Putting payloads into model rockets can be more complex than simply shoving stuff into an open spot, so [concretedog] put some work into making a modular payload tube for his current rocket.

See how Relativity's Terran 1 rocket got from the 3D printer to the launch pad in these highlights. Credit: Relativity Space ...

Hybrid rocket engines offer perks from both worlds, with simple solid fuel and the ability to throttle down by regulating oxidizer flow. Naturally, [Integza] decided he should try and 3D print one.