Air-water rockets are a fun, safe and inexpensive way for children to explore the basics of rocket science. As the laws of motion and the forces they experience in flight are similar to those of larger liquid fuel rockets.
Isaac Newton first described these laws in 1687 and these very same laws are used today and helped send humans into space and the moon 280 years later.
- Momentum and Inertia – An object either remains at rest or continues to move at a constant velocity unless acted upon by a force.
- F = ma – The sum of the forces (F) on an object is equal to the mass (m) of that object multiplied by the acceleration (a) of the object.
- Exchange of force – When one body exerts a force on a second body, the second body simultaneously exerts a force of equal magnitude in the opposite direction. Classically described as “For every action, there is an equal and opposite reaction.”.
There are also a number of forces (F) a rocket will experience in flight:
- The thrust of the engin
- Weight due to gravity
- and the aerodynamic forces such as lift and drag.
Further that these forces (F) will change dramatically during flight as the propellent is pushed out from the nozzle to create thrust accelerating (a) the rocket up. But also by doing this the mass (m) of the rocket also decreases as propellant leaves the rocket along with its centre of gravity affecting stability. Then as acceleration slows as it the propellant exhausted aerodynamic forces slow the momentum and of the rocket.
Consequently, there are many things to consider to achieve the best results. In a conventional liquid fuel rocket, the propellant is pushed out through the nozzle by mixing explosive chemicals like Liquid Oxygen and Hydrocarbons together as the energy source. In an Air-Water rocket, the propellant is water and the energy source is compressed air.