"I'm suing you !!" Let's get this straight right now. This is dangerous and you could seriously hurt yourself. If you decide to play with these things, that's *your* decision and *your* responsiblity. Not mine. Nod in agreement to proceed.
"What if it hits somebody?" is one factor people are concerned about. If you use 30 feet or more of rope to launch the rocket, there should be no problem. Not that it can't go sideways, but after 100's of launches, I've never seen it go anywhere except straight up. I have heard of some wild flights recently. *STAND BACK*, think about what you are doing and watch where the kids are when you launch. It could give someone quite a punch when full of water. If it scares you, hide behind something! A baseball backstop is a great place, with the launcher out by the pitcher's mound. At least the bottle's not pointed.

"Won't it explode from the pressure?" is another worry. Again, very unlikely. The plastic 2 litre (2 quarts aprox. to you Americans) pop bottle is made of PET, an old and strong plastic. A PET (polyethylene terephthalate) bottle can withstand 150 PSI depending on the temperature. They *can* blow at 50 PSI or less. Be aware of this! Never go near a pressurized bottle. We have never been able to get a seal at the mouth good enough to come anywhere near that pressure. The water always begins to squirt out of the bottle long before that. We did pop a vinyl hose once (LOUD!), but that was with a small air compressor. If you can devise a better seal, I think you have the brains to realize the possible danger of the bottle or air line bursting. Limit the kids to a bicycle pump if you want. Again, think about what you are doing.

"It might fall on somebody's head!" Come on now, how much does an empty, 2 liter plastic pop bottle weigh? Now if you are into multi-stage, weighted, finned, etc., ones, there could be trouble. The impact velocity from 300 feet up is significant (read dangerous).

Any other questions on safety? Feel free to use that last link to tell me of your concerns and/or wounds. Of course, any modifications of this plan and/or misuse of this water rocket may result in a dangerous, high speed missle.. Please carefully consider what you are doing and the consequences. We are not responsible for stupidity! In fact, we are not responsible for anything you chose to do. Please, *PLAY SAFE*.