Jim

If you have read the article __How Helium Balloons Work__, then you know that
helium has a lifting force of **1 gram per
liter**. So if you have a balloon that contains 5 liters of helium,
the balloon can lift 5 grams.

A normal balloon at an amusement park might be
30 centimeters (about 1 foot) in diameter. To determine how many liters of
helium a sphere can hold, the equation is 4/3*pi*r*r*r. The radius of a
30-centimeter-diameter balloon is 15 centimeters, so:

**4/3 * pi * 15 * 15 * 15 = 14,137 cubic
centimeters = 14 liters **

So a normal amusement park balloon can lift
about 14 grams, assuming that the weight of the balloon itself and the string
is negligible.

If you weigh 50 kilograms (about 110 pounds),
then you weigh 50,000 grams. Divide your 50,000 grams by the 14 grams per
balloon and you find that you need 3,571.42 balloons to lift your weight. You
might want to add 500 more if you actually would like to rise at a reasonable
rate. So you need roughly 4,000 balloons to lift yourself if you weigh 50
kilograms, and you can adjust that number according to your weight.

Let's say that instead of going to the amusement
park, you go to an army surplus store and buy one 3-meter (about 10-foot)
balloon. It can hold:

**4/3 * pi * 150 * 150 * 150 = 14,137,000 cubic
centimeters = 14,137 liters **

It would only take four of those to give you the
same lift.

One balloon that is 30 meters (about 100 feet)
in diameter displaces 14,137,000 liters, so it can lift 14,000 kilograms (about
31,000 pounds) -- this is roughly the size of a large __blimp__.

-----Original Message-----

**From:**
[email protected] [mailto:[email protected]] **On Behalf Of **James Moritz

**Sent:** 27 August 2004 10:49

**To:** [email protected]

**Subject:** LF: RE: Re: Gas for
balloons

Dear
David, LF group,

From
what I remember of chemistry at school, 1mole of gas at room temp and
atmospheric pressure occupies 22.4 litres of volume, and 1 mole of He weighs
about 4g, whilst 1 mole of H2 weighs 2g. So a cubic metre of helium will weigh
about 180g, whilst the same amount of hydrogen about 90g. Air is mostly
nitrogen N2 at 28g/mole, so the air displaced weighs about 1250g. So the
increased buoyancy of the hydrogen will only give 90g, about 7%, extra lift
– ignoring the weight of the actual balloon itself.

What I
would like to know is - what is a good source for the balloons?

Cheers,
Jim Moritz

73 de
M0BMU