The water rocket simulator

Water rocket simulation for one and two stage rockets
with water fill and weight optimizer
Version 1.0

Here the first version of my water rocket simulator. Although it still has limited functionality it is capable of simulating a two stage rocket.
Something i could not find on the net. This simulator is also capable of optimizing for the best water fill and optimal rocket weight (at a certain launcher pressure).

Some pictures and explanations:
See below, this is the main screen, with the numeric flight results.
You can enter the data from the launcher and the rocket on separate forms, just hit the launcher and rocket buttons.
All data entered?, then hit the launch button, and your virtual rocket is launched the flight-results are displayed in the main screen. simulation main screen

Results of the flight are found under the graphs button. As an example you see below a sample-plot from the thrust, during thrust phase only.
Colors are used to mark the various phases, RED for launchtube phase, GREEN for the water thrust phase and BLUE for the air-blow down phase.
Trust is in Newtons and time in seconds, the graph shows the driving force of the rocket "motor" minus drag-forces from the air. The simulator uses meters/ millimeters for dimensions and bar for pressure, sorry folks for all you that are used to work with inches and psi's. Other graphs available are: VELOCITY, HEIGHT, THRUST, ACCELLERATION, PRESSURE, VOLUME (rocket+launcher), AIR TEMPERATURE and the dependency between apogee height and water fill amount (WATER VOL. VS. MAX H).
On the shown thrust graph, after about 0.29 sec, you see a little hick-up in the trust, this is the point where the vapor condenses in the rocket, the condensation warmth increases the temperature (and pressure), this causes the little extra kick. (neat isn't it?!).

An other feature are the two optimizer buttons, the WATER VOLUME button calculates the optimal amount of water at given launcher pressure. The WATER AND WEIGHT button optimizes for both optimal weight and water fill. In this version 1.0 these buttons work correctly, only for single stage rockets.

airtemp

(You can download the simulator here [size=441Kb])

Download the program (an .exe file) and put it in its own directory. Start the simulator named rocketsim.exe. The first time waterrocketsim starts it will create a sub-directory named "..\simulator_data", in this directory your rocket and launcher data are stored.
Waterrocketsim works best with screen resolution of 1600x1200 or higher.

Water rocket sim does not make entry's in the registry, the simulator programm only consists of an exe. If you want to remove the simulator from your system then delete the waterrocketsim.exe file and the directory "simulator_data".

The waterrocket simulator makes uses of a variation of variables and formulas and assumption/ simplifications. To see more of this, click the link.
explanation of used variables, formulas and assumptions

Is it accurate?. Naturally a simulator is only worth while if it produces results that reasonably predicts the real time behaviour.
To demonstrate the accuracy of rocketsim simulation results are compared with a real flight, altitude is measured with an altimeter from perfectflite type ALT15K. The altimeter measures the changing air pressure during flight and logs this in flash memory every 0.1 second.
The displayed flight is the logging from a lawn dart style flight, the recovery flaps did not trigger.
The wrocket was a write off, luckily the electronics survived.
The used data in the simulator are all measured dimensions from the rocket / launcher, except for CW value, (0.8) is a estimate.

comparisson between rocketsim simulation and real flight

comparisson between rocketsim simulation and real flight

As can be seen the height and velocity curves compare reasonably. Maybe i underestimated the CW just a little. (flight time of simulation is below really measured flight time). The graph "measured velocity" was calculated from height-difference / time. Because of the subtraction and noise on the height measurement the relative large variation in speed is displayed.

Have fun!