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#1 2004-10-02 07:21:12

Palomar
Member
From: USA
Registered: 2002-05-30
Posts: 9,734

Re: Running on Compressed Air?

Click

*What are the chances something of this nature could be developed or used on Mars?

--Cindy


We all know those Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#2 2004-10-02 08:06:35

Rxke
Member
From: Belgium
Registered: 2003-11-03
Posts: 3,658

Re: Running on Compressed Air?

Wow.

Seen this before, on a board that's now down...  sad  It was a prototype, and it worked really good... To be thruthful, I daren't put it up here, because of the giggle-factor...

Hmmm... Given the Martian atmosphere, and the need to do a lot of compressing gases and stuff there, for a multitude of applications, if one wants to live there, pumping-tech might be an important part of everyday life... So the idea would somewhat seem less crazy, no?

(Edit:) I'll try to contact the person who submitted about the prototype.


ExoMars' launcher's 2nd stage is probably en route to Mars. Unsterilised... yikes

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#3 2004-10-02 10:29:13

C M Edwards
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From: Lake Charles LA USA
Registered: 2002-04-29
Posts: 1,011

Re: Running on Compressed Air?

Cindy is usually immune to giggle factor. 

She also really has something here. 

Marsian air compresses to a solid at pressures where Earth air is still just pressurized gas.  The same tank that can only hold 50 kilos of compressed Earth air can hold half a ton of CO2 at the same pressure. 

In short, compressed gas cars could have ten times the range on Mars that they do on Earth.  Perhaps more due to lower gravity and air pressure. 

Methane powered rovers have more range, but also require their own weight in infrastructure to make that fuel on Mars.  Maybe compressed gas is the way to go with the first missions.


"We go big, or we don't go."  - GCNRevenger

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#4 2004-10-02 10:44:39

Rxke
Member
From: Belgium
Registered: 2003-11-03
Posts: 3,658

Re: Running on Compressed Air?

yikes  yikes

Is that so? If it is: Very good point, C M!

Also, with ambient temperatures so low, what about liquefeing CO2? Shouldn't take too much energy, no? then, once in the tank, pump it through   a heat exchanger, doubling up as coolingsystem for your electronics etc... So that it expands.. (mh, won't be very efficient, forget it...)


ExoMars' launcher's 2nd stage is probably en route to Mars. Unsterilised... yikes

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#5 2004-10-02 12:58:13

Commodore
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From: Upstate NY, USA
Registered: 2004-07-25
Posts: 1,021

Re: Running on Compressed Air?

Interesting.

Would it be practical it compress air while moving? Say put an air dam in the hood (real sporty :laugh:), and compress the air in real time?


"Yes, I was going to give this astronaut selection my best shot, I was determined when the NASA proctologist looked up my ass, he would see pipes so dazzling he would ask the nurse to get his sunglasses."
---Shuttle Astronaut Mike Mullane

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#6 2004-10-02 13:04:53

John Creighton
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From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
Website

Re: Running on Compressed Air?

Interesting.

Would it be practical it compress air while moving? Say put an air dam in the hood (real sporty ), and compress the air in real time?

Why would you get the power for that? The sun?

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#7 2004-10-02 13:11:55

Commodore
Member
From: Upstate NY, USA
Registered: 2004-07-25
Posts: 1,021

Re: Running on Compressed Air?

Interesting.

Would it be practical it compress air while moving? Say put an air dam in the hood (real sporty ), and compress the air in real time?

Where would you get the power for that? The sun?

Ah... the alternator?

Thats why I'm asking if its pratical for a car to produce enough power while in motion to run an air compressor. It can run a radio, AC, and countless other gizmos.

After all 50 miles might get you from one end of Luxemburg to the other 3 times, but anywere else requires more range.


"Yes, I was going to give this astronaut selection my best shot, I was determined when the NASA proctologist looked up my ass, he would see pipes so dazzling he would ask the nurse to get his sunglasses."
---Shuttle Astronaut Mike Mullane

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#8 2004-10-02 13:36:45

John Creighton
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From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
Website

Re: Running on Compressed Air?

Thats why I'm asking if its pratical for a car to produce enough power while in motion to run an air compressor. It can run a radio, AC, and countless other gizmos.

Of course you would loose energy unless maybe you are breaking.

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#9 2004-10-02 14:02:19

Rxke
Member
From: Belgium
Registered: 2003-11-03
Posts: 3,658

Re: Running on Compressed Air?

Commodore, you mean on Mars or on Earth?

anyway it's pretty inefficient, so not much practical use...

Better would be for instance windmills at the side of the road, that compress atmosphere... 'loading' it in pressure vessels that you can use...


ExoMars' launcher's 2nd stage is probably en route to Mars. Unsterilised... yikes

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#10 2004-10-02 14:33:53

RobS
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From: South Bend, IN
Registered: 2002-01-15
Posts: 1,701
Website

Re: Running on Compressed Air?

The compressed air on Earth is probably at a pretty high pressure. But liquid CO2 produces gas at only 100 pounds per square inch (7 bars) at ambient Martian temperatures and that may be too low to power a vehicle efficiently. The pressure could be raised, however, if the liquid CO2 were heated. Possibly this provides a mechanism for capturing solar energy more efficiently than converting it to electricity. If a surface vehicle had a large solar concentrator on its roof, maybe the CO2 could be heated to several hundred degrees centigrade and the expanding gas run through a small turbine. Some of the rotary power could be converted to electricity to run the compressor to obtain the compressed air; the actual surplus power would come from the heating.

        -- RobS

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#11 2004-10-02 14:44:53

Rxke
Member
From: Belgium
Registered: 2003-11-03
Posts: 3,658

Re: Running on Compressed Air?

From the guys that are building it, they use 300 bar...

Great site, BTW, lots of info and nifty pics and all that 21st century multimediastuff, heh. But not overdone, IMO...

Check out their MULTICAT! looks great for Mars, with a bit of tinkering...


ExoMars' launcher's 2nd stage is probably en route to Mars. Unsterilised... yikes

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#12 2004-10-04 09:58:02

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 16,831

Re: Running on Compressed Air?

Compressed air is used to run a lot of short term use items in many auto repair shops. So why not intergrate it into normal mission use as well a rover sounds very feasable since it has a lot of stop and go motion allowing for it to regenerate the compression needed for using it to propel the vehicle.

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#13 2004-10-04 16:00:44

Dook
Banned
From: USA
Registered: 2004-01-09
Posts: 1,409

Re: Running on Compressed Air?

There isn't any specific information on how the engine works.  I don't see how using a gas engine (or electric from batteries) to compress air then using the air to power a vehicle is more efficient than just using the gas engine alone.

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#14 2004-10-04 17:04:12

GCNRevenger
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From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Running on Compressed Air?

How it works? Just like any piston engine, except the expansion in the cylender is from high-pressure air being injected instead of gasoline burning or steam expanding or whatever. It looks to be relativly portable and powerful, but not terribly efficent or long lasting.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#15 2004-10-04 17:35:51

Ian Flint
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From: Colorado
Registered: 2003-09-24
Posts: 437

Re: Running on Compressed Air?

I remember making those CO2 powered drag racer model cars in high school.  Now that's an Air Car!  I can see it now -- Bruce Willis in his Mars Air Car (MAC, like the truck) saving all humanity in 90 minutes.  He's sure to have a punctured CO2 tank somewhere along the line.  In a gross exaggeration of Martian gravity it will rocket him over Valles Marineris, no doubt.   cool

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#16 2004-10-04 20:55:47

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 16,831

Re: Running on Compressed Air?

Inside the Air Car, an electric pump compresses air into a tank. The air in turn pumps pistons that take the vehicle up to 70 mph. The car can travel 50 miles at top speed on a full tank, and farther at lower speeds.

Looks pretty good enough when solar power could be used to re-top off the tank for extra distance. Think refueling stations also where you drive up the a solar powered compressed air storage tank. Simply plugin the external tank hose to the vehicle and recharge the system for even further distance.

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#17 2004-10-04 22:50:57

Austin Stanley
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From: Texarkana, TX
Registered: 2002-03-18
Posts: 519
Website

Re: Running on Compressed Air?

One of the problems I see with using compressed air is the potential for a disterous explosion if the tank is somehow punctured.  If the tank was to be punctured, it would probably rupture in a horendus explosion that would put anything that any chemical engine could conceviable produce, because there is little way for a chemical engine to release all that energy at once.

The same problem exists for another potential energy store, flywheels.  If for some reason the flywheel was to be damaged, you could have a serious disaster when all the energy was released at once.

But if you can succesfuly contain that energy, compressed air could probably be usable, for short distances at least.


He who refuses to do arithmetic is doomed to talk nonsense.

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#18 2004-10-05 05:26:55

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 16,831

Re: Running on Compressed Air?

I will not say who I work for but, they have a compressed air tank that will hold 5,000 psi and still take a direct shot and not rupture.

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#19 2004-10-05 08:37:09

Dook
Banned
From: USA
Registered: 2004-01-09
Posts: 1,409

Re: Running on Compressed Air?

I'm not seeing how this is efficient at all.  If you have an electricity source (batteries or solar panels) why not just use that to power electric motors?

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#20 2004-10-05 10:10:22

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 16,831

Re: Running on Compressed Air?

I guess depending on the weight of the vehicles plus the equipment and crew the electric motor that must be even larger and heavier to move the vehicle around as compared to powering a small compessor.

JIMO I would want the power to run other stuff such as communications, instrumentation measuring equipment and other such sciencetific tests that might be preformed.

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#21 2004-10-05 12:59:46

C M Edwards
Member
From: Lake Charles LA USA
Registered: 2002-04-29
Posts: 1,011

Re: Running on Compressed Air?

If the tank was to be punctured, it would probably rupture in a horendus explosion that would put anything that any chemical engine could conceviable produce, because there is little way for a chemical engine to release all that energy at once.

Actually, my limited experience with catastrophic ruptures in high pressure storage tanks is that they act more like rocket engines than bombs.  With the inertia of an entire vehicle, the passengers would survive long enough to be launched.

The end would suck, but the ride would be spectacular.   cool


"We go big, or we don't go."  - GCNRevenger

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#22 2004-10-05 17:36:01

MarsDog
Member
From: vancouver canada
Registered: 2004-03-24
Posts: 852

Re: Running on Compressed Air?

Instead of driving to an execercise club to loose weight, take out a pedal powered air pump.
But if everyone did it, another ice age could be the result.

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#23 2004-10-05 18:17:55

Austin Stanley
Member
From: Texarkana, TX
Registered: 2002-03-18
Posts: 519
Website

Re: Running on Compressed Air?

It becomes more difficult to build a robust tank the bigger the tank becomes.  Building a small robust tank that only has to hold say 10 cubic feet of air is much easier than a larger tank that has to hold 100 cubic feet of air at the same pressure.  I have no doubt that a small tank could be built to withstand practicaly any force that could be subjected to it, but a large tank is a diffrent story.  For any compressed air vehicle to have any kind of range it is going to need a pretty big tank, under fairly high pressure.  On mars this is even more true as the requirments for endurance and performance are more stringint then they are on earth, all of which pressure a larger tank.  Since you are also seeking to keep mass down, this is yet another pressure that makes for a rupture prown tank.

Also, the larger and weaker the tank, the more likely it is to rupture in an explosive fasion, then it is to contain the site of the leak and take of like a rocket.  A weaker tank has (obviously) less body strength, and so is not able to withstand the forces trying to expand the size of the whole, so the whole expands rapidly and the tank ruptures.

Thridly, you would be supprised by the kind of pressures a vehicle can experince during a traumatic accident.  Although much less speed is involved then in a bullet impact, much, much, much greater mass (tons as opposed to grams) is involved, so often times the force is much greater.

-----------

In a CA vehicles favor, the lower martian temperatures would make it easier to compress and store greater quantities of air.  Also, since you generaly do not have to worry about two-car accidents, the magintude of possible accidents is greatly reduced.

I'm not trying to say that CA vehicles are impossible, they are very possible.  I just doubt they would be usefull as replacments for long range rovers.   As vehicles with tanks of practicle size will not have the necessary range or performance.  For scooting around the base, they might be great.

--------

Oh, and for some who are confused, the point of a CA vehicle is not that you compress air as you go and use that to power your engine.  You use the compressed air as an energy store, using your bottle tank of it to power you vehicle.  You then travel to your base (where you persumably have excess power), and fill up the tank from a compressor.


He who refuses to do arithmetic is doomed to talk nonsense.

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#24 2004-10-05 18:38:10

GCNRevenger
Member
From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Running on Compressed Air?

Compressed air as a long-range rover power source isn't going to happen, the size and engineering of the tank pretty much prevents that. What it is good for is short-range tooling around, which would be great since you wouldn't have to bother with liquid methane or methanol or LOX/GOX/Peroxide and capturing the exhaust Water.

I wonder if compressed air would be much good for light to medium machinery or even portable heavy power tools.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#25 2004-10-06 01:36:40

Rxke
Member
From: Belgium
Registered: 2003-11-03
Posts: 3,658

Re: Running on Compressed Air?

Austin, about the catastrophic exploding:

on the site somewhere they argue the system is quite safe, it doesn't explode, but rupture, has been tested/used for years already on trucks (I guess they use the pressure vats tucks use for their pneumatics)

Dook,

it is *not* efficient, but it is simple, so probably lighweight too etc. Ideal for midrange rovers, easy to repair etc...

Long-range rovers will undoubtedly need another way for powering them, but I guess it would be ideal to scuttle around the general vincinity of the base-nuclear generator-launchplatform etc... Distances too big to do on foot, too small to take out the big machines... (who might be unavailable for day-to-day tasks because in use for other stuff, like exploring)


ExoMars' launcher's 2nd stage is probably en route to Mars. Unsterilised... yikes

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