Editing Water rocket (section)

===Nozzles===
Water rocket nozzles differ from conventional combustion rocket nozzles in that they do not have a divergent section such as in a [[De Laval nozzle]]. Because water is essentially incompressible the divergent section does not contribute to efficiency and actually can make performance worse.

There are two main classes of water rocket nozzles:

* '''Open''' also sometimes referred to as "standard" or "full-bore" having an inside diameter of ≈22mm which is the standard soda bottle neck opening.
* '''Restricted''' which is anything smaller than the "standard". A popular restricted nozzle has an inside diameter of 9mm and is known as a "Gardena nozzle" named after a common garden hose quick connector used to make them.

The size of the nozzle affects the thrust produced by the rocket. Larger diameter nozzles provide faster acceleration with a shorter thrust phase, while smaller nozzles provide lower acceleration with a longer thrust phase.