oh shit that does sound dangerous just mixing the 2 items aluminum and hydrocloric acid. I've once did it ouside in a glass flash. I'm not sure if it was enough to inflate a balloon completely. I won't do that, however a gas filled blimp that exploded would be cool caught on video! the dangerous by-produce of chlorine gas I wouldn't worry about too much because the experiment would be outside and we would be plenty aware of the gas. At a higher height no one should be affected. :*
do you guys think Spark Gap ignitor create a spark hot enough to lite a medium sized bottle rocket or even a model rocket engine??? How cool would it be to have a model airplane that could shoot bottle rockets by IR control! 