Q&A for How to Make a Rocket

If you're using a 2-liter bottle, filling it about halfway with water and then pressurizing with air will cause it to go the highest.

A regular bottle will work, but you have to adjust the size of the other parts.

Yes, you could use a air tank or a helium air tank, but both are quite expensive.

Actually it would make the bottle not go at all. If there is an opening in the bottle, the pressure won't be able to build up and the rocket won't launch.

Yes, just try not to add too much extra weight, as that can weigh the rocket down, and then it won't go as high.

A local bike store or on Trade Me or eBay. They are very cheap. They are not only helpful for this but for lots of other things, like blowing up balloons.