Water Rocket Modeling

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Water Rocket Modeling

• Sean MunsonBen Donaldson Alex Dillon

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Design Goals

• Range
• Accuracy
• Aesthetics
• These tell us little about how to build a rocket!

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The Model
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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
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Boost Phase
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Boost Phase Thrust
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Coast Phase
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Coast Phase Drag
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Whoa, what about the Air Phase?

• Us We neglected it, sort of.
• You You cant just do that
• Us Well, actually, since we made some other
  assumptions

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Whats Important?

• Cross Sectional Area (Nozzle, bottle)
• Coefficient of Drag (CD, Surface area)
• Mass of Rocket
• Pressure
• Volume of Water

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Validation of the Model Experiments
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A Preface

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

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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

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Volume H2O vs. Range

• Mass 0.150 kilograms
• Pressure 70 psig
• Angle 30

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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

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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?

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Questions?