Colored construction paper is both durable and nice-looking!
If you want to add a bit of color to your rocket, you can use colored duct tape to wrap the nose cone. You can also paint the plastic bottle if you’d like to decorate it further. Feel free to also add a design or logo to the plastic bottle (or body of) the rocket.
Try to put it on as straight as you can onto the bottle and make sure it is secure.
Use cardboard, construction paper, or normal paper as material for the fins. Signboards, such as the ones that say “For Rent” or “For Sale” are also very good fin material. Place the fins on the lower part of the rocket. Bend “tabs” into the sides of the fins so that they can attach to the rocket body more easily. Then, tape or glue them on. If you line up the bottoms of the fins with the bottom of the rocket, it should be able to stand on its own.
Use Play-Doh or clay as ballast as it is soft, malleable, and unlike pebbles or marbles, won’t fall out or scatter when the rocket launches. Mold about half a cup of Play-Doh or clay into the ridges on the bottom of the bottle to form a rounded end on the outside of the bottle. Cover it with duct tape to keep it secure.
Hold the rocket by the neck of the bottle and pump air into it. The rocket will go off when the cork can no longer withstand the pressure building up in the bottle. [4] X Research source Let go of the bottle. The water will shoot out everywhere when the bottle rocket takes off, so be prepared to get a bit wet. Do not approach the rocket once you start pumping, even if it appears that nothing is happening with the launch, as this can lead to injury. [5] X Research source
Cutting off the cap end of the bottle will make the rocket more aerodynamic and durable. A rounded end is also softer so it will do less damage to any objects if the rocket hits something when it lands.
To put in the kitty litter, tip the cut bottle and pour in about ½ inch of kitty litter. Then, add enough water to wet the kitty litter completely. Add another ¼ inch of kitty litter and soak it again. Avoid dumping in too much kitty litter as this can create a dry layer of kitty litter than could get loose and scatter when the rocket is launched. Too much kitty litter, or weight, in the rocket, can also cause the rocket to hit hard when it comes down. Dry the inside walls of the bottle and use duct tape to help hold the kitty litter in place.
Place the fins on the lower part of the cut bottle. Bend “tabs” into the sides of the fins so that they can attach to the rocket body more easily. Then, tape or glue them on.
Pump air into the bottle. The rocket will go off when the cork can no longer withstand the pressure building up in the bottle. [7] X Research source This is usually at around 80 psi. Release the bottle. The water will shoot out everywhere when the bottle rocket takes off, so be prepared to get a bit wet. Be cautious once you start pumping and do not approach the rocket, even if it appears that nothing is happening with the launch, as this can lead to injury. [8] X Research source
