efforts that just hasn't got any good solutions atm.

Last edited by SeaDragon (2020-07-29 16:40:11)

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#173 2020-07-28 17:43:59

tahanson43206
Member
Registered: 2018-04-27
Posts: 3,106

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

Bravo SeaDragon! Your sketch looks terrific on my display.  I hope it looks as good for everyone, but it is worth remembering that we have readers of the forum with every kind of OS and hardware imaginable. 

It appears I need to come back with a sketch showing a suspension bridge design, since my attempt to show one to SpaceNut apparently was not successful.

I'll use your sketches as a starting point.

Also ... have you had a chance to dip into the rich history of the archive of this forum?

You could not possibly read everything, and no one would expect you to try.

However, there are some contributors here who deserve a visit by any new member who intends to stick around for a while.

There are many names I could suggest are worth a few minutes of your time, but I'll wait to see if you are interested before tossing out a suggestion.

And! Best wishes for success in trying out for the Mars colony competition.

(th)

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#174 2020-07-28 19:01:49

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,235

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

Tram or cable cars or gandola do not use rails and require cable movement between rollers. The car attaches to the cable simular to a ski chair lift. The have limited transport mass in each car.

Nice sketch work SeaDragon.

Now I am reminded of the gravity storage to power topic.

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#175 2020-07-29 09:38:10

kbd512
Administrator
Registered: 2015-01-02
Posts: 3,588

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

We could use conductive CNT yarn to supply both power and take up the suspension loads associated with the cable cars.  I'm not sure about how much effort would be required to make those frozen regolith spires work as envisioned, but we have to suspend the cars somehow.  This could be an even more mass-efficient way to deal with cargo and personnel transport than trains or off-road heavy cargo vehicles.  It's actually rather creative.  It doesn't require the resource inputs associated with trains or tracked vehicles.  Provided we can grow the CNT cabling using Martian atmosphere, it may be the most resource-efficient design anyone has proposed to date.  I still think we'll have to substitute a cable-stay-based suspension structure (a series of tall poles or A-frames sunk into frozen regolith and held up using ropes in plain language) for these regolith spires, else we'd require truly massive earth moving machines, but it's pretty appealing otherwise.

I'm imagining a kind of "bucket brigade" of raw materials suspended from small electrically-powered trucks fed by electrified CNT cables.  A loader would load chemicals like Sulfur or metal ores into the buckets / bags / "cable cars" (again CNT is ideal since it has extreme abrasion resistance, far surpassing aramid fibers like Kevlar), the system would whisk the materials away to a chemical refinery or smelter, and a single operator would monitor the buckets to ensure adequate spacing between loads.  Alternatively, we could put the hauling motors in the towers and that way the "cable car trucks" are simple mechanical devices riding on a rope and don't require an electrified power cable or much in the way of maintenance.  I think I like that idea even better.  The cars may require brief transfer operations between towers, but that keeps the electrified infrastructure at fixed sites, so only the towers and lines have to be run.

A solar powered satellite in orbit, not subject to dust degradation, could wirelessly transmit microwave power to a CNT mesh rectifying antenna feeding power to the towers, thus limiting the infrastructure on the ground requiring maintenance to the towers, cables, electric motors and control electronics in the towers.  We could obtain water directly from the poles using this solution instead of excavating regolith or drilling wells.

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