At takeoff a rocket can not benefit from the action of its fins that from sufficient speed, so it is prudent to guide it until it reaches this critical speed. We saw at the stability page that the water rockets are not stable for takeoff of the made of the body of water that they take away that lowers their center of Gravity.

Even if the duration of the propulsion phase is low, this function of guidance is not useless. It is also interesting to be able to direct the rocket in a chosen direction so as to privilege a Secure landing zone.

Several solutions are possible, here are at least 3.

the stem or rail, which necessitates the installation on the rocket, of Slides or skates. Simple enough to do and cheap.

In the example below, a metal rod is enough. It is necessary Then you have to stick a piece of straw on the body of the rocket. Predict it long enough or put 2 tips up and down for better guidance.

More luxurious, the metal rod can be replaced by an Aluminum profile in which slides two pads (one at the top and one at the bottom of the rocket) like this one below.Guidage par profiléGuidage par profilé

3 or 4 rails. It's the must, but complicated to achieve and bulky. The one below is planned for rockets pyrotechnics, so for a rocket we can aim more modest.

It can also be constructed from aluminum profiles opposite or simple angles.

The inner tube.

In fact we just prolong the tube that allows put the rocket under pressure and possibly fill it in water. The length of the tube is obviously limited by the Depth of the tank.

Simple to do, but when the rocket comes out of the tube, it has always all his water and so is always potentially unstable. However, the rocket has acquired sufficient speed For its fins to have effectiveness.

Guidage par tige

Guidage par rampe à glissière

Guidage par tube interieur