Subject:
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Re: LEGO RCX Skydivers
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 9 Nov 1999 21:43:31 GMT
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Viewed:
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882 times
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Either my calculations are wrong, or you have a different concept of what is a
"staggering" amount of helium. Here are my calculations:
Each gram-mole of gas at STP [1] takes up 22.41 liters (cubic decimeters) of
space.
The weight of a mole of air is about 28 grams (a little more actually, but I'm
being generous), and the weight of a mole of helium is 4 grams; thus the net
bouyancy per mole of helium is 24 grams [2]
Net bouancy per liter of helium = 24 / 22.41 = 1.07
Volume of a sphere 1 meter in diameter is 4/3 pi r^3, where r is 5 decimeters,
which comes out to about 523.6 liters.
So a spherical balloon of 1-meter diameter and filled with helium would have
about 560 grams of bouyancy, or about 19 ounces for you non-Metric dudes.
For comparison, the "fish" blimp that swam around in the Media Lab during its
first year or two was about 2-3 times this volume (same diameter but about 3
times the length)
What am I missing?
- Robert Munafo www.mrob.com
[1] Standard temperature and pressure: approximately 25 degrees centrigrade at
approximately sea-level pressure.
[2] This includes an implicit assumption that the magnitude of the net
acceleration plus gravitational field is 1 G, i.e. 9.98 meters/second^2.
In lugnet.robotics, lego-robotics@crynwr.com (Pete Hardie) writes:
> Robert Munafo wrote:
> >
> > [...] you should consider, [building] a balloon (or blimp) that can
> > lift the RCX/Cybermaster and the mechanisms [...]
>
> I dunno.
>
> Some coworkers and I were investigating home-made helium blimps
> for a homegrown robotic dirigible race competition, and the amount
> of helium required to hold up a few ounces was staggering.
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Message has 1 Reply:
Message is in Reply To:
 | | Re: LEGO RCX Skydivers
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| (...) I dunno. Some coworkers and I were investigating home-made helium blimps for a homegrown robotic dirigible race competition, and the amount of helium required to hold up a few ounces was staggering. (25 years ago, 8-Nov-99, to lugnet.robotics)
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