High power model rocketry
REB, you'd be astounded at how high the hobbyists are getting these days. There are launches now that are going miles up and the rockets are huge. Where the little Estes rockets you buy in the toy store have engines with designations up to "D" level that are gunpowder based, the high power enthusiasts typically launch with clustered "M", "N", "O", and "P" engines that are filled with ammonium perchlorate, the same stuff in the Space Shuttle SRB's. We're talking thousands of pounds of thrust.
Those launches, to be legal, must have FAA approval if they go past a certain altitude but there are rogues out there that push the envelope. They usually don't last long.
Art