Sometimes surfing brings up the most interesting memories.
I was going through the morning web pages, and there was a link to building your own water bottle rocket. I remember seeing these things in the stores when I was a kid. You used to be able to get them for a couple of dollars a piece and they'd consist of a pump that is about 9 inches long, a funnel, and a plastic rocket that looked something distantly like a V2 Rocket. You would fill the funnel with clear water, fill the rocket with it to a pre-measured level, then attach it to the pump end. The pump would be clamped onto the bottom of the rocket and you would pump it an arbitrary amount of times until you couldn't any more. Then you would turn the rocket upright and pull the lever to launch your rocket.
The Wikipedia Page for Water Rockets has some general info on them but my little store bought rocket was much more modest than some of these monsters.
I could launch these things probably 100 times each rocket until either I was bored with it, or the rocket ended up in a tree, then it was a trip to the toy store and get another. They were commonplace and I had even seen one lately when I was in a store here within the last year so they're still made.
One time I was sitting on the front porch and had been launching this thing and wanted to see how far it could go so I started aiming it lower to the ground instead of straight up into the air. I figured I could manage to fly it across the street, and if it was one of those Hot New Jersey Summer Days, the added benefit was a cold blast of pressurized water and air all over me to cool me off.
When ever I think of those little red domed, white rockets, I would think of aiming it toward the street and firing. You see once I did that just as a car was coming by and it managed to go in one of the open windows, and out the other side. The driver of the car was just as surprised as I was to have this projectile fly through the car like something out of a Warner Brothers' cartoon.
Years later, I remembered this scene and started talking to my sister and her then school-age son about it and decided he needed this memory. Off to the toy store I went and finally found one. I filled it up with water with Jonathan on the porch next to me, pumped it up, and launched. We got a couple shots out of it before I turned it over to Jon. He had some fun that day launching it and we went inside.
The next visit we tried it again only first shot it went up on the roof. Seeing that that house was two full stories high and we had no ladder that would get to the high roof, it was done.
Somehow, I doubt he thinks of it as fondly as I did.
The website that had it, make.com, has a video and a web page about how to build a rather complex rocket if you want to see them... They're fun but this rocket is really involved... I'd stick to the little store bought thing if I went to do it again.