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Author Topic: why does a flame become spherical in micro-gravity-ISS  (Read 2416 times)

Offline gazza711

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Why does a flame not flow up in microgravity.it curls into a sphere?


 

Offline chiralSPO

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Re: why does a flame become spherical in micro-gravity-ISS
« Reply #1 on: 06/07/2015 19:56:42 »
A flame on earth "goes up" because the cold air around it sinks (hot air is more buoyant than cold air). In microgravity, there is no up or down, and no buoyancy...
 

Offline jccc

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Re: why does a flame become spherical in micro-gravity-ISS
« Reply #2 on: 06/07/2015 20:37:40 »
gravity makes all gas and liquid form into sphere, because on the surface of the sphere the strength of gravity is equal.

gravity will make solid matters attract together, but not enough to break the structure of the matters, so they stay same shape.

that's why all the stars and planets are sphere.
 

Offline chiralSPO

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Re: why does a flame become spherical in micro-gravity-ISS
« Reply #3 on: 06/07/2015 21:19:15 »
There are many different underlying factors that lead to spherical bodies.

Gravity causes large bodies to adopt a spherical shape because the sphere allows every part to be as close as possible to the center. Any deviation from the sphere increases the distance from whatever moved to the center (the only way to move is away, or "up").

Intermolecular forces (the underlying cause of "surface tension") cause bodies of water or other liquids to adopt spherical shapes because the sphere allows the greatest number of molecules (or atoms) to be next to other molecules (or atoms) of the same type, which is favorable. For instance, a water molecule is "happiest" or most stable, when it is in contact with two other water molecules. This means that there is an "energetic tax" for having water molecules with only one neighbor (water molecules at the surface). So the shape with the least amount of surface area will be the most stable (and this happens to be a sphere).

Of course, this spherical preference can be overridden when other forces are at play. For instance, most lakes are not spherical, because the gravity of the Earth is strong enough to collapse a sphere of water large enough to be a lake. For smaller amounts of water (drops/droplets) the spherical preference overrides the gravitational force.
 

Offline gazza711

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Re: why does a flame become spherical in micro-gravity-ISS
« Reply #4 on: 06/07/2015 21:23:32 »
gravity makes all gas and liquid form into sphere, because on the surface of the sphere the strength of gravity is equal.

gravity will make solid matters attract together, but not enough to break the structure of the matters, so they stay same shape.

that's why all the stars and planets are sphere.
im talking about a flame on the international space station-not earth.Im sure you knew that and agree that gravity is still pulling down,but the flame is not accelerating in any direction due to inertia,and if heat rises-where did the heat go?
Gravity causes things to collide-possibly but not proven-joking-joking.
If things collide,how do they remain spherical.have you seen the trick of inflating a balloon by sucking the air out of a bottle.the balloon is inserted into the bottle an the open end of the balloon tightly wraped round the bottle neck hanging into the bottle.You then have a sealed bottle.Then pierce a hole in the side and suck air out-the balloon inflates.
I know that has nuthin to do with this but was interesting enough to post-youtube#crackpot
 

Offline gazza711

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Re: why does a flame become spherical in micro-gravity-ISS
« Reply #5 on: 06/07/2015 21:26:03 »
There are many different underlying factors that lead to spherical bodies.

Gravity causes large bodies to adopt a spherical shape because the sphere allows every part to be as close as possible to the center. Any deviation from the sphere increases the distance from whatever moved to the center (the only way to move is away, or "up").

Intermolecular forces (the underlying cause of "surface tension") cause bodies of water or other liquids to adopt spherical shapes because the sphere allows the greatest number of molecules (or atoms) to be next to other molecules (or atoms) of the same type, which is favorable. For instance, a water molecule is "happiest" or most stable, when it is in contact with two other water molecules. This means that there is an "energetic tax" for having water molecules with only one neighbor (water molecules at the surface). So the shape with the least amount of surface area will be the most stable (and this happens to be a sphere).

Of course, this spherical preference can be overridden when other forces are at play. For instance, most lakes are not spherical, because the gravity of the Earth is strong enough to collapse a sphere of water large enough to be a lake. For smaller amounts of water (drops/droplets) the spherical preference overrides the gravitational force.
just talking about a flame here.i understand the liquid part,but not the flame example.
 

Offline chiralSPO

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Re: why does a flame become spherical in micro-gravity-ISS
« Reply #6 on: 06/07/2015 21:44:29 »
The thing to remember here is that a flame is not an object. It is a chemical reaction. The spherical shape here (
) is because flammable molecules are moving out from the tip of the wick in random directions. Close to the wick the only molecules around are the fuel molecules, but slightly further out there is some oxygen. Too far from the wick is only oxygen, and no fuel. The flame occurs in a very thin shell around the wick at a distance where there is the right ratio of fuel to oxygen.

On Earth, this pattern is disrupted by turbulence and airflow generated from the difference in buoyancy between the flame and surrounding atmosphere.
 

Offline alancalverd

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Re: why does a flame become spherical in micro-gravity-ISS
« Reply #7 on: 07/07/2015 01:03:22 »
Why does a flame not flow up in microgravity.it curls into a sphere?

Because by definition there is no "up" in microgravity - or at best only a "micro-up" - so the process of combustion takes place symmetrically.
 

Offline gazza711

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Re: why does a flame become spherical in micro-gravity-ISS
« Reply #8 on: 07/07/2015 19:27:52 »
Why does a flame not flow up in microgravity.it curls into a sphere?

Because by definition there is no "up" in microgravity - or at best only a "micro-up" - so the process of combustion takes place symmetrically.
Ok.how would you heat up the interior of iss if no convection?
 

Offline Colin2B

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Re: why does a flame become spherical in micro-gravity-ISS
« Reply #9 on: 07/07/2015 20:09:17 »
Ok.how would you heat up the interior of iss if no convection?
Radiated heat would still work. You could also use fans to circulate the air.
I assume fans would be needed to prevent CO2 building up  in pockets near someone's face. They would also be needed to circulate air otherwise the flame would burn up the O2 around it and go out!
 

Offline alancalverd

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Re: why does a flame become spherical in micro-gravity-ISS
« Reply #10 on: 07/07/2015 20:27:01 »

Ok.how would you heat up the interior of iss if no convection?


Air stagnation can be a problem in a space station. Instrument racks require either liquid or forced air cooling as convection is nonexistent. In the main cabin areas you can rely to some extent on people moving around to mix warm and cold air but you have to force-circulate the atmosphere anyway to remove carbon dioxide and water as well as regulate the temperature. 
 


The Naked Scientists Forum

Re: why does a flame become spherical in micro-gravity-ISS
« Reply #11 on: 07/07/2015 20:31:41 »

 

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