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When I was teen, a proud, card-carrying member of the National Association Rocketry, and a staunch adherent to the Model Rocketry Safety Code, I never would have entertained the idea of powering homemade rockets with C02. In fact, all of the horror stories I heard about kids blowing their fingers off trying to fill C02 casings with powdered match heads struck fear into my young rocket-nerdy heart.
But the truth is, with a few safety precautions and a basic understanding of physics, force, and fire, there are some interesting things you can go with compressed C02. Case in point are these 3D printed rockets that this maker, Austin from Austiwawa, has been experimenting with. Really a C02 gun more than a rocket, the 3D printed rocket/shell has a C02 cartridge in the back end. A spring-loaded firing mechanism at the bottom of a long PVC tube that the rocket is fed into drives a nail point into the C02 cartridge. And away the rocket goes.
Austin even experimented with mounting a pen camera into the rocket to get some aerial shots. The results aren’t all that great, but I think that, with some improvements, things could be vastly improved.
There are definitely some things he can do to improve the aerodynamics of his system. The long PVC tube is bendy, causing oscillation on the launch and a chaotic flight path. Making the tube rigid would help. His fins, which need to stay within the diameter of the launch tube, are little more than an affect. If he could figure out a way to make bigger fins, that would go a long way toward making a more stable, more impressive flight. Someone in the comments suggested using a square launch tube with 4 fins on the rocket fit into each of the corners of the box.

In this final video, Austin experiments with launching an unpowered 3D printed rocket affixed to the barrel of a more conventional PVC “potato cannon.”