International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 12 Issue: 07 | Jul 2025
p-ISSN: 2395-0072
www.irjet.net
Experimental Investigation of Nozzle Diameter Optimization for Maximum Altitude in Water Bottle Rockets Taarak Harjai1 1The Doon School, Mall Road, Dehradun, India
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Abstract - This study investigates the effect of nozzle
Center has developed sophisticated computational tools for water rocket simulation, yet experimental verification remains essential for parameter optimization [6]
diameter on the maximum altitude achieved by water rockets constructed from 750ml soda bottles. While theoretical models provide limited insights due to complex multiphase flow dynamics, experimental validation remains essential for optimization. Using computational predictions from NASA Glenn Research Center's water rocket simulator followed by systematic experimental testing, we evaluated nozzle diameters ranging from 1.0cm to 3.5cm in 2mm increments. All rockets were pressurized to 135 psi with a 1/5 water fill ratio. High-speed video analysis at 60 fps enabled precise trajectory tracking and kinematic calculations. Results demonstrated that a 1.2cm nozzle diameter achieved a maximum altitude of 5.7m, while the largest 3.5cm nozzle yielded only 0.83m. Frame-by-frame analysis using pixel-to-meter conversion with the bottle as reference provided position, velocity, acceleration, and jerk profiles. These findings validate theoretical predictions of optimal nozzle diameters between 9-15mm and demonstrate the critical importance of balancing thrust magnitude with burn duration for altitude optimization.
1.1 Theoretical Background The fundamental physics governing water rocket propulsion involves the conversion of stored pneumatic energy into kinetic energy through water expulsion. The exhaust velocity can be approximated using Bernoulli's equation: ve = √(2(pin - pout)/ρw) where pin represents internal pressure, pout is atmospheric pressure, and ρw denotes water density [7]. The resulting thrust force follows: Fthrust = 2πrn²(pin - pout) where rn is the nozzle radius [8]. These equations suggest that larger nozzles produce greater instantaneous thrust but shorter burn duration due to increased mass flow rate.
Key Words: Water rocket, Nozzle optimization, Experimental validation, Video analysis, Thrustduration trade-off, High-speed imaging, NASA simulator, Altitude maximization
1.2 Research Objectives This study aims to experimentally determine the optimal nozzle diameter for maximizing altitude in water rockets constructed from standard 750ml bottles. Specific objectives include:
1. INTRODUCTION Water rockets represent an accessible platform for investigating fundamental rocket propulsion principles while providing valuable insights into complex fluid dynamics phenomena [1]. The optimization of water rocket performance involves multiple interdependent parameters including water fill ratio, operating pressure, nozzle diameter, and rocket mass [2]. Among these variables, nozzle diameter presents particular challenges for theoretical analysis due to the complex multiphase flow dynamics during water expulsion [3]. Previous studies have demonstrated that nozzle diameter significantly affects rocket performance through its influence on mass flow rate and thrust duration [4]. While Bernoulli's equation provides first-order approximations for exhaust velocity, the transient nature of water rocket propulsion necessitates experimental validation of theoretical predictions [5]. The NASA Glenn Research
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Validating computational predictions systematic experimental testing
using
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Quantifying the relationship between nozzle diameter and maximum altitude
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Developing high-precision techniques using video analysis
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Providing empirical data for future theoretical model validation
measurement
2. Methodology 2.1 Experimental Setup The experimental apparatus consisted of 750ml polyethylene terephthalate (PET) soda bottles modified
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