P3D Re: Floating 3D

[roberts@xxxxxxxxxxxxxxxxx (John W Roberts)]

>Date: Wed, 17 Dec 1997 21:53:35 -0700
>From: roberts@xxxxxxxxxxxxxxxxx (John W Roberts)
>Subject: P3D Re: Floating 3D

>>From: Sam Smith <3dhacker@xxxxxxxxxxxxx>

>>Does anyone know the lifting power of the average helium-filled party balloon?

>If I recall correctly, 22.4 liters of helium at 1 atmosphere pressure would 
>give a lift of about 10.4 grams [Note] (1 atm ambient, 1 gravity). 

Oops! I temporarily forgot that oxygen and nitrogen are typically not monatomic
in the atmosphere. That gives the atmosphere a molecular weight of about
28.8 (28.8 grams per mole), and since helium has a molecular weight of ~4,
that would be about -24.8 (say -25) grams per 22.4 liters. Any pressure
above ambient inside the balloon will decrease the buoyancy slightly.

Several months ago, there was discussion of using a large kite as a platform
for 3D photography.

John R


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