The neat thing about the rocket car is that it was totally legal provided you didn't activate the rocket; correct weight, length, wheelbase, etc. Our troop had a "Parent" class so the big kids could have fun as well. Sheer dumb luck allowed me to make it all the way to the Finals without using the rocket.
I'd been watching the times and knew I couldn't beat the other guys in the Finals, so I armed the rocket for the last run. The rocket was still burning when it crossed the Finish line, blew through the runout and ran down the hall out of sight. The kids went nuts! They booed when it was announced I was disqualified.
My son thought I was a pretty cool guy that day . . .
One of my aunts is a retired USAF nurse...when we were kids back in the 70's, she'd always bring my brother and I model airplane kits when she'd come home on leave. One of these was a relatively large scale model F-16. Well, when we opened the kit, one of the wings had somehow been damaged during packing and we realized it would never work as just an F-16. As fate would have it, the engine nacelle was sized perfectly to house an Estes D-size engine. Before long this became our first rocket car, which had an extremely successful first run, but a somewhat less auspicious first stop. Mind you all of this was conducted outside the sanction of scouts or parents....