Quote:
Originally posted by Faceman:
Okay, I'll give you a hint: I'm looking for REAL rainfall, i.e. Water.
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Combustion of compounds containing hydrogen (e.g. hydrocarbons) produces water. Water contains 2 hydrogen atoms and 1 oxygen atom. The oxygen is present in the air surrounding the balloon, so we need a source of hydrogen. The simplest source is hydrogen gas, which btw was used in zeppelins.
Now to calculate:
What is 'noticable rainfall'? Maybe 1 mm of rain? If somebody can inform me of the approximate surface of a city like New York, a volume of water can be calculated. Let's assume a nice round 100 square kilometers.
The comes the question of how much hydrogen is needed to produces that volume of water. Water contains 1/8 part hydrogen by mass. For 1 kg (= 1 liter) of water we need 125 grams of hydrogen.
The density of hydrogen is (I believe) approximately 90 grams per cubic meter.
Thus for 1 liter of rain we need 125 grams or 1.4 m
3 of hydrogen.
100 km
2 with 1 mm of rain equals 10
5 m
3 of water. This is 10
8 or 100,000,000 kg (or liter) of water!
For 10
8 kg water we need 1.25*10
7 kg of hydrogen. This equals a volume of 1.4*10
8 m
3 of hydrogen.
To visualise: This means a hydrogen filled balloon with a diameter of almost 800 meter (yes half a mile [img]smile.gif[/img] )
I hope I did all the calculations correctly
It sounds like a lot of hydrogen!
Final note: In my calculation I ignored the pressure of the hydrogen inside the balloon. If, for example, the pressure inside is 10 times the air pressure, the diameter of the balloon decrease by a factor 3. But I have no idea at what pressure you should fill a balloon with hydrogen.
