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Test Design
Our test design includes a six inch tip, a two paper-thick body, four straws, four parallelogram shaped tail fins, a breadboard to simulate the mass of the databot. The extra breadboard across our dummy databot was required because having only one breadboard with the strings attached to the parachute caused it to dangle freely, increasing drag. Adding the extra breadboard acts a counterweight and also solves the drag problem when the two are taped together. This design was based off the instructions provided to us on BrightSpace with a few modifications that our group added based off of our previous experiences with the stomp and straw rocket activities. Our group weighed various objects within the lab room to find an object that shared a similar mass with the databot and discovered that a breadboard has the exact same mass the databot, leading us to use this as our dummy test in replace of the actual databot. Four fins shaped in a parallelogram carved and sanded from a plank of balsa wood was chosen over three fins to provide additional stability for the rocket. The four straws were unnecessary and added by accident but we didn't want to risk damaging our rocket by attempting to remove any of the straws so we left them on for the test launch. The parachute is tied to one of the breadboards and is stored inside the body of the rocket. Ideally, the tip of the rocket is supposed to pop off as the rocket falls back to the ground and the parachute deploys.
Parachute Design
As for the parachute, our group went with an octogon shape with the goal of making our parachute as circular as possible. A square trash bag was divided into equal thirds using simple origami folds. Triangles were then cut from the outer four corners to create the octagon. Finally, one string was attached to each point, 8 total. Those 8 strings were then tied together in a knot so that it could be tied to the payload.
Square cut from trash bag
Folded in half, then a diagonal fold from the opposite corners
From there, an intersection is made which can be taken and folded into thirds, this is repeated on the opposite side to fold the trah bag into thirds both vertically and horizontally
Four triangles are cut from each corner to make the final shape of the parachute
IMG_0211.MOVThis parachute was very successful as shown in the video it expands within one story after being compressed tightly.
Engine Mount
Originally, the rocket engine was too loose inside our rocket as its circumference was smaller than that of our rocket. To solve this issue, we reused balsa wood strips from last week's bridge project and attached four strips the length of the engine and sanded it down to the right thickness so that it would just slightly be less than the rocket's circumference. This allowed the motor engine to tightly slide into the bottom of our rocket.
IMG_0212.MOVVertical String Test
As seen in this video, our test rocket successfully passed the vertical string test and achieved a smooth circular motion. Our group learned that we did not need the additional breadboard counterweight as this test was performed with one breadboard on the side of our rocket simulating the databot. However, the test rocket still required two breadboards taped together to reduce the drag formed from having one breadboard attached by a string.
Test Launch
As observed in the video, the rocket achieved liftoff however it flew less than 15 feet in the air before it sputtered and came back down. This was due to the engine at the bottom of our rocket propelling itself through the body of the rocket and thus prohibiting our rocket from achieving a higher altitude. Our group was lucky to have every part of our rocket salvaged except for the body due to the heroic act of our TA Chetun coming in to extinguish the flames of our rocket body. After further analysis, our group concluded that our rocket was also too heavy and that we would have to decrease the weight of our rocket significantly so that it can fly higher.
IMG_6318.MOVThis is the video of our test launch with our test rocket. The rocket's performance was not what we were aiming for but our group was ready to make adjustments and modifications for the final design.
With the help of Mr. Irvine and our TA, we decided to make multiple modifications to our test model rocket with the goal of making it lighter so that it could fly higher. These modifications included smaller rocket fins, a shorter body, smaller parachute, less straws, and a shorter tip.
FINAL DESIGN
Our final rocket design contained the same materials as the test model, but with modifications in every area to decrease weight and ensure our rocket would be able to fly as high as it could while also deploying the payload with a successful parachute. The image on the right is our final rocket. Starting with the bottom, our group reused the engine mount idea using balsa wood strips only this time, to prevent the engine from propelling up our rocket body we poked 4 holes into the body of our rocket near the fins. We then slid balsa wood strips in an X formation to act as a barrier that would prevent the motor engine from rising. The fins are half the size of the original fins in our test rocket. We took two of our original rocket fins and cut them in half to create the new four, smaller fins for our final rocket. The body of the rocket is also 2/3 the original length of the prototype. The wooden tip of the rocket was sanded down by 2 inches. Additionally, the counterweight was removed as the string test with our test model demonstrated that a counterweight was not needed for our rocket to achieve smooth circular motion. The drag problem from the test rocket was resolved by taping the databot to the wooden tip so that it would be more secure. This way, the nose and databot would be attached to the parachute. All of these modifications decreased the weight of our rocket significantly from around 120 grams to 88 grams.
NEW PARACHUTE
We decided to make a smaller parachute to decrease weight and also so it would fit in the new rocket body which was 2/3 the length of the original. It was made using the same methods as the parachute used in the test rocket only it was smaller.
New parachute
Size comparison: New(left) vs old(right)
LAUNCH DAY
Our rocket successfully launched and flew the highest with the payload attached. Unfortunately, the parachute did not deploy but it survived the crash and was durable enough for another attempt. In between the first and second video, the used motor engine was swapped with a new one and in place of the balsa wood engine mount we wrapped the bottom up with electrical tape. Additionally, we loosened the tip of the nose so that it would be easier for the nose to pop off in the air so that the parachute may deploy. In the second video, the rocket launched successfully again and the parachute deployed as it entered its descent. The modifications made from our test model enabled our rocket to soar and reach new heights as well as deplot a working parachute that safely restored the databot to the ground, undamaged.
IMG_6345.MOVFirst launch, successful ignition, no parachute deployment
IMG_2856.MOVSecond launch, successful ignition and parachute
WHAT WE LEARNED
Our group learned the importance of lift, thrust, weight, drag, and how each are detrimental to flight. We also were reminded the importance of carefully choosing what to use for the rocket and what measurements as any extra amount creates weight and a good rocket minimizes weight while maximizing efficiency and performance. Managing resources and making certain areas shorter or thinner required testing and the efforts of every member. Overall, our group succeeded in creating a rocket capable of launching into the air and deploying a parachute that protects the payload as it floats back to the ground.
Rocket, databot, and parachute intact after 2 launches
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