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October 7, 2008 7:53 AM

How can I make a totally awesome mini hot air balloon that doesn't crash and burn?

Okay. The two previous launch attempts died in fiery balls. Phoenix 1 was, admittedly, a rush-job - a fairly small plastic bag attached to a crossbeam made from two disposable chopsticks lined with birthday candles, with a basket made from a coke bottle lid hanging by thread from the bottom. The plastic bag immediately sucked inward, crumpled and burned, then it all caught alight and was reduced to a gnarled lump of smouldering plastic. You'll be relieved to hear that the tiny pilot rolled free at the last minute, and escaped without injury.

Phoenix 2 was more elaborate - a papier-maché balloon, with a burner hanging underneath, made from the wire from a champagne bottle with a strip of a methylated spirit soaked J-cloth wrapped round the bottom, the pilot suspended via a small wire harness beneath this. Tragically, we underestimated the height of the flames from the burner, the balloon caught fire, and the entire thing fell in on itself. This time, the tiny pilot was not so lucky. We retrieved his charred remains, but he is now a flattened clot of rubber, permanently fused with his wire harness.

So it's becoming clear I'm useless at aeronautical engineering. I need help. What's the best way to create a mini hot air balloon strong enough to lift a small, mangled pilot about the size and weight of three beer bottle caps? I'm thinking a flame-powered design rather than inflating a bin liner with a hair dryer, which I've found several examples of on the net, but which feels to me like cheating. Bear in mind that financial resources for this project are limited, as is the skill of the ground crew. Have any Mefites successfully launched a model balloon?

Any help or suggestions will be gratefully received!

posted by RokkitNite to sports, hobbies, & recreation (8 comments total)

Here you go.
But follow the suggestion made in the comments to eliminate the candle, use a black plastic garbage bag, and do it on a sunny day, so the thing is solar powered, floats for miles, and won't burn anything down by accident.
posted by beagle at 8:01 AM on October 7, 2008

Try heating the air inside the balloon with a hair dryer just before you light the candle. That should keep it from collapsing long enough for you to get the candle lit.
posted by backseatpilot at 8:21 AM on October 7, 2008

Suspend a can of sterno from a trash bag. If you do this though, keep the balloon tethered or launch it over the ocean. I wouldn't want a flaming can of sterno landing on my house.
posted by bondcliff at 8:24 AM on October 7, 2008

You need to reduce weight and increase volume. Use the thinnest available plastic. Trash bags are much too heavy. 1/2 mil drycleaner bags are perfect. To get more volume, you can scotch tape two bags end to end. Chop sticks are too heavy. Use soda straws for your x-frame -- paper and wax ones if you can find them. You need to insert the ends of the straws into each other to make them long enough for a 2-foot diameter drycleaner bag. Attach the ends of the straws to the bag with scotch tape.

You will need about two dozen birthday candles which you attach to the straws by melting wax. This contraption will lift itself, but may not handle much of a payload. The whole thing should weigh only a couple of ounces.

Be aware that this is a flying fire starter, so be careful where you do this.
posted by JackFlash at 9:00 AM on October 7, 2008

When I've done this in the past, I've used a tissue paper balloon and alcohol swabs as my fuel. To prevent it from escaping and burning down the local orphanage I keep it tethered with a fishing reel.
posted by piedmont at 9:16 AM on October 7, 2008

Drycleaning bags - very thin light plastic, big volume of air.
posted by Meatbomb at 11:59 AM on October 7, 2008

See also sky lanterns [via].
posted by dhartung at 4:12 PM on October 7, 2008

Candle Powered Hot Air Balloon of painter's plastic at Instructables.
posted by chazlarson at 4:46 PM on October 7, 2008