Build and fly. It’s interesting because it attracts a lot of engineers. So you have groups who are experts in propulsion that make their own solid (and now liquid bi-prop) motors. You also have groups that focus on electronics and make flight controllers, gps trackers etc. then you have software people who make build/fly simulators and things like OpenRocket. There’s regional and national events that are sort of like festivals. Some have FAA waivers to fly to around 50k ft. There’s one at Blackrock Nevada where you can fly to space if you want. A handful of amateurs have made it to the karman line too.