[Integza] was reading about a World War II-era rocket plane created near the end of the war by the Germans. The Heinkel He-176 wasn’t very practical, but he was intrigued when he read the rocket was cold and combustionless. He did a little research and found the engine was a monopropellent engine using hydrogen peroxide. This led to some interesting experiments and a 3D printed rocket engine, as you can see in the video below.
Usually, liquid-fueled rocket engines have a fuel and an oxidizer that mix and are either ignited or, in a hypergolic rocket, spontaneously combust on contact. With a monopropellent, the thrust comes from a chemical reaction between the propellant — hydrogen peroxide, in this case, and a catalyst.
There’s a common science demonstration that creates a huge volume of foam using common peroxide and a simple catalyst. For a rocket, though, you need concentrated hydrogen peroxide and certain catalysts. For some reason [Integza] tried different catalysts before settling on what the Germans had used, potassium permanganate. That was much more effective.
Since the reaction isn’t hot, this is a rocket where 3D printing on a consumer-grade printer is practical. In particular, he used a resin printer to create nozzles and a guide to properly mix the peroxide and a liquid catalyst.
For this test, the rocket didn’t go anywhere. Strapped to a fixed mount, [Integza] simply injected the materials with a syringe. The results, though, were impressive and we’d love to see an actual flying rocket or aircraft using this system.