If I ever get a 3D printer and a bigger backyard I'll try to make a launched backyard coaster (the launch will be using a spring(a lever will be attached to the front of the spring. Once the rider is all strapped up and ready to go, the ride OP will pull the car to the middle of the station, the Op will pull the big lever to the back of the station, and pull the lever to the left. The spring will hopefully will hit a block of wood under the trains with incredible force which will then launch the train at high speeds. How safe the method would be, I don't know.)