Why are hot air balloons so large?

Question

Why are hot air balloons so large?

Answer 1

To hold a bunch of hot air?

Answer 2

Hot air has very little lifting capacity (small change in density over unheated air), and you need a LOT of it to ascend. Therefore, you need a big enveloppe.

Answer 3

the balloon has to be large enough so that the entire balloon and basket will be lighter than the air it displaces.

Answer 4

So the warm air can rise enough so that it will lift the basket.

Answer 5

It's simply a matter of physics, my dear. Hot air is less dense, so rises thru colder air. There is a certain amount of "tiny"  weight difference per cubic foot of air when  you heat it, and you have to multiply that slight amount to find out the volume you need. Here's a description I lifted from another website :

" A typical hot air balloon holds 90,000 cubic feet of air and can lift 1,600 pounds.

We can assume then that to lift a 200 pound person we would need about 12,000 cubic feet of hot air.

Since volume increases linearly with absolute temperature (Charles' Law) we know that the weight of the air in the balloon will be about 90% of an equivalent volume of air outside the balloon.

Air weighs about 0.075 pounds per square foot outside the balloon, and 90% of that inside the balloon (0.067), so a cubic foot of air at 120 degrees can lift 0.075 - 0.067 pounds, or about 0.008 pounds.

This means we will need about 25,000 cubic feet to lift 200 pounds.

So the balloon is going to be a cube 30 feet on a side, or a sphere 37 feet in diameter. "

Hope this simple explanation helps. Takes alot of hot air to get some big donkey off the ground. :) You also gotta remember you're not just flying alone, also you need a basket, the tanks, propane burner, so more weight is added, so an even bigger balloon is needed.

Answer 6

The larger the balloon, the more lifting capacity.