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Wednesday, May 22, 2013

Giant Hot Air Balloons

Disasters seem to be the topic this week. I was talking to Jack on Monday and he mentioned the hot air balloon crash that happened in Egypt earlier this year that killed 19 people. I vaguely remember hearing about it, and while 19 is a lot of people for a balloon crash, it could have been a freak accident that involved a bus or something, and I didn't think any more about it. Turns out that all of the people who died were riding in the same balloon.

Some random group of tourists.

I didn't know they made such large ones. All I have ever seen is the small baskets that hold three or maybe four people. A balloon big enough to lift three people is huge, a balloon big enough to lift two dozen must be ginormous! I spent some time trying to find chart that would illustrate the different sizes of balloons, but all I could find was this chart from the Red Bull record setting high altitude parachute jump from last year.

Eventually I realized that a balloon's lifting capacity goes up by the cube of the diameter, so a balloon that is twice as big in diameter as a normal 3 or 4 person balloon would be able to lift 8 times as many people (2 x 2 x 2), or 24 to 32. One of these giant tourist balloons would not be as big as number 2 on this chart. Spreadsheet of popular commercial balloon sizes and capacities here.  It takes about 64 cubic feet of hot air to provide one pound of lift.

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