That basically is plastic welding. Solvent welding, so almost brazing? I don't know. I'd call it welding informally.
I think the engines blow up just like a full size one might. It also is interesting how they start getting to sounding like actual engines a tiny bit minus the exhaust notes. It's rad.
The video definitely makes me want to put together a large 3D printed or LEGO radial styled after the ones we import from Czechia. Would be very cool display piece for events and I have access to most of the CAD data from the mfg...
IF only there were more hours in the day