Ch 10 - Water Bottle Rockets!

What is a Water Bottle Rocket?

A water bottle rocket is a 1 or 2-liter (soda) bottle with compressed air and water released in an upward direction.  The rockets will be graded based on their construction and the completion of the and a first place award will be given to the rocket that reaches the highest altitude.

Here are some pictures of us building the nose cones in class.  Students will do the fins at home...

Construction

#1 Main body/pressure chamber

Almost any 1 or 2 liter bottle will work.When launching, the pressure inside the bottle will cause the walls to expand. This expansion leads to a loss of energy and will make the rocket fly to a lower altitude. To solve this problem take some or duct tape and pre-wrap three bands around the pressure chamber. You don't want the tape to be too bulky and watch for wrinkles.

#2  Nose cone

Research different shape possibilities and add a small amount of weight to the base to raise the center of gravity of your rocket.  Be SURE not to puncture the Pressure Chamber.

#3 Fins

3-4 fins are the guidance system for your

rocket. Without them a rocket would tumble end over end.

• Fins should be straight and firm; if they flop around they are useless.

• Fins should not be too heavy.

• Fins should have a water proof covering (cut from plastic, styrofoam or covered with tape?)

• Fins should be adequately secured; duct tape works well. Do not use glue because it does not expand with the pressure chamber and may cause it to become brittle.

• The best fins are made of rigid cardboard or styrofoam board.

• The size of the fin does matter! The best rockets fly well with long and narrow fins.

• Fins should be evenly spaced around the base.

#4  Optional Test Flight

This is Mrs. Tiday's Rocket... the Lady Hawk!  She flies great!!
Click HERE to watch her go.

Using several feet of string, tie the rocket around the middle so that it balances. Because of the nose cone weight, the balance point will be towards the nose. When the rocket hangs level, a small piece of tape should be temporarily fixed to the string and bottle to keep the string from slipping. The rocket is then twirled in a circle. If the rocket tumbles while circling, it is not stable and needs more nose cone weight, bigger fins, or a combination of both. If the rocket circles with the nose always pointed forward, it is stable and ready for flight.

Bonus points for a Recovery System (such as a parachute) that slows the decent of the rocket.  Check out pages 6-9 of this link for ideas:  http://www.siouxbsa.org/pubs/c/98_waterbottlerocket.pdf