Alain JUGE : Contribution on water rockets
The launch bases fulfill 4 main functions. Whose two are essential and two others only useful:
This function is essential, it is indeed a question of putting the rocket tank under pressure, being able to control it and completely safe. Throughout this pressurization phase, it is necessary keep the rocket firmly on the ground (on the base) as long as the pressure desired is not achieved without water or compressed air flowing go.
Another essential function is to be able to maintain the rocket under pressure and be able to release it, if possible, at a chosen time and safely.
Although not essential, this function is however very comfortable. It
is not very easy to put the rocket already full of water on the base.
Either we lose a good part of the water by returning the rocket on the
base, or we turn the base to put it into the rocket, but in this case,
the manipulations are complicated then do not forget to anchor the base
to the ground again, in short, it is tedious. The idea is therefore to
put the water on once the rocket is on the ramp and locked. Problem:
when the rocket will start to go fill with water, the air volume
decreases, so the pressure increases and the water can no longer enter.
We will see how to solve this problem.
On take off, a rocket will not be able to benefit from the action of its fins while speed is not sufficient, It is therefore prudent to guide it until it reaches that critical speed. We saw at chapter stability that water rockets are not stable on takeoff due to their low center of gravity, even if the duration of the phase propulsion is low, this guidance function is not useless.
It is also interesting to be able to steer the rocket in a direction chosen so as to favor a landing zone secure.