Everyone who sees the air rocket the first time just can't believe how high it goes. - SciencetoyMaker
If I had to pick just one science project that would appeal to the most people, this air rocket would be the one. Everyone who sees one the first time just can't believe how high it goes. It costs less than $3 to make the launcher, and the rockets are free.
Air rockets appeal to a vast range of ages. Pre-schoolers (under the watchful eye of an adult) can send rockets higher than their houses. Teenagers and adults can engineer rockets that go higher than the tallest trees. The rockets can take up helicopters and maple seeds and release them at the highest point.
Two sets of instructions will get you to launch: Instructions for making the launcher and Instructions for making the rockets.