Water Bottle Rockets

Click here to see the rocket that set the record for the 1999-2000 school year!!!

Bottle rockets are excellent devices for investigating Newton's Three Laws of Motion.

The rocket will remain on the launch pad until an unbalanced force is exerted propelling the rocket upward (???? Law).

The amount of force depends upon how much air you pumped inside the rocket (???? Law). You can increase the force further by adding a small amount of water to the rocket. This increases the mass the rocket expels by the air pressure.

Finally, the action force of the air (and water) as it rushes out the nozzle creates an equal and opposite reaction force propelling the rocket upward (???? Law).

Building a Bottle Rocket

Stability and Control Systems

Building an efficient rocket engine is only part of the problem in producing a successful rocket. The rocket must also be stable in flight. A stable rocket is one that flies in a smooth, uniform direction. An unstable rocket flies along an erratic path, sometimes tumbling or changing direction. Unstable rockets are dangerous because it is not possible to predict where they will go. They may even turn upside down and suddenly head back directly to the launch pad.

Making a rocket stable requires some form of control system. There are three we are going to focus on.

Fins-This helps keep the rocket staight up (stabilizing) The fins raise up from the rocket body for the purpose of giving the rocket directional stability. Usually located at the rear of the rocket.

Nose cone--The front surface of a rocket, generally pointed in shape. It reduces drag (the resistance of moving air) by moving the air smoothly around the rocket.

Mass-- All matter, regardless of size, mass, or shape, has a point inside called the center of mass (CM).The center of mass is the exact spot where all of the mass of that object is perfectly balanced.

In addition to center of mass, there is another important center inside the rocket that affects its flight. This is the center of pressure (CP).

The center of pressure exists only when air is flowing past the moving rocket. This flowing air, rubbing and pushing against the outer surface of the rocket, can cause it to begin moving in a wild manner.

Tips on Building a Bottle Rocket

You may want to wrap and glue or tape a tube of construction paper around the bottle.

Design/draw several fins of any shape. Bring the designs to Mr. Zielinski to cut out wood and/or plastic and to glue them to the tube.

Form a nosecone and hold it together with tape or glue.

Use a wad of modeling clay to help with your center of mass (You must use clay!).

Glue or tape nosecone to upper end of bottle.

Decorate your rocket.

Perform to Center of Mass balance test. If you have time the Center of Pressure swing test.