Design and Simulation of a Water Rocket Flight Performance

 

Physik  |  Technik

 

Aayush Mehrotra, 2006 | Basel, BS

 

This thesis aims to improve the accuracy of water rocket simulations, commonly used in educational settings to teach rocket science. While many existing simulators are useful, they often oversimplify key physical effects or fail to account for critical factors like air resistance, water flow dynamics, and nozzle efficiency, leading to discrepancies between predicted and actual performance. The goal of this study was to develop a more accurate simulator by considering variables such as water volume, pressure, and rocket shape. The simulator was tested against experimental launches, with results showing good accuracy, especially at higher water volumes, with very small deviations. However, larger deviations were observed at smaller volumes due to lower thrust forces and measurement inaccuracies.

Introduction

The aim of this study was to develop a simulator that predicts the maximum height of water rockets based on water volume, pressure, and rocket shape. The goal was to create the most accurate simulation possible, comparing the simulation predictions to experimental data to evaluate the accuracy of the model and identify areas for further improvement.

Methods

Experimental Measurements:
Experiments were conducted using a custom-built rocket and an electric air compressor to gather data. Parameters such as initial water volume, pressure, and maximum height were measured. The experiments were performed outdoors, where factors like wind and turbulence were not controlled, which may have influenced the results.
Excel Simulation:
An Excel-based simulator was developed to model the rocket’s flight in very small time increments, this would ensure a higher accuracy. The simulator utilized key physics principles, including Newton’s laws of motion, Bernoulli’s principle, and the drag force equation. The model calculated various parameters like thrust, mass flow rate, and velocity, using inputs such as water volume, pressure, and nozzle diameter.

Results

The experimental results confirmed that both pressure and water volume influenced the rocket’s height. Increased pressure and water volume generally led to higher altitudes. However, at lower pressures and smaller water volumes, the rocket’s height sometimes decreased, as seen with 300 mL at 10 psi. The simulator showed similar trends, with accuracy improving at larger volumes. At 900 mL, the deviation between experimental and simulated results was under five percent. Further adjustments to the drag and discharge coefficients helped to refine the simulation and improve the match with experimental results.

Discussion

The study confirmed that both pressure and water volume affect the rocket’s performance. Higher pressures resulted in greater altitudes, primarily due to the higher exit velocity of the water. However, the effect of water volume was more complex. At lower pressures, the increased mass from larger water volumes decreased performance, as the thrust generated by lower pressures was insufficient to overcome the added mass.
The consistency of results also improved with larger water volumes, likely due to the more consistent thrust provided by the longer water expulsion duration. In contrast, smaller volumes led to more variable results, as indicated by higher standard deviations. The simulator’s predictions were more accurate at larger volumes, where it achieved a deviation of 3.8%. At lower volumes, the simulator tended to underestimate the rocket’s height, likely due to not accounting for the thrust provided by compressed air.

Conclusions

This study demonstrated that higher pressures and larger water volumes lead to greater altitudes. The experimental results confirmed that both factors significantly affect performance. The simulator’s accuracy improved with larger volumes, achieving a deviation of 3.8% at 900 mL with 30 PSI. However, at smaller volumes, the simulator underestimated the rocket’s height due to limitations in the model’s handling of thrust dynamics and due to the inaccuracies while measuring the height.
Future work should focus on improving the simulator’s accuracy at lower water volumes by refining the modelling of air resistance and thrust dynamics. Additionally, using more precise measurement tools, such as a rocketry altimeter, would help improve the reliability of the experimental data. The rocket’s aerodynamic design should also be explored further to understand its influence on stability and performance.

 

 

Würdigung durch den Experten

Maximilian Kirchhoff

Aayush hat ein Fundament erarbeitet, um Raumfahrtbegeisterten eine Lücke beim Verständnis der Basis von Raketentechnologien zu schliessen. Durch seine einfach verständliche Zusammenfassung komplexer physikalischer Zusammenhänge und durch seine saubere wissenschaftliche Vorgehensweise hat er einen wirksamen Flugsimulator erstellt und validiert und somit für die Nutzung und Weiterentwicklung zugänglich gemacht – und dadurch Anderen den Einstieg in das aktuelle Thema der Raumfahrt vereinfacht !

Prädikat:

gut

 

 

 

Gymnasium Kirschgarten, Basel
Lehrer: Thomas Strub