Rocket Design

The design I chose for my rocket was in order to make a low drag low weight rocket to go the highest, because those are some of the contributing factors to making the rocket go the highest. I chose a 6 inch carboard body tube because it was lighter than the polycarbonate but still significantly short. I chose then elliptical fins because they were deemed as optimal in the article that Mr. Dubick shared, so I figured that it would be the best design accounting for lift and drag. Using the balsa wood fins that would also reduce weight because of their lightweight properties. I also discovered that I could made the fins thinner by sanding them to further reduce weight without adverse effects on the height. The nose cone I used was an ogive cone, which I figured would work well, and I did not have much of a choice because that was what I was assigned. When I put all the pieces together including the mass object for the altimeter, I made sure that the center of gravity was ahead of the center of thrust. When doing this I discovered that the close the two were together the higher the rocket went, but I decided it would be best to make them further apart to account for building error and be more safe with the design. When designing the fin shape I came upon 4 smaller fins which worked well, I made them longer rather than wider which seemed to work much better in the overall design. Changing the center of gravity also had an effect as I said earlier, so moving the altimeter was something I tried. Moving the fins back also moved the center of thrust further forward, which was something I did to make the rocket both look cooler and accomplish a higher theoretical altitude. 

The motor we used was an Estes B4-4 rocket, so a B4 rocket with a 4 second ejection charge. This was all held onto the main body via an inner tube and a centering ring attached to the end of the rocket. For the launch conditions, I tested this at mostly optimal conditions, with a consistent wind speed of two miles an hour, anticipating similar conditions to the first launches we made. This resulted in a height of 861.03 feet maximum altitude for my rocket. Before I changed the ejection delay to four seconds, I was frustrated how my rocket would only fly around 200 feet, since the parachute was deploying, but after I fixed this it went fine. 

The construction process was very simply because it was so similar to the other rocket we built. I applied many of the same skills, except I placed the fins on the rocket before painting. Other than this I made sure that everything was measured out to fitting precisely, I cut the tube down to 6 inches, and made sure the fins were half hanging off the edge of the rocket. I chose to paint the body mainly black to make it easier to see in the sky, but chose to add a hint of green towards to top in order to make it look nicer.

The rocket did not behave as I expected, as it rapidly spun out which was unexpected and could be classified as a failure. This did not achieve the full flight predictions, however the parachute did deploy, only it happened after it was on the ground due to the much lower expected altitude and how long it took to eject the parachute. The rocket went up 164 feet as measured by the altimeter, where we had drilled holes into the sides of my rocket to account for the change in pressure measured by the altimeter. The device was secured via tying it into my parachute which was attached to the nose cone, and this resulted in a very stable connection which did not sever during the flight.