one of the most simplest rockets i have come across, was using water jet propulsion.
u take a water or cooldrink plastic bottle. either 1,5 or 2 liters. this is now filled from 1/4 to 1/3 with water and corked up. through the cork we drive an old tyre valve. then place the bottle onto a suitable launch ramp, a pipe that the bottle fits into will do.
then take a wheel pump and pump away.
the bottle can withstand amazing pressures, the bottle will then blast off, the pressure forcing the water out which drives the rocket. the heights reached may be enhanced by keeping the bottle on the cork mechanically, and by choking the bottle neck and thus extending the time the water pushes the bottle along. we reached heights exeeding a hunderd and fifty meters, but i never got it right to stabilize the rocket when choking the bottle neck. so i reckon even greater heights can be attained.
no chemicals no explosives, quite innocent actually.

*tries hard to contain laughter*

*fails*

I used to have one of them when I was younger I used a modifyed bike brake to hold the bottle on and after puming it up all I needed to do was squeeze the brake and I would launch it. I had the whole setup mounted in a piece of gutter tubing which greatly improve the range and accuracy (and ment you don't get wet) Just look for some tubing a little larger than the bottle...

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Do as I say, Not as I do.
Visit my BSS Deaths Kitchen www.fieldings43.freeserve.co.uk/DK.htm

hmmm, ever wonder how much pressure a regular coke bottle can take? i reckon the answer will be quite scary.

125 PSI, give or take.


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Day must fade to night,
Night must give in to sunrise,
I watch, silently.

~A Haiku, Minami Sasake

I used to have one of these that i made when I was about ten years old. They're pretty fun, and can get pretty good distance. I used to launch bottles over my house, and it would clear it no problem