Interactive Water Rocket Simulator | Physics Experiment

Water Rocket Simulator

Created By : Ir. MD Nursyazwi

Instructions on How To Use

1. Review the default parameters in the **Data Input** panel to the left, or click **Load Ideal Setup** to get a great starting point.
2. Adjust any of the values, such as water volume, launch pressure, or drag coefficient, to see how they affect the rocket's flight.
3. Click the **Launch Rocket** button to start the simulation.
4. Watch the rocket's flight path in the graphic simulation on the right. You can also view real-time data in the results section below it.
5. Use the dropdown menu to switch between **Altitude**, **Velocity**, and **Acceleration** graphs to analyze the flight data.
6. To run a new simulation with different parameters, simply change the input values and click **Launch Rocket** again.

Data Input

Bottle Volume (L): 1.0 L 1.5 L 2.0 L 3.0 L

Water Volume (% of bottle):

33% (0.50 L)

Launch Pressure (psi):

60 psi

Dry Rocket Mass (g):

150 g

Nozzle Diameter (mm):

20 mm

Rocket Body Diameter (mm):

100 mm

Drag Coefficient:

0.8

Launch Angle (°):

90 °

Wind Speed (m/s):

0 m/s

Wind Angle (° from horizontal):

0 °

Graphic Simulation & Results

Graph: Altitude Velocity Acceleration

Simulation Results

Status: Awaiting launch

Max Altitude: 0 meters

Max Distance: 0 meters

Flight Time: 0 seconds

High Quality Science Explanations

A water rocket's flight can be divided into two main phases: the **thrust phase** and the **coasting phase**. The physics that governs each part of the flight is different, and understanding these principles is key to building a successful rocket.

Key Ideas Used in the Simulator

This simulator models the rocket's flight using several key physics principles. Here's how it works:

• **Thrust Force:** This is the powerful push that gets the rocket moving. It's created by the pressurized air inside the bottle forcing water out of the nozzle at high speed. The higher the pressure, the stronger the push.
• **Aerodynamic Drag:** As the rocket flies through the air, the air pushes back on it, slowing it down. This force is called drag. It's stronger when the rocket is moving faster and when the rocket has a less streamlined shape. The force of drag is calculated as: "Drag Force" is equal to one-half of the air density, times the rocket's velocity squared, times the drag coefficient, times the rocket's cross-sectional area.
• **Air Pressure & Density:** The air at the top of the atmosphere is thinner than the air at sea level. The simulator uses a special formula, the **Barometric Formula**, to figure out how much the air's pressure and density change as the rocket climbs higher. This helps make the drag calculation more accurate. The air density at a given altitude is calculated based on the density at sea level, the temperature lapse rate, the standard temperature, gravity, the molar mass of air, and the universal gas constant.
• **Newton's Second Law:** This is a fundamental law of physics that connects all the forces acting on the rocket to its acceleration. It helps us calculate how fast and in what direction the rocket will move. The total force is the sum of all forces, and the acceleration is calculated by dividing the net force by the mass of the rocket.

Thrust Phase

This phase begins the moment the rocket is launched and ends when all the water has been expelled. The primary force driving the rocket upward is **thrust**, which is a direct application of **Newton's Third Law of Motion**. As the pressurized air forces the water out of the nozzle at high speed, the rocket is pushed in the opposite direction. The magnitude of this thrust depends on how fast the water is leaving the bottle and how much water is being pushed out each second.

The **launch pressure** and the **water volume** are the most critical factors during this phase. More pressure means a greater initial force, and a higher water volume provides a longer duration of thrust. The rocket's total weight decreases as the water is ejected, which actually causes the rocket's acceleration to increase over time.

The pressure inside the bottle decreases as the air expands. This is modeled using the **adiabatic expansion** principle, which states that the pressure is proportional to the volume raised to a certain power. The thrust force is then calculated from the pressure difference between the inside and outside of the rocket, and the nozzle's area.

Coasting Phase

Once all the water is gone, the thrust stops. The rocket continues to climb due to its momentum but is now only under the influence of two main forces: **gravity** and **aerodynamic drag**. Gravity constantly pulls the rocket back toward Earth, while drag opposes the direction of motion, slowing the rocket down. The simulation also accounts for wind, which adds an additional force.

The **drag coefficient** and **rocket body diameter** become very important here. A lower drag coefficient (achieved with a streamlined nose cone) and a smaller cross-sectional area will reduce the drag force, allowing the rocket to coast to a higher altitude and fly for a longer duration. As the rocket climbs, the air density decreases, which is accurately modeled to simulate the effect of altitude on drag.

The Optimal Water Volume

Finding the right amount of water is a classic trade-off problem. There isn't a single "perfect" volume, as it depends on your specific rocket and what you're trying to achieve (e.g., maximum altitude, maximum acceleration, or longest flight time). For most designs, the ideal water volume is typically between **30% and 50%** of the bottle's total volume. The simulator is a great tool for experimenting with this trade-off and finding the best volume for your particular rocket design and launch pressure.

References

• Water Rocket Design and Operation
• Principles of Aerodynamics
• Newton's Laws of Motion
• The Ideal Gas Law

Other Science Simulators

• Projectile Motion Simulator
• Buoyancy Simulator - Interactive Physics
• Photosynthesis Interactive Simulator
• Interactive Microalgae CO2 Absorption Simulator
• Hand Crank Generator Simulator - Energy Transfer