Water Bottle Rocket Analysis

Our rocket included, 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. Next, 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.

The picture above is what we started with today. At the start of class, both Joy and I took out our rocket to launch. We launched about three times and could not get up to 7 seconds. We knew it was because we needed our parachute to come out, because all three tries the parachute didn't come out and our rocket nosedived to the ground even when we tried to adjust the position of the nosecone. Each time the launches squished the nosecone even more. After the third try, we decided to take the rocket back in and redo the nosecone because the it was squished and the parachute wasn't deploying.

After watching other groups succeed at deploying their rockets we decided to try a new approach to our nosecone. Instead of adding weight to the tip, we tossed the rock-at-the-tip idea and when for a more lightweight approach. We used the same card stock paper, and a lighter tape. Also, I left a small 3mm hole at the tip of the cone because the groups that succeeded used a funnel, which has a hole at the tip.

Then we went out again to launch some more and the first try we got 9.1 seconds!!!!! YAY! The cone fell off and the parachute deployed. We found it worked best with the bottle filled about halfway and pumped to 60 to 80 psi. Not only did our bottle go very high, which it usually did, but the rocket also came down a lot slower with the parachute.

But, after the first launch, the next couple of launches did not do as well. Either the parachute did not deploy or the launcher fell sideways. I think it might be because after the first time, the cone was still a little beat up.

I learned that there needs to be balanced mass on either side of the rocket but also not TOO much mass because then it will weight too much and won't accelerate. Also, its better when weight is distributed evenly and for the rocket to be longer because then it will be more stable. The closer the fins were to the back of the rocket, the farther back the center of gravity would be which makes it more stable. When there was around 60-80 psi, the rocket had just enough pressure to shoot, but not too much where it would explode. I also learned to be persistent because we kept trying over and over again until we got it right and until we could no longer launch our rocket. Also, I learned that sometimes watching others succeed can help you succeed too.

Overall, I am really happy that our rocket was pretty sturdy and well built because even though our rocket hit the ground hard almost every time, the fins, bottles, tape and parachute all stayed perfectly intact. YAY!

Here is Joy and I with Rocky the rocket.
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