We have been taking the cardboard wind tunnel to various public events, but it is starting to get a little beat up. We've also been wanting to have some space exploration themed displays, so in September 2014 we made a couple in that category.
Air Rocket
We found plans for this on the national AIAA STEM web pages. It is actually on page 87 in a large NASA booklet of classroom exercises and demos for space topics. You can find the entire long document at this link. For your convenience, the pages of interest can be found at this link.
The basic idea is to use a bike pump to pressurize a soda bottle, hold it down with some sort of clamp, then release it and watch it go. All the parts can be obtained from a hardware store and a bike shop (for the connection to the pump.) Most of our displays are indoors, so I needed to have a feature that would restrain its flight. So I added a 0.25 inch dowel launch rod and a small box serving as a cap that stops the flight. It still shows the basic concept (air pressure pushes equally on all sides of the bottle, then you open the bottom nozzle, allowing the pressure on the opposite side to push the bottle into the air).
I customized the demo based on some parts I had and the
configuration of my bike pump. That is one reason the boards
are so tall off the base.
Gravity Jugs
This exhibit is a great way to tactilely experience the relative gravity on different planets. The basic idea is having three bottles filled with different amounts of water that simulates the weight of the same mass on Earth, the Moon, and Mars.
I made the labels you see on the bottles, and you can find them linked here. The size of the planets on the labels are to scale. These were very popular and got good reactions from visitors. They are easy to make and could be a good classroom project.