I'm not allowed near the model rocket engines anymore. In years past I came up with this great idea about making a model rocket car. I had it all figured out. It was a flywheel powered model of a land speed car that I used. I was able to fit a D size engine in it. And it even had a guidance setup. A length of 1/8 aircraft cable stretched down the block with a huge stop plate. The stop plate was a 4x8 sheet of 1/4 steel, well strong enough to stop a plastic model car. By the time I had it set up half the neighborhood was out helping. The rocket car lived up to it's name when it was launched. It made it about halfway before the cable broke from the friction of the guide loops, and took off for the sky like a scud missle. I never found out where it went or any news of it skewering a cat on a fence or anything. I think I have figured out how to fix the friction problem. Maybe I'll try it again.