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From: Doug Craigen <dcc@cyberspc.mb.ca>
To: phys-l@atlantis.cc.uwf.edu
Subject: Re: Balloons without gases...
Date: Tuesday, March 04, 1997 10:14 AM
withGreetings everyone. I've been working on a few labs dealing
airthe gas laws when a thought occurred to me. Is it possible to make a
"floating" balloon without the use of any "light" gases (hydrogen,
helium, etc.)? What I was wondering, would it be possible to take a
rubber balloon like material and seal it all the way around so that
sortcannot get in or out of the inside envelope. The inside lacks any air
(vacuum or near - vacuum). If the inside of this balloon had some
wallsof light, strong rib material that flexes outward pushing the outer
beso that the balloon has a greater volume. I know the pressure inside
will greatly decrease and the "skin" of the balloon will be "sucked"
inwards, but if it were rigid enough, could this work? Has it already
earlydone? Am I onto something that could bring me instant success and
retirement? :-)
Dwight
Ashland, OH
Dwight--
Dwight your proposal certainly sounds like it would work provided the
right materials could be found. That is a pretty "heavy" provision
though. The first question to pop to mind is whether balloon materials
themselves hold up very well to 15 psi (oops, I've slipped out of metric
mode). My recollection is that the excess pressure that they hold is
typically much less than atmospheric, but I don't have a source on hand.
Perhaps someone else has a number for the pressure difference that
would burst a balloon skin. In general, I'm sure we've all seen what
atmospheric pressure can do to fairly rigid materials. I used to do a
demo for elementary school kids where I boiled water in a big metal can,
then screwed the lid back on. It twisted and collapsed, but didn't float
up. Clearly you need what are on average much stronger and lighter
materials than a metal can provides. i.e. strong ribs and a balloon type
side.