Water Bottle Rocket Engineering

The picture on the left is of our rocket. It is made out of two 2L bottles, although we cut off a fourth of one in order to elongate our rocket without making it too long. As you can see, we fit the bottle without the bottom onto the other bottle so they overlapped a bit. We made four fins out of cardboard and taped them with scotch tape to keep them waterproof. We then glued the fins to the bottom of our rocket as well as taping them, to make sure they didn't fall off our break off when the rocket landed. Our cone was made out of a lot of paper which Rachel and I folded into a cone shape and then taped it up as well. Not only that, but in order to add a little extra weight to the top of the rocket to keep it from getting out of control, we taped a rock to the inside of the top of the cone. We also made a parachute out of a trash bag. We connected the parachute to the bottle by poking four holes into the parachute, then threading string through them. 

While launching the rocket today, we didn't use the cone, since we hadn't yet finished the parachute and only had thirty minutes left for launching practice. Our rocket, surprisingly enough, did a lot better than Rachel and I expected it to, since we didn't actually have any added weight on the top of the rocket to make it steadier. However, both times we launched the rocket, it was in the air a little over six seconds both times. We filled the rocket about halfway with water, and pumped it to around sixty psi. While the rocket did wobble a bit while in the air, it went really high, so hopefully we can fix it by adding more weight to the top of the rocket. 

Hopefully tomorrow after testing the rocket with the parachute and making adjustments it manages to stay in the air for at least ten seconds. While I'm still really worried, I think that with the two hours we have for launching the rockets, Rachel and I will manage to do whatever we need to do to get our rocket to stay in the air for those four extra seconds.