Bottle Rockets !

materials:
2 - 2-Liter soda bottles
3 - cardboard wings
1 - tennis ball
3 - garbage bags
6 - 3-foot-long pieces of string
2 - balloons, blown up to the point where they can safely fit inside the open bottle.
-electrical tape.
1 - liter water.

Remove all covering from your bottles, and cut the bottom segment off of one of them.

cut the following shape wings out of cardboard.
they're aerodynamic. and they look funky.

flatten out three garbage bags by cutting along their seam, then tape them all together, side-by-side. the result should look like a rectangle. on the two shorter sides, hole-punch and reinforce three holes each - two for the corners, and one in the center of the side. put a piece of string, about three feet long, through each hole, and knot. take all the strings and, with strong tape, secure them to the tennis ball.

take a blown up balloon, and put it in the bottle. put the garbage bag parachute with the tennis ball in the bottle, and put another balloon in with it.

Go outside and launch your rocket with a pump and a stopper.
Hope the air pressure makes your balloons make the parachute deploy.
Hope really hard.