| Topic: |
Religions > Atheism |
| User: |
"Uncle Buck" |
| Date: |
02 Oct 2005 05:46:29 AM |
| Object: |
OT: Vacuum baloons? |
Helium-filled baloons float because helium is lighter than air. A
vacuum is even lighter still, but you can't fill a baloon with a
vaccum.
I've often contemplated the problems involved with making such a thing
as a vacuum baloon. The problem as I understand it is that we don't
have a material that's both sturdy enough to withstand collapsing into
the vacuum while being light enough to acquire any sort of bouyancy
from it. The baloon as I imagine it would be almost like bubble-thin
glass which - while perhaps fragile - would of necessity not break
simply from the vacuum.
Are we anywhere _near_ such a thing yet? Just curious.
--
L8r,
Uncle Buck
_o-O=~_o-O=~_o-O=~_o-O=~_o-O=~_o-O=~_o-O=
Those first to step up and say,
"Now is not the time for placing blame"
...
...are quite often to blame....
_o-O=~_o-O=~_o-O=~_o-O=~_o-O=~_o-O=~_o-O=
.
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| User: "Therion Ware" |
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| Title: Re: OT: Vacuum baloons? |
02 Oct 2005 06:09:17 AM |
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On Sun, 02 Oct 2005 06:46:29 -0400 in alt.atheism, Uncle Buck (Uncle
Buck <UncleBuck@SpamMeNot.com>) said, directing the reply to
alt.atheism
Helium-filled baloons float because helium is lighter than air. A
vacuum is even lighter still, but you can't fill a baloon with a
vaccum.
I've often contemplated the problems involved with making such a thing
as a vacuum baloon. The problem as I understand it is that we don't
have a material that's both sturdy enough to withstand collapsing into
the vacuum while being light enough to acquire any sort of bouyancy
from it. The baloon as I imagine it would be almost like bubble-thin
glass which - while perhaps fragile - would of necessity not break
simply from the vacuum.
Are we anywhere _near_ such a thing yet? Just curious.
As you say the problem is the strength to weight / volume ratio of the
material that contains the vacuum.
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| User: "Denis Loubet" |
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| Title: Re: Vacuum baloons? |
02 Oct 2005 11:30:56 AM |
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"Uncle Buck" <UncleBuck@SpamMeNot.com> wrote in message
news:qgevj1t36n2pl5chkl712q1tgs4e5cmvlu@4ax.com...
Helium-filled baloons float because helium is lighter than air. A
vacuum is even lighter still, but you can't fill a baloon with a
vaccum.
I've often contemplated the problems involved with making such a thing
as a vacuum baloon. The problem as I understand it is that we don't
have a material that's both sturdy enough to withstand collapsing into
the vacuum while being light enough to acquire any sort of bouyancy
from it. The baloon as I imagine it would be almost like bubble-thin
glass which - while perhaps fragile - would of necessity not break
simply from the vacuum.
Are we anywhere _near_ such a thing yet? Just curious.
We'd just get emotional reports over the radio of the Hindinburg Implosion.
--
Denis Loubet
dloubet@io.com
http://www.io.com/~dloubet
http://www.ashenempires.com
.
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| User: "Uncle Buck" |
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| Title: Re: Vacuum baloons? |
02 Oct 2005 02:27:40 PM |
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On Sun, 2 Oct 2005 11:30:56 -0500, "Denis Loubet" <dloubet@io.com>
wrote:
"Uncle Buck" <UncleBuck@SpamMeNot.com> wrote in message
news:qgevj1t36n2pl5chkl712q1tgs4e5cmvlu@4ax.com...
Helium-filled baloons float because helium is lighter than air. A
vacuum is even lighter still, but you can't fill a baloon with a
vaccum.
I've often contemplated the problems involved with making such a thing
as a vacuum baloon. The problem as I understand it is that we don't
have a material that's both sturdy enough to withstand collapsing into
the vacuum while being light enough to acquire any sort of bouyancy
from it. The baloon as I imagine it would be almost like bubble-thin
glass which - while perhaps fragile - would of necessity not break
simply from the vacuum.
Are we anywhere _near_ such a thing yet? Just curious.
We'd just get emotional reports over the radio of the Hindinburg Implosion.
Ah, yes, the craft would develop a leak and everyone would
mysteriously <FWOOP!> disappear....
--
L8r,
Uncle Buck
_o-O=~_o-O=~_o-O=~_o-O=~_o-O=~_o-O=~_o-O=
Those first to step up and say,
"Now is not the time for placing blame"
...
...are quite often to blame....
_o-O=~_o-O=~_o-O=~_o-O=~_o-O=~_o-O=~_o-O=
.
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| User: "Denis Loubet" |
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| Title: Re: Vacuum baloons? |
02 Oct 2005 05:34:12 PM |
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"Uncle Buck" <UncleBuck@SpamMeNot.com> wrote in message
news:44d0k1te88305e1oeo29513evejsrr44al@4ax.com...
On Sun, 2 Oct 2005 11:30:56 -0500, "Denis Loubet" <dloubet@io.com>
wrote:
"Uncle Buck" <UncleBuck@SpamMeNot.com> wrote in message
news:qgevj1t36n2pl5chkl712q1tgs4e5cmvlu@4ax.com...
Helium-filled baloons float because helium is lighter than air. A
vacuum is even lighter still, but you can't fill a baloon with a
vaccum.
I've often contemplated the problems involved with making such a thing
as a vacuum baloon. The problem as I understand it is that we don't
have a material that's both sturdy enough to withstand collapsing into
the vacuum while being light enough to acquire any sort of bouyancy
from it. The baloon as I imagine it would be almost like bubble-thin
glass which - while perhaps fragile - would of necessity not break
simply from the vacuum.
Are we anywhere _near_ such a thing yet? Just curious.
We'd just get emotional reports over the radio of the Hindinburg
Implosion.
Ah, yes, the craft would develop a leak and everyone would
mysteriously <FWOOP!> disappear....
"I see the vast vacship approaching the pylon--Oh no! The vacuum envelope
has collapsed into itself. I can see it falling to the ground! It's about
the size of a deck of playing cards. Hang on--"
(static)
"Ok, I'm tapping the envelope with the toe of my shoe. Oh, the humanity."
--
Denis Loubet
dloubet@io.com
http://www.io.com/~dloubet
http://www.ashenempires.com
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| User: "quibbler" |
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| Title: Re: OT: Vacuum baloons? |
02 Oct 2005 11:01:24 AM |
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In article <qgevj1t36n2pl5chkl712q1tgs4e5cmvlu@4ax.com>,
UncleBuck@SpamMeNot.com says...
Helium-filled baloons float because helium is lighter than air. A
vacuum is even lighter still, but you can't fill a baloon with a
vaccum.
Perhaps not a complete vacuum. However, you could fill it with something
like mutually repelling electrostatically charged gas molecules. Their
tendancy to repel each other and to repel the sides of the gas envelope
should preserve a large displacement volume without the normal weight
associated with gases. Of course, a simpler technique is to use heated
helium or heated hydrogen balloons. Many plastic canopies can be made
fairly heat resistant so that lower density, heated lift gases can be
used.
I've often contemplated the problems involved with making such a thing
as a vacuum baloon. The problem as I understand it is that we don't
have a material that's both sturdy enough to withstand collapsing into
the vacuum while being light enough to acquire any sort of bouyancy
from it. The baloon as I imagine it would be almost like bubble-thin
glass which - while perhaps fragile - would of necessity not break
simply from the vacuum.
Are we anywhere _near_ such a thing yet? Just curious.
I'd imagine that we might be able to use nano-technology to build things
like lattices of carbon fiber. But I'm not sure if the lattice gaps
could be made small enough to keep out things like hydrogen. You could,
however, continuously expel hydrogen that did leak in, or possible use
use an electric charge to try to repel certain kinds of atoms and ions.
Actually, it doesn't seem like a perfect vacuum should be necessary, as
there are light atmospheric gases going up hundreds of miles above the
earth.
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| User: "" |
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| Title: Re: OT: Vacuum baloons? |
02 Oct 2005 05:47:56 PM |
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On Sun, 02 Oct 2005 06:46:29 -0400, Uncle Buck
<UncleBuck@SpamMeNot.com> wrote:
Helium-filled baloons float because helium is lighter than air. A
vacuum is even lighter still, but you can't fill a baloon with a
vaccum.
I've often contemplated the problems involved with making such a thing
as a vacuum baloon. The problem as I understand it is that we don't
have a material that's both sturdy enough to withstand collapsing into
the vacuum while being light enough to acquire any sort of bouyancy
from it. The baloon as I imagine it would be almost like bubble-thin
glass which - while perhaps fragile - would of necessity not break
simply from the vacuum.
Are we anywhere _near_ such a thing yet? Just curious.
Good questions and wonderful problems to contemplate. Glass sounds
good because you need something that is also non porous. Even helium
balloons lose the helium because of porosity.
The material itself doesn't have to be as light or lighter than air,
the same way boats float even though heavier than water.
Metal should work but it'd have to be perfectly round to withstand the
air pressure from the outside, assuming a perfect vacuum.
The thing would have to be manufactured in a vacuum, as a valve used
to evacuate it would act as a structural flaw, defeating the strength
provided by the perfectness of the roundness. Once manufactured, and
introduced into the atmosphere, it should rise rapidly and higher than
a gas filled sphere since there is nothing to expand and burst it as
atmospheric pressure diminishes.
Now, if a practical use for it is found! Like, imagine hollow parts of
airplanes filled with these "vacuum balls" - not to expect the plane
to fly itself, but to reduce it's weight a bit and save fuel? Imagine
trying to explain that to the people who have to spend money on their
aircraft. BZZZZTTT! They don't even do enough PM to avoid unexplained
tragic explosions on takeoff and landing anymore. It ain't worth the
money to save lives anymore. Money now. ***** later.
Someone with enough of his or her own money would have to do it, test
it, prove it then try to sell it - and be bought off by the special
interest lobbyists.
DAMN! OOPS I did it again.
Drat.
TheRain
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| User: "Jim Burns" |
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| Title: Re: OT: Vacuum baloons? |
02 Oct 2005 02:25:33 PM |
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Uncle Buck wrote:
Helium-filled baloons float because helium is lighter than air.
A vacuum is even lighter still, but you can't fill a baloon
with a vaccum.
I've often contemplated the problems involved with making such
a thing as a vacuum baloon. The problem as I understand it is
that we don't have a material that's both sturdy enough to
withstand collapsing into the vacuum while being light enough
to acquire any sort of bouyancy from it. The baloon as I imagine
it would be almost like bubble-thin glass which - while perhaps
fragile - would of necessity not break simply from the vacuum.
Are we anywhere _near_ such a thing yet? Just curious.
I did a little physics to get an idea of what might be
required for your vacuum balloon.
The critical condition seems to be
3/2 RT/M < S/D
where M is the (average) gram-molecular weight of the gas,
R is the gas constant, T is the absolute temperature of the gas,
S is the /compressive/ strength and D is the density of
the material the balloon is made of. (I'm assuming an ideal gas.)
If the strength/density ratio is less than that, then there
is no vacuum balloon possible. If it's more, then there will
be a range of values for the radius and thickness where the
ballon's skin is thick enough to keep from collapsing and also
thin enough to float.
I'm going to find a really good material and see how close
it comes to working. <google google>
http://www.matweb.com/search/SpecificMaterial.asp?bassnum=O4210
Overview - Thermoplastic Polyimide, Glass Fiber
Density 1.35 - 1.9 g/cc
Compressive Yield Strength 220 MPa
Which (optimistically) gives me S/D = 160 J/g
For a 79/21 N2/O2 mix at room temperature, I get M = 28.8 g/mol
and T = 300 K, and thus 3/2 RT/M = 130 J/g
So, I would have to say, as a first guess, that, yes, we could
just barely make a vacuum balloon under Earth conditions with
known materials.
I would have to go back and do some more physics to know, but
my hunch is that the vacuum ballon would settle at a particular
height above sea level, where the skin+vacuum density matches
the local air density. While the ballon would not collapse
at that height, it might do so lower down where the pressure is
higher. The trick would seem to be getting the ballon up
to the altitude it was designed for. One method might be to keep
it "inflated" lower down with heated helium or whatever,
and only evacuate it at or near its design altitude.
I suppose there is no absolute reason that we couldn't have
a vacuum balloon floating all the way up to the edge of space,
100 km or so. It would have to have very thin walls though,
and would be very delicate and very difficult to get high
enough that it wouldn't collapse. Also, I suppose it would
be as susceptible to punctures letting air in as a normal
balloon would be to punctures letting its helium or
whatever out.
If you look at the formula, it looks like it gets easier to
find an accceptable skin material as the surrounding gas gets
colder and heavier. Of course this is just the opposite of
what you want on the inside of, for example, a hot air balloon
or a hydrogen or helium balloon, so it looks like I didn't
go too far wrong there.
Jim Burns
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| User: "Mike Painter" |
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| Title: Re: OT: Vacuum baloons? |
02 Oct 2005 06:08:48 PM |
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Jim Burns wrote:
Uncle Buck wrote:
Helium-filled baloons float because helium is lighter than air.
A vacuum is even lighter still, but you can't fill a baloon
with a vaccum.
I've often contemplated the problems involved with making such
a thing as a vacuum baloon. The problem as I understand it is
that we don't have a material that's both sturdy enough to
withstand collapsing into the vacuum while being light enough
to acquire any sort of bouyancy from it. The baloon as I imagine
it would be almost like bubble-thin glass which - while perhaps
fragile - would of necessity not break simply from the vacuum.
Are we anywhere _near_ such a thing yet? Just curious.
I did a little physics to get an idea of what might be
required for your vacuum balloon.
The critical condition seems to be
3/2 RT/M < S/D
where M is the (average) gram-molecular weight of the gas,
R is the gas constant, T is the absolute temperature of the gas,
S is the /compressive/ strength and D is the density of
the material the balloon is made of. (I'm assuming an ideal gas.)
If the strength/density ratio is less than that, then there
is no vacuum balloon possible. If it's more, then there will
be a range of values for the radius and thickness where the
ballon's skin is thick enough to keep from collapsing and also
thin enough to float.
I'm going to find a really good material and see how close
it comes to working. <google google>
http://www.matweb.com/search/SpecificMaterial.asp?bassnum=O4210
Overview - Thermoplastic Polyimide, Glass Fiber
Density 1.35 - 1.9 g/cc
Compressive Yield Strength 220 MPa
Which (optimistically) gives me S/D = 160 J/g
For a 79/21 N2/O2 mix at room temperature, I get M = 28.8 g/mol
and T = 300 K, and thus 3/2 RT/M = 130 J/g
So, I would have to say, as a first guess, that, yes, we could
just barely make a vacuum balloon under Earth conditions with
known materials.
If a gas were used with the same material it would not have to be rigid,
just gas tight, so it could be a lot thinner. I suspect that a vaccuum
balloon would have to be monsterous in size before the saving in material
would be overcome by the rigid structure.
I would have to go back and do some more physics to know, but
my hunch is that the vacuum ballon would settle at a particular
height above sea level, where the skin+vacuum density matches
the local air density.
Archimedes Principal says it would but only if it is rigid and I don't think
you've solved that problem. The force on the bottom of the balloon would be
greater than that at the top.
If it is not rigid then this force will collapse it a little, reducing lift.
It then sinks a little, collapse a bit more and it's on it's way back to
earth.
I suspect only General Products could supply such a craft.
While the ballon would not collapse
at that height, it might do so lower down where the pressure is
higher. The trick would seem to be getting the ballon up
to the altitude it was designed for. One method might be to keep
it "inflated" lower down with heated helium or whatever,
and only evacuate it at or near its design altitude.
I suppose there is no absolute reason that we couldn't have
a vacuum balloon floating all the way up to the edge of space,
100 km or so. It would have to have very thin walls though,
and would be very delicate and very difficult to get high
enough that it wouldn't collapse. Also, I suppose it would
be as susceptible to punctures letting air in as a normal
balloon would be to punctures letting its helium or
whatever out.
If you look at the formula, it looks like it gets easier to
find an accceptable skin material as the surrounding gas gets
colder and heavier. Of course this is just the opposite of
what you want on the inside of, for example, a hot air balloon
or a hydrogen or helium balloon, so it looks like I didn't
go too far wrong there.
Jim Burns
.
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| User: "Harry F. Leopold" |
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| Title: Re: OT: Vacuum baloons? |
03 Oct 2005 01:01:28 PM |
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On Sun, 2 Oct 2005 18:08:48 -0500, Mike Painter wrote
(in article <4MZ%e.1055$xD7.616@newssvr29.news.prodigy.net>):
Jim Burns wrote:
Uncle Buck wrote:
Helium-filled baloons float because helium is lighter than air.
A vacuum is even lighter still, but you can't fill a baloon
with a vaccum.
I've often contemplated the problems involved with making such
a thing as a vacuum baloon. The problem as I understand it is
that we don't have a material that's both sturdy enough to
withstand collapsing into the vacuum while being light enough
to acquire any sort of bouyancy from it. The baloon as I imagine
it would be almost like bubble-thin glass which - while perhaps
fragile - would of necessity not break simply from the vacuum.
Are we anywhere _near_ such a thing yet? Just curious.
I did a little physics to get an idea of what might be
required for your vacuum balloon.
The critical condition seems to be
3/2 RT/M < S/D
where M is the (average) gram-molecular weight of the gas,
R is the gas constant, T is the absolute temperature of the gas,
S is the /compressive/ strength and D is the density of
the material the balloon is made of. (I'm assuming an ideal gas.)
If the strength/density ratio is less than that, then there
is no vacuum balloon possible. If it's more, then there will
be a range of values for the radius and thickness where the
ballon's skin is thick enough to keep from collapsing and also
thin enough to float.
I'm going to find a really good material and see how close
it comes to working. <google google>
http://www.matweb.com/search/SpecificMaterial.asp?bassnum=O4210
Overview - Thermoplastic Polyimide, Glass Fiber
Density 1.35 - 1.9 g/cc
Compressive Yield Strength 220 MPa
Which (optimistically) gives me S/D = 160 J/g
For a 79/21 N2/O2 mix at room temperature, I get M = 28.8 g/mol
and T = 300 K, and thus 3/2 RT/M = 130 J/g
So, I would have to say, as a first guess, that, yes, we could
just barely make a vacuum balloon under Earth conditions with
known materials.
Of course pumping down to a perfect vacuum is impossible, (and just getting a
pretty decent vacuum is expensive) so you would have to build the thing even
larger, and heavier, to get the same lift.
Far better would be to start with some gas, does not really matter what it
is, and use heat to cause it to expand. Cheaper all the way around. Even
plain, old air would work, add heat to cause it to expand. (For extra lift,
use hydrogen, just be damned careful not to blow yourself or the neighbors
up.)
If a gas were used with the same material it would not have to be rigid,
just gas tight, so it could be a lot thinner. I suspect that a vaccuum
balloon would have to be monsterous in size before the saving in material
would be overcome by the rigid structure.
I would have to go back and do some more physics to know, but
my hunch is that the vacuum ballon would settle at a particular
height above sea level, where the skin+vacuum density matches
the local air density.
Archimedes Principal says it would but only if it is rigid and I don't think
you've solved that problem. The force on the bottom of the balloon would be
greater than that at the top.
If it is not rigid then this force will collapse it a little, reducing lift.
It then sinks a little, collapse a bit more and it's on it's way back to
earth.
I suspect only General Products could supply such a craft.
And, unfortunately, they are no longer in business.
--
Harry F. Leopold
aa #2076
AA/Vet #4
The Prints of Darkness
(remove gene to email)
America, making tomorrow's terrorists today.
.
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| User: "Walter Bushell" |
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| Title: Re: OT: Vacuum baloons? |
03 Oct 2005 11:54:05 PM |
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In article <0001HW.BF66DC280032AC4DF0284550@news.central.cox.net>,
Harry F. Leopold <hleopold@coxyx.net> wrote:
On Sun, 2 Oct 2005 18:08:48 -0500, Mike Painter wrote
(in article <4MZ%e.1055$xD7.616@newssvr29.news.prodigy.net>):
Jim Burns wrote:
Uncle Buck wrote:
Helium-filled baloons float because helium is lighter than air.
A vacuum is even lighter still, but you can't fill a baloon
with a vaccum.
I've often contemplated the problems involved with making such
a thing as a vacuum baloon. The problem as I understand it is
that we don't have a material that's both sturdy enough to
withstand collapsing into the vacuum while being light enough
to acquire any sort of bouyancy from it. The baloon as I imagine
it would be almost like bubble-thin glass which - while perhaps
fragile - would of necessity not break simply from the vacuum.
Are we anywhere _near_ such a thing yet? Just curious.
I did a little physics to get an idea of what might be
required for your vacuum balloon.
The critical condition seems to be
3/2 RT/M < S/D
where M is the (average) gram-molecular weight of the gas,
R is the gas constant, T is the absolute temperature of the gas,
S is the /compressive/ strength and D is the density of
the material the balloon is made of. (I'm assuming an ideal gas.)
If the strength/density ratio is less than that, then there
is no vacuum balloon possible. If it's more, then there will
be a range of values for the radius and thickness where the
ballon's skin is thick enough to keep from collapsing and also
thin enough to float.
I'm going to find a really good material and see how close
it comes to working. <google google>
http://www.matweb.com/search/SpecificMaterial.asp?bassnum=O4210
Overview - Thermoplastic Polyimide, Glass Fiber
Density 1.35 - 1.9 g/cc
Compressive Yield Strength 220 MPa
Which (optimistically) gives me S/D = 160 J/g
For a 79/21 N2/O2 mix at room temperature, I get M = 28.8 g/mol
and T = 300 K, and thus 3/2 RT/M = 130 J/g
So, I would have to say, as a first guess, that, yes, we could
just barely make a vacuum balloon under Earth conditions with
known materials.
Of course pumping down to a perfect vacuum is impossible, (and just getting a
pretty decent vacuum is expensive) so you would have to build the thing even
larger, and heavier, to get the same lift.
Far better would be to start with some gas, does not really matter what it
is, and use heat to cause it to expand. Cheaper all the way around. Even
plain, old air would work, add heat to cause it to expand. (For extra lift,
use hydrogen, just be damned careful not to blow yourself or the neighbors
up.)
If a gas were used with the same material it would not have to be rigid,
just gas tight, so it could be a lot thinner. I suspect that a vaccuum
balloon would have to be monsterous in size before the saving in material
would be overcome by the rigid structure.
I would have to go back and do some more physics to know, but
my hunch is that the vacuum ballon would settle at a particular
height above sea level, where the skin+vacuum density matches
the local air density.
Archimedes Principal says it would but only if it is rigid and I don't
think
you've solved that problem. The force on the bottom of the balloon would be
greater than that at the top.
If it is not rigid then this force will collapse it a little, reducing
lift.
It then sinks a little, collapse a bit more and it's on it's way back to
earth.
I suspect only General Products could supply such a craft.
And, unfortunately, they are no longer in business.
hey, they still are. Only they haven't contacted us yet. They won't go
out of business for hundreds of years.
--
Guns don't kill people; automobiles kill people.
.
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| User: "Uncle Buck" |
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| Title: Re: OT: Vacuum baloons? |
02 Oct 2005 05:37:42 PM |
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On Sun, 02 Oct 2005 15:25:33 -0400, Jim Burns <burns.87@osu.edu>
wrote:
Uncle Buck wrote:
Helium-filled baloons float because helium is lighter than air.
A vacuum is even lighter still, but you can't fill a baloon
with a vaccum.
I've often contemplated the problems involved with making such
a thing as a vacuum baloon. The problem as I understand it is
that we don't have a material that's both sturdy enough to
withstand collapsing into the vacuum while being light enough
to acquire any sort of bouyancy from it. The baloon as I imagine
it would be almost like bubble-thin glass which - while perhaps
fragile - would of necessity not break simply from the vacuum.
Are we anywhere _near_ such a thing yet? Just curious.
I did a little physics to get an idea of what might be
required for your vacuum balloon.
And for that, I am both astonished and deeply grateful. :-)
The critical condition seems to be
3/2 RT/M < S/D
where M is the (average) gram-molecular weight of the gas,
R is the gas constant, T is the absolute temperature of the gas,
S is the /compressive/ strength and D is the density of
the material the balloon is made of. (I'm assuming an ideal gas.)
If the strength/density ratio is less than that, then there
is no vacuum balloon possible. If it's more, then there will
be a range of values for the radius and thickness where the
ballon's skin is thick enough to keep from collapsing and also
thin enough to float.
I'm going to find a really good material and see how close
it comes to working. <google google>
http://www.matweb.com/search/SpecificMaterial.asp?bassnum=O4210
Overview - Thermoplastic Polyimide, Glass Fiber
Density 1.35 - 1.9 g/cc
Compressive Yield Strength 220 MPa
Which (optimistically) gives me S/D = 160 J/g
For a 79/21 N2/O2 mix at room temperature, I get M = 28.8 g/mol
and T = 300 K, and thus 3/2 RT/M = 130 J/g
So, I would have to say, as a first guess, that, yes, we could
just barely make a vacuum balloon under Earth conditions with
known materials.
YES!!! :-) This is fascinating stuff you're hittin' me with, here.
:-)
I would have to go back and do some more physics to know, but
my hunch is that the vacuum ballon would settle at a particular
height above sea level, where the skin+vacuum density matches
the local air density.
That's my guess as well. I wonder what practical uses such a baloon
could have? :-?
While the ballon would not collapse
at that height, it might do so lower down where the pressure is
higher. The trick would seem to be getting the ballon up
to the altitude it was designed for. One method might be to keep
it "inflated" lower down with heated helium or whatever,
and only evacuate it at or near its design altitude.
I suppose there is no absolute reason that we couldn't have
a vacuum balloon floating all the way up to the edge of space,
100 km or so. It would have to have very thin walls though,
and would be very delicate and very difficult to get high
enough that it wouldn't collapse. Also, I suppose it would
be as susceptible to punctures letting air in as a normal
balloon would be to punctures letting its helium or
whatever out.
If you look at the formula, it looks like it gets easier to
find an accceptable skin material as the surrounding gas gets
colder and heavier.
Sounds about right. The thicker the gas, the greater the potential of
the density differential between the inside and outside of the baloon.
Greater density differentials convey greater buoyancy, thus permitting
thicker, heavier (and therefore stronger) materials to be used.
It does make me wonder. Just looking at their structure and
disregarding the probability of implosion (I don't believe this would
work in a real-world sense), would ordinary "vacuum-sealed" light
bulbs as we produce them today be structurally capable of floating in
a chamber of sufficiently compressed gas of a certain type? Or would
the gas need to be so dense that it has effectively become a liquid?
:-? Hmmnn... I would guess that most gasses would at least need to
come close to their precipitation point for 'modern' light bulbs to
float (assuming unbreakability for argument's sake), but then I've not
looked into the matter very deeply.
Of course this is just the opposite of
what you want on the inside of, for example, a hot air balloon
or a hydrogen or helium balloon, so it looks like I didn't
go too far wrong there.
Not at all! Nice lobe-work! :-)
It all brings to mind a novelty which, if I understand you correctly,
we could actually produce now (though I guess it'd be pretty
expensive): Have a large sphere (or other container if it's more to
your liking) filled with compressed gas, and inside this container
little "vacuum baloons" (of whatever sort we're capable of making now
- they wouldn't have to be buoyant in our atmosphere, only in the
compressed gas of the container). It would make for an interesting
kind of leveller measuring device, perhaps an interesting toy as well.
And if they ever _could_ become practical for production in normal
Earth atmosphere, vacuum baloons would be a pretty nifty advertising
gimmick, I'd think. Take the scenario of a sphere with a marble
inside it and using inertia to make the marble roll around on the
inside "equator" of the thing. Trying to do that to a sphere with a
vacuum baloon inside of it instead of a marble would make for a rather
unusual sensation, I would think.
Hhhhmmmnnnn.... I think I've got an idea.... Later, dude! :-)
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