P3D Re: Floating 3-D

[jacob@xxxxxxxxxxxxxx (Gabriel Jacob)]

John Bercovitz writes,
>>There is another advantage and that is that you don't want to waste 
>>helium which is, believe it or not, a precious resource.

Bill Davis writes,
>Wow, didn't realize this.  Now I feel bad about mentioning the helium party
>kits. Thanks for enlightening me.
>(some stuff deleted)
>P.P.S. I'm not at all serious about the hydrogen.  I don't think it would
>be fun or wise to play with large quantities of hydrogen in balloons or
>garbage bags.  Especially not near any source of spark or ignition.  You
>might never report back to us.

I second that wow, ;-), and never knew that also. Interesting! I do
remember though that helium is only obtainable in certain parts of the
world. Bill Davis writes tongue in cheek about using hydrogen as a lifting
device but then warns about it's flammablity. Of course some might remember
the famous newsreel (~1930's) about the German airship disaster in New
Jersey (?). The Germans used hydrogen in that one and were fully aware of
the dangers. Now one might wonder why they didn't use helium. This was
because the Germans weren't able to get any helium and the US government
refused to supply them with it due to the military tension at that time.

Now getting back (somewhat) to 3-D and lifting devises, I vaguely
remember reading about a project/prank that involved getting those
transparent thin bags, used by dry cleaners. The bag is set up up so
the bottom is arranged to stay open with some light material (straws
or balsa wood?) in an X configuration and where the beams cross a
small candle is placed. As the air gets hot it lifts but don't know
of the lifting power. The prank part is that when this is done at 
night, it supposedly looks like eerie U.F.O.'s, especially if dozens
are launched! Never personally tried it though. 

What I have tried and is another plausible idea, is to use hot air
but generated by the sun. Edmund Scientific sells this balloon
tube-like thin black plastic. It is about 3 feet in diameter and
roughly 20 feet long. You tie one end and let the wind inflate it
from the other end. When it is fully inflated you tie the remaining
end and tether it. Now the fun begins. (as opposed to the hot air
with a candle which can be done at night, this one only works on
bright sunny day) Since the balloon is black, the air inside starts
to get appreciably warmer than the outside air. About 10 minutes
later, it lifts off the ground and can go quite high. A few of these
might be needed to get the lifting power required but the advantage
is that only the sun radiant energy is requireddd! 

Gabriel  


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