In this instructable, you will learn how to make a genuine Dr. Thunder Water Rocket. It's not too hard, and can be very rewarding in the end!

You will need:

- Four 2 liter bottles (pepsi works well)
- 1 Styrofoam board
- 1 Clear plastic garbage bag
- Duct Tape
- Nylon String
- A tennis ball
- Scissors/ Knife
- Painter's tape

Step 1: The Wings

First, you will make the wings. Trace a parallelogram pattern onto the Styrofoam board. Cut out three of them. They should resemble the wings in the pictures. Then take the wings and tape them to the 2 liter bottle. You should make sure to space them evenly around the bottle. Tape them on an angle, so the bottle spins when launched. The angle should resemble the second picture.

Step 2: The Top

Now you'll make the top of the rocket which covers the parachute and ball. Take another 2 liter bottle and pressurize it with a bicycle pump. (Use the skinny tip meant for basketballs and soccer balls, and stick it through the cap). Then rotate the bottom slowly over a heat source, such as a hot plate. You will see the bottom start to round. Once it looks like the pictures, stop applying heat. Cut off the top, and your done!

Step 3: Middle

To make the middle, you have to cut another 2 liter bottle. Cut off the top so that there will be enough room for the parachute to fit. Then cut off the bottom of that two liter bottle so you are left with a middle piece. Take the top from your rounded top bottle that you have already cut off, and tape that to the end of the engine bottle. Then tape the newly cut top to that top, taping them both at the opening. Slide the middle piece over the tops, and tape it to the end of the engine bottle. It should look like the pictures.

Step 4: The Parachute

To make the parachute, you need to lay out the garbage bag. Cut two of the sides so you are left with one large square. Now you need to cut a perfect circle out of the square. I'll leave that method up to you, since there are many different ways to do that. Once you have a circle, you'll need to cut the string. Cut 8 strings, all of them the same length. I made them the diameter of the parachute. Then take the painter's tape and tape 8 squares evenly around the edges of the parachute. Cut a small hole in the center of each square for the string to go through. Then tie all of the strings through all of the holes, making sure to tie them tight. Then take your tennis ball and cut a slit in the top and bottom, making sure to have the holes line up. Then take all of the strings and put them through the tennis ball, pull to the desired length and tie them several times so they stay in the tennis ball. Fold up the parachute and it's ready to put in!

Step 5: Launch!

Place the parachute in the top "cup" and place the tennis ball on top of it. Put on the rounded top so that it sits on the middle piece. Fill it up with a little less than 1 liter of water, pressurize, and launch! The tennis ball should float gently down to the ground.