Make:

This rules - "The problem with water rockets is that you need acres of space to launch them without risk of losing them. It's hard to restrain yourself when friends come over and do "just a little launch" in front of your house to show them how it works. Inevitably you launch again, increasing the pressure by 10 or 20 psi and before you know it you're back up to 140 psi, spectacular flights, and then meeting your neighbors by asking if they mind if you climb up on their roof, and by the way, do they have a ladder you could borrow? Well I started thinking about the Blue Flame, the Bonneville salt flats, Evil Knievel and the like, and realized that a rocket powered car is feasable, given the right car" Thanks Dan! - Link.

Related:
Soda Bottle Rocket. You don't have to be Burt Rutan to start your own rocket program. With a few empty soda bottles and some PVC pipe, you can build a high-performance water rocket. MAKE 05 - Page 78.