Recently, I was given the chance to run a series of all day projects with some of my students. This gave us all day to focus on big projects, start to finish. Following the theme of ‘Aerial Explorations’, we took to the sky to explore flight.
Perhaps the most interesting project to come out of these experiments was the 3D printed model rockets. The idea was simple…print basic rockets that would accept a small model rocket engine, and see if they’d fly. I took inspiration from the ‘disposable rocket‘ by Thingiverse user kebes22. I was worried that this minimal two piece design was the consequence that the small engines couldn’t launch solid plastic rockets. Presumably the off the shelf rockets are made of thin cardboard for a reason…
However, after some back-of-the-napkin calculations, I decided that the rockets would launch just fine. Likely the additional mass would act pretty significantly against the thrust, but we weren’t attempting to go into orbit, simply trying to take flight!
We turned to Tinkercad as our design tool of choice. This was mostly because my students had the greatest experience with it. If I were using this project to introduce students to 3D design and printing, I likely would have used 123D Design instead. 123D Design has features that make designing with specific dimensions much easier. And, the cylindrical model of a rocket lends this to a perfect example case for the revolve tool, that is often times a bit confusing to students new to CAD.
We used 1/2A3-4T rocket engines from Estes (who has some great teacher resources), from Amazon in a bulk pack. Using the 13mm dimension for the diameter, we left a cavity in our design to accept the rocket engines. In Tinkercad, I instructed students to make a cylinder with the same dimensions of the engine, then had them define it as a hole and instructed them to make sure to place the component in the center of the rocket. Students also design ringlets for the launch pad guide rod to connect to. However, in the long term, adding the guide after the print would be easier. Perhaps as simple as a drinking straw, or even a stirring straw from the breakroom would work better.
The instructions were very limited, as I wanted to allow the students to be creative with this project. However, any level of aerodynamics, or rocketry lessons would be easy to attach. The lesson can even be expanded to attach to Kerbal Space Program and KerbalEdu for interactive video game based simulations. (I found the demo of Kerbal Space Program supplied plenty of content for our one day lesson.)
Finally, we printed the rockets on the Printrbot Simple Metal. The prints took no more then 30 mins each printing at 0.25mm layers at 65mm/sec speed. The prints weren’t beautiful at that speed and resolution, but they were functional!
The launches were all successful! They all took off to a height of around 100-150′ before returning to earth. For safety, I kept all students a good 50′ from the pad unless they were at the pad launching their rocket. I connected the leads to the engine, then gave the nod to the rocketeer, stood back and allowed them to launch. Launching at a sleight angle downwind ensured no rockets returned back onto anyone’s head.