I read that article on the first commercial vehicle in space, and it got me thinking about rocketry again. Well its a hybrid engine, so it has a solid chunk of fuel, and an oxidizer (liquid) is sprayed in there. Easy enough. I think rockets NASA uses are liquid fueled? And ICBM's are solid fuel for quick launching.
For a fun little experiment (which I won't do for safety concerns) would be to make your own tiny bit of solid rocket fuel and launch a toilet paper roll into the next city. I was looking into gun cotton a ways back, and now I'm thinking wouldn't it work for rocket fuel too? I mean, take anything organic and shove it into nitric acid for a while, then you should have all the necessary elements of a flaming ball of goodness. Insert flaming ball of goodness into metal container with one small opening, and you have a rocket, right?