Make a Water Rocket

People have been making and launching water rockets for generations. Some passionate hobbyists have spent years honing their rocket designs, and there are thousands of different ways to do it.[1] It can be intimidating to start making your first bottle rocket, with the wealth of technical information available.[1] The principle is pretty simple, though, and making a bottle rocket doesn’t need to involve bringing a long shopping list to the hardware store.

Steps

Making a Rocket

  1. Make a nose cone out of paper. This will give your rocket more stability in flight. It is also an important decorative element in making your water rocket look recognizably like a rocket, so be sure to pick out a color paper you like.
    • Draw a circle about 1’ in diameter. The measurement doesn’t need to be precise, as you can make adjustments later. The simplest way to do this is to find a bowl of about the right size, place it upside down on the piece of paper, and trace it.[2]
    • Cut out the circle, and cut a straight line from the outside to the approximate center of the circle. Again, precision isn’t particularly important, just estimate where you think the center is.[2]
    • Slide the cut edges over each other to create a cone shape. Hold it over the cone to figure out the right size, and then tape or glue the paper together so it holds that cone shape.
  2. Cut three fins out of cardboard. Like the nose cone, these will aid in stability, and make your rocket look more rocket-like. There is no one right way for the fins to look, but they will likely be right angled scalene triangles (i.e. the sides will all be different lengths) with the second-longest sides of the triangles attached to the sides of the rocket. [1]
    • It’s up to you to decide the exact dimensions of your fins. Start by cutting a triangle out of cardboard, and holding it up to the side of the rocket to see how it looks. Adjust the shape until you’re satisfied, then trace it onto the cardboard twice and cut two more identical triangles.
  3. Attach the nose and fins to the bottle. The nose cone goes on the bottom of the bottle. The fins go midway up the body, spaced equally apart from each other around the circumference. Use a low-heat hot glue gun to avoid melting the plastic.[3][1]

Making a Launcher

  1. Cut the bottom off an oatmeal can. You can use another kind of food can or a piece of PVC piping as well. Just make sure it is the right width for the bottle rocket to be able to sit snugly on it, with the neck of the bottle (the bottom of the rocket) facing down. This will serve as a launch pad for your rocket.
  2. Duct tape a dowel or garden stake to the side of the can. You will stick this stake down into the dirt to stabilize your rocket launcher, so it should protrude 0.5’ – 1’ down off the can. Be sure to tape it firmly in place.
  3. Drill a narrow hole through a cork. Use the thinnest drill bit you can find. This hole needs to allow the needle of a bicycle pump to fit snugly into the cork and come out the other side, so that you can pump air into the rocket.[4][3]
    • Artificial corks work best for this, as real ones tend to crumble.[4]
    • The cork will likely be too long, and need to be trimmed down a bit to allow the needle to go all the way through.[3]
  4. Assemble the pieces. Thread the nozzle of the bike pump up through the can, so that it comes out of the top. Push the needle of the bike pump’s nozzle through the hole in the cork.[3]

Launching the Rocket

  1. Put water in the bottle and seal it. Fill the bottle to about 1/3 of the way full.[3] Insert the cork (already attached to the pump) into the mouth of the bottle. It needs to be as airtight as possible to work, so make sure it is wedged firmly in there.[4]
  2. Prepare for liftoff. Pull any excess tubing from the bike pump out of the bottom of the oatmeal can. Sit the rocket on top of the can, and drive the dowel attached to the can all the way into the ground, so that the bottom of the can is resting on the ground. Stand back.
  3. Increase the pressure inside the rocket. Start pumping air into the rocket via the bike pump. Before long, the pressure should increase to the point that the rocket is propelled into the sky overhead.[1]
    • If the rocket does not launch, it is probably because it is not airtight. Make sure there are not any holes in the bottle. If there are, patch them up with duct tape. If not, the cork is probably not sealing the bottle tightly enough. Try applying hot glue or industrial strength glue around the lip of the bottle. You may also have drilled too wide a hole in the cork, in which case you will need to try again with another cork and a narrower drill bit.

Things You’ll Need

  • A 2-liter soda bottle
  • Colored paper
  • Cardboard
  • Scissors
  • A low-heat hot glue gun and glue
  • An oatmeal can, or something with a similar cylindrical shape and width
  • Duct tape
  • A 1’ dowel or garden stake
  • An electric drill
  • A cork
  • A bike pump

Warnings

  • Always be careful with hot glue guns. Keep a cup of ice handy so that if you burn your finger, you can immediately apply ice. Unplug the glue gun as soon as you are finished with it.
  • Stand as far back from the rocket as your air pump will allow, and make sure any spectators stand at least 10 feet back from the rocket as you launch it.

Related Articles

Sources and Citations

  1. ↑ 1.0 1.1 1.2 1.3 1.4 https://www.nasa.gov/pdf/153405main_Rockets_Water_Rocket_Launcher.pdf
  2. ↑ 2.0 2.1 http://mymommymanual.com/how-to-make-a-jet-pack
  3. ↑ 3.0 3.1 3.2 3.3 3.4 http://www.science-sparks.com/2012/03/12/making-a-bottle-rocket
  4. ↑ 4.0 4.1 4.2 http://www.artofmanliness.com/2012/07/13/weekend-diy-dad-activity-how-to-make-a-quick-n-easy-water-rocket
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