Well, today was our science fair (for a homeschool group) and we had a great time. To prepare, we built a 1-liter and another 2-liter rocket (cut off top of one bottle and taped to bottom of the rocket bottle for nosecone, hot-glued foam board fins). The plan (as we had seen) was to hook up a bicycle pump to provide pressure. Well, the pump we bought wouldn't attach to the inflation needle I had... so I figured I would try the small air compressor I have in my shop. I rigged a thumb trigger in the middle of hoses through a cork to connect to the business end of the rocket.
We then tested with 1, 2, & 3 cups of water as well as no water. Our first test flight was at night just to see if it would work... and we couldn't even see the rocket it went so high. And it took so long to hear it come down that I was beginning to wonder what had gone wrong. It landed on the other side of our house a few seconds later.
Today, for the science fair, we did a few demonstration shots and then let kids launch it themselves. Then, I decided to experiment a bit more and switched the cork out for a rubber stopper. It easily doubled or tripled the altitude! So afterwards, there were a group of dads standing around discussing the physics of water rockets and what we might have to do to break a record.
![Smile :)](./images/smilies/icon_smile.gif)
Anyway, hello to all - just stumbled across this group on my first search of the evening and am looking forward to learning from what everyone else has done. Who knew there were different classes of water rocket records!