Hedgehog space program.Foot on the launch pad, hook the double-handed sling to the two hooks at the top. Stretch the bands as far as you could reach---make sure it did NOT point toward your face!---and ease pressure on the pad. A hook at the bottom of the rocket would slide out of its slot and the thing would fling itself hundreds of feet up.
How does that not count as a rocket? Propulsion by expulsion of gas from onboard combustion, said combustion using both fuel and oxidizer that are on board prior to launch (i.e. not air breathing). That's a rocket.Doesn't really count as a rocket, but when I was a kid, we would take an expired CO2 cartridge from a BB gun, cut the nozzle off of it with a hacksaw, stuff it full of paper match heads, stick three out of the back as a "fuse", stick the whole thing in a steel pipe, light the "fuse," and let 'er rip. Very exciting.
Two more I want to try but haven't. My father had a tool for puncturing the seal on seltzer bottle cartridges, a spring loaded pin in a tube with a simple hold-back to be released when ready. Insert the cartridge in the bottom of a rocket shaped object or the back or a pinewood derby car. Puncture the cartridge and off it goes. I'd have to remake the tool if I ever get up the time, energy, inclination, and tools all at the same time.
The other is another form of water rocket based on the dry ice bomb. Score a circle in the middle of the bottle cap so that it breaks out before the bottle bursts, but not too much before. Tape cardboard fins to the bottle for good performance, and tuck a launch lug under the label.