AirTalk.org

manofsan@gmail.com · Guest

What is the maximum theoretical size possible for a lighter-than-air
balloon, using ideal materials, before it loses its integrity?

Here's an article from a month ago, about sheets being made from the
famous nanotubes:

http://www.eurekalert.org/pub_releases/2005-08/uota-utd081505.php

http://en.wikipedia.org/wiki/Nanotube

quote from Wikipedia:

"Ray Baughman's group from the NanoTech Institute at University of
Texas at Dallas produced the current toughest material known in
mid-2003 by spinning fibers of single wall carbon nanotubes with
polyvinyl alcohol. Beating the previous contender, spider silk, by a
factor of four, the fibers require 600J/g to break. In comparison, the
bullet-resistant fiber Kevlar is 27-33J/g. In mid-2005 Baughman and
co-workers from Australia's Commonwealth Scientific and Industrial
Research Organization developed a method for producing transparent
carbon nanotube sheets 1/1000th the thickness of a human hair capable
of supporting 50,000 times their own mass.

In August 2005, Ray Baughman's team managed to develop a fast method to
manufacture up to seven meters per minute of nanotube tape. Once washed
with ethanol, the ribbon is only 50 nanometers thick; a square
kilometer of the material would only weigh 30 kilograms."

-------

So if the limiting factor is tensile strength, and nanotube fibres are
the record-holder at 600J/g tensile strength (20x stronger than
kevlar??) while also having a mass of 30 kg per sq km, then how big can
one make a balloon held together by the nanotubes? And what kind of
displacement lift force would it exert?

anybody43@hotmail.com · Guest

Hi,

I am just trying to assist here.

"toughest material ....600J/g"
......
"at 600J/g tensile strength"

Are incompatible.

Toughness and tensile strength are not the same thing AT ALL.

IIRC toughness is the Energy required to break a test specimen.
The energy is delivered in a short time (e.g. with a hammer blow).

The units will be I guess Energy per unit Area.

Tensile strength is the force per unit area required to (slowly)
break the material in tension.

So not only are the two not directly related, it looks to me as if the
wikipedia article is misleading.

http://en.wikipedia.org/wiki/Nanotube
Says:
"was tested to have a tensile strength of 63GPa"
I say: - This is a unit of Pressure (force per unit area )
which I agree with.

http://en.wikipedia.org/wiki/Nanotube
Says:
"In comparison, the bullet-resistant fiber Kevlar is 27-33J/g"

Maybe there is some sense to the idea of toughness
having the units 27-33J/g however I can't see it at present.

nokia_p900i@yahoo.com · Guest

hello der!. try to visit this,
http://www.tpub.com/aviation1.htm
it might provide answer. the link was posted on the other group, im
already visited it, so im sure it wasnt a virus or whatever that can
harm ur comp.

[email]manofsan (AT) gmail (DOT) com[/email] wrote: