Available for downwload is a CO2 rocket. We launch these in my class and do some projectile motion calculations with them and try to hit a target. Their are two versions of the fin base, one that easier to 3D print, and one that will require supports. They are a lot of fun, all you need is a 16 gram CO2 cartridge and a 6-7 foot long 2 inch diameter PVC pipe. Put a cap on one end of the PVC pipe and install either a sharp 2 inch long screw or nail though the center of the cap. Then, just drop the loaded rocket down into the tube and let the fun begin. After printing, you may need to remove any burs on the fins so they fit perfectly in the PVC pipe. Remember to always use common sense when launching them, do not obstruct the rocket's path and make sure you are launching them in safe location. I recommend launching them in a grassy field so the fins don't break. They fly fairly straight, I adjusted the center mass through various test flights, so they should fly fairly straight for a while before they start to rotate. If the fins break, simply print the part again or glue them with some super glue. Click on the link below to check out all the action: https://www.youtube.com/watch?v=UlXUcDgDC3Y&ab_channel=JohnFuller