| |
 |
|
|
Science Forum Index » Chemistry Forum » Can a solid be lighter than air?...
Page 1 of 1
|
| Author |
Message |
| Doug Wedel... |
 Posted: Fri Jun 20, 2008 11:24 am |
|
|
|
Guest
|
Is there a materials scientist out there who could resolve a factual dispute
about aerogel?
Here is a website about aerogel
http://members.tripod.com/~geobeck/frontier/aerogels.html
that states: "Aerogels can actually be made lighter than air by forming them
in an atmosphere of helium, resulting in the world's only lighter-than-air
solids."
And here is another webite partly about aerogel
http://stardust.jpl.nasa.gov/overview/faq.html
that states: "Aerogel cannot be made less dense than air by filling it with
helium."
Does anyone know: which is it? |
|
|
| Back to top |
|
| Uncle Ben... |
| Posted: Fri Jun 20, 2008 2:21 pm |
|
|
|
Guest
|
On Jun 20, 12:24 pm, "Doug Wedel" <dougwe... at (no spam) earthlink.net> wrote:
Quote: Is there a materials scientist out there who could resolve a factual dispute
about aerogel?
Here is a website about aerogel
http://members.tripod.com/~geobeck/frontier/aerogels.html
that states: "Aerogels can actually be made lighter than air by forming them
in an atmosphere of helium, resulting in the world's only lighter-than-air
solids."
And here is another webite partly about aerogel
http://stardust.jpl.nasa.gov/overview/faq.html
that states: "Aerogel cannot be made less dense than air by filling it with
helium."
Does anyone know: which is it?
Is a helium balloon enough like an aerogel, although with only one
cell? If so, the answer is clear. If not, why not?
Ben |
|
|
| Back to top |
|
| prk via NatScience.com... |
| Posted: Fri Jun 20, 2008 7:30 pm |
|
|
|
Guest
|
|
| Back to top |
|
| N:dlzc D:aol T:com (dlzc)... |
| Posted: Fri Jun 20, 2008 10:19 pm |
|
|
|
Guest
|
Dear prk via NatScience.com:
"prk via NatScience.com" <u42669 at (no spam) uwe> wrote in message
news:85fb039ee339f at (no spam) uwe...
....
Quote: Aerogel is about 1 gram per cubic foot. If
you're talking about sea level air, the
answer seems to be yes. NASA's picking
nits.
Aerogels are formed by evaporation, so are porous. Aerogels are
"1 gram per cubic foot, plus air", so are neither capable of
retaining helium, nor floating.
I *don't* think NASA is picking nits. I think the first web page
is talking about something else, and just calling it an aerogel.
David A. Smith |
|
|
| Back to top |
|
| Bret Cahill... |
| Posted: Sat Jun 21, 2008 4:58 pm |
|
|
|
Guest
|
Quote: Is there a materials scientist out there who could resolve a factual dispute
about aerogel?
Here is a website about aerogel
http://members.tripod.com/~geobeck/frontier/aerogels.html
that states: "Aerogels can actually be made lighter than air by forming them
in an atmosphere of helium, resulting in the world's only lighter-than-air
solids."
And here is another webite partly about aerogel
http://stardust.jpl.nasa.gov/overview/faq.html
that states: �"Aerogel cannot be made less dense than air by filling it with
helium."
Does anyone know: which is it?
Helium doesn't get it. He is a _gas_ that is lighter than air. Any
balloon can be filled with He.
A _real_ lighter than air "solid" must be evacuated and still be able
to withstand 14.7 psi pressure on it's outer surface.
First, scaling doesn't change anything. If a small one doesn't work
neither will a big version.
Second, only a carbon nanotube structure is strong enough to withstand
14.7 psi pressure yet still be light enough to float.
And I'm not even sure nanotubes are strong enough.
This was a recurring and useless invention of mine -- I actually went
through the calculations three times completely forgetting my previous
attempts -- that I had to kill by driving a stake through its heart.
Bret Cahill |
|
|
| Back to top |
|
| Doug Wedel... |
| Posted: Sat Jun 21, 2008 10:29 pm |
|
|
|
Guest
|
Doug Wedel wrote
Quote: Is there a materials scientist out there who could resolve a factual
dispute
about aerogel?
Here is a website about aerogel
http://members.tripod.com/~geobeck/frontier/aerogels.html
that states: "Aerogels can actually be made lighter than air by forming
them
in an atmosphere of helium, resulting in the world's only lighter-than-air
solids."
And here is another webite partly about aerogel
http://stardust.jpl.nasa.gov/overview/faq.html
that states: ?"Aerogel cannot be made less dense than air by filling it
with
helium."
Does anyone know: which is it?
Bret Cahill wrote:
Quote: Helium doesn't get it. He is a _gas_ that is lighter than air. Any
balloon can be filled with He.
I sympathize. Aerogels are not "pure" solids. They certainly have some of
the
characteristics of solids, and some which balloons don't share -- eg. a
chunk of
aerogel has a definite shape and volume, and it is firm to the touch. But
on the
other hand aerogels do seem to violate other criteria of "solidity,"
i.e. aerogels are part fluid, therefore, they do not satisfy the criteria of
being "neither
liquid nor gaaseous;" also they are not "incapable of being seen through" --
aerogels
are bluish translucent semi-solids.
Quote: A _real_ lighter than air "solid" must be evacuated and still be able
to withstand 14.7 psi pressure on it's outer surface.
This comment reveals your special definition of "solid." After all, all
solids have voids in them. These voids are usually not filled with vacuums,
but rather, air. In some cases, these voids occur in airtight vesicles or
cells. So why isn't an aerogel a "solid" when we replace the standard
atmospheric air in the encapsulated cells with helium? Also: aerogels are
_very_ strong. Depending on the aerogel, the material
can support anywhere from 2,000 to 8,000 times its weight.
Quote: ... only a carbon nanotube structure is strong enough to withstand
14.7 psi pressure yet still be light enough to float.
You don't know that, you certainly can't prove it. However the idea of
building a geodesic dome structure out of carbon nanotubes, evacuating
the air inside, and then seeing if it would float, would be an interesting
experiment. |
|
|
| Back to top |
|
| |
|
Page 1 of 1
All times are GMT - 5 Hours
The time now is Fri Sep 05, 2008 5:09 am
|
|