Author Topic: How to develop lots of good surface vehicles for Mars colonists?  (Read 66857 times)

Offline Robotbeat

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Right, but greasing a bearing is just a /tad/ less complicated than the oil system in a car, for instance.

The moving parts in oil system of regular car engine:

1. oil
2. two rotors making up a gerotor pump
3. uh .. that was it.
Still have oil filters, channels in the engine and oil lines, etc. It's one of the many fluid systems needed for an internal combustion engine:
1) fuel (fuel filter, fuel pump, injectors, fuel tank, fuel lines)
2) air (air filters, possibly turbo or supercharger, radiator fan, etc)
3) exhaust system (needs to run through the turbo, possibly needs catalytic converter or muffler if on a place like Earth, on the Moon and Mars you might want to capture the water exhaust)
4) oil system (all the things you mentioned plus oil reservoir, filter, oil lines, oil channels in engine, oil pressure gauge, etc)
5) another system for brakes (including brake oil), which gets used less often in an electric vehicle because of regen braking doing vast majority of the work... you could probably get by with a simpler brake system in an electric vehicle, and electric brakes certainly exist.
6) cooling system (if not air-cooled) (sometimes needed for high-performance electric vehicles, but generally optional for electric vehicles), pump and radiator and reservoir, etc.

Plus, you still need a complicated mechanical system for converting the mechanical energy of the pumping cylinders to rotation, then a transmission and clutch to convert to the right rpm to be suitable for the wheels (and you need transmission oil).

In a gasoline vehicle, you need a spark generation/distribution system.

Plus you still need a starting motor and alternator and a decent battery, basically duplicating in miniature all the systems needed for an electric car.

I say with honesty that it is remarkable that we've gotten the price of ICEs down as low as they are, considering how complicated they are. There are just SO many systems that you need for them to work reliably and with decent performance and/or efficiency. Getting all those systems to work on another planet is going to be an enormous challenge.

An ICE vehicle needs 5 or 6 different fluid systems to work reliably. An electric vehicle needs basically none (just electricity), enormously simplifying the entire thing. Charging an electric vehicle is vastly simpler than mining water, purifying it, electrolyzing it, liquifying the gases, storing the fuel cryogenically, and then transferring it to a vehicle (in a vacuum, far below the boiling point of the liquid).
« Last Edit: 01/14/2014 11:19 pm by Robotbeat »
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Offline A_M_Swallow

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Also I would like to point out that if you were simply moving from one colony to another cable cars would be the most efficient as you could use power centralized at the colony by moving the cable.

Is there a maximum length limit for a cableway?  The longest on Earth was just under 100 km.  I imagine there would be, unlike road or rail, given the need to move the capble.
Also have lower gravity, remember.

Cableway would make more sense if faced with steep slopes, though, like on Earth. Like from the deep parts of Hellas Basin to the rim. Probably too steep for conventional rail there.

A cableway can cross flat ground that is not very flat.  When building a road big rocks have to be moved out of the way (or broken up).  Ordinary railways can only take small incline angles.  Building the tracks, foundations, bridges and embankments takes large amounts of on the spot manpower and processed materials.

The cableway may need wheelhouses every 50km - 100km to move the cables.  A method of moving the cars between cable sections will be needed.

Offline Dalhousie

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Cableway would make more sense if faced with steep slopes, though, like on Earth. Like from the deep parts of Hellas Basin to the rim. Probably too steep for conventional rail there.

I measured four profiles normal to the rim round Hellas using google Mars.  Here are the climbs and the distances

3.8 km in 750 km ~1:200
4 km in 550 km ~1:140
5 km in 300 km ~1:60
4.6 km in 500 km ~1:110

For comparison the famous railway from Arica on the Pacific Ocean in Chile to La Paz in Bolivia climbs 4.2 km in 325 km, as measured in a straight line.  This is ~1:80.  I think railways in and out of Hellas appear quite feasible, based on this.
« Last Edit: 01/15/2014 07:03 am by Dalhousie »
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Offline Oli

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Problem with batteries is they're useless when you need lots of power.

For heavy machinery or trucks you'd need something based on hydrogen or methane.

Offline rockinghorse

Problem with batteries is they're useless when you need lots of power.

This cannot be further from the reality. Electric drivetrain offers huge torque and this is very useful for super heavy duty vehicles. Electric vehicles can easily output megawatt level power and on Mars conditions cooling of electric drivetrain is easier than the cooling of comparably powerful ICE drivetrain.

Energy density of lithium sulphur batteries is about 1 MJ per kg where as methane+oxygen has perhaps 3–6 MJ / kg real world energy density. Difference in energy density is so small, that ease of charging and superior simplicity of heavy hauling electric trucks trumps ICE and even Fuel Cell vehicles.

The problem with ICE vehicles on Moon and Mars is not heating, but it is cooling. Due to 100 times thinner atmosphere, the radiator of cooler must be huge and very heavy in order to prevent IC engine from overheating.
« Last Edit: 01/15/2014 11:30 am by rockinghorse »

Offline Oli

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Ok I forgot you have to carry along your oxygen so its a lot less superior. Maybe ~3.5 times more than your hypothetical sulphur batteries with questionable durability.

However if you need lots of energy it still matters. In addition you can quickly refill your tanks, which is of particular importance for machinery that is operating non stop for hours.

The lack of oxygen, gravity, and thick atmosphere make ICE definitely a less attractive option than on Earth though.

I just realized there is already a thread in the Moon section about this.

« Last Edit: 01/15/2014 01:31 pm by Oli »

Offline Robotbeat

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...
However if you need lots of energy it still matters. In addition you can quickly refill your tanks, which is of particular importance for machinery that is operating non stop for hours.
...
Fast, automated battery swap (more automated than fueling) is already commercially deployed on Earth:
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Offline rockinghorse

I personally think that Tesla battery swapping is just a marketing gimmick. It will be very useful however when old batteries must be replaced with new batteries after 10 years or so.

Charging is not an issue as it takes only 20–30 minutes to recharge battery. Tesla can charge battery already in 30 minutes and they are talking that it should be possible to go under 10 minutes. Japanese have already demonstrated 180 kW EV charging with two parallel Chademo fast chargers.
« Last Edit: 01/15/2014 06:49 pm by rockinghorse »

Offline Oli

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Quote from: Robotbeat
Fast, automated battery swap (more automated than fueling) is already commercially deployed on Earth:

Well, first of all, I assume your batteries would have to be transported from earth. ICEs/tanks are lightweight because the fuel is on Mars, imagine you'd have to bring along so many reserve batteries. A Formula E car for example eats one 200kg battery every 20 minutes despite an overall weight of only 800kg.

Also I'm not convinced that such an automated battery swap and distribution system would come at low cost, there is nothing easier than pumping fuel around. At least gasoline. Methane/LOX on Mars may be more difficult.

Quote from: rockinghorse
Charging is not an issue as it takes only 20–30 minutes to recharge battery.

Half the charge. Also I wonder what the effect on the lifetime of the battery is if you do it often.

Offline Robotbeat

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You also have to bring all the equipment for power production and electrolysis from Earth, too. And you can use that battery for decades.
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Offline R7

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1) fuel (fuel filter, fuel pump, injectors, fuel tank, fuel lines)
2) air (air filters, possibly turbo or supercharger, radiator fan, etc)
3) exhaust system (needs to run through the turbo, possibly needs catalytic converter or muffler if on a place like Earth, on the Moon and Mars you might want to capture the water exhaust)
4) oil system (all the things you mentioned plus oil reservoir, filter, oil lines, oil channels in engine, oil pressure gauge, etc)
5) another system for brakes (including brake oil), which gets used less often in an electric vehicle because of regen braking doing vast majority of the work... you could probably get by with a simpler brake system in an electric vehicle, and electric brakes certainly exist.
6) cooling system (if not air-cooled) (sometimes needed for high-performance electric vehicles, but generally optional for electric vehicles), pump and radiator and reservoir, etc.
7) In a gasoline vehicle, you need a spark generation/distribution system.
8) Plus, you still need a complicated mechanical system for converting the mechanical energy of the pumping cylinders to rotation, then a transmission and clutch to convert to the right rpm to be suitable for the wheels (and you need transmission oil).
9) Plus you still need a starting motor and alternator and a decent battery, basically duplicating in miniature all the systems needed for an electric car.

1. Yup.
2. Not air but oxygen, similar to 1. definitely no turbo nor supercharger.
3. If CO/O probably just straight pipe. Vroooom!
4. Yup.
5. Regen break work in nice smooth breaking, in emergencies it's overwhelmed so you need "real" brakes anyway. Brake mechanism could be mechanical (similar to parking brake in cars), electric and possibly pneumatic (utilizing abundant atmosphere).
6. Yup. Coolant could be pressurized CO2 too.
7. Yup.
8. Yup. Crankshaft, pistons and connecting rods, quite proven technology. Transmission can be also electric.
9. Yup.

Quote
I say with honesty that it is remarkable that we've gotten the price of ICEs down as low as they are, considering how complicated they are. There are just SO many systems that you need for them to work reliably and with decent performance and/or efficiency. Getting all those systems to work on another planet is going to be an enormous challenge. An ICE vehicle needs 5 or 6 different fluid systems to work reliably. An electric vehicle needs basically none (just electricity), enormously simplifying the entire thing.
It's because making of most of the metal parts can be reduced to casting, forging, milling and turning. You know those romantic metalworking  techniques which are well understood, quick and about to become obsolete due to 3D-printing .. or not. I recommend "How X is made" videos from Utub to take a look how various engine parts are made like sausage. Enormous is such a strong word, and poorly defined. Already reduced to four fluid, so now it is enormously easier.  ;)

Quote
Charging an electric vehicle is vastly simpler than mining water, purifying it, electrolyzing it, liquifying the gases, storing the fuel cryogenically, and then transferring it to a vehicle (in a vacuum, far below the boiling point of the liquid).

Those things and machinery for it is going be done anyway, to extract and make base consumables, rocket propellant, resources for higher chemistry. So using it to propel vehicles is more about sizing the machines than whether you need them or not.
AD·ASTRA·ASTRORVM·GRATIA

Offline R7

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Problem with batteries is they're useless when you need lots of power.
This cannot be further from the reality. Electric drivetrain offers huge torque and this is very useful for super heavy duty vehicles. Electric vehicles can easily output megawatt level power and on

Provide an example of battery powered electric vehicle that outputs a megawatt or more. Remember to tell the battery specs, especially Wh/kg.

Quote
Energy density of lithium sulphur batteries is about 1 MJ per kg

Provide an example of such battery, any reference to a real world. Manufacturer's specification link or something. Especially the discharge C-rate is interesting.

And the 220kWh/550kg Tesla battery spec link too.

Quote
The problem with ICE vehicles on Moon and Mars is not heating, but it is cooling. Due to 100 times thinner atmosphere, the radiator of cooler must be huge and very heavy in order to prevent IC engine from overheating.
1/100 is pressure figure. Density on surface is about 1/60th of Earth sealevel, according to http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html Average temperature -63C. Faster fan speeds.

Quote
Mars conditions cooling of electric drivetrain is easier than the cooling of comparably powerful ICE drivetrain.

Since drivetrain excludes the engine do elaborate.
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Offline R7

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Fast, automated battery swap (more automated than fueling) is already commercially deployed on Earth:
*Tesla stage(d) show utub link removed*

Don't seem to be deployed yet. Announcement anywhere? Googoling fails.
Déjŕ vu

Quote
As if filling Audi A8 running on fumes (gas tank is 23.8 gallons) is equal to Model S battery switch. Pump delivered 23.22 gallons after which the sloth spent a minute meditating or something before getting the car moving again. A8 does 21 mpg combined so the fuel load gives 488 miles, 650 miles if highway. Had the sloth pumped the mileage equivalent of model S larger battery pack (265 miles) he would have pumped 75 seconds + meditating. OT I know but the stench of marketing horse excrement overwhelmed me.

The romantic obsolete gas stations are fighting back to help the sloth pump faster.

http://www.rfidjournal.com/articles/view?8761

http://www.quikq.com/QQ-video.html

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Offline R7

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Also I wonder what the effect on the lifetime of the battery is if you do it often.

That's a good question. Also the charging efficiency may drop the faster you charge, this happens at least in NiCD batteries. (a course paper, see attached chart) The persistent problem with batteries seems to be that there's always a catch:

1. high Wh/kg
2. high charge/discharge efficiency
3. high charge/discharge rates
4. high DOD possible
5. high cycle durability

You want all five, but thus far get to pick only about three. For instance Ni-Fe battery fails in 1 and 3, 2 is a so-so.
« Last Edit: 01/16/2014 12:55 am by R7 »
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Offline JasonAW3

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Generally speaking, any sort of vehicle that is used on Mars is going to HAVE to use fairly loose mechanical tolerances to avoid locking or jamming up, not altogether unlike the tolerances for the AK-47 Assault Rifle.

As has been illustrated in recent conflicts in the Middle Eastern theater, fine talcum powder like sand, literally gets into EVERYTHING.  As such, many weapons systems and most mechanical equipment, have required excessive amounts of cleaning and general maintenance.

On Mars, the problem is exacerbated by buy the chemical content of the atmosphere and soil.  As an example, the current Mars Laboritory is showing signs of excessive wear on the wheels due to the rocks and soil that it is damaging the wheels faster than had been anticipated.

The Spirit rover was partially incapacitated when a couple of it's wheels locked up and it finally became trapped in a sand dune in a crater.

Overall, some form of self cleaning or clearing of critical components will be required for maximum mission success.  Perhaps some form of dust repellant nanocoatings combined with self clearing electric motors could do the job as well as advanced teflon like coatings to replace lubricants where needed.

Overall, and Mars vehicles should be Wheeled and / or continious belt (Tracked) driven.  Standard tank type treads provide too many possible points of failure while a semi-"Rubberized" belt system would give equivelent grip, ground pressure and stability to that of a Tank Tread, with far less points of failure.  (Plus, given the available resources, repairing said belt would be relatively simple using both recycled materials and 3d printing).

Power wise, nuclear thermal has worked quite well so far, but whether or not it can be adapted to Human inhabited vehicles is open to question.  Some form of high capacity batteries or supercapaciters would be required at the least.

Jason
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Offline CuddlyRocket

Interesting article about the development of a new catalyst that converts carbon monoxide and water into ethanol:

http://phys.org/news/2014-04-scientists-ethanol-corn.html

Carbon monoxide is easy to obtain from electrolysing carbon dioxide. (Indeed, this reaction is mooted as providing the colony's oxygen supplies, with the carbon monoxide normally envisaged as being vented as waste.) Ethanol has an obvious application for transport; probably by way of a direct-ethanol fuel cell rather than an ICE.

Another option to consider in any event. Ethanol has other uses (as indeed does acetate, which is a byproduct).

It's not clear from the article, but it seems some of the water may also be electrolysed to H2 and O2, which would be killing two birds with one stone!
« Last Edit: 04/12/2014 10:45 am by CuddlyRocket »

Offline Llian Rhydderch

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There is a new thread over in the SpaceX general forum that is specifically addressing SpaceX-specific Mars Colony Development & Planning.

One idea that is being discussed relates to a set of surface vehicles that are made from an entire MCT but would be explicitly designed to be trailerable, so that it might be towed around by some sort of a more generic Mars utility truck.  MCT is the Mars Colonial Transporter proposed by SpaceX.

This Ground-transportable MCT sled, a purpose-built MCT that would be able to straightforwardly convert to a towable platform for a variety of surface uses as an equipment sled is first mentioned here: http://forum.nasaspaceflight.com/index.php?topic=34667.msg1196263#msg1196263.

Those of you interested in surface vehicles on Mars might consider coming over and adding to the discussion.
Re arguments from authority on NSF:  "no one is exempt from error, and errors of authority are usually the worst kind.  Taking your word for things without question is no different than a bracket design not being tested because the designer was an old hand."
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Offline Darren_Hensley

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I watched "Moon Machines, The Lunar Rover" last night, we should probably revisit some of those ideas again. Conical tires keep dust down/out of mechanical parts. 6 wheel advantage seems to work well, expand on that. Collapseable rovers, save on space, expand on that. Parifin Wax as a cooling agent for electronics packs. Very novel idea. I like the idea of a modular system, from remotes, to passenger, to pickup, to trailer platform. Use the same stuff inside the habs, as you use outside on the surface to keep spares consistant. It also makes k-balling easier, and hangar queens a possibility. Junk yards will be minimal. Rotate your fleet to even out wear, and lots of ORUs or MRUs to keep maintenance simple, and upgrades possible. Use three fleets, light duty, general purpose, and terra-forming. All based on a uniform frame, that can be altered for the task in minutes.
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Offline JasonAW3

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Had an idea a while back about a rover whose base frame could be used much the same as the ATHLETE system that NASA created, (it could be remote controlled or controlled by the astronaut on board it)  but an inflatable cabin would be installed on it with a lower hard section to prevent punctures of the habitat segment.  It could be configured as a full length habitat module or a half length, allowing the back half to be used as either a spacesuit storage area, or to be configured as a pickup truck.  I called the idea a Conestoga type rover.
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Offline MickQ

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I have been thinking along similar lines.  A rigid chassis which carries all the major mechanical and life support equipment.  Habitable space would be folded down flat on the chassis for space saving during transit to Mars and inflated when ready to be used.  Might fit two of these in the space of one 'normal' design rover.

Also been thinking about using an RTG to provide heating for the crew space as well as power.  If the RTG was fitted under the rover with it's heats sink being the cabin floor then excess thermal energy would not be wasted.
I know the RTG would not power the rover totally but would it be able to maintain critical life support in the event of a breakdown until help arrived ?

Mick.

 

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