Of the roughly 10,000 balloons—or “Fu-go”—launched, about 10 percent made it across the ocean. But the timer couldn’t control where the bombs dropped, so most fell in unpopulated areas. The strategy never amounted to much. Still, these balloons were the first successful intercontinental weapons. Last year, a pair of foresters found a 70-year-old Fu-go, half-buried but intact, in the mountains of eastern British Columbia. That amazing discovery inspired me to build my own fire balloon—without the dangerous payload. My design is much simpler than the historical one. Because my fire balloons lift off with hot air rather than helium, I need to use only lightweight materials. First I smear a dab of Sterno inside a small aluminum pie tin. Once lit, the fuel heats the air in a flimsy, plastic dry-cleaner bag, attached to the pie tin with thin wire. The volume of heated air gives the device enough buoyancy to rise hundreds of feet. To prevent my DIY Fu-go from setting fires, I tether it with a spool of fine wire. On a cool, still night, it looks like a jellyfish floating toward the clouds. WARNING: Play with fire, and you could get burned. So be careful, and keep your balloon under control!
Build Your Own Fire Balloon
You can make a model Fu-go fire balloon from a dry-cleaner bag and an aluminum pie tin. Dry-cleaner bags work well because they are extremely light and the volume of heated air inside them provides enough buoyancy to make them rise to astounding heights. I chose magnet wire to hold the bag to the pie tin because it is light and won’t burn if exposed to flame. The final piece, jellied alcohol, burns hot and provides a sustained source of heat for the duration of the flight.
WARNING: This project literally puts fire in the air—so be careful near the flame and build at your own risk. Keep the balloon under control at all times: attempt only on still days or nights and fly only in areas free of flammable items and materials.
Stats
Time: 10 minutesCost: $6Difficulty: Easy
Tools + Materials
Punch or needle2-inch aluminum-foil mini pie panScissorsSpool of 34-gauge magnet wireDry-cleaner bagJellied alcohol (such as Sterno)Lighter
Instructions
This article was originally published in the May/June 2016 issue of Popular Science, under the title “Attack of the Fire Balloons.”
