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# Water Rocket Modeling PowerPoint PPT Presentation

Water Rocket Modeling. Sean Munson Ben DonaldsonAlex Dillon. Design Goals. Range Accuracy Aesthetics These tell us little about how to build a rocket!. The Model. What happens to the rocket?. Air Thrust Phase remaining air pressure leaves rocket.

Water Rocket Modeling

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## Water Rocket Modeling

Sean MunsonBen DonaldsonAlex Dillon

### Design Goals

• Range

• Accuracy

• Aesthetics

These tell us little about how to build a rocket!

## The Model

### What happens to the rocket?

Air Thrust Phaseremaining air pressure leaves rocket

Coast PhaseGravity, drag act on rocket until it smashes to the ground

Boost Phase

Water leaving rocket under pressure

### “Whoa, what about the Air Phase?”

Us: “We neglected it, sort of.”

You: “You can’t just do that…”

Us: “Well, actually, since we made some other assumptions…”

### What’s Important?

• Cross Sectional Area (Nozzle, bottle)

• Coefficient of Drag (CD, Surface area)

• Mass of Rocket

• Pressure

• Volume of Water

## Validation of the Model& Experiments

• Launchers don’t workmost launches required a kickto free the rocket, making itdifficult to measure the angle

### A Preface

• Rocket for tests was constructed in ~20minutes, with cardboard fins

### Mass vs. Range

• Pressure: 70 psig

• Volume H20: 0.7 liters

• Angle: 35°

• Observations:

• Launch without ballast (rocket mass: 70 grams) highly erratic

• Stability problems above or below 0.11 kg

• Determined CD to be 1.8

### Volume H2O vs. Range

• Mass: 0.150 kilograms

• Pressure: 70 psig

• Angle: 30°

What the #&\$% ?The stout kick requiredlikely changed the angleto 20° or 25°.

### Pressure vs. Range

• Mass: 0.186 kilograms

• Volume H20: 0.8 liters

• Angle 30°

• Observations:

• Last set of tests. Fins  mush Data  unreliable

• Clearly, more pressure is good so long as you do not exceed safety margins

### Design Goals:

• Low CD, A

• Parabolic, smooth nose

• Experiment with multiple 1L bottles

• Mass: ~115 grams

• Experimentation with nozzle area?

• Difficult with these launchers

• Tight but loose fit on launcher?