Water Bottle Rocket

The picture above is of Rachel and my whole rocket, including the cone and parachute. As you can see by the picture, we made the cone by folding paper into a cone shape and taping it up for durability. The parachute was made out of a garbage bag, which we cut into a circle. We then poked four holes into the bag on opposite sides after putting tape on it first, so the string wouldn't rip the bag if anything happened to it. After tying the string through the holes, we threaded them back to the rocket, where we tied them around the neck of the bottle. When launching the rocket, we folded the parachute into the cone, and then put the extra string from the parachute into the bottle of the rocket, so they wouldn't get in the way or open prematurely. The rocket itself was made out of two two-liter bottles. We cut off a fourth of one of the bottle's bottoms, so we could fit the bottles together, since longer rockets work better. At the bottom of the rocket, we had four fins, which were made out of cardboard that we had cut into triangles and then taped up afterwards.


The picture on the left shows our two cones. The cone on the right was our original cone, but we had taped a rock into the top of the cone, and when we tried getting it out, ended up ripping the paper a bit. We had to leave the tape in there so we didn't have to make a new cone (we did anyway), but the tape ended up sticking to the parachute, so the parachute wouldn't work. We then made a new cone, which was, as you can see, taller and skinnier. The cone being skinnier was actually a good idea, because it didn't really fit on the bottle, so it came off a lot easier. We also didn't put any tape on the inside of the cone this time, so the parachute had an easier time coming out. The first time we used the new cone, the parachute came out easily and helped the rocket land easier. Our rocket was able to stay in the air for 9.1 seconds, which was still a lot better than I was hoping for. Unfortunately though, after that one launch, our parachute didn't work after that, which might have been because of the cone getting squished a bit, or because Rachel and I got worse and worse at folding the parachute and putting it into the cone.
However, besides our mishap with the cones, everything else worked out pretty fine. The fins didn't break off, which was a big relief, and they, along with the cone, stabilized the rocket when it was in the air, making it a lot less wobbly.

Rachel and I found that filling the bottom bottle of the rocket halfway was the optimal amount of water.  Too much water means that there is too much mass, so the rocket wouldn't launch very high. Funnily enough, if you don't have enough water, you get the same results. Our psi, when launching the rocket, was always somewhere between 60 and 80.

Some of the physics I learned was that one side of the rocket couldn't be too much heavier than the other side. If the bottom was too heavy compared to the top, then when launched, it would be really wobbly. I also learned that it was better to have a cone rather than not, especially when you have a parachute. If you use a cone, it also acts as an extra weight for the top of the rocket, but also makes the rocket more aerodynamic. Also, if you didn't use a cone when using a parachute, the parachute would just add drag to the rocket when launched, so it wouldn't launch as high, resulting in less time in the air for the rocket.

Overall, I had a lot of fun with this project. Rachel (she's the one on the right in the picture) and I worked well, and we are both really happy that our rocket didn't break, although the head of the rocket got dented every time it nose-dived into the ground. We're really happy with our nine seconds, and had a lot of fun while building our rocket and launching it.