As a final school assignment for the Physics 11 course, teams were given the task of creating a water bottle rocket, with the objective to travel as far as possible (horizontally) without injuring the passenger (an egg).
However, my partner (Peter Deutsch) and I, did not want to settle for the conventional single-bottle rocket approach. We wanted to challenge our design and engineering abilities by designing a rocket with double the volume.
Unique designs and innovations
A greater volume will allow a greater volume of rocket fuel (water and air) to be stored. Therefore, greater thrust would be produced. However, manufacturing the system to be pressure-tight proved to be a challenge. Different plastics, drills, drill bits, and drilling methods were examined to find the most appropriate solution. The most effective manufacturing process used a drill on low speed to cut the initial hole. Then, using an industrial-strength drill on full power, the hole was heated and slightly enlarged to fit the second bottle. When the plastic cooled, it molded around the first bottle. Water-tight glue was used to make the final seal. Extra safety precautions were taken on launch day to accommodate for the extreme force created by this rocket.
Streamlined water flow
Through research, it was discovered that fire hoses use a special nozzle which streamlines the water thus creating a more streamlined flow of water and allowing the water to travel farther. The same approach was used in this project. Through experimental trial-and-error, we were able to prove and apply the fire hose nozzle concept to our rocket. Several straws were secured in a piece of PCB pipe, which was then fitted to the bottom of the rocket. A more streamlined and laminar flow of water would allow the rocket to travel in a straight path and give it more propulsion.
The crash capsules utilize the concept of crumple zones, similar to what car manufacturers use to increase the safety of automobiles. The top capsule of the rocket was designed to crumple on impact and separate from the rest of the rocket. This was achieved by cutting the top in such a way that it acts like a spring. Several capsule prototypes were created to find the most effective, durable design. This specially designed capsule increases the duration of impact when the rocket hits the ground, therefore better protecting the egg (as proven by the formula mv=Ft).
We were not informed of the modifications made to the rocket launcher. Therefore, in correspondence with Murphy's Law, the mass of our rocket was too great to be fully supported. As a result, the rocket was launched at a very low angle (i.e. not the optimal 45º) and did not reach its full potential.