The single stage rocket goes straight up and returns to earth very gently sideways. Launch it as many times as you want.

If you’ve already got the spin launcher, filling hose, and rotating lander payload, you need the rocket only.
You just need to supply a standard 2-litre plastic pop bottle for the upper stage, a bicycle pump or air compressor, some water, and a big open field.

The single stage rocket also works without the spin launcher: you can launch it directly off of the ground. If you are on a tight budget, you don’t even need the filling hose; you can make your own filling hose out of a cork and a 1/4 inch diameter plastic hose.