For today‘s launch credit, we were required to conduct two launches; a second launch of just the bottle itself and a launch of a new bottle that contained some sort of alteration or improvement. For both launches we also needed to time how long the bottle would stay in the air. First, we once again launched the two liter bottle itself with no modifiers. We filled the bottle with 500mL of water that would act as the rocket fuel, attached it to the launcher, then pumped air into the bottle with a bicycle pump. For our launch yesterday, we pumped 45 PSI into our rocket according to the dial on the pump. But today, the pump we used did not have a dial that read how much pressure we were adding ot the bottle so we feel that this could have been a reason as to why our bottle didn‘t stay in the air as long as we would have liked it to. After fueling our rocket with water and air pressure, we launched the rocket by releasing the clasp. This launch lasted for 5.0 seconds, which was not to bad considering no modifiers were used. Another reason as to why our rocket may have stayed in the air as long as it did was because of the wind. As I launched our rocket, the wind picked up for a second which may have allowed our rocket to rise higher in the air and take longer to reach the ground.
After completing a launch of just the bottle itself, we launched our modified bottle. Our modified bottle contained three fins that were mounted to the bottle by masking tape. Each fin was made of cardboard shaped as a right triangle whose dimensions included a base of 2.75 inches, a hypotenuse of 6 inches, and a side of 5.3 inches.
Instructions on how to create these fins can be found by clicking on the following link: http://tclauset.org/21_BtlRockets/BTL.html
To launch this rocket, we once again followed the same procedure. We filled the bottle with 500mL of water, attached it to the launcher, and this time accurately pumped 40 PSI of air into the bottle (we only pumped 40 PSI this time because we forgot how much we pumped last time, not smart at all!) After launch, the bottle only stayed in the air for 2.3 seconds :( I was so disappointed! We came to a conclusion that what may have caused such an unsuccessful launch would be the fact that right as we launched, there was no wind factor, we only pumped 40 PSI of air into the bottle, and because of this mistake, there was not enough fuel to carry both the bottle and fin weight. What may also have caused a failed launch could have been the material of the fins. Cardboard just might be too heavy. But luckily, we still have time to perfect our rocket. Hopefully all goes well tomorrow (:
-Lehua
I think it was smart of you guys to accurately measure out the PSI; me and Keana had some troubles with that... our pump was not working properly, but we've found that pumping it at around 50-60ish PSI and launching it right after so that way the pressure doesn't escape as quickly is better to keep your rocket going.
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