This rocket was designed to keep a tennis ball in the air for as long as possible. At the launch it flies in to the air, when it reaches its highest point, the cone is designed to fall off, at which time the ball, attached to a parachute, will fly out, and will carry the tennis ball down slowly to the ground.
Step 1: The Bottle
Take a water bottle, and remove the label
Step 2: The Fins
Cut triangles from cardboard, fold them in half, and cut tabs in them. Make three of these fins. The tabs will make the rocket spin on the way up, making it go higher.
Step 3: Attach the Fins
Use electrical tape to attach the three fins at regular intervals.
Step 4: The "container"
Take a second bottle, and cut the top and bottom off, and cut tabs to hold up a nose cone. Later, this container will be used to house the parachute and tennis ball
Step 5: The Cone
Either make a cone, or use a traffic type cone.
Step 6: The Parachute
Take a piece of painter's drop cloth (a plastic that is fairly light, and folds up small) or a plastic garbage bag, then cut it into a parachute shape. Instructions to build a parachute are on this site in the 'making the parachute' section http://www.lnhs.org/hayhurst/rockets/.
Step 7: Finishing Up
Connect everything together (tape the container to the original bottle) connect the parachute to strings, and put the strings on a tennis ball. Put all of this in the container, and put the cone on, you are now ready to fire