How to Make a Double Parachute Rocket

Empty the bottle and remove the cap. Fashion a nose cone out of one of the pieces of poster board. Tape it down with duct tape or a glue gun. The bottom of the cone must be the same size as the bottom of the bottle. Cut the bottom of the cone straight with scissors.

Add weight to the nose cone to stabilize your rocket. You can use a 3 ounce ball of clay or a metal nut for this purpose. Tape the weight into the inside tip of the nose cone. Tape or glue the nose cone to the bottom of the bottle.

Cut 4 fins of any size or shape from the poster board. Glue them evenly around the neck of the bottle. The tips of the fins should extend just beyond the bottle top.

Drill a small hole into the rubber stopper. The hole must be just big enough to fit the bicycle pump needle snugly. Push the needle into the stopper, and fill the bottle one-third to one-fourth full with water. Close the bottle with a stopper.

Smooth out the plastic shopping bag. Use the marker to draw as big of a circle that can fit on the bag. Cut the circle out with a pair of scissors through both layers of the bag. You should have two equally sized circles.

Make eight holes in the plastic, placing them evenly around the circle. Cut eight lengths of string for each circle. All 16 pieces of string should be about one foot long. Tie the string through each of the holes. Gather the bottom ends of the string, and then tape it to the bottom of the rocket.

Place the rocket on the launch pad. It should be resting on its fins. Start pumping. When the pressure inside the bottle gets too high, the stopper will come out, and the bottle will fly up into the air. When it starts coming down, the parachutes will scoop up air and slow its descent.