Water (or Bottle) Rockets

Bottle rockets or water rockets, what are they?

When someone mentions bottle rockets, do you envision placing a firecracker attached to a stick into a glass bottle and launching it?

Water rockets have been a source of entertainment and education for many years. They are usually made with an empty two-liter plastic soda bottle by adding water and pressurizing it with air for launching.

Bottle Rocket With Parachute

source:
http://www.aircommandrockets.com/construction.htm

http://en.wikipedia.org/wiki/Water_rocket