Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

karov · 2004-08-11 08:15:51

I think we shouldn`t relly on Mars for the innitial manned mission`s ground transport on slow, uncapacios, sophisticated and non-tested enough ground wheeled vehicles with electrical power. The present on market, cheap, and extensivelly tested on mars-like difficult terrains cars, bykes and trucks are the best choice...

see: http://www.dakar.euromaster.com/index_u … dex_uk.htm

Each of these machines in the first several missions couild be shipped in slow, economical orbits to Mars, can land there on parachuted airbag impact protection containers, and to be easily assembled by the astronauts - delivered later with other ship, and fueled with produced en situ fuel ( methan or better Methanol) and oxidiser (liquid oxigen or H2O2, or some acid...). One of these trucks could house astronauts for weeks and to carry all the necesarry for itself fuel and O2+food and water for the expoloration team. Able to traverse THOUSANDS of miles of the martian surface. The importance and the convivience of the bykes and the cars have not to be ignored...

Later such vehicles could be easiliy entirelly constructed there, when even in the begining at least some of the parts can be made on Mars with local chemicals by the shipped fuel producing factories.

SpaceNut · 2004-08-11 12:11:33

Both yours and the other topic post are of Mars crew planet(moon) surface transportation and of combined lab resource availablity mix for mode of use, crew count and day excursion distance in mind. The easy of use and of capability of each.
Both can be presented together much like Earth current system. Each has there blurred lines of use or flexibility of use.

Dook · 2004-08-11 13:16:48

You couldn't use one of these trucks without major modifications. Reasons why these vehicles are not such a good choice:
1) too heavy, I estimate one of these trucks to weigh 8,000 lbs, and this is without oxygen bottles for breathing, oxygen/methane tanks, C02 removal equipment, sleeping bunks.
2) A 67 horsepower methane/oxygen engine would consume 173,850 cubic inches a minute of methane/oxygen. Ten 435 cu ft bottles would weigh an additional 1,500 pounds and only provide 43 minutes of fuel. You would get 50 miles before running out of fuel.
3) Inflated tires on mars? The rubber would shatter like glass.
4) Frozen wheel bearings, frozen fluid in the axles, frozen master brake and wheel cylinders, engine belts would probably instantly break, valves would stick, pistons would stick to the wall of the cylinders.
5) Have to incorporate some kind of heating system for the entire engine compartment and likely leave engine running the entire time to have power for the internal heating.
6) No double pressure bulkhead
7) Have to modify it so you could get to the driving cab from the back of the truck
8) Assembly on mars???

MarsDog · 2004-08-11 13:30:23

Mobitat designs, the size of a large mobile home, could perhaps cruise around indefinetively, as do the nuclear powered submarines. However, most of the scouting will be done by satellites and the robotic rovers will add to the details.
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The initial activity will be mainly settlement site development, and given the short distances, running an electrical extension cord from a vehicle, to the power grid will be expedient.
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Simplicity is just creating a platform, add motor-wheels below and a habitat above. The maximum will be walking speed ?

karov · 2004-08-11 13:36:09

Yes, we need maximum versatile, powerfull, longrange and secure vehicle for on-ground exploration there. The nowaday earth car manifacturing industry provides now everithing one would want to explore Mars. The only difference is that these mars-adapted cars would need to have another tank onboard to hold the necesarry amount of oxidizer. The combination methanol+liquid O2 is perfect for the standart gasoline engines. Some hypergolic fuel or way of combustion to allow common rail gen.2 Diesels could be found.

My point is that such gasoline and diesel engines traversed already BILLIONS and billions of miles totaly, here on earth during all the last century. Standart combustion engines cars participate in enormous activities in every terrain and area.
No matter how much money we`ll pump in the development of the bateries and fuel cells, the old good combustion engine is the most proper power aggregate for such risky bussiness.

One way or another O2 and methan will be produced there for the return trip fueling of rockets and so on.

Why to built entirelly new and different infrastructure for maintenance of electric buggies, when we could ship rally trucks in parts, assemble them in-situ, fuel them with miniscule part of the ready fuel and oxidizer produced for the interplanetary rocket ships and cover millions of square kilometers from a single base?

The platform of one rally truck could be loaded with everything one wants: mobile laboratory, habitation module for several explorers, massive excavation and drilling equipment, even little nuclear reactor for establishing another base. The trucks of course could have trailers...

A standart truck wouldn`t be essentially more massive than the discussed brand new electric off-roads or fuel cell buses.

This lies within the mass budget of any thinkable Mars manned mission. The Mars mission is intrinsically hundreds of times longer than the lunar one, so inevitably any manned landing there will be predecessed by many landings of equipment shipped separatelly in slower chemically powered Hofman trajectories to some point on Mars. The arriving team on faster ship of human explorers should be awaited by hundreds of tonnes of equipment: nuclear reactor, chemical factory, cranes, rocket ship for the return trip, some materials and/or parts for habitat and laboratories construction... and why not several KAMAZ or TATRA rally trucks, couple of HAMMER off-road cars and... a HONDA motocycle for each exploration team member?

MarsDog · 2004-08-11 13:57:32

The caravan or wagon train approach would provide safety by redundancy. Took a long while to supplement the internal combustion engine with the electric hybrid. For distance, endurance, efficiency; the simplicity of solar, fuel cell, and electric motor cannot be beat. The sophisticated wheel-motor replaces the mechanics of the driveshaft with electronics. All you have is 2 bearings for the wheel, and another support bearing for steering.

Dook · 2004-08-11 19:27:28

The reason that vehicles on the earth can travel so far on a relatively small tank of gasoline is because they do not have to provide the air supply. On mars however a vehicle would have to carry not only the fuel but the oxygen as well. Just how are you going to provide it?

I think there are better ideas rather than a large mobile home for surveying mars.

Why design and build a new vehicle rather than use a rally truck? Because a rally truck will not work. See my post above with 8 reasons why. And it won't cover millions of square miles, 25 miles out and 25 miles back, that's it.

Rally vehicle with built on hab module- 8,000 lbs at least
Massive excavation and drilling equipment- 1,000 lbs
Nuclear reactor- 7kwe 2,200 lbs minimum

My simple mars vehicle weighs in at 4,500 lbs, and goes farther, has more redundancy for critical systems, it doesn't require a separate launch, and it can be included in the Mars Direct plan with no changes (once I get the weight down to 2.2 tonnes total).

Karov the rest of your post reminds me of the 90 day report in that it totally goes against the efficient idea called Mars Direct.

Another problem with a 'sophisticated' wheel motor is how to get the electricity to a moving wheel. You need to have whats called a slip ring. Mars dust and cold would ruin it in seconds.

In my idea the steering is controlled by an electric actuator.

MarsDog · 2004-08-11 21:36:06

Without a convoy, it would be dangerous to take long trips.
And on the first few missions there will not be enough vehicles to form a convoy.
The exploration will be done by armchair explorers and robots.
The single Mars vehicle will be a valuable asset, not to be risked.
Main function of the vehicle will be to assist in habitat development.
Sort of like a tractor on a farm, not designed to go on a vacation trip.
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Since the required speed is slow, simple methods can be used.
The wheel-motor has permanent magnets rotating around the stationary coils.
A flexible cable, such as in a printer would allow for steering movement.
A small motor & pinion gear for steering could be substituted.
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My design goal would be for walking speed, and a 20 km operating range.

Dook · 2004-08-12 09:53:25

Your idea completely misses the reason to go to send humans to mars at all which is to conduct science and to explore. The first missions will be purely for that reason. Why send humans if all you would have them do is operate small robotic rovers? We are doing this now? Also once the Mars Direct habitat lands on the surface there isn't much more to develop other than setting up the solar array. A vehicle with only a 20 km range? Why even include it? Leave it at home.

karov · 2004-08-12 10:18:40

You couldn't use one of these trucks without major modifications. Reasons why these vehicles are not such a good choice:
1) too heavy, I estimate one of these trucks to weigh 8,000 lbs, and this is without oxygen bottles for breathing, oxygen/methane tanks, C02 removal equipment, sleeping bunks.
2) A 67 horsepower methane/oxygen engine would consume 173,850 cubic inches a minute of methane/oxygen. Ten 435 cu ft bottles would weigh an additional 1,500 pounds and only provide 43 minutes of fuel. You would get 50 miles before running out of fuel.
3) Inflated tires on mars? The rubber would shatter like glass.
4) Frozen wheel bearings, frozen fluid in the axles, frozen master brake and wheel cylinders, engine belts would probably instantly break, valves would stick, pistons would stick to the wall of the cylinders.
5) Have to incorporate some kind of heating system for the entire engine compartment and likely leave engine running the entire time to have power for the internal heating.
6) No double pressure bulkhead
7) Have to modify it so you could get to the driving cab from the back of the truck
8) Assembly on mars???

Antarctic vehicles:
http://www.pageplanet.com/coolrunner/Tr … nsport.htm

...warming up of the machines before use, special sinthetic lubricants...

KAMAZ:
http://www.kamaz.net/eng/auto/testdrive … ive/sever/
==========================================
Such Kamaz "tested by north" UNMODIFIED has payload of 15-18.5 tonnes, average speed of 15-60 km/h in the quoted severe conditions in ambient temperarture of -20 to -40 degrees Celsius, and consumes 50-60 litters of fuel per 100 km. Trade , say two tonnes of the payload for two one tonnes-when-filled tanks for methanol and LOX and you have ~1000 km range. On Mars the temperature range is between ~-80 and ~+20 degrees at the equator -- in such thin air, hence very low termal conductivity it will not be such big problem the machinery to be kept warm enough to be operational ( see the simple Antarctic solution ) if 'blanketed' well. The freezing of the rubber and plastic details and the lubricants could be avoided with simple modifications...

A slow, weak, fragile electric mobitat will not be ehough. I think antarctic base provided with all the shown in the site vehicles is closer view of future Mars base.

Dook · 2004-08-12 13:38:53

You want to send dump trucks to mars? Sigh...

The website does not say how much these trucks weight but they are definately over 10,000 lbs without including the weight of the oxygen/methane bottles for supplying the engine, and oxygen bottles for life support. The maximum weight for a vehicle to be included in Mars Direct is 2.2 tonnes! Your vehicle is amost 3 times that weight, it does less, and provides less redundancy for mission critical and life support systems than my idea. You really have not put any serious thought into this.

The web site says the engine size is 740. 740 what? Cubic inches? That means the engine uses 1,850,000 cubic inches of fuel (methane/oxygen) a minute at 2,500 rpm. A compressed gas cylinder holds 751, 680 cubic inches so if you carried 100 gas cylinders your dumb truck would have an operating time of 41 minutes. And the cylinders weight 148 lbs each so that would be an extra 14,800 lbs???? Do the math. It won't work.

EDIT: I forgot to divide the number of cubic inches the engine uses a minute in half. It's a four cycle engine so instead of 1,850,000 it really uses 92,500. Thus this vehicle will go twice as far-82 miles.

karov · 2004-08-12 14:38:09

No, I don`t want to send dump trucks to Mars.

My thought is that slightly modified, i.e. ordered and produced on conventional assembly line, trucks could be used there. The Otto cycle four stroke gasoline engine is may be the mostly tested one and reached almost the theoretical limit of it`s possible improvements. Such engine could work without major modification with methanol. Having on hand CO2 ( compressed martian atmosphere ) + H2O ( from the regolith ) + electricity + catalysers it is easier to produce methanol CH3OH than methane CH4. The methanol is easier for storage because in all the diurnal and latitude range of the martan temperatures ( except the polar nights) it is liquid. The solid freezed methanol unlike the H2O is denser than the liquid, so even if the fuel in the tank freezes, it wouldn`t burst the tanks and could be liquifyed easiliy with built in electric heaters. LOX could be stored in comperativelly low mass tanks. Because of the methanol is hypergolic, i.e. it selfignites mixed with oxidiser at certain pressure, hence even Diesel cycle can be used, perhubs. The methanol + O2 can be used in fuel cells to replace other type of car battery. Both the little fuel cell car battery and the main Otto/Diesel will produce CO2 + H2O as residue. The H2O -- for drinking, cooling... etc. The major O2 tank if tied up to the life-support can provide the exploration team with breathable air for weeks (?)... The mass of capable and robust ( say, 200-300 h.p.) internal combustion engine is not more than several hundred kilograms. ( How much is one "lb" ?) The mass of the steel frame - several tonnes... Four wheels drive. Drive-by-wire. View it as a flat platform with the engine, gear box, steering and brakes, tanks built in. Make it from lighter materials if you want. Load it with whatever you want. For example put inflatable habitation modul...

740 is may be the model number. What cubic inches in Russia?
According to your maths appears that no combustion engine vehicle could pass more than 30-40 km without refueling. Don`t you have a car? BTW, how old are you, Dook?

MarsDog · 2004-08-12 15:04:07

Efficiency dictates electric drive.
Even on Earth, combustion engine, electric hybrids are preferred, and will become standard as oil prices rise.
Otto cycle primary power is an option, but is a lot more complicated on Mars. High performance on Mars is not needed. A supersized Moon Buggy based habitat could not go fast because of all the bumps and low gravity.

Dook · 2004-08-12 18:51:13

Don`t you have a car?

Yes I have a car, a 2001 Dodge Intrepid. No, I'm not going to send it to mars.

You might be able to store enough liquid methane for it to work. I don't know. At what temperature does it turn to a gas and what is it's expansion ratio?

Oxygen turns from liquid to gas at anything above -298 so even on mars it is going to just evaporate and you must vent this evaporation. You cannot contain it because it will burst your container. Oxygen expansion ratio is 862 parts liquid to 1 part gas.

I still think your idea is the wrong approach. It's too heavy by a factor of almost 3, it needs a lot of modification, and has NO redundancy. What if the engine fails? Everyone dies.

karov · 2004-08-13 03:30:56

Methane (CH4) boils at 111 K ( -162 C) -- far bellow the extreme martian colds, but I`m talking about METHANOL(CH3OH, synonyms - Methyl alcohol, wood alcohol, carbinol). Methanol is as you know the simplest alcohol. It melts at 176 K ( - 96 C), and boils at 337.8 K (64.7 Celsuis). The solid phase methanol is denser than the liquid, hense methanol freezing in the tanks in the polar regions of Mars is not a danger for ice-bursting. When the fuel freezes - just heat the reserviors.

As far as I remember the Mars-Direct envisions namely storage of methane in the tanks of the return ships, so your argument about the disadvantages of the methane storage conserns the mars-Direct itself, not my proposal for methanol instead methane...

Methanol is simpler to produce, store and handle, and burns not much worse than methane. 2xCH3OH + 3xO2 = 2xCO2 + 4xH2O . Autoignition temperature - 445 degrees Celsuis.

From wiki for methanol:
Poduction - "...of synthesis gas from methane produces 3 moles of hydrogen for every mole of carbon monoxide, while the methanol synthesis consumes only 2 moles of hydrogen for every mole of carbon monoxide. One way of dealing with the excess hydrogen is to inject carbon dioxide into the methanol synthesis reactor, where it, too, reacts to form methanol according to the chemical equation" : CO2 + 3xH2 = CH3OH + H2O, catalyst: mixture of copper, zink oxide and alumina... All these elements could be easily extracted from the regolith and the atmosphere in-situ if one has enough energy ( the nuclear reactor !)
Combustion engines on methanol - "one cannot use BA100 (100% bioalcohol) in modern petroleum cars without modification...", because it is not as much flamable as the gasoline, but injecting pure O2 to form the right mixture with CH3OH in the cilinders, changes the picture greatly.
OTHER USES! - "Methanol is also used as a solvent and as an antifreeze in pipelines. The largest use of methanol by far, however, is in making other chemicals. About 40% of methanol is converted to formaldehyde, and from there into products as diverse as plastics, plywood, paints, explosives, and permanent press textiles." -- we`ll need all this up there.

The storage of O2 in Dewar containers, would delay the final evaporation for weeks, hence well within the timescale and scedule of any ground exploration and construction trip. The described from you venting is inevitable, but this is the way to hold the major part in liquid form. See the neurosuspensional cryonics -- how often do you think the ALCOR workers refill the liquid N2 coffins ( in hot earth area!!!)?

AGAIN!!! - I Mars-Direct version you also should produce and store LOX ( liquid oxigen) for MONTHS to breathe the return rockets... To store LOX for fuel (methanol) oxidizer is far more safer than to use peroxide H2O2 ( melting -0.5 C, boiling at 150 C) which is monopropelant on its own... or some acid, for which one would need N2 or Sulfur, Chlore or Fluor to produce on Mars. From all possible oxidizers the O2 is the best!

So, methanol + O2, possesses enormous advantages: produced from ambiently available simple local resourses ( air and dirt), directly used to propel rockets and ground vehicles...

About the redundancy - I think the several hundred kg Otto or Diesel cycle engine + several hundred kg of tanks, gives much more horse powers per kg hardware than the non-tested bateries. The whole mars-rally truck made by localy produced polyethylene or other plastics or foamed metals (thanks, MarsDog and for you - the performance and speed depends on the power of the engine and the gearbox) would weight much less than your vehicle. The Antarctic and Russian Far North examples were just to be shown that combustion engines behave quite well in extreme colds. I repeat with this thin atmosphere of several milibars on Mars, the heat losses can be minimized very efficiently.

If the engine fails, one could with almost no tools replace it with another form the cargo department of the vehicle, for several hours maximum. If it weights say ~100 kg you don`t even need a crane... And the martian rally truck can carry several replacement engines, gearboxes and other parts sets representing just several % of the total payload... See:

http://www.mountain.ru/eng/climb/2003/A … gradarsky/

http://www.mountain.ru/eng/climb/2003/A … ntarktida/

http://www.yellowairplane.com/Adventure … Exp_1.html

This team was under the same level of isolation conditions as potential ground exploration team on Mars and Antarctica is even more hostile than Mars in wather conditions. Mars is like a sand beach compared to the ice cracks and storms in Antarctica... You see the reports about 'tremendous failures' but recovered with on-board spare parts and from the crews themselves. Martian combustion engine can be elaborated better with far bigger budget in order to fail more difficult and to be repaired easier.

And finally, my question in terms of economicity ifn the technology diversification is: Why to use entitelly different electrical drive tech for the ground vhicles ( still non-made) when the mars-direct-like plan include production of fuel/oxidizer for return trip. You already have plenty of electricity from the supplied nuclear reactor and plenty of fuel. The simplest and less risky way is to use it for ground transportation, too.

Dook · 2004-08-13 16:10:52

Multiply engine size by the rpm to get X.

Take X and divide by 2 (four cycle, fuel/oxygen is used on half of the revolutions).

This is how much fuel/oxygen a combustion engine uses per minute. Just guessing 10% of that is fuel and the other 90% oxygen.

Now come up with some way to carry all this fuel and oxygen. Plain and simple, you can't do it.

You think a crew on mars can replace a 1 kg (220 pound) engine easily and without tools?

I would like to see specific weights for everything in your design: vehicle structure, engine, fuel and oxygen carried, life support systems, drilling equipment, extra engines, gearboxes. I'm betting you are somewhere around 15,000 pounds.

Not sure what you mean about the electrical drive not being made. I have provided web links for everything. There is no component in my design that is not already built and tested other than maybe the drive gearboxes and the structure.

MarsDog · 2004-08-13 22:01:12

Liquid http://www.airliquide.com/en/business/p … 78]Propane C3H8 582 kg/m3
Molecular weight : 44.096 g/mol

Liquid http://www.airliquide.com/en/business/p … =78]Oxygen O2 1141 kg/m3
Molecular weight : 31.9988 g/mol

Each Propane mole combustion produces 3(CO2) and 4(H2O)
Or 5 moles of O2 is needed for 1 mole of Propane.

Total O2=5*32=160 grams for each mole of Propane (44 grams)

Total weight O2 to combust 1m3 Propane is
(160/44)*582 = 2116 kg Or 1.85 m3 of liquid O2

US measure: 264 gallons of Propane uses 489 gallons of O2
30 miles per gallon on Propane gives 7,920 miles.

Dook · 2004-08-14 01:06:13

How can you say how many miles per gallon the engine will get if you don't say the engine size and expected rpm? Are you planning on driving a motorcycle on mars?

Also you say that 5 molecules of oxygen are needed for 1 molecule of propane that means you need 5 times as much oxygen to propane so how do you get 264 gallons of propane used to only 489 gallons of oxygen? If the number for the propane is correct then you would actually need 1,320 gallons of oxygen.

Propane is 270 times more compact as a liquid than a gas so 264 gallons of liquid propane will convert to 71,280 gallons of propane gas.

How are you going to carry a 264 gallon propane tank and a 1,320 gallon liquid oxygen tank?

MarsDog · 2004-08-14 01:37:32

Liquid Propane is similar, but less, in performance to gasoline. Mars has less gravity, so you get better mileage per mass, and you can build the vehicle with less mass.
-
The 30 miles per gallon guess could be fine tuned for energy content per fuel volume, and lower energy required in a low gravity, low air resistance, environment to travel the same distance. 30 miles per gallon is common on Earth, and a good guess on Mars.
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All the calculations were done for liquid volumes.
2.85 m^3=660 galons total (Liquid O2 and Liquid Propane).
Total 2,698 kilograms would weigh less on Mars.
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Cyrogenic method is to insulate the holding tank well and provide pressure relief.

----------------------------------------------------------

Also you say that 5 molecules of oxygen are needed for 1 molecule of propane

Molecular weight in grams is just used to derive the ratio of weights between 5 Oxygen (5*32) and 1 propane (1*44), then get the weight of Oxygen by using the ratio on the weight of 1 cubic meter of Propane. From the weight of Oxygen used and weight of one cubic meter of Oxygen, calculate volume of Oxygen used.

karov · 2004-08-14 08:09:09

One needs 3 moles of O2 to combust 2 moles of methanol (CH3OH). Or 1.5 moles of O2 per each methanol mol.

Propane is super, MarsDog, but I think methanol will be quite easier to be produced on Mars from ground water and atmosphere`s CO2 than propane (?). Easier I mean with less massive chemical factory in terms of delivery ship`s payload.

O2 ~32 g/mol, LOX- 1141 kg/m3
CH3OH ~32g/mol, liquid methanol - 792 kg/m3

So, one needs about ~1.5 kg of O2 to combust entirely 1 kg of CH3OH or for each liter (0.79 kg) of methanol ~1.040 liters of LOX are necesarry to be extracted the total thermal energy of this exact chemical recombination.

The data from IndyCar ( runing entirelly on M100 or pure high grade methanol) and the experience form some american cities operating lines with both sparc-ignition and compression-ignition (diesel) modified for M100 engines` buses, shows that methanol gives you higher power - better performance than the gasoline, but twice less energy per galon. So to use M100 as fuel one needs twice bigger fuel tanks for the same mileage.

If a car has 1 m3 liquid methanol in fuel tanks onboard, i.e. ~800 kilograms of CH3OH, + the necesarry amount of 1.040 m3 of LOX in oxidizer tanks onboard ( a tonne and a half together with the LOX-cryotank mass ?), and if we envision the engine to consumes 20 l/ 100km of M100 ( + of course 20,8 l of LOX) it could pass ~5000 km without refueling. 20 L/100 km - equals ~10 L/100 km in gasoline car, or ~100 h.p. engine is applicable. The trips lenght of course should not exhaust the total capability of the machine, so assuming 500 km to the target + 500 km return trips, we have REDUNDANCY FACTOR of 5 !!!!

The total mass of the rover - several hundred kilos for the engine and ~2.5 tonnes fuel and oxidiser, ~5 tonnes construction... With say 7 tonnes empty weight one could pull another 7 tonnes around with great ease. Of course the figures could be pefectly scaled to fit the dook`s requirements for 2.2 tonnes total mass of the unloaded with crew and equipment rover.

Dook · 2004-08-14 11:09:05

Mars has less gravity, so you get better mileage per mass, and you can build the vehicle with less mass.

The main factor in any vehicle getting 30 mpg is ENGINE SIZE AND RPM! Not gravity! Atmospheric resistance only becomes a factor at high speeds. Sure you can have an engine get 30 mpg on mars but it would be in a motorcycle! Also, the 30 mpg figure only includes fuel, not the oxygen.

Why don't you pick an engine, pick a vehicle to put it in, and pick some way to carry all the fuel and oxygen that it would need? Your posts keep avoiding critical problems with your idea like: weight, vehicle design, fuel tank, oxygen tank, your cryotank cooling system, electricity created, electricity used...

Dook · 2004-08-14 11:42:02

The trips lenght of course should not exhaust the total capability of the machine, so assuming 500 km to the target + 500 km return trips, we have REDUNDANCY FACTOR of 5 !!!!
Of course the figures could be pefectly scaled to fit the dook`s requirements for 2.2 tonnes total mass of the unloaded with crew and equipment rover.

I don't understand, at first you say you need 3 times the amount of LOX for methanol then later you say "If a car has 1 m3 (1 cubic meter) methanol the necessary amount of 1.04 m3 (1.04 cubic meter) of LOX???? So you are saying two different things. If you need 3 times the amount of LOX for methane then with a 1 cubic meter of methane you need 3 cubic meters of LOX.

I don't understand your gross assumptions of 5,000 km range but it is obviously not well thought out. Sigh, once again, the formula is engine size multiplied by rpm to tell you how much fuel is used per minute. You conveniently avoided this in your assumptions.

Your redundancy factor of 5 only covers mission range not other critical things such as power supply (engine) and life support for the crew. If the engine fails your crew dies! That is not a redundancy of 5, it's NO redundancy!

You say your vehicle is around 8 tonnes but the figures could be perfectly scaled to fit 2.2 tonnes? I would really like to see you try to do it. I don't think you can. You are making a lot of guesses and you never give any links to support your claims. You haven't fully thought out everything needed by a crew on mars: oxygen for breathing, CO2 removal, water supply, latrine (water closet), internal heating, external heating of equipment, drilling equipment. Your idea is over 3 times the maximum weight and you haven't even included any life support! Also it would be nice if you could include some actual proof to support your claims.

karov · 2004-08-14 14:38:01

I don't understand, at first you say you need 3 times the amount of LOX for methanol then later you say "If a car has 1 m3 (1 cubic meter) methanol the necessary amount of 1.04 m3 (1.04 cubic meter) of LOX???? So you are saying two different things. If you need 3 times the amount of LOX for methane then with a 1 cubic meter of methane you need 3 cubic meters of LOX.

My calculations about the necesarry quantity of LOX to combust certain amount of methanol are right!

Simply you have to start making difference between METHANE ( CH4 ) and METHANOL ( CH3OH )...

I have no time now, but tomorrow I`ll support with proofs from the practice my statements. You`ll see that internall combustion engine runing on M100 ( this the AMERICAN trade abreviation for CH3OH ) is OK for Mars rover, and far better than the batteries. I`ll explain you about the redundancy.

If any engine fails than the crew is dead if it is out of the walking distance to the station.

Motocycles on Mars -- I think they are super and already posted this in previous posts about the usability on Mars of combustion-engines vehicles.

You didn`t tell me how old are you. Bellow 20 regarding your agressive tone?

Dook · 2004-08-14 16:19:57

We have gone back and forth, 2 whole pages of posts, with you avoiding critical problems with your design. Your idea is way too heavy, it doesn't include all the oxygen and fuel you need to carry, and it provides no backup for life support or critical vehicle functions. I feel like I'm arguing with a child.

Let me make it as simple as it can be:

A very small combustion engine, .5 liter (30 cubic inches) operating at 2,500 rpm requires 75,000 cubic inches (1.229 cubic meters) of fuel/oxygen every minute. A giant LOX container that holds 500 liters would provide 431,000 liters (26,301,175 cubic inches) of oxygen gas. Even this huge container would only supply enough oxygen to your tiny little combustion engine for 350 minutes or 5.8 hours. You could travel maybe 75 miles. I didn't even consider the weight because it would be way to much to go on Mars Direct. Also that small of an engine wouldn't provide enough power. I don't know how to make it more simple than that. You can't do it.

RobS · 2004-08-14 22:50:47

Dook, I have a question. Why do you choose a particular rpm? Internal combustion engines sometimes run faster and sometimes slower, depending on the power they need to make. At least that's true of my car. It may be true that 2500 rpm will burn up all the fuel in a certain small number of miles, but maybe that's too much power to travel those miles at the expected speed. Wouldn't it be a better approach to determine the horsepower needed to travel over rough terrain at, say, 30 km per hour, and then determine the rpm and engine size from that?

By the way, in *The Case for Mars* page 144 Zubrin says a surface vehicle with an internal combustion engine will consume 0.5 kg of methane/oxygen bipropellant to move a 1-tonne vehicle 1 kilometer. From this one can convert fuel and oxygen masses into a vehicle range if you know the vehicle's mass.

-- RobS

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#1 2004-08-11 08:15:51

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

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Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#3 2004-08-11 13:16:48

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#4 2004-08-11 13:30:23

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#5 2004-08-11 13:36:09

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#6 2004-08-11 13:57:32

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#7 2004-08-11 19:27:28

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#8 2004-08-11 21:36:06

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#9 2004-08-12 09:53:25

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#10 2004-08-12 10:18:40

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#11 2004-08-12 13:38:53

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#12 2004-08-12 14:38:09

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#13 2004-08-12 15:04:07

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#14 2004-08-12 18:51:13

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#15 2004-08-13 03:30:56

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#16 2004-08-13 16:10:52

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#17 2004-08-13 22:01:12

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#18 2004-08-14 01:06:13

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#19 2004-08-14 01:37:32

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#20 2004-08-14 08:09:09

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#21 2004-08-14 11:09:05

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#22 2004-08-14 11:42:02

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#23 2004-08-14 14:38:01

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#24 2004-08-14 16:19:57

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

#25 2004-08-14 22:50:47

Re: Simplest Mars Vehicles - Paris-Dakar rally + 02 onboard tanks

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