There is a reason building a rocket engine is harder than most things you want to build. If you are building, say, a car, your goal is to not have it explode. If you are building a bomb, you want that to explode. But a rocket engine needs to explode just enough and not a bit more. That’s tough, as [Ryan Kuhn] discovered. He’s behind ABL’s E2 rocket, a LOX/kerosene engine for small vehicle launches. You can catch a video of the engine’s qualification tests below.

[Ryan] shares many of the problems encountered from many problems, each requiring finetuning of the design. True, there are plenty of publicly available NASA documents about what works and doesn’t work for rocket engines, but that can only take you so far. You can’t learn to bowl by reading about bowling, and you can’t design a successful rocket on paper just by reading about what others have done.

The post is long, but it is a rare glimpse into what goes into a major engineering project like this. [Ryan] started with a blank page, and the team created almost everything outside of some commodity parts, such as bearings, seals, and sensors. They even built all their own test infrastructure and software.

So, while you might never get the chance to build a rocket engine on this scale, just looking inside the process is fascinating. Who knows? It might help you with your next model rocket project.

Even starting a rocket engine can be a challenge. Today, we have many interesting fabrication techniques, but engines from the Shuttle and Apollo eras had to resort to some interesting tricks to get the precision parts they needed.