Water Bottle Rocket Engineering

The picture above is the finished product. Our rocket is made up of two 2-liter bottles, card stock for the cone, duct tape, cardboard for the fins, and string and a plastic bag for the parachute. Then we named the rocket Rocky Jr. and wrote its name on the side for some flare. We first cut the bottom of one of the bottles and attached the open side to the bottom of the other bottle with a hot glue gun and duct tape. This way, there were openings on either side. Next we cut out four fins from cardboard and then glued and taped them on evenly spaced.

Our rocket unexpectedly did better than we thought when we tested it without the parachute and cone. Both times we shot the rocket we got over 6 seconds. We found it worked best with the bottle filled about halfway and pumped to 60 to 80 psi. The went pretty straight up and only swiveled a bit, but I expect that is from the lack of weight on the tip of out rocket.

To fix that and to add more time to our launch, we cut out a circle from a trash bag and then cut four small holes on the edges of the circle to tie string in. We then tied the other ends of the four pieces of string to the bottle's neck. Also, we took the card stock and formed a cone and used duct tape to make it sturdier. We taped a rock to the inside tip of the cone to add weight.

At one point, we thought of cutting off the top of the connected water bottle to add the rock to the inside of the water bottle and then tape it back on. We not only found out that it is really hard to tape or glue the water bottle top back on, but it is also not a good idea to put the rock inside the bottle because after adding the cone, the weight would be closer to the center of the rocket, which is not good.

We hope tomorrow, our parachute will deploy and the weight from the cone will add stability. We made the parachute strings long so hopefully that will work well. Tomorrow, we just have to figure out how to connect the cone to the bottle, but that won't be too hard.