Hypothetical physics question....

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Boz Mon

Boz Mon

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I dont know if this is going to make sense but here goes nothing:

Lets say you have a car in a vacuum environment. The engine compartment and gastank etc are sealed. The car runs off of an airtank. Assuming that this post makes sense, what would happen to the car and the environment? Or would this even work?
 
Let's see...

The gas tank is filled with gasoline, correct? And the airtank you speak of is the source of air/oxygen for the intake of the engine. To make it simple we'll forget about the pressure of the tank or its capacity and disregard all the air-tite business and say this:
The ingine runs as usual but is doing so inside a perfect vacuum. It gets air from an air tank and gas from the gas tank. The battery is sealed, also.

The battery is the ony thing I could think of that is necessary for the engine to run that may be effected by the vacuum, but I took care of that by sealing it off. You just want to know what would happen if it ran in a vacuum. The engine would run fine; it has spark, gas, and oxygen. It makes sense to me that your vacuum would be short-lived because it would start to fill with whatever gases are expelled from the exhaust. By the way, I'm picturing the car sitting in a box-shaped room maybe as big as a house, though size wouldn't matter, with nothing else in it but the car. You could get more complicated, sure, but in the perfect scenario of vacuum room, car, gasoline, oxygen, and sealed battery the car should run fine and start pumping the once-vacuum full of exhaust immediately. Well, it'd run fine until Famine came along.
 
keef
Let's see...

The gas tank is filled with gasoline, correct? And the airtank you speak of is the source of air/oxygen for the intake of the engine. To make it simple we'll forget about the pressure of the tank or its capacity and disregard all the air-tite business and say this:
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thats what I was getting at. Any other thoughts from anyone?
 
Small_Fryz
why would the battery need to be sealed?
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I think there is water in car batteries. I could be wrong though. Another general comment, not to get off topic but whenever I put 2 spaces after a period something weird happens in the little typing window.
 
The "un-seales" ones do not have water, they have something else that I cant remember at the moment. But other cheaper batteries do contair water and you sometimes hav to fill them up, its a pain in the a$$ if you ask me, just get a sealed one.:)
 
The vacuum would have a scavenging effect on the exhaust. :)

Being in a complete vacuum you wouldn't have wind resistance meaning the cars top speed would only be limited to gearing, friction and gravity.

Small_Fryz
why would the battery need to be sealed?
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Because the vacuum would suck out all the electrolyte.
 
VIPERGTSR01
The vacuum would have a scavenging effect on the exhaust. :)
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In fact, wouldn't the vacuum just use the exhaust pipe/system as a big straw, pulling some air/gas from the engine during the time that the intake and exhaust valves are both open?
 
Wolfe2x7
In fact, wouldn't the vacuum just use the exhaust pipe/system as a big straw, pulling some air/gas from the engine during the time that the intake and exhaust valves are both open?
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Yeah it would, if the engine management was to supply enough fuel then it wont be a problem, except bad fuel economy and maybe some nice flames. :)
 
Other question is how would you cool the engine?

Vacuum means there is no air for the heat energy to be transfered to, be it directly or through a radiator.
 
VIPERGTSR01
Yeah it would, if the engine management was to supply enough fuel then it wont be a problem, except bad fuel economy and maybe some nice flames. :)
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Or not, considering you're in a vacuum.

Oh yeah... Your windows would also explode and you would die of from the lack of oxygen, and the deoxygenation of your blood. Basically, all your vessels would explode and your eyeballs would go off like cherry bombs. ;)


...but there wouldn't be flames.
 
Wolfe2x7
No point in having a freezer if there's no air or anything for the freezer to cool.
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encase the engine in a sealed freezer

an after thought what would happen to the tyres? they wouldnt seal properly would they?
 
Omnis
...but there wouldn't be flames.
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No? They have flames in space don't they? coming out of the back of all those space ships? Except in Red Dwarf, of course, which is powered by a 60W light bulb...💡

If there's an oxygen supply and a fuel supply, then shurely there will be flames.:dopey:

Let there be flames, please.
 
FastEddie12
If there's an oxygen supply
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I think we've just run into the first problem with Fast Eddie's Flames in Space Theory... :D
 
ExigeExcel
Other question is how would you cool the engine?

Vacuum means there is no air for the heat energy to be transfered to, be it directly or through a radiator.
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Space is cold. If the vacuum is also very cold, engine cooling won't be a problem. Heat would escape the engine like the heat of your body if you went for a spacewalk with an uninsulated suit. All you need is a tempurature difference, and the heat will be shed through radiation.
 
Omnis
Or not, considering you're in a vacuum.
...but there wouldn't be flames.
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Well the oxygen and fuel is being supplied by a seperate source and if they are being drawn through the exhaust by the vacuum while there is a slight valve overlap period, you would have a mix of oxygen, fuel and heat in the exhaust that could ignite a flame in the exhaust, could it not? Or would the vacuum draw it out so fast that it wouldnt have a chance?
 
You guys are making this waay compicated. The bottom line is that an engine would run just fine if the battery, gas tank, and oxygen supply were sealed. I don't know about cooling--it seems to me that there would have to be some particles for the heat to tranfer to, but since the exhaust gases would fill the room I'm imagining, you would have particles immediately. Maybe you shoud try the experiment.
 
keef
Maybe you shoud try the experiment.
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OK, I'll nick some oxygen bottles from the hospital; if we use a car that runs on LPG the tank will already be pressurised; now has anyone got a vacuum chamber big enough to hold a car?

DAMN!:ouch:
 
I've been reading this one since the beginning, and I'm still trying to figure out how to vacuum-proof the rubber hoses (any bubbles in the coolant will pop the radiator hoses)... not to mention the fact that the air intake itself would have to be vacuum proofed.

Considering everything is vacuum proofed... you'd have to figure how much greater the scavenging effect the vacuum would create over normal air. Too great a scavenging effect and the engine won't idle at all (ever drive a c ar without an exhaust?... this just makes it ten times worse) but if the exhaust is tight enough, the engine will probably run until it overheats.

How long it will run is entirely dependent on where the vacuum chamber is located. Is it on Earth, at say, 80 degrees F? Is it in space, at some unimaginably cold temperature? (In which case, you'd have to have the engine running already to keep the coolant from freezing).

If it's out in a cold vacuum, you could keep the engine semi-cool by opening the hood and removing the front bumper, exposing both radiator and engine to space, painting the radiator black and positioning the front end of the car in shadow (away from any light sources), to allow the heat to radiate away.

Don't know if it's enough, though... you might need a bigger radiator.
 
This is all way beyond my knowledge. The whole discussion got way bigger than I ever thought. Makes for a pretty good read even though I may not be able to contribute very much.
 

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