When you blow up a balloon and release it, the balloon can fly all over the place for a short while. This doesn't happen because the air from the balloon is pushing against the air outside the balloon. It happens because the balloon pressure is no longer in equilibrium.
Imagine the balloon is tied off with the air inside. In that case, the pressure is equalized in all directions. It's pushing with constant pressure at every point inside the balloon. When you release the opening, the air inside the balloon is pushing against every place on the inside of the balloon - except the opening. The pressure is no longer in equilibrium.
This is a demonstration of Newton's third law. (Every action has an equal and opposite reaction.) The air coming out the balloon on the other side causes a force that is counter-balanced by the force on the other side that is pushing the balloon.
The same principle is what would make the compressed air canister work (or not work). I did not see the mythbuster's episode, but I'll look for it in future.
The same principle is what makes rockets work. It's not that the burning fuel is pushing against the air outside the rocket (although that happens, it's not what's producing the lift). Rather, the force of the expanding gas is pushing against the rocket and NOT pushing against the exhaust area.
And regarding the mirror panel left behind on the moon - it's irrelevant for the moon-hoaxers. I recently heard someone say that you can't reason a person out of an opinion they didn't use reason to get into in the first place. For those of us whose brains are not broken, it has produced highly relevant and useful information.
