Difference between revisions of "Railroad"

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'''Railroad''' is a commonly used transportation system on [[Earth]], and it can be used on [[Mars]] as well. [[Iron]] as the main construction material is abundant on the Martian surface. Compared with most other transportation systems, the railroad is basically [[hi-tech versus lo-tech|lo-tech]] and can, therefore, be maintained with low effort.
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'''Railroads''' are a commonly used [[transportation]] system on [[Earth]], and they can be used on [[Mars]] as well. [[Iron]], the main construction material, is abundant on the Martian surface. Compared with most other transportation systems, the railroad is basically [[hi-tech versus lo-tech|lo-tech]] and can, therefore, be maintained with lower effort.  Compared with [[rover]]s or roads a railroad system is rather inflexible, but it can have an advantage for frequently used ways. On the long run it allows energy optimized transport. No batteries or fuels are necessary if electrical engines and power lines are used. Especially for driver-less material transport, it can be a central part of the [[settlement]]'s infrastructure.
  
Compared with [[rover]]s a railroad system is rather inflexible, but it can have an advantage for frequently used ways. On the long run it allows energy optimized transport. No batteries or fuels are necessary if electrical engines are used. Especially for driverless material transport it can be a central part of the [[settlement]]'s infrastructure.
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__NOTOC__
  
Elon Musk's initiative to develop the ''hyperloop'' technology allows the anticipation of a very similar transportation system on Mars. Compared to the terrestrial concept it would require only a thin-walled tube. The air pressure in the tube would be slightly higher than the surrounding Martian atmosphere, preventing the invasion of dust. Musk himself imagines a version without a tube on Mars.
+
Elon Musk's initiative to develop the ''hyperloop'' technology allows the anticipation of a very similar transportation system on Mars. Compared to the terrestrial concept it would require only a thin-walled tube. The air pressure in the tube would be slightly higher than the surrounding Martian atmosphere, preventing the invasion of dust. Musk himself imagines a version without a tube on Mars(ref needed).
  
 
==Energy requirements==
 
==Energy requirements==
Rolling equipements is subject to a number of forces, which together define the energy requirements of a rail system.     
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Rolling equipment is subject to a number of forces, which together define the energy requirements of a rail system.     
  
=== Air resistance ===
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===Air resistance===
On Mars, the air resistance is negligible and can be discounted except at very high velocities.   
+
On Mars, the air resistance is negligible and can be discounted except at very high velocities.  The drag force F<sub>D</sub> = ρ v² C<sub>D</sub> A / 2 where ρ is the mass density of the atmosphere. On Mars, ρ is ~0.020 kg/m³, compared to 1.225 kg/m³ on Earth, i.e. about 1.6%.  So a freight train that could achieve 110km/h or 30m/s on Earth would theoretically be capable of exceeding the speed of sound on Mars, which is only about 250m/s.   
  
=== '''Rolling friction''' ===
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A=Area (m<sup>2</sup>), C<sub>D</sub> is the [[w:Drag_coefficient|drag coefficient]] (experimental-dimensionless), v is the velocity (m/s) and ρ is the mass density of the atmosphere(kg/m³).
Rolling friction should also be significantly lower.  friction is defined by the equation: F=uN.  Where (u) being a property of materials remains the same, but N is reduced by the lower gravity. N is a force, and F=ma. m is invariant, but a, the acceleration, is proportional to gravity. So trains will have less roll resistance and can be larger, but will have trouble going up steep grades.
 
  
=== '''Inertia of the train''' ===
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Drag coefficient vary from 0,03 for streamlined bodies to over 1 for a brickA typical train might have a C<sub>D</sub> of about 1-2<ref>Engineering Toolbox https://www.engineeringtoolbox.com/drag-coefficient-d_627.html</ref>.
The inertia of the train remains the same on Earth as on Mars.  So the kinetic energy of the train, for the same velocity, will not be changed by the lower gravityHowever, for electrical trains, regenerative braking could be used, returning the energy required to accelerate the train up to speed to the grid when the train is stopped. Regenerative braking may also be used to return to the grid the energy required to climb grades on Mars.
 
  
=== Construction energy ===
+
===Rolling friction===
Steel rails would require about xx MJ/kg for their fabrication, according to the concepts on [[embodied energy]]
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Rolling friction should also be significantly lower on Mars.  Friction is defined by the equation: F=uN.  Where the friction factor (u) being a property of materials remains the same, but the vertical force (N) is reduced by the lower gravity. N is a force, and F=ma.  Mass (m) is invariant from Earth to Mars, but  the acceleration (a), is 38% of the acceleration on Earth. So trains will have less roll resistance and can be larger. 
 +
 
 +
As on Earth, the rolling friction of a train  should be significantly lower than the rolling friction of a truck.  A significant amount of energy is also lost in truck tire walls as they flex and roll, which is less important for steel wheels.  The average relationship found in reference tables puts the rolling friction of trains as about one tenth of the rolling friction of trucks. 
 +
 
 +
===Inertia of the train===
 +
The inertia of the train remains the same on Earth as on Mars.  So the kinetic energy of the train, for the same velocity, will not be changed by the lower gravity.  However, for electrical trains, regenerative braking could be used, returning to the grid when the train is stopped the energy that was required to accelerate the train up to speed.  Regenerative braking may also be used to return to the grid the energy required to climb grades on Mars. 
 +
 
 +
Train stations could be placed on the top of low hills or mounds.  The train will naturally slow when coming into the station, and accelerate as it rolls out of the station.  This trick is used in some stations in England. 
 +
 
 +
===Construction energy===
 +
Steel rails would require 30-50 MJ/kg for their fabrication, according to the concepts on [[embodied energy]].  Considering rails with an average mass of 50 kg/m, one km of rail might mass 100 000 kg (100 tonnes) and require 5 000 000 MJ to fabricate.  Supposing the [[Cost of energy on Mars]] to be about 150 $/GJ (in 2019 dollars), this represents a value of about 750 000$.  To this we would need to add the cost of the ballast, the ties and of all the logistical support systems required.
 +
 
 +
===Energy example===
 +
A 100 000 kg truck is competing against a 100 000 kg train.  We can remove air resistance as a factor.  If both systems use regenerative breaking, then we can remove kinetic energy as a factor.  As they have the same mass it would be excluded anyway.  So the only difference left is the difference in rolling friction.  For steel wheels on steel rails vs truck wheels on gravel, the ratio is about 10 to 1 in favor of rail. The Power of a moving system is W=F(n)*v(m/s), where all values are the average values. Supposing both vehicles are running at 100 km/h (28 m/s), then we find:
 +
 
 +
Train: 100 000 kg * 3,8 m/s2 * 0,001 *28 m/s = 10 640 W or 10 kW or 14.2 hp
 +
 
 +
Truck: /100 000 kg* 3,8 m/s2 * 0,01 *28 m/s = 106 400 W or 106 kW or 142 hp
 +
 
 +
If the train and the truck are carrying the same load, for example 50 000 kg out of their 100 000 kg mass, then the cost of transportation per 100 km is:
 +
 
 +
Train: 10,6 kW * 1hr = 10,6 kWh * [[Cost of energy on Mars|cost of energy]] (0,83 $/kWh) = 8,8$  or 8,8/50 = '''0,18 dollars per tonne of freight.'''
 +
 
 +
Truck: 106 kW * 1hr = 106 kWh * 0,83 $/kWh = 88$ or 88/50 = '''1,8 dollars per tonne of freight.'''
 +
 
 +
So purely on the basis of transportation energy costs, rail is clearly advantaged compared to roads.
 +
 
 +
=====[https://docs.google.com/spreadsheets/d/1W86t8xqX2Oqn16cGOCN_cOFcmhuTLaMkI3tr87cnMnk/edit?usp=sharing '''Spreadsheet of train calculations''']=====
  
 
==Use cases==
 
==Use cases==
  
 
===The transport of a maintenance team===
 
===The transport of a maintenance team===
Peripheral parts of a Martian settlement might be several kilometers away from the [[house|living quarters]]. [[Energy]] generating stations (e.g. [[solar panel]]s, [[wind turbine]]s) are spread over a large area. A light weight railroad system reduces the maintenance costs on the long run.
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Peripheral parts of a Martian settlement might be several kilometers away from the [[house|living quarters]]. [[Energy]] generating stations (e.g. [[solar panel]]s, [[wind turbine]]s) are spread over a large area and have fixed positions. A lightweight railroad system might reduce the maintenance costs on the long run.
 +
 
 +
If the railway runs along power, communication, or water lines, then the maintenance of these becomes cheaper.
  
 
===Transportation in tunnels===
 
===Transportation in tunnels===
Parts of the colony will be underground. During [[mining]] activities a railroad system provides a comfortable transportation of material and persons over long underground distances.
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Parts of the colony will be underground. For [[mining]] activities, a railroad system provides a comfortable transportation of material and persons over long underground distances.
 +
 
 +
A tunnel system would reduce the radiation load on passengers and crew.  Although this may be less important if the rail system is entirely automated, so there is no crew that can accumulate excess radiation. 
 +
 
 +
Using surface trains for commuter travel might be problematic in the long run due to radiation exposure.  However, a center/suburb model for Mars City development may not make much sense, as the lower density suburb would not bring significant advantages to the Martin inhabitants.
  
 
===Connection between two settlements===
 
===Connection between two settlements===
Railroad covers both short and long distances. Even in the far future with more than one settlement on Mars, people will still be interested in efficient transportation systems. Only a magnetic levitation system might have a better energy balance.
+
Railroad cover both short and long distances. Even in the far future with more than one settlement on Mars, people will still be interested in efficient transportation systems. Only a magnetic levitation system might have a better energy balance.
  
 
==Railroad construction==
 
==Railroad construction==
Much of the cost of railroad construction lies in the cost of the infrastructure required to support the rails.  Mars has interesting advantages as there are no swamps and essentially no soil, therefore it should be fairly simple to create a track way that is structurally sound without moving too much regolith around.
+
Much of the cost of railroad construction lies in the cost of the infrastructure required to support the rails.  Mars has interesting advantages as there are no swamps and essentially no soil, therefore it should be fairly simple to create a track way that is structurally sound without moving too much regolith around.  However, this also applies to road construction, so the construction of roads on Mars should also be relatively cheap.
 +
 
 +
As the friction of the train will be less, the grades that a Martian railroad can climb may be less than on Earth.  However, the trains will also have a lower weight, so the actual grades may be quite similar.
 +
 
 +
For the same mass, the weight on Mars will be less than on Earth, so the strain on the infrastructure should be less.  Ballast might be less extensive, or the trains might be larger for the same quality of track and bed as on Earth.
  
As the friction of the train will be less, the grades that a Martian railroad can climb will be less than on EarthSo the preparation of very low slopes might require extensive Earth worksOn the other hand, a track might be provided with linear motors over steep grades, making the grade requirements much less important.
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== Railway Ties and Support ==
 +
Until terraforming happens, and trees are growing enmass on Mars, railway ties are likely to be formed of hard plastic.  Since there are no hydrocarbon deposits on Mars, these plastics will have to be slowly created from simpler resources.  The Ties will likely be as small and thin as possible, on well prepared beds of gravel or brickAlternately, it may be cheaper to set the ties in concreteIt is likely that building rail on Mars will be far more expensive than on Earth for this reason.
  
==Open issues==
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== Railway Gage ==
 +
A wider railway gage, of perhaps 2 meters, is considered desirable, but has never happened because of the cost of converting over our current infrastructure, and the cost of widening the right of ways.  On Mars, it is likely that a wider gage will be chosen.
  
*Can the railroad be built lighter because of the lower [[gravity]], or is the inertia of the train the main parameter?
+
======Breaking trains======
*How much [[energy]] is needed under Martian conditions to produce 1 km railroad?
 
  
 +
==References==
 
[[Category:Surface Transportation Networks]]
 
[[Category:Surface Transportation Networks]]
 +
<references />

Revision as of 09:27, 21 May 2021

Railroads are a commonly used transportation system on Earth, and they can be used on Mars as well. Iron, the main construction material, is abundant on the Martian surface. Compared with most other transportation systems, the railroad is basically lo-tech and can, therefore, be maintained with lower effort. Compared with rovers or roads a railroad system is rather inflexible, but it can have an advantage for frequently used ways. On the long run it allows energy optimized transport. No batteries or fuels are necessary if electrical engines and power lines are used. Especially for driver-less material transport, it can be a central part of the settlement's infrastructure.


Elon Musk's initiative to develop the hyperloop technology allows the anticipation of a very similar transportation system on Mars. Compared to the terrestrial concept it would require only a thin-walled tube. The air pressure in the tube would be slightly higher than the surrounding Martian atmosphere, preventing the invasion of dust. Musk himself imagines a version without a tube on Mars(ref needed).

Energy requirements

Rolling equipment is subject to a number of forces, which together define the energy requirements of a rail system.

Air resistance

On Mars, the air resistance is negligible and can be discounted except at very high velocities. The drag force FD = ρ v² CD A / 2 where ρ is the mass density of the atmosphere. On Mars, ρ is ~0.020 kg/m³, compared to 1.225 kg/m³ on Earth, i.e. about 1.6%. So a freight train that could achieve 110km/h or 30m/s on Earth would theoretically be capable of exceeding the speed of sound on Mars, which is only about 250m/s.

A=Area (m2), CD is the drag coefficient (experimental-dimensionless), v is the velocity (m/s) and ρ is the mass density of the atmosphere(kg/m³).

Drag coefficient vary from 0,03 for streamlined bodies to over 1 for a brick. A typical train might have a CD of about 1-2[1].

Rolling friction

Rolling friction should also be significantly lower on Mars. Friction is defined by the equation: F=uN. Where the friction factor (u) being a property of materials remains the same, but the vertical force (N) is reduced by the lower gravity. N is a force, and F=ma. Mass (m) is invariant from Earth to Mars, but the acceleration (a), is 38% of the acceleration on Earth. So trains will have less roll resistance and can be larger.

As on Earth, the rolling friction of a train should be significantly lower than the rolling friction of a truck. A significant amount of energy is also lost in truck tire walls as they flex and roll, which is less important for steel wheels. The average relationship found in reference tables puts the rolling friction of trains as about one tenth of the rolling friction of trucks.

Inertia of the train

The inertia of the train remains the same on Earth as on Mars. So the kinetic energy of the train, for the same velocity, will not be changed by the lower gravity. However, for electrical trains, regenerative braking could be used, returning to the grid when the train is stopped the energy that was required to accelerate the train up to speed. Regenerative braking may also be used to return to the grid the energy required to climb grades on Mars.

Train stations could be placed on the top of low hills or mounds. The train will naturally slow when coming into the station, and accelerate as it rolls out of the station. This trick is used in some stations in England.

Construction energy

Steel rails would require 30-50 MJ/kg for their fabrication, according to the concepts on embodied energy. Considering rails with an average mass of 50 kg/m, one km of rail might mass 100 000 kg (100 tonnes) and require 5 000 000 MJ to fabricate. Supposing the Cost of energy on Mars to be about 150 $/GJ (in 2019 dollars), this represents a value of about 750 000$. To this we would need to add the cost of the ballast, the ties and of all the logistical support systems required.

Energy example

A 100 000 kg truck is competing against a 100 000 kg train. We can remove air resistance as a factor. If both systems use regenerative breaking, then we can remove kinetic energy as a factor. As they have the same mass it would be excluded anyway. So the only difference left is the difference in rolling friction. For steel wheels on steel rails vs truck wheels on gravel, the ratio is about 10 to 1 in favor of rail. The Power of a moving system is W=F(n)*v(m/s), where all values are the average values. Supposing both vehicles are running at 100 km/h (28 m/s), then we find:

Train: 100 000 kg * 3,8 m/s2 * 0,001 *28 m/s = 10 640 W or 10 kW or 14.2 hp

Truck: /100 000 kg* 3,8 m/s2 * 0,01 *28 m/s = 106 400 W or 106 kW or 142 hp

If the train and the truck are carrying the same load, for example 50 000 kg out of their 100 000 kg mass, then the cost of transportation per 100 km is:

Train: 10,6 kW * 1hr = 10,6 kWh * cost of energy (0,83 $/kWh) = 8,8$ or 8,8/50 = 0,18 dollars per tonne of freight.

Truck: 106 kW * 1hr = 106 kWh * 0,83 $/kWh = 88$ or 88/50 = 1,8 dollars per tonne of freight.

So purely on the basis of transportation energy costs, rail is clearly advantaged compared to roads.

Spreadsheet of train calculations

Use cases

The transport of a maintenance team

Peripheral parts of a Martian settlement might be several kilometers away from the living quarters. Energy generating stations (e.g. solar panels, wind turbines) are spread over a large area and have fixed positions. A lightweight railroad system might reduce the maintenance costs on the long run.

If the railway runs along power, communication, or water lines, then the maintenance of these becomes cheaper.

Transportation in tunnels

Parts of the colony will be underground. For mining activities, a railroad system provides a comfortable transportation of material and persons over long underground distances.

A tunnel system would reduce the radiation load on passengers and crew. Although this may be less important if the rail system is entirely automated, so there is no crew that can accumulate excess radiation.

Using surface trains for commuter travel might be problematic in the long run due to radiation exposure. However, a center/suburb model for Mars City development may not make much sense, as the lower density suburb would not bring significant advantages to the Martin inhabitants.

Connection between two settlements

Railroad cover both short and long distances. Even in the far future with more than one settlement on Mars, people will still be interested in efficient transportation systems. Only a magnetic levitation system might have a better energy balance.

Railroad construction

Much of the cost of railroad construction lies in the cost of the infrastructure required to support the rails. Mars has interesting advantages as there are no swamps and essentially no soil, therefore it should be fairly simple to create a track way that is structurally sound without moving too much regolith around. However, this also applies to road construction, so the construction of roads on Mars should also be relatively cheap.

As the friction of the train will be less, the grades that a Martian railroad can climb may be less than on Earth. However, the trains will also have a lower weight, so the actual grades may be quite similar.

For the same mass, the weight on Mars will be less than on Earth, so the strain on the infrastructure should be less. Ballast might be less extensive, or the trains might be larger for the same quality of track and bed as on Earth.

Railway Ties and Support

Until terraforming happens, and trees are growing enmass on Mars, railway ties are likely to be formed of hard plastic. Since there are no hydrocarbon deposits on Mars, these plastics will have to be slowly created from simpler resources. The Ties will likely be as small and thin as possible, on well prepared beds of gravel or brick. Alternately, it may be cheaper to set the ties in concrete. It is likely that building rail on Mars will be far more expensive than on Earth for this reason.

Railway Gage

A wider railway gage, of perhaps 2 meters, is considered desirable, but has never happened because of the cost of converting over our current infrastructure, and the cost of widening the right of ways. On Mars, it is likely that a wider gage will be chosen.

Breaking trains

References