Hypothetically speaking, one might have used a shotgun primer inserted into an Estes "D" engine. Then put a wooden block with a carefully inserted nail into the bottom of the pipe to operate like a mortar. A sand-filled Pepsi bottle could suffix as the holder for the aforementioned engine.
That way the engine would not fly way off over a hill and nearly catch a hay barn on fire.
Which would have been a Very Bad Thing, if someone had been caught.